Method for Calibration of Thread Plug Gauges

[bakhtiar - 2009]

Is there any way that I can find the method to calibrate my thread plug gauge.

I intend to do it internally (in-house) but I don't have the outer diameter spec and the pitch spec for M2x0.4, M3x0.5 and M5x0.8 type

I wish to have a table of minimum and maximum spec forboth outer diameter and pitch diameter including the wire gauge diameter.

[Govind]

You may want to check Machinery handbook. I believe this book will have the required dimensions and tolerances. There is also a BS standard. You may find the standards reference in the book.

Here is a web page with various pitch diameter table.
Thread Pitch Diameter Table

If you purchase metric “3 wire set”, you can measure pitch diameter in house using your regular micrometer. (Low cost)

There are more sophisticated measuring equipments like horizontal/ Universal metroscope that can perform more precise measurements,floating carriage micrometers with fiducial indicators.
Regards,
Govind.

[bakhtiar - 2009]

Thanks Govind,

But still I have an enquiry.

Normal gauge will wear-and-tear and become worn out after long time usage. They would be a plus or minus on the specification. Please advice

[Govind]

In Reply to Parent Post by bakhtiar

Thanks Govind,

But still I have an enquiry.

Normal gauge will wear-and-tear and become worn out after long time usage. They would be a plus or minus on the specification. Please advice

Yes, if you refer the machinery handbook, BS standards you will notice both manufacturing & Wear allowances for “Go” end and manufacturing allowance for “No Go end”.
Regards,
Govind.

[Govind]

It has been over 20 years since I last did these calculations. I was not able to respond with specific details yesterday night.

Here is a webpage from one of the Indian manufacturer that I have used in the past. This page has lots of standards references.

Thread Standards

Basic Dimension refers to standards pertaining to thread dimensions
Gauging Practice refers to standards pertaining to gauge dimensions (manufacturing, wear allowances)

Hope this helps.

Regards,
Govind.

[Jeff Frost]

In Reply to Parent Post by bakhtiar

Is there any way that I can find the method to calibrate my thread plug gauge.

I intend to do it internally (in-house) but I don't have the outer diameter spec and the pitch spec for M2x0.4, M3x0.5 and M5x0.8 type

I wish to have a table of minimum and maximum spec forboth outer diameter and pitch diameter including the wire gauge diameter.

You first need to identify which standard gages have been procured to. British Standards for Gages differ from ANSI/ASME B1 Gage Standards used here in the United States. Also how much is your company willing to invest in inspection equipment and environmental controls to do this calibration?

You’re looking at a Super Mic, Master Gage Block of Grade 0.5 or 1 and a room with a controlled temperature of 68 Degrees F (20 C) for starters.

[bakhtiar - 2009]

Thanks for you all, Govind and Jeff.

The details is sufficient enough.

Since I'm working with the Japanese company, they are using the JIS standard and I have a lot of trouble to refer on the standard since it has been written in Japanese.

Thanks to you all

[Wayne]

As usual I am late to the conversation, and this is an old conversation, but the question is still valid and the answers good.

I would like to add that the 3-wire method is THE way to calibrate thread plug gages. Thread wires are available in inexpensive 'sets' which do not use the "best wire" sizes. If you wish most accurate measurement the best wire size should be used to take the measurement. With the best wire size the wire is sized to touch the screw flanks at the pitch diameter cylinder. Here is a link to a list of best wire sizes and their constants. The inexpensive wires will more likely touch the flank angles at some point above or below the pitch diameter cylinder and in doing that will give a faulty measurement if the flank angles are out-of-tolerance or worn. By using the best wire size you will be using the same tool that a gage maker or calibration laboratory would use, and in doing so your measurement will more likely match the value that they would get if they measured the gage.

The gage standards give an amount of pressure to be used when measuring thread plug gages with thread wires. For a shop application with a micrometer it is unlikely that the pressure will be able to be controlled, so again there may be some discrepancy in the measurement between two people, but unless it is near the size limit of the thread gage the variation should be insignificant.

There are many styles of threads and each has their own standard. You may spend a small fortune in purchasing the official standards so that you can have the correct numbers to calibrate the gages. Once you own the standards you will spend another small fortune in reading them and doing the math required to determine the sizes and tolerances for each feature. I suggest thread engineering software to do this for you. The price of the software will be less than the price of the standards and on top of that much time will be saved by not doing the calculations. Here is a link for a Free 30-Day Trial of ThreadTech software. There are other brands of software which will work as well as ThreadTech. It is just the only one for which I have a link for a free trial.

I hope that you find this information interesting well at least helpful.