How to Measure the Depth of a Female Thread?

That's how far the gauge is screwed in.

or poke a bit of wire into the hole pull it out and measure the the bit that went in.

http://www.tresnainstrument.com/depth_gauges.html

http://www.mini-lathe.com/mini_lathe/operation/drilling/drilling.htm

cant belive you have tell people this,

http://www.wonderhowto.com/how-to-post-hole-digger-as-measuring-stick-318271/view/

http://www.wonderhowto.com/how-to-post-hole-digger-as-measuring-stick-318271/view/

I would define you as an optimist!

Hello peter.

Well, these techniques and tools will tell us how deep the drilled hole is.

"Now I have a question:How to measure the depth of a female thread?" is the question. A drilled hole measured 20cm deep may only be tapped to 12cm. Thus, 12cm is as far as a screw can be turned in. I think this is what OP is after.

Or, am I misreading the question?

If that is the right question, the OP steps 1 thru 4 are correct.

ah i see what you mean the depth of the thread cut into the walls of the hole.

well done

http://www.colinusher.info/Livesteam/mewdata.html

http://en.wikipedia.org/wiki/Screw_thread

Thanks to all.

Now we have no other tools,if the (A-B) is not correct,we have to count the threads N.

and N*pitch=depth,right?

If both the worker and QC use the same tooling and procedures to measure the thread depth I see no problem. Your reading should always match if the gauges are alike.

Your method is as good as any simple tooling method. And if you try to count threads, you'll have to be sure to find the deepest part of the thread lead every time.

Use the depth gauges and measure the difference.

Yes,in the factory both the workers and QC check the depth in the same way.

The factory once manufactoried a kind of parts ,in the drawing there is a dimention 1.85" min for a female thread.

Again,both the works & QC measured the depth in the same way,and of course they considered the depth was OK.

But the customer complained about the depth when they received the parts.

That's the customer measured the depth in a different way which was more reasonable,they just count the threads.

In this case customer should not have complained .

The number of threads count will give you more depth than actual.

When the threading is done in a blind hole,

First (starting from down side) You have a paritial unthreaded portion in the end after the cone of the drill (kept as a safety margin for tapping chips to rest, just in case)

Then you have partially formed threads (normally inevitable, unless you use special techniques/ taps)

Finally the fully formed threads.

While counting you are likely to count atleast a few of partial threads.

BTW: we specify in our drawing :

tapping depth (x mm minimum) drilling depth (y mm maximum): when the drilling over-depth matters.

Else there are standard guidelines in our procedure to calculate drilling extra depth for the tap sizes.

Use a same size threaded bolt/Gage BUT MAKE SURE YOU HAVE TO GRIND A TIP OF BOLT/GAGE FLAT WHERE THREADS START TO WRAP then use a digital caliper to measure the whole length and set a reading to zero. Now turn bolt/gage into threaded hole until it stops. Measure the length sticking out of the bolt/gage.

Both of your machinist/QC guys did right but not accurate as you mentioned. They need to grind the top of bolt/gage otherwise the result is ADDED that much length which tells the depth is deep but in fact it's not. The tip of the bolt/bage is not counted because it does not stop at end of thread. It goes further....

Common_Sense's way is the way most of us use.