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How to Measure Tapping Depth

03/25/2009 1:29 AM

Hi.....

I need an instrument to check the Tapping depth measurement.Is there any manufacturer in INDIA Who is making such type of Instruments or Gauges?

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Guru
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#1

Re: tapping Depth Measurement

03/25/2009 4:45 AM

How about grinding a bolts lead thread off, zero your vernier on the length of the bolt, insert bold and measure the bit sticking out. That will give you your tapping depth! (Forget about the minus sign, that only indicates the thread is sub surface!)

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#3
In reply to #1

Re: tapping Depth Measurement

03/25/2009 6:03 AM

I want an instrument for checking the depth, I know the methods that how i can measure this alternatively,But moreover i want instrument

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#4
In reply to #3

Re: tapping Depth Measurement

03/25/2009 7:48 PM

You will need to use the sharp end of the calipers - or if your calipers have an RS232 connection you could read on a display http://www.compendiumarcana.com/caliper/ - or you could buy

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#5
In reply to #4

Re: tapping Depth Measurement

03/25/2009 11:07 PM

Isn't this a micrometer?

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#2

Re: tapping Depth Measurement

03/25/2009 5:54 AM

How about one of these available locally from here?

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#6
In reply to #2

Re: tapping Depth Measurement

03/25/2009 11:27 PM

Why would a normal standard depth gauge from Mitotoyo not suffice? Hole too tiny for a caliper or too large? I remember looking at a depth micrometer with a range of tool end sizes for measuring smaller than 6 mm hole diameter. Since I was into engine rebuilding at the time I did not bother to get the others.

Do you not have access to a regular catalog of measruing instruments?

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#11
In reply to #6

Re: tapping Depth Measurement

03/26/2009 8:44 AM

Hey ELNAV,

You can not reliably tell where a thread stops by bottoming out a measurement in the hole. Even if it is threaded with a bottoming tap, you will still have a variance in screw insertion. A non-bottoming style tap is even worse!

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#7

Re: How to Measure Tapping Depth

03/26/2009 12:54 AM

Chinese digital calipers are so cheap nowadays if the hole to be measured are smaller than the width of the calipers depth probe it is simple to grind down the width to suit. also it does not spoil the ability to alter the width again even if it is shortened as the calipers can be zeroed at any position.

Buy two or thee if you need to measure a lot of holes of different diameters.

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#8

Re: How to Measure Tapping Depth

03/26/2009 1:03 AM

U can calculate by how many round of the thd you had engage. example 5 round X1.5 pitch=7.5 mm depth

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#9

Re: How to Measure Tapping Depth

03/26/2009 2:06 AM

If you want to measure tap depth instead of hole depth, you need to measure the depth of the point where the thread reaches a critical diameter or percentage of thread depth. Inserting standard threaded body like a gage screw or sectioning the hole are 2 ways to do this. If you work for the manufacturer of the threaded holes, it might be fruitful to qualify the process instead of inspect all of the output.

If you just need the depth of the hole, get a depth micrometer. Use a point on the end of the measuring rod if the bottom of the hole is not flat.

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#10

Re: How to Measure Tapping Depth

03/26/2009 6:17 AM

Hello Rajesh verma;

Please we need method of tapping, type machinery used and depth dimention etc. to give informed reply, thanks.

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#12

Re: How to Measure Tapping Depth

03/26/2009 10:46 AM

I'm not sure how accurately you need to check the tapping depth - that will depend upon circumstances. But I've seen a shop-made device used; it used two half-balls, each with a diameter of maybe twice the pitch [or = crest-to-crest-to-crest]. They were on the end of a long U-shaped wire spring, with an outside width just less than the hole diameter. The round surfaces faced outward, and when the two halves were squeezed together to form a full sphere, the device was pushed down the hole. It was then lifted until a "click click click" sound a feel indicated that it had been raised to where the threads started. A reading at this position was used as reason to accept or reject; the first three or so threads were assumed to be incomplete.

It is easy to adjust the number of threads to ignore, assuming that the same type of tap was used for a series of holes. A simple mark on the legs of the spring will say whether adequate depth is seen. If this will be used for several sizes, a small block higher up the U, with a hole parallel to the legs and holding a straight wire with smooth end, can provide an adjustment (set screw on the wire leg for position).

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#13
In reply to #12

Re: How to Measure Tapping Depth

03/26/2009 5:14 PM

It is a very simple thing to assess depth of thread when tapping.

Using a starting seven and one half threads are lost due the lead angle.

Using a plug tap three and one half threads are lost due the lead angle

Using a bottoming tap 1 and one half threads are lost.

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#14
In reply to #13

Re: How to Measure Tapping Depth

03/26/2009 6:13 PM

Sounds like a good rule of thumb - thanks! - but my ancient Machinery's Handbook gives a wider variation. The "American Standard Straight Shank Tapper Taps - Fractional Sizes" table calls for 11 -12 chamfered threads for NC [National Coarse], and 15 -17 for NF. Nut and pulley taps are chamfered over as much as half of the thread length, which could easily mean 10 threads. Of course, none of these would be appropriate for use in blind holes, so Plug or Bottoming should be used. Because this is an old copy of the book, it doesn't mention metric taps, and there may be newer standards for the ones it does contain. I would never count on a purchased tap meeting a particular standard, unless the manufacturer explicitly claims compliance.

In any case, if a few holes are measured by counting turns when installing a bolt, and the same holes checked using the simple push-in / pull-out device I tried to describe, the total number of crests found by the device, minus the number of turns the bolt will go in, will say how many to ignore.

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#15
In reply to #14

Re: How to Measure Tapping Depth

03/26/2009 10:11 PM

We generally figure by number of threads x pitch

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#16
In reply to #15

Re: How to Measure Tapping Depth

03/27/2009 11:24 AM

Hi, BWire -

Not sure I follow. By "number of threads" are you referring to the number of chamfered threads on the tap? That is, the number which will not produce full-depth cutting, and so must be ignored? "Pitch" can be synonomous with "lead", or crest-to-crest distance, though in ordinary American usage it is often used for the number of threads per inch (the inverse of pitch) - even by screw manufacturers*! Metric nomenclature uses pitch properly. Since the original poster specified India, I don't think that American / inch-based usage can apply.

The vagaries of language usage, jargon, and other influences were why I deliberately tried to use only descriptive terms - I'm not claiming that I was successful!- and attempted to keep everything generic. Counting turns of a bolt (is that what you mean by "number of threads"?) and using pitch in the correct way will indeed permit multiplying to obtain a depth measurement.

*A supplier of specialty twin-start high/low threaded screws for thermoplastics insists that one size has a pitch of 14, though it measures 14 threads per inch, or 7 high crests, and 7 low ones. And this is an extremely large manufacturer supplying the auto industry. Minimum quantities begin at 500,000 pieces/year, and they do not sell through distribution. They don't get really interested until you speak of boxcar loads under blanket orders. So, even though their nomenclature is dead wrong, they have so much clout that they get their way.

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#17
In reply to #16

Re: How to Measure Tapping Depth

03/27/2009 5:17 PM

Hello Ron,

When we veer away from commonly held standards mayhem may result. The standards in place when I attended school are still upheld as described here I sincerely hope these are maintained across continents too.

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#18
In reply to #17

Re: How to Measure Tapping Depth

03/27/2009 6:10 PM

"When we veer away from commonly held standards mayhem may result."

You will get no argument from me on that issue. I can't really say what standards were being taught when I was in school (for this context), because I got my degree in physics, and never took an engineering course of any sort. Yet I've held the title of engineer, with various preceding adjectives ("research", "design", "mechanical", and "manufacturing"), at several companies for nearly 39 years now. I've had no problem finding, using, following, or specifying standards, but I've routinely run into instances of someone else ignoring - or being ignorant of - methods, procedures, standards, and other basic rules. Mayhem might be a slight exaggeration, but it certainly points in the correct direction for what usually followed! I have no problem with deliberately using non-standard methods, materials, etc., but only for those who first understand the whys and wherefores of normal ways, and can explain why the current situation is an exception.

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#19
In reply to #18

Re: How to Measure Tapping Depth

03/28/2009 1:50 AM

I concur

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alfredngai (1); Anonymous Poster (1); AussieBob (1); bwire (5); elnav (1); garth (1); lyn (1); moon161 (1); Mr. Truman Brain (1); PWSlack (1); Rajesh verma (1); Ron (4)

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