Guidance on aspects of cleaning validation in active pharmaceutical ingredient plants
Table of Contents
1.0FOREWORD 3
2.0OBJECTIVE 3
3.0SCOPE 3
4.0ACCEPTANCE CRITERIA 4
4.1 Introduction 4
4.2 Methods of Calculating Acceptance Criteria 4
4.2.1Based on Therapeutic Daily Dose 4
4.2.2Based on Toxicological Data 6
4.2.3General Limit7
4.2.4Swab Limits9
4.2.5Rinse Limits14
5.0LEVELS OF CLEANING 16
5.1 Introduction 16
Procedure 16
5.2
6.0 BRACKETING AND WORST CASE RATING 20
6.1 Introduction 20
Procedure 20
6.2 Bracketing
6.3 Cleaning Procedures 22
6.4 Investigations and Worst Case Rating (WCR) 23
6.5 Worst Case Rating 26
7.0DETERMINATION OF THE AMOUNT OF RESIDUE 30
7.1 Introduction 30
7.2 Validation Requirements 30
7.3 Sampling Methods 37
7.4 Analytical Methods 39
8.0 CLEANING VALIDATION PROTOCOL 40
8.1 Background 41
8.2 Purpose 41
8.3 Scope 41
8.4 Responsibility 42
8.5 Sampling Procedure 42
procedure 43
8.6 Testing
8.7 Acceptance
criteria 44
8.8 Deviations from protocol 46
9.0 VALIDATION QUESTIONS 47
10.0REFERENCES 53
11.0 GLOSSARY 54
12.0COPYRIGHT AND DISCLAIMER 55
1.0 Foreword
This document has been prepared by the cleaning validation task force within the
active pharmaceutical ingredient committee (APIC) of CEFIC.
In recent years the subject of cleaning validation in active pharmaceutical ingredient
manufacturing plants has received a large amount of attention from regulators, companies and customers alike. It is important that the requirements for the finished
manufacturing companies are not transferred back in the process to active pharmaceutical ingredient manufacturers without consideration for the different processes that take place at this stage.
The document reflects the outcome of discussions between APIC member companies
on how cleaning validation requirements could be fulfilled and implemented as part
of routine operations.
It should be read in conjunction with the APIC document entitled …Cleaning Validation in Active Pharmaceutical Ingredient Manufacturing Plants“
2.0 Objective
This document has been prepared only to assist companies in the formulation of cleaning validation programmes and should not be considered a technical standard
but a starting point for internal discussions. The document includes examples on how
member companies have dealt with specific areas and issues that arise when performing cleaning validation.
3.0 Scope
Five specific areas are addressed in this Guidance document, namely:
? Acceptance Criteria
? Levels of Cleaning
? Bracketing and Worst Case Rating
? Determination of the amount of residue
? Cleaning Validation Protocol
Finally the most frequently asked questions are answered.
4.0 Acceptance Criteria
4.1 Introduction
Companies must demonstrate during validation that the cleaning procedure routinely
employed for a piece of equipment limits potential carryover to an acceptable level.
That limit established must be calculated based on sound scientific rational.
This section provides practical guidance as to how that acceptance criteria can be
calculated. It is important that companies evaluate all cases individually. There may
be specific instances where the product mix in the equipment require further consideration.
4.2 Methods of Calculating Acceptance Criteria
4.2.1 Based on Therapeutic Daily Dose
The principle for the requirement is that the standard Therapeutic Daily Dose (TDD)
of the following substance (‘contaminated’ substance, in this case called "next") may
be contaminated by no more than a certain proportion (usually 1/1000 part) of the
TDD of the substance investigated in the cleaning validation (contaminating substance, in this case called "previous"). This method only applies when the therapeutic daily dose is known. It is generally used for final product changeover API
Process “A” to API Process “B.
Procedure
Establish the limit for Maximum Allowable Carryover (MACO) according to the
following equation.
TDD previous x MBS
MACO = ------------------------------
SF x TDD next
MACO Maximum Allowable Carryover: acceptable transferred amount from the investigated product ("previous")
TDD previous Standard therapeutic dose of the investigated product (in the same dosage form as TDD next)
TDD next Standard therapeutic dose of the daily dose for the next product
MBS Minimum batch size for the next product(s) (where MACO can end up)
SF Safety factor (normally 1000 is used in calculations based on TDD)
Example 1:
Product A will be cleaned out. The product has a standard daily dose of 10 mg and the batch size is 200 kg. The next product B has standard a daily dose of 250 mg and the batch size is 50 kg. Both A and B are administrated orally and SF is set to 1000. Calculate the MACO for A in B!
10 (mg) x 50 000 000 (mg)
MACO = ------------------------------------ = 2 000 (mg)
1000 x 250 (mg)
Result: MACO is 2 g (2000 mg)
Example 2:
Now product B in example 1 will be cleaned out. The following product is product A in example 1. Calculate the MACO for B in A!
250 (mg) x 200 000 000 (mg)
MACO = ---------------------------------------- = 5 000 000 (mg)
1000 x 10 (mg)
Result:MACO is 5 kg (5 000 000 mg)
In API manufacture it is possible to obtain a very high MACO figure. In example 2, the figure obtained is clearly unacceptable. Although there would be no effects expected, the equipment would be obviously dirty and a general GMP limit should be chosen (see 4.2.3 - page 7 - how to select limits).
Instead of calculating each potential product change situation, the worst case scenario can be chosen. Then a case with most active API (lowest TDD) is chosen to end up in the following API with the smallest ratio of batch size divided with TDD (MBS/TDD ratio). This could be done if the safety factor is the same for all products (otherwise the lowest MBS/(TDDxSF) ratio should be chosen).
4.2.2 Based on Toxicological Data
In cases in which a therapeutic dose is not known (e.g. for intermediates and detergents), toxicity data may be used for calculating MACO.
Procedure
Calculate the so called NOEL number (No Observable Effect Level) according to the
following equation and use the result for the establishment of MACO. (See [3] – page 53 - for reference.)
LD50 (g/kg) x 70 (kg a person)
NOEL = -----------------------------------------
2000
From the NOEL number a MACO can then be calculated according to:
NOEL x MBS
MACO = ------------------------------
SF x TDD next
MACO Maximum Allowable Carryover: acceptable transferred amount from the investigated product ("previous")
NOEL No Observed Effect Level
LD50Lethal Dose 50 in g/kg animal. The identification of the animal (mouse, rat etc.) and the way of entry (IV, oral etc.) is important.
70 kg70 kg is the weight of an average adult
20002000 is an empirical constant
TDD next Largest normal daily dose for the next product
MBS Minimum batch size for the next product(s) (where MACO can end up)
SF Safety factor
The safety factor (SF) varies depending on the route of administration. Generally a factor of 200 is employed when manufacturing APIs to be administered in oral dosage forms. SF can vary depending on substance/dosage form according to (suppose tox values from oral administration) as for example as presented on the next
page.
Safety factors: Topicals 10 – 100
Oral products 100 – 1000
Parenterals 1000 – 10 000
Remarks: API`s in development may require higher safety factors due to lack of
knowledge.
To calculate MACO values from tox data is frequently done when therapeutic dosage
data is not available or not relevant. It is generally employed if the previous product
is an intermediate and the following product an API.
4.2.3 General
Limit
If the calculation methods based on therapeutic doses or toxicological data (see 4.2.1
or 4.2.2, page 4 – 7) result in unacceptably high or irrelevant carryover figures, or toxicological data for intermediates are not known, the approach of a general limit may be suitable. Companies may chose to have such an upper limit as a policy. The
general limit is often set as an upper limit for the maximum concentration (MAXCONC) of a contaminating substance in a subsequent batch.
The concentration (CONC) of the investigated substance which can be accepted in the next batch, according to dose related calculations, is:
MACO
CONC = ------------------------------
MBS
MACO Maximum Allowable Carryover: acceptable transferred amount
from the investigated product ("previous"). Calculated from
therapeutic doses and/or tox data.
MACO ppm Maximum Allowable Carryover: acceptable transferred amount
from the investigated product ("previous"). Calculated from general
ppm limit.
CONC Concentration (kg/kg or ppm) of "previous" substance in the next
batch. Based on MACO calculated from therapeutic doses and/or
tox data.
MAXCONC General limit for maximum allowed concentration (kg/kg or ppm)
of "previous" substance in the next batch.
MBS Minimum batch size for the next product(s) (where MACO can end
up)
A general upper limit for the maximum concentration of a contaminating substance in a subsequent batch (MAXCONC) is often set to 5-100 ppm depending on the nature of products produced from the individual company (e.g. toxicity, pharmacological activity, 10 ppm in APIs is very frequent).
Note - If you decide to employ the concept of levels of cleaning (ref. section 5, page 16), then different safety factors (ppm limits) may be used for different levels. Especially if the product cleaned out is within the same synthetic chain and covered by the specification of the API, much higher (qualified) levels are acceptable.
If the calculated concentration (CONC) of the previous product (based on MACO calculated from therapeutic doses/tox data) exceeds the general upper limit (MAXCONC), then MAXCONC level will be the limit.
Procedure
Establish MACO ppm, based on a general limit, using the following equations.
MACO ppm= MAXCONC x MBS
E.g. for a general limit of 100 ppm: MACO = 0.01% of the minimum batch size (MBS), and for a general limit of 10 ppm: MACO = 0.001% of the minimum batch size (MBS).
Remarks: The ICH impurity document (Q 3) indicates that up to 0.1% of an individual unknown or 0.5% total unknowns may be present in the product
being tested.
Example 3:
A product
B will be cleaned out. The product has a standard daily dose of 250 mg and the batch size is 50 kg. The next product A has a standard daily dose of 10 mg and the batch size is 200 kg. The general limit of the company is 10 ppm. Calculate the MACO ppm for B in A!
MACO ppm = 0.00001 (mg/mg) x 200 000 000 (mg) = 2000 (mg) Result: MACO ppm is 2 g (2 000 mg)
In the worst case a maximum of 2 g of B may appear in API A. This is more reasonable than the limit 5 kg calculated in example 2.
4.2.4 Swab
Limits
If homogeneous distribution is assumed on all surfaces, a recommended value can be
set for the content in a swab. This can be used as basic information for preparation of
a method of analysis and detection limit.
Procedure
Establish the target value for swab limit for the whole equipment train, using the following equation:
MACO [μg]
------------------------------
Target value[μg/dm2]
=
Total surface[dm2]
Also other methods with different swab limits for different surfaces in a piece of equipment and/or equipment train can be used. Using this approach, the total amount
found on the equipment train has to be below the MACO (see 4.2.4.2 - page 12 - how
to evaluate this).
4.2.4.1 Setting Acceptance Criteria for Swab Limits
For each item tested, normally two acceptance criteria (AC) are set.
AC1. The acceptance criterion “no visible residue” shall always be applied.
AC2. The most stringent of the following swab limits are normally used for swab tests:
?Swab limit based on therapeutic dose or tox calculations (see 4.2.1, page
4 and 4.2.2, page 6)
?Swab limit based on a general "ppm limit" (see 4.2.3, page 7) AC3. The MACO must not be exceeded for the total equipment train (see 4.2.4.2, page 12).
Usually either AC2 or AC3 is used (swab limits are calculated from MACO).
However, both can be used and then different swab limits can be set for different types of equipment. Some swab limits can be higher than the target value, if others to
compensate are lower. This as long as the total calculated amount is below the MACO (see 4.2.4.2, page 12).
In determining acceptance limits, all possible cases of following products in the relevant equipment shall be taken into account. It is proposed that a matrix be set up
in which the limits for all cases are calculated. Either acceptance criteria for each product in the equipment can be prepared or the worst case of all product combinations may be selected.
Example 4:
Several substances are produced in the same equipment train (Dryer X), as presented in the following table. Any of the other six substances can be produced after Substance C. Substance C can be administered both in oral and parental dosage form.
The company policy is based on three requirements:
1. No product shall contain more than 10 ppm of a contaminating substance from
a previous batch.
2. No patient shall be exposed to more than 1/1000 of the therapeutic dose (TDD
for the same dosage form) of another API.
3. If the TDD is not known for the same dosage form, then no patient shall be
exposed to more than 1/10000 of the NOEL for another API (with not known
TDD for the same dosage form).
Calculate the MACO value and swab limit for Substance C! In this case the same
swab limit shall apply to all surfaces.
Data table:
Area: 1500 dm2MBS
kg TDD
mg
Safety factor
(SF)
NOEL
mg
Dryer X Oral Par Inhal Oral Par Oral Par Inhal Substance A 200 10 375 1000 1000
Substance B 50 250 1000 10000 2500 Substance C 200 40 120 1000 1000
Substance D 120 40 40 1000 1000
Substance E 200 400 10000 1000 8000 Substance F 1000 400 10000 1000 11000
Substance G 50 15 35 1000 1000
Calculation of upper general limit (10 ppm):
The next batches may contain maximum 10 ppm of Substance C. The upper general limit for Substance C is calculated (from equation in 4.2.3, page 8) from the lowest MBS of the possible “substance of next batches”; in this case 50 kg valid for Substance B and G:
MACO ppm= 10 x 10-6(kg/kg) x 50 (kg) = 5 x 10-4 (kg) = 500 (mg)
This corresponds to a swab limit equal to a target value (from equation in 4.2.4, page 9): MACO 500 000 [μg ]
Target value [μg/dm 2] = --------------------- = -------------------- = 333 [μg/dm 2] Total surface 1500 [dm 2]
So the general upper MACO is 500 mg - corresponding to a swab limit of 333 [μg/dm 2]. This has to be compared to the limits calculated based on doses / NOELs.
Matrix calculations of swab limit according to requirement based on therapeutic dose/NOEL:
For each possible "next product", the MACO is calculated according to the equation in 4.2.1 – page 4 - (when TDD is known) or according to the equation in 4.2.2 – page 6 - (NOEL is used when TDD is not known). The corresponding concentration in ppm is calculated in accordance with the equation in 4.2.3 – page 7. Then a target value for swabs is calculated according to 4.2.4 – page 9.
The safety factor for Substance C is 1000 both for oral and parental use, and will be constant in all calculations. The TDD previous is 40 mg for all the "oral calculations" and 120 mg for all the "parental calculations". For the "next substance", batch size and TDD next /NOEL have to be collected from the data table for each substance in each dosage form. The results are inserted in the following table (two valid figures in the results). The worst cases for MACO and swab limits are indicated with bold. The total worst case comparing oral and parental calculations are indicated with bold on the last line of the table.
Substance MACO [mg] CONC [ppm] Target value for swabs
[μg/dm 2]
Oral Par Inhal * Oral Par Inhal Oral Par Inhal* Substance A 800 000 64 000 - 4000320
- 530 000 43 000 -
Substance B 8 000 2 400 - 16048- 5 300 1 600 - Substance D 120 000 360 000 - 10003000- 80 000 240 000 - Substance E 1 000 60 000 - 5300- 670 40 000 - Substance F 3 600 300 000 - 4300- 2400 200 000 - Substance G 130 000 170 000 - 27003400- 89 000 110 000 - Worst case
1000
2 400
- -
-
- 670
1 600 -
* The symbol ‘-’ indicates that these values are missing, because no product is administrated by inhalation.
The lowest swab limit occurs, according to dose calculations (670 μg/dm2), when Substance E is manufactured after the Substance C. This also results in the lowest MACO (1000 mg = 1 g). As evident from the table, the corresponding CONC is
5 ppm. This value is below the general limit because the MBS for Substance E (200
kg) is larger than the MBS for the worst case (50 kg).
A comparison, of MACO and swab limit, for values based on the general 10 ppm
limit and values based on TDD/NOEL calculations, is presented in the following table.
Value of 10 ppm limit TDD/NOEL based limit Most stringent case MACO 500 mg 1000 mg 500 mg Target value swabs 330 μg/dm2 670
μg/dm2
μg/dm2 330
As evident from the comparison, the most stringent requirements result from the calculations based on the 10 ppm limit.
Result: The swab limit for Substance C in Dryer X will be 330 μg/dm2 and the MACO will be 500 mg.
Note that in example 4, the limits for Substance C were calculated. To determine the limits for the other substances, a matrix must be set up for each substance. Then for each substance, MACO and target values are calculated. For each Substance a similar comparison against the limit calculated from MAXCONC should be done and the most stringent limits to be selected.
4.2.4.2 Evaluation of results
When all surfaces have been sampled and the samples have been analysed, then the results are compared to the acceptance criteria. Below the case when a MACO is set as an acceptance criteria is used. In this case the total amount shall be calculated, and this implies that some results can be above the target limit, if of course others are below.
Procedure
Establish the possible Carry Over (CO) from the swab results, using the following equation:
CO [μg] = Σ ( A i[dm2] x m i [μg/dm2] )
CO True (measured) total quantity of substance (possible carryover) on
the cleaned surface in contact with the product, calculated from
results of swab tests.
A i Area for the tested piece of equipment # i.
m i Quantity, in μg/dm2, for each swab per area of swabbed surface (normally 1 dm2)
Example 5:
A company has carried out a cleaning validation study according to an approved protocol. The results of the swabs are presented in the following table. The individual swab results have been calculated as well as the CO.
Swab # Swab position Swab result
non
compensated
(mg/dm2) Swab result
comp-ensated
for 95%
recovery
(mg/dm2)
Area of
part of
dryer
(dm2)
Amount on part
of dryer (g)
Swab 1 Inlet valve 0.30 0.32 2 0.0006
Swab 2 Outlet valve 0.40 0.42 2 0.0008
Swab 3 Dryer roof 0.20 0.21 249 0.052
Swab 4 Dryer bottom 0.20 0.21 250 0.053
Swab 5 Dryer centre
left
0.24* 0.25* 997 0.25* (calculated
Swab 5 Dryer centre
right
0.20 0.21 from worst case) - Total
area - - 1500 0.36 * When several swabs are taken on the same surface, the worst case result is used to
calculate the CO.
Now it is time to evaluate the results. Do that for case a) and b) below!
a) If the acceptance criterion is a swab limit of 0.33 mg/dm2: are the results
acceptable?
b) If the acceptance criterion is a MACO of 0.50 g: are the results acceptable?
Answer a): The results are not acceptable. The swab of the outlet valve is not approved. This must be treated as a deviation, and action must be taken.
The current cleaning procedure is not qualified for the outlet valve
(however, for the other areas).
Answer b): The results are acceptable since the total amount is lower than the MACO.
As evident from the different results in a) and b), companies may find it easier to evaluate against the MACO. However, it is advisable to have a policy for swab limit as well. Especially because analytical methods are validated within a certain range for swab results. Another reason is that some pieces could be very contaminated, and it is not good practice to clean certain pieces very thoroughly in order to let other be dirty. One example of policy, to set limits for both MACO and swabs, is to have the following acceptance criteria:
AC 3: The MACO must not be exceeded for the total equipment train (see 4.2.4.2, page 12).
AC 2: The most stringent of the following swab limits:
Swab limit based on therapeutic dose (see 4.2.1, page 4) or NOEL (see 4.2.2,
page 6).
Swab limit based on a general "ppm limit" (see 4.2.3, page 7)
AC 2.1 For all areas except for valves: the calculated swab limit.
AC 2.2 For valves: 10 times the calculated swab limit if AC 3 can still be
fulfilled.
As mentioned before, AC 2.2 implies that in order to have a higher swab limit on valves or other pieces of equipment, the swab results for other areas have to be lower than the target value, in order for the CO to be below the MACO.
4.2.5 Rinse Limits
The residue amount in the equipment can be assumed to be equal to the amount of residue in the last wash /boil) or rinse solvent portion. The assumption is based on the worst case consideration, that a further washing or rinsing run (or any reaction) would not wash more than the same amount of residue out of the equipment as the analysed solvent portion did.
The MACO is usually calculated on each individual product change over scenario according to the procedures outlined in chapter 4.2.1 – 4.2.3 (page 4 – 8) and individual acceptance criteria are established using the following equation:
MACO [mg]
Target value[mg/l] = ------------------------------
Volume of rinse or boil[l]
For quantitation a solvent sample (e.g. 1 l) is taken, the residue in the sample is determined by a suitable analytical method and the residue in the whole equipment is calculated according to the following equation:
M = V * (C - C B)
M Amount of residue in the cleaned equipment in mg.
V Volume of the last rinse or wash solvent portion in l.
C Concentration of impurities in the sample in mg/l.
C B Blank of the cleaning or rinsing solvent in mg/l. If several samples are taken
during one run, one and the same blank can be used for all samples provided
the same solvent lot was used for the whole run.
Requirement: M < Target value.
5.0 Levels of Cleaning
5.1 Introduction
The manufacturing process of an Active Pharmaceutical Ingredient (API) typically
consists of various chemical reaction and purification steps followed by physical changes. In general early steps undergo further processing and purification and so
potential carryover of the previous product would be removed.
The amount or as we will call it here, level of cleaning required in order to ensure
that the API is free from unacceptable levels of contamination by previous substances
varies depending on the step being cleaned and the next substance being manufactured in the same piece of equipment (train).
API`s and related intermediates are often produced in multi-purpose equipment
with frequent product changes which results in a high amount of cleaning. During
the course of this chapter the reader will be introduced to the concept of using different levels of cleaning, thereby giving the opportunity to minimize the amount of
cleaning and cleaning validation required without effecting the safety of the API.
5.2 Procedure
The CEFIC – APIC Guide to Cleaning Validation recommends three levels of cleaning that may be implemented. This approach is outlined in the table below, however it should be mentioned that additional levels might be necessary depending
on the nature of the process and requirements of individual companies.
Level Thoroughness of cleaning Cleaning
Validation
2 Carry over of the previous product is critical. Cleaning
required until predetermined stringent carry over limits are
met.
Essential.
1 Carry over of the previous product is less critical. Cleaning
should reduce the potential carry over to a less stringent limit as required for level 2. Increase from not required to necessary (lower acceptable carry over limits).
0 Only gross cleaning if carry over of the previous product is not
critical.
Not required.
A general approach how these levels could be established for typical product changeover situations in a multi-purpose API-plant is outlined in figure 1.
The levels established as shown in figure 1 are based on the approach that in general the thoroughness of cleaning will increase and the acceptable carry over of the previous product will decrease from early steps in the route of synthesis to the final API due the fact that early steps undergo further processing and/or purification and so the potential carry over will be reduced by further processing.
Principally two different product changeover scenarios exist which have a big impact on the cleaning level required:
1. Previous and following product do belong to the same synthetic chain (product
changeover within process …A“ or within process …B“
2. Previous and following product do not belong to the same synthetic chain (
…A-x-“ to …B-x“; x = 0; 1; 2; 3 including crude and final API …A“ and …B“)
If the product changeover is within the same synthetic chain (1.) there are two different situations possible:
Previous and following product is identical (in campaign cleaning).
In this instance level 0 may be applied with no cleaning validation required. However potential degradants, accumulation of side products and microbiological growth should be considered. If applicable idle time (maximum period of time until complete and thorough cleaning of the equipment has to be done) for cleaning should be established.
In some instances e.g. at the physical steps no equipment cleaning at all may be performed between batch to batch changeover (dryer, blender, micronizer). Complete cleaning is done after finishing the campaign or after an idle time if established. Cleaning between different steps of the same synthetic chain.
There are two different situations possible:
1. The following product is the next step in the synthetic chain.
There is a very low risk to effect the quality of the final API, because the previous product is the starting material of the following process and the analytical methods applied for the following product are usually suitable to detect the previous product which is covered and limited by the impurity profile. For this situation level 0 also applies.
2. The following product is not the next step of the synthetic chain.
In general there is a higher potential for contamination of the API if the following product in a sequence is close to the final API - step. So progression of levels from early steps to later steps in the synthetic chain is expected as outlined in figure 1.
In the example of product changeover …A – 2“ to …Final API A“ level 2 may be chosen if …A – 2“ is not specified in the specification of …API A“ or …A – 2“ is a toxic compound. If it is specified or harmless, level 1 may be acceptable.
If the product changeover is not within the same synthetic chain (2.) the level of cleaning required depends of the stage of manufacture. If the following product is an early stage in the API – chain, in general lower levels are required than if it is an intermediate or final stage.
The progression of levels is outlined in figure 1, however an individual risk assessment for each potential product changeover scenario has to be performed to decide which level is applicable. This risk assessment should address the following topics:
?Toxicological / pharmacological activity of the previous product, its side products or degradants
? Maximum daily dose of the following product
growth
? Microbiological
?Batch size of the following product
?Solubility, experience, difficult to remove previous product
Instead of the investigation of each individual cleaning situation similar situations could be grouped and classified using bracketing concepts (ref. section 6, page 20).
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螺纹通止规
螺纹通止规 定是:螺纹止规进入螺纹不能超过2.5圈,一般的要实际不得超过2圈,并且用得力度不能大,我们的经验是用拇指和食指轻轻夹持螺纹规以刚好能转动螺纹规的力度为准.力大了就相当于在使用丝锥或牙板了,那样规就用不了几次了. 螺纹通止规 螺纹通止规是适用于标准规定型号的灯头作为灯用附件电光源产品时候的设计和生产、检验的工具设备。 用途 一般用于检验螺纹灯头或灯座的尺寸是否符合标准要求，分别检验螺纹灯头的通规和止规尺寸或灯座的通规或止规尺寸。 工作原理 具体检验要求及介绍详见中国人民国国家标准：GB/T1483.1-2008或 IEC60061-3:2004标准规定容。 操作方法 具体检验要求及介绍详见中国人民国国家标准：GB/T1483.1-2008或 IEC60061-3:2004标准规定容。 通止规
通止规，是量规的一种。作为度量标准，用于大批量的检验产品。 通止规是量具的一种，在实际生产批量的产品若采取用计量量具（如游标卡尺，千分表等有刻度的量具）逐个测量很费事．我们知道合格的产品是有一个度量围的.在这个围的都合格，所以人们便采取通规和止规来测量． 通止规种类 （一）对统一英制螺纹，外螺纹有三种螺纹等级：1A、2A和3A级，螺纹有三种等级：1B、2B和3B级，全部都是间隙配合。等级数字越高，配合越紧。在英制螺纹中，偏差仅规定1A和2A级，3A级的偏差为零，而且1A和2A级的等级偏差是相等的等级数目越大公差越小，如图所示：1B 2B 3B 螺纹基本中径3A 外螺纹2A 1A 1、1A和1B级，非常松的公差等级，其适用于外螺纹的允差配合。 2、2A和2B级，是英制系列机械紧固件规定最通用的螺纹公差等级。 3、3A和3B级，旋合形成最紧的配合，适用于公差紧的紧固件，用于安全性的关键设计。 4、对外螺纹来说，1A和2A级有一个配合公差，3A级没有。1A级公差比2A级公差大50，比3A级大75，对螺纹来说，2B级公差比2A公差大30。1B级比2B级大50，比3B级大75。 （二）公制螺纹，外螺纹有三种螺纹等级：4h、6h和6g，螺纹有三种螺纹等级：5H、6 H、7H。（日标螺纹精度等级分为I、II、III三级，通常状况下为II级）在公制螺纹中，H 和h的基本偏差为零。G的基本偏差为正值，e、f和g的基本偏差为负值。如图所示：公差G H 螺纹偏差基本中径外螺纹f g h e 1、H是螺纹常用的公差带位置，一般不用作表面镀层，或用极薄的磷化层。G位置基本偏差用于特殊场合，如较厚的镀层，一般很少用。 2、g常用来镀6-9um的薄镀层，如产品图纸要6h的螺栓，其镀前螺纹采用6g的公差带。 3、螺纹配合最好组合成H/g、H/h或G/h，对于螺栓、螺母等精制紧固件螺纹，标准推荐采用6H/6g的配合。 （三）螺纹标记M10×1–5g 6g M10×1–6H 顶径公差代号中径和顶径公差代号（相同）中径公差代号。 通止规是两个量具分为通规和止规．举个例子：M6－7h的螺纹通止规一头为通规（T）如果能顺利旋进被测螺纹孔则为合格，反之不合格需返工（也就是孔小了）．然后用止规（Z）如果能顺利旋进被测螺纹孔2.5圈或以上则为不合格反之合格．且此时不合格的螺纹孔应报废，不能进行返工了．其中2.5圈为国家标准，若是出口件最多只能进1.5圈（国际标准）．总之通规过止规不过为合格，通规止规都不过或通规止规都过则为不合格。
英语造句
一般过去式 时间状语：yesterday just now (刚刚) the day before three days ag0 a week ago in 1880 last month last year 1. I was in the classroom yesterday. I was not in the classroom yesterday. Were you in the classroom yesterday. 2. They went to see the film the day before. Did they go to see the film the day before. They did go to see the film the day before. 3. The man beat his wife yesterday. The man didn’t beat his wife yesterday. 4. I was a high student three years ago. 5. She became a teacher in 2009. 6. They began to study english a week ago 7. My mother brought a book from Canada last year. 8.My parents build a house to me four years ago . 9.He was husband ago. She was a cooker last mouth. My father was in the Xinjiang half a year ago. 10.My grandfather was a famer six years ago. 11.He burned in 1991
螺纹通止规要求螺纹通规通
螺纹通止规要求螺纹通规通，止规止。 但是如果螺纹通规止，说明什么？ 螺纹止规通，又说明什么？ 我也来说两句查看全部回复 最新回复 ?wpc (2008-11-07 20:11:20) 在牙型正确的前提下螺纹通止规检测螺纹中径 ?lobont (2008-11-08 11:16:32) 对外螺纹而言，螺纹通规是做到中径上偏差，所以能通过就表示产品合格，通不过就表示螺纹做大了，要再修一刀； 螺纹止规做到中径下偏差，所以只能通过2～3牙，如果也通过，就表示外螺纹做小了，产品成为废品 ?qubin8512 (2008-11-18 15:36:05) 螺纹赛规与螺纹环规主要测量螺纹的中径。 ?datafield (2008-11-29 19:12:51) 检具不是万能的，只是方便而已。具体没什么的我有在哪本书上看过，是一本螺纹手册上的。 ?ZYC007 (2009-2-09 20:31:13) 在牙型正确的前提下螺纹通止规检测螺纹中径。 对外螺纹而言，但是如果螺纹通规止，说明螺纹中径大；螺纹止规通，又说明螺纹中径小。 ?WWCCJJ (2009-3-19 09:27:19) 检测的是螺纹的中径,螺纹检测规在检定时,也是检测其中径. ?tanjiren (2009-3-20 22:23:06) 螺纹通止规只能检测螺纹的作用中径,大径和底径等均无法准确测量出来. ?月夜(2009-4-01 21:47:13) 用来测量中径 ?丽萍(2009-4-02 10:11:41)
只能检测工件螺纹的中径 yg196733456 (2009-4-03 09:15:56)原来是测中径的知道了
NPT螺纹以及检测方法详解
N P T螺纹以及检测方法详 解 Prepared on 22 November 2020
一、目的：规范公司技术员，检验员，操作员对NPT螺纹的了解。 二、适用范围：适用于公司任何NPT螺纹类产品，参考资料为通用管螺 纹和国家标准GB/T12716-2011。 三、目录 1、NPT和NPTF介绍 2、螺纹技术参数参数讲解 3、NPT与NPTF加工工艺 4、NPT和NPTF的检测方法 四、内容： NPT和NPTF螺纹介绍 NPT 是 National (American) Pipe Thread 的缩写，属於美国标准的 60 度锥管 密封螺纹，用於北美地区，美国标准为13)通用管螺纹．国家标准可查阅 GB/T12716-2011。NPTF：美制干密封圆锥管螺。NPTF = National Pipe Thread Fine 称之为一般用途的锥管螺纹，这也是我们以前称之为的布氏锥螺纹。NPTF 螺纹称之为干密封式锥管螺纹，它连接密封的原理是在没有润滑剂或密封填 料情况下完全依靠螺纹自身形成密封，设计意图是使内、外螺纹牙的侧面、 牙顶和牙底同时接触，来达到密封的目的。它们两者的牙型角、斜度等指标 都是相同的，关键是牙顶和牙底的削平高度不一样，所以，量规的设计也是 不一样的。NPTF干密封管螺纹的牙形精度比NPT螺纹高，旋合时不用任何 填料，完全依靠螺纹自身形成密封，螺纹间无任何密封介质。干密封管螺纹 规定有较为严格的公差，属精密型螺纹，仅用在特殊场合。这种螺纹有较高 的强度和良好的密封性，在具有薄截面的脆硬材料上采用此螺纹可以减少断 裂现象。NPTF内、外螺纹牙顶与牙底间没有间隙，是过盈配合，而NPT螺 纹是过渡配合。NPTF螺纹主要用于高温高压对密封要求严格的场所。NPT
学生造句--Unit 1
●I wonder if it’s because I have been at school for so long that I’ve grown so crazy about going home. ●It is because she wasn’t well that she fell far behind her classmates this semester. ●I can well remember that there was a time when I took it for granted that friends should do everything for me. ●In order to make a difference to society, they spent almost all of their spare time in raising money for the charity. ●It’s no pleasure eating at school any longer because the food is not so tasty as that at home. ●He happened to be hit by a new idea when he was walking along the riverbank. ●I wonder if I can cope with stressful situations in life independently. ●It is because I take things for granted that I make so many mistakes. ●The treasure is so rare that a growing number of people are looking for it. ●He picks on the weak mn in order that we may pay attention to him. ●It’s no pleasure being disturbed whena I settle down to my work. ●I can well remember that when I was a child, I always made mistakes on purpose for fun. ●It’s no pleasure accompany her hanging out on the street on such a rainy day. ●I can well remember that there was a time when I threw my whole self into study in order to live up to my parents’ expectation and enter my dream university. ●I can well remember that she stuck with me all the time and helped me regain my confidence during my tough time five years ago. ●It is because he makes it a priority to study that he always gets good grades. ●I wonder if we should abandon this idea because there is no point in doing so. ●I wonder if it was because I ate ice-cream that I had an upset student this morning. ●It is because she refused to die that she became incredibly successful. ●She is so considerate that many of us turn to her for comfort. ●I can well remember that once I underestimated the power of words and hurt my friend. ●He works extremely hard in order to live up to his expectations. ●I happened to see a butterfly settle on the beautiful flower. ●It’s no pleasure making fun of others. ●It was the first time in the new semester that I had burned the midnight oil to study. ●It’s no pleasure taking everything into account when you long to have the relaxing life. ●I wonder if it was because he abandoned himself to despair that he was killed in a car accident when he was driving. ●Jack is always picking on younger children in order to show off his power. ●It is because he always burns the midnight oil that he oversleeps sometimes. ●I happened to find some pictures to do with my grandfather when I was going through the drawer. ●It was because I didn’t dare look at the failure face to face that I failed again. ●I tell my friend that failure is not scary in order that she can rebound from failure. ●I throw my whole self to study in order to pass the final exam. ●It was the first time that I had made a speech in public and enjoyed the thunder of applause. ●Alice happened to be on the street when a UFO landed right in front of her. ●It was the first time that I had kept myself open and talked sincerely with my parents. ●It was a beautiful sunny day. The weather was so comfortable that I settled myself into the
通止规的用法及管理
通止规的用法及管理 1、止规 使用前：应经相关检验计量机构检验计量合格后，方可投入生产现场使用。 使用时：应注意被测螺纹公差等级及偏差代号与环规标识公差等级、偏差代号相同（如M24*1.5-6h与M24*1.5-5g两种环规外形相同，其螺纹公差带不相同，错用后将产生批量不合格品)。 检验测量过程：首先要清理干净被测螺纹油污及杂质，然后在环规与被测螺纹对正后，用大母指与食指转动环规，旋入螺纹长度在2个螺距之内为合格，否则判为不合格品。 2、通规 使用前：应经相关检验计量机构检验计量合格后，方可投入生产现场使用。 使用时：应注意被测螺纹公差等级及偏差代号与环规标识的公差等级、偏差代号相同（如M24*1.5-6h与M24*1.5-5g两种环规外形相同，其螺纹公差带不相同，错用后将产生批量不合格品)。 检验测量过程：首先要清理干净被测螺纹塞规油污及杂质，然后在环规与被测螺纹对正后，用大母指与食指转动环规，使其在自由状态下旋合通过螺纹全部长度判定合格，否则以不通判定。 3、注意事项 在用量具应在每个工作日用校对塞规计量一次。经校对塞规计量超差或者达到计量器具周检期限的环规，由计量管理人员收回、标识隔离并作相应的处理措施。 可调节螺纹环规经调整后，测量部位会产生失圆，此现象由计量修复人员经螺纹磨削加工后再次计量鉴定，各尺寸合格后方可投入使用。 报废环规应标识隔离并及时处理，不得流入生产现场。 4、维护与保养 量具（环规）使用完毕后，应及时清理干净测量部位附着物，存放在规定的量具盒内。生产现场在用量具应摆放在工艺定置位置，轻拿轻放，以防止磕碰而损坏测量表面。 严禁将量具作为切削工具强制旋入螺纹，避免造成早期磨损。可调节螺纹环规严禁非计量工作人员随意调整，确保量具的准确性。环规长时间不用，应交计量管理部门妥善保管。
英语句子结构和造句
高中英语~词性~句子成分~语法构成 第一章节：英语句子中的词性 1.名词：n. 名词是指事物的名称，在句子中主要作主语.宾语.表语.同位语。 2.形容词;adj. 形容词是指对名词进行修饰~限定~描述~的成份，主要作定语.表语.。形容词在汉语中是（的）.其标志是: ous. Al .ful .ive。. 3.动词：vt. 动词是指主语发出的一个动作，一般用来作谓语。 4.副词：adv. 副词是指表示动作发生的地点. 时间. 条件. 方式. 原因. 目的. 结果.伴随让步. 一般用来修饰动词. 形容词。副词在汉语中是（地）.其标志是：ly。 5.代词：pron. 代词是指用来代替名词的词，名词所能担任的作用，代词也同样.代词主要用来作主语. 宾语. 表语. 同位语。 6.介词：prep.介词是指表示动词和名次关系的词，例如：in on at of about with for to。其特征：
介词后的动词要用—ing形式。介词加代词时，代词要用宾格。例如：give up her（him）这种形式是正确的，而give up she（he）这种形式是错误的。 7.冠词：冠词是指修饰名词，表名词泛指或特指。冠词有a an the 。 8.叹词：叹词表示一种语气。例如：OH. Ya 等 9.连词：连词是指连接两个并列的成分，这两个并列的成分可以是两个词也可以是两个句子。例如：and but or so 。 10.数词：数词是指表示数量关系词，一般分为基数词和序数词 第二章节：英语句子成分 主语：动作的发出者，一般放在动词前或句首。由名词. 代词. 数词. 不定时. 动名词. 或从句充当。 谓语：指主语发出来的动作，只能由动词充当，一般紧跟在主语后面。 宾语：指动作的承受着，一般由代词. 名词. 数词. 不定时. 动名词. 或从句充当. 介词后面的成分也叫介词宾语。 定语：只对名词起限定修饰的成分，一般由形容
六级单词解析造句记忆MNO
M A: Has the case been closed yet? B: No, the magistrate still needs to decide the outcome. magistrate n.地方行政官，地方法官，治安官 A: I am unable to read the small print in the book. B: It seems you need to magnify it. magnify vt.１．放大，扩大；２．夸大，夸张 A: That was a terrible storm. B: Indeed, but it is too early to determine the magnitude of the damage. magnitude n.１．重要性，重大；２．巨大，广大 A: A young fair maiden like you shouldn’t be single. B: That is because I am a young fair independent maiden. maiden n.少女，年轻姑娘，未婚女子 a.首次的，初次的 A: You look majestic sitting on that high chair. B: Yes, I am pretending to be the king! majestic a.雄伟的，壮丽的，庄严的，高贵的 A: Please cook me dinner now. B: Yes, your majesty, I’m at your service. majesty n.１．［Ｍ－］陛下（对帝王，王后的尊称）；２．雄伟，壮丽，庄严 A: Doctor, I traveled to Africa and I think I caught malaria. B: Did you take any medicine as a precaution? malaria n.疟疾 A: I hate you! B: Why are you so full of malice? malice n.恶意，怨恨 A: I’m afraid that the test results have come back and your lump is malignant. B: That means it’s serious, doesn’t it, doctor? malignant a.１．恶性的，致命的；２．恶意的，恶毒的 A: I’m going shopping in the mall this afternoon, want to join me? B: No, thanks, I have plans already. mall n.（由许多商店组成的）购物中心 A: That child looks very unhealthy. B: Yes, he does not have enough to eat. He is suffering from malnutrition.
通止规的用法及管理
通止规的用法及管理 令狐采学 1、止规 使用前：应经相关检验计量机构检验计量合格后，方可投入生产现场使用。 使用时：应注意被测螺纹公差等级及偏差代号与环规标识公差等级、偏差代号相同（如M24*1.56h与M24*1.55g两种环规外形相同，其螺纹公差带不相同，错用后将产生批量不合格品)。 检验测量过程：首先要清理干净被测螺纹油污及杂质，然后在环规与被测螺纹对正后，用大母指与食指转动环规，旋入螺纹长度在2个螺距之内为合格，否则判为不合格品。 2、通规 使用前：应经相关检验计量机构检验计量合格后，方可投入生
产现场使用。 使用时：应注意被测螺纹公差等级及偏差代号与环规标识的公差等级、偏差代号相同（如M24*1.56h与M24*1.55g两种环规外形相同，其螺纹公差带不相同，错用后将产生批量不合格品)。 检验测量过程：首先要清理干净被测螺纹塞规油污及杂质，然后在环规与被测螺纹对正后，用大母指与食指转动环规，使其在自由状态下旋合通过螺纹全部长度判定合格，否则以不通判定。 3、注意事项 在用量具应在每个工作日用校对塞规计量一次。经校对塞规计量超差或者达到计量器具周检期限的环规，由计量管理人员收回、标识隔离并作相应的处理措施。 可调节螺纹环规经调整后，测量部位会产生失圆，此现象由计量修复人员经螺纹磨削加工后再次计量鉴定，各尺寸合格后方
可投入使用。 报废环规应标识隔离并及时处理，不得流入生产现场。 4、维护与保养 量具（环规）使用完毕后，应及时清理干净测量部位附着物，存放在规定的量具盒内。生产现场在用量具应摆放在工艺定置位置，轻拿轻放，以防止磕碰而损坏测量表面。 严禁将量具作为切削工具强制旋入螺纹，避免造成早期磨损。可调节螺纹环规严禁非计量工作人员随意调整，确保量具的准确性。环规长时间不用，应交计量管理部门妥善保管。
base on的例句
意见应以事实为根据. 3 来自辞典例句 192. The bombers swooped ( down ) onthe air base. 轰炸机 突袭 空军基地. 来自辞典例句 193. He mounted their engines on a rubber base. 他把他们的发动机装在一个橡胶垫座上. 14 来自辞典例句 194. The column stands on a narrow base. 柱子竖立在狭窄的地基上. 14 来自辞典例句 195. When one stretched it, it looked like grey flakes on the carvas base. 你要是把它摊直, 看上去就象好一些灰色的粉片落在帆布底子上. 18 来自辞典例句 196. Economic growth and human well - being depend on the natural resource base that supports all living systems. 经济增长和人类的福利依赖于支持所有生命系统的自然资源. 12 1 来自辞典例句 197. The base was just a smudge onthe untouched hundred - mile coast of Manila Bay. 那基地只是马尼拉湾一百英里长安然无恙的海岸线上一个硝烟滚滚的污点. 6 来自辞典例句 198. You can't base an operation on the presumption that miracles are going to happen. 你不能把行动计划建筑在可能出现奇迹的假想基础上.
英语造句大全
英语造句大全English sentence 在句子中，更好的记忆单词！ 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character. （2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n.
(完整版)主谓造句
主语+谓语 1. 理解主谓结构 1) The students arrived. The students arrived at the park. 2) They are listening. They are listening to the music. 3) The disaster happened. 2．体会状语的位置 1) Tom always works hard. 2) Sometimes I go to the park at weekends.. 3) The girl cries very often. 4) We seldom come here. The disaster happened to the poor family. 3. 多个状语的排列次序 1) He works. 2) He works hard. 3) He always works hard. 4) He always works hard in the company. 5) He always works hard in the company recently. 6) He always works hard in the company recently because he wants to get promoted. 4. 写作常用不及物动词 1. ache My head aches. I’m aching all over. 2. agree agree with sb. about sth. agree to do sth. 3. apologize to sb. for sth. 4. appear (at the meeting, on the screen) 5. arrive at / in 6. belong to 7. chat with sb. about sth. 8. come (to …) 9. cry 10. dance 11. depend on /upon 12. die 13. fall 14. go to … 15. graduate from 16. … happen 17. laugh 18. listen to... 19. live 20. rise 21. sit 22. smile 23. swim 24. stay (at home / in a hotel) 25. work 26. wait for 汉译英： 1.昨天我去了电影院。 2.我能用英语跟外国人自由交谈。 3.晚上7点我们到达了机场。 4.暑假就要到了。 5.现在很多老人独自居住。 6.老师同意了。 7.刚才发生了一场车祸。 8.课上我们应该认真听讲。9. 我们的态度很重要。 10. 能否成功取决于你的态度。 11. 能取得多大进步取决于你付出多少努力。 12. 这个木桶能盛多少水取决于最短的一块板子的长度。
通止规的用法及管理修订稿
通止规的用法及管理 WEIHUA system office room 【WEIHUA 16H-WEIHUA WEIHUA8Q8-
通止规的用法及管理 1、止规 使用前：应经相关检验计量机构检验计量合格后，方可投入生产现场使用。 使用时：应注意被测螺纹公差等级及偏差代号与环规标识公差等级、偏差代号相同（如M24*与M24*两种环规外形相同，其螺纹公差带不相同，错用后将产生批量不合格品)。 检验测量过程：首先要清理干净被测螺纹油污及杂质，然后在环规与被测螺纹对正后，用大母指与食指转动环规，旋入螺纹长度在2个螺距之内为合格，否则判为不合格品。 2、通规 使用前：应经相关检验计量机构检验计量合格后，方可投入生产现场使用。 使用时：应注意被测螺纹公差等级及偏差代号与环规标识的公差等级、偏差代号相同（如M24*与M24*两种环规外形相同，其螺纹公差带不相同，错用后将产生批量不合格品)。 检验测量过程：首先要清理干净被测螺纹塞规油污及杂质，然后在环规与被测螺纹对正后，用大母指与食指转动环规，使其在自由状态下旋合通过螺纹全部长度判定合格，否则以不通判定。 3、注意事项
在用量具应在每个工作日用校对塞规计量一次。经校对塞规计量超差或者达到计量器具周检期限的环规，由计量管理人员收回、标识隔离并作相应的处理措施。 可调节螺纹环规经调整后，测量部位会产生失圆，此现象由计量修复人员经螺纹磨削加工后再次计量鉴定，各尺寸合格后方可投入使用。 报废环规应标识隔离并及时处理，不得流入生产现场。 4、维护与保养 量具（环规）使用完毕后，应及时清理干净测量部位附着物，存放在规定的量具盒内。生产现场在用量具应摆放在工艺定置位置，轻拿轻放，以防止磕碰而损坏测量表面。 严禁将量具作为切削工具强制旋入螺纹，避免造成早期磨损。可调节螺纹环规严禁非计量工作人员随意调整，确保量具的准确性。环规长时间不用，应交计量管理部门妥善保管。
初中英语造句
【it's time to和it's time for】 ——————这其实是一个句型,只不过后面要跟不同的东西. ——————It's time to跟的是不定式（to do）.也就是说,要跟一个动词,意思是“到做某事的时候了”.如： It's time to go home. It's time to tell him the truth. ——————It's time for 跟的是名词.也就是说,不能跟动词.如： It's time for lunch.(没必要说It's time to have lunch) It's time for class.(没必要说It's time to begin the class.) They can't wait to see you Please ask liming to study tonight. Please ask liming not to play computer games tonight. Don’t make/let me to smoke I can hear/see you dance at the stage You had better go to bed early. You had better not watch tv It’s better to go to bed early It’s best to run in the morning I am enjoy running with music. With 表伴随听音乐 I already finish studying You should keep working. You should keep on studying English Keep calm and carry on 保持冷静继续前行二战开始前英国皇家政府制造的海报名字 I have to go on studying I feel like I am flying I have to stop playing computer games and stop to go home now I forget/remember to finish my homework. I forget/remember cleaning the classroom We keep/percent/stop him from eating more chips I prefer orange to apple I prefer to walk rather than run I used to sing when I was young What’s wrong with you There have nothing to do with you I am so busy studying You are too young to na?ve I am so tired that I have to go to bed early
螺纹规使用方法
螺纹规使用方法 一、目的 规范塞规、环规使用的操作方法，保证测量结果的准确性。螺纹塞规使用者应根据操作规范要求，确保操作过程正确，并负责仪器的维护和保养。 二、说明 螺纹规又称螺纹通止规、螺纹量规，通常用来检验判定螺纹的尺寸是否合格。 螺纹规根据所检验内外螺纹分为螺纹塞规和螺纹环规，目前我们所使用的只有螺纹塞规。 图1 三、使用方法 1、选择螺纹规时，应选择与被测螺纹相匹配的规格。 2、使用前，先清理干净螺纹规和被测螺纹表面的油污、杂质等。 3、使用时，使螺纹规的通端（止端）与被测螺纹对正后，用大拇指与食指转动螺纹规或被 测零件，使其在自由状态下旋转。通常情况下（无被测零件的螺纹的图示说明时），螺纹 规（通端）的通规可以在被测螺纹的任意位置转动,通过全部螺纹长度则判定为合格，否 则为不合格品;在螺纹规（止端）的止规与被测螺纹对正后，旋入螺纹长度在2个螺距之 内止住为合格，不可强行用力通过，否则判为不合格品。（有被测零件的图示说明时，应 按照图示说明做判定。） 图2 图3 图中英文字母“GO”或“T”:表 示螺纹塞规的通端。 图中“G 3/8-19”或“M3 6H” 表示该螺纹规规格. 图中英文字母“NO GO”或“Z”: 表示螺纹塞规的止端。 螺纹塞规
4、检验工件时旋转螺纹规不能用力拧，用三只手指自然顺畅地旋转，止住即可，螺纹规退 出工件最后一圈时也要自然退出，不能用力拔出螺纹规,否则会影响产品检验结果的误差,螺纹规的损坏。 图4 图5 如上图4操作方法是正确的，图5是错误的，无需手握。 5、使用完毕后，及时清理干净螺纹规的通端（止端）的表面附着物，并存放在工具柜的量 具盒内。 四、注意事项 1、被测件螺纹公差等级及偏差代号必须与塞规标识公差等级、偏差代号相同，才可使用。 2、只有当通规和止规联合使用，并分别检验合格，才表示被测螺纹合格。 3、应避免与坚硬物品相互碰撞，轻拿轻放，以防止磕碰而损坏测量表面。 4、严禁将螺纹规作为切削工具强制旋入螺纹，避免造成早期磨损。 5、螺纹规使用完毕后，应及时清理干净测量部位附着物，存放在规定的量具盒内。 五、维护和保养 1、每月定期涂抹防锈油，以保证表面无锈蚀、无杂质（我们的螺纹规使用频繁且所 处环境干净无需上油保护）。 2、所有的螺纹规必须经计量校验机构校验合格后并在校验有效期内，方可使用。 3、损坏或报废的螺纹规应及时反馈处理，不得继续使用。 4、经校对的螺纹规计量超差或者达到计量器具周检期的螺纹规，由计量管理人员收回 并做相应的处理。
The Kite Runner-美句摘抄及造句
《The Kite Runner》追风筝的人--------------------------------美句摘抄 1.I can still see Hassan up on that tree, sunlight flickering through the leaves on his almost perfectly round face, a face like a Chinese doll chiseled from hardwood: his flat, broad nose and slanting, narrow eyes like bamboo leaves, eyes that looked, depending on the light, gold, green even sapphire 翻译：我依然能记得哈桑坐在树上的样子，阳光穿过叶子，照着他那浑圆的脸庞。他的脸很像木头刻成的中国娃娃，鼻子大而扁平，双眼眯斜如同竹叶，在不同光线下会显现出金色、绿色，甚至是宝石蓝。 E.g.: A shadow of disquiet flickering over his face. 2.Never told that the mirror, like shooting walnuts at the neighbor's dog, was always my idea. 翻译：从来不提镜子、用胡桃射狗其实都是我的鬼主意。E.g.:His secret died with him, for he never told anyone. 3.We would sit across from each other on a pair of high