The correct way to check thread depth???

[Rob B]

We are having a discusion about how to check the depth of thread of a tapped hole. We are using a thread plug gage to determine depth. We are wondering should the print spec for depth be from the centerline of the thread crest or the thread root of the last perfect thread.

The way that we measured the thread was from centerline of the thread crest of the last full thread to the end of gage. Then we then screwed thread gage into part and re-measured from the end of the gage to the top of the part.

 

Our custmor is measuring the total length of the thread gage, then screwing it into the part and measuring the overall length of the gage from the top of the part.

 

Does anyone have anything in writing to tell what the correct way to measure thread depth.

[EZ3PUTT]

We always measure thread depth as perfect threads. If our print calls out an M10 x 1.5 thread by say 12mm deep we must have 12mm of perfect thread. Using a thread gage we would need to see 8 turns of the gage to insure 12mm depth.

[crazy^millman]

Not in writing but some people count the revolutions. If it is a 32 thread then evey revolution is .0312 deep so if you turn it 14.5 turns the depth of thread is .453 deep so if they called out .45 you are .003 deeper than what they called for on the print. Most have a +.00/-.03 on thread depths for this very reason.

 

HTH

[Psychomill]

Count revolutions here...

[Mike Whitten CAD/CAM Contractors]

Does your customer have this documented in their fab specs? Are there fab specs referenced on the drawing that you could obtain.

 

If not, I think that the right way to check the parts is how they check them.

 

I dont like to count turns. It seems to work against you.

 

 

Mike

[Guest]

revolutions here too.

[TheePres]

I say..if print calls for revolutions / count revolutions. If calls for depth / measure depth.

[kinglouie V]

I do it the same way with the gage.

[M. Anderson]

quote:

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I say..if print calls for revolutions / count revolutions. If calls for depth / measure depth

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+1

 

Have done both ways - but for a depth call out - screw in gage and mic to face. IMHO

[Rob B]

Counting the revolutions is new to me, but I like it. The print calls for thread depth. Saya nothing about rev. I think the rev gives a closer measurment to the true total thread depth.

 

Thanks for the input!!

[biss03]

we use a product from leitech for checking depths. most of our customers were supplying these to us so we just started using them as standard. here is the link (if i can do this right).

 

leitech combi gage

[crazy^millman]

I think this is where you were trying to go.

[biss03]

yeah. some how i got the http:// in there twice.

 

thanks Ron.

[specv]

COUNT REVOLUTIONS HERE TOO, IM NOT YELLING IM JUST TOO LAZY TODAY

[Dave_noob_user]

Make the thread deeper.

 

When a print calls for a thread eg 1/2-13 .5 deep. If I have alot of material under the hole Ill drill and tap deeper just to be on the safe side. I honestly can`t see what they would want a picky depth on a threaded hole for.

[Dave_noob_user]

COUNT REVOLUTIONS HERE TOO, IM NOT YELLING IM JUST TOO LAZY TODAY

 

 

lol. Too lazy to hit capslock but not too lazy to type "IM NOT YELLING IM JUST TOO LAZY TODAY"

[Psychomill]

quote:

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I say..if print calls for revolutions / count revolutions. If calls for depth / measure depth.

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The issue is by what method.... I rarely see (if I've ever seen one... I can't remember this morning) a print say "1/4-20 x 12 turns".

 

However, I think biss has the right idea. The gage will measure functional depth. Which is essentially counting turns. Although that can be effected by the chamfer size and make the physical depth slightly deeper or shallow. I like the gage. Will have to check it out.

 

quote:

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I honestly can`t see what they would want a picky depth on a threaded hole for.

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Some industries, in particular aerospace or satellite communications stuff, gets real finicky about this. Especially on parts that gets launched into space. Weight becomes a critical issue. Countersinks and chamfers size are held to .001 or less for Christ's sake.

[Guest]

quote:

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Some industries, in particular aerospace or satellite communications stuff, gets real finicky about this. Especially on parts that gets launched into space. Weight becomes a critical issue. Countersinks and chamfers size are held to .001 or less for Christ's sake.

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Yup.

 

Or they give you a hole that cannot break thru the .130 depth and they want .110 of full thread on an #0-80.

 

Engineers

[GVM]

That link to Leitech Thread gages caught my eye. Found them in the MSC catalog, WoW those things aren't cheap, 320.00 to 446.00 each depending on size. Pretty neat though.

[TheePres]

Sorry,

Just a pet peeve of mine, watching inspectors count threads.

[biss03]

yeah, they aren't cheap but well worth it when you show the customer (not aerospace or anything like that) that you are measuring the depth with a fancy instrument that measures "effective" thread use. we haven't had one argue yet with it vs the old methods of counting threads or using gages with notches. saved us from traveling to sort a couple of times.

[TFesta]

If you count the revolutions you need to add 1 revolution to the number that you get cause of the chamfer on the part and the thread gage. So count 10 turns + 1 = 11 and on a 1/2-13 it would be .846 depth of threads.