madmachinst
Stainless
- Joined
- Jan 15, 2007
- Location
- Central FL
Do they have to be within .0001 of the stated size? mine are +/- .0025
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thread measuring wires
- Thread starter madmachinst
- Start date
- Replies 15
- Views 9,900
the wires themselves? they have to be within .00001" of the stated size. Ten millionths.
and you need a certain diameter for every thread pitch you want to measure. 24 wires are different from 28 wires. 11 pitch wires are different from 12 pitch wires.
Spee Dee slash Brown & Sharpe thread measurement wires set for $11 or whatever is not adequate for the job. When I first started out I made a bunch of junk based on those things.
and you need a certain diameter for every thread pitch you want to measure. 24 wires are different from 28 wires. 11 pitch wires are different from 12 pitch wires.
Spee Dee slash Brown & Sharpe thread measurement wires set for $11 or whatever is not adequate for the job. When I first started out I made a bunch of junk based on those things.
howiesatwork
Aluminum
- Joined
- Apr 22, 2006
- Location
- San Jose, CA
Ten millionths is the Maximum tolerance for for roundness, size, and taper, as stated by apestate. Really good ones are five millionths tolerance on size. And pricey? indeed... $48+ for sets, and we have them all the ones Van Keuren makes at the lab.
You CAN make fairly decent measurements using slightly off Best Wire Size, if you can measure the wires accurately, then calculate the pitch diameter tolerance from measurements.
I've done that for Metric threads using TPI wire, when we didn't have the metric wire sets. It is a pain, though it does work.
You end up measuring slightly above or below the 50% point of the thread, which is where the P.D. is supposed to be read.
I'd post the calculations, but I have to go look them up again, and I'm lazy, and in my garage.
Have fun measuring.
You CAN make fairly decent measurements using slightly off Best Wire Size, if you can measure the wires accurately, then calculate the pitch diameter tolerance from measurements.
I've done that for Metric threads using TPI wire, when we didn't have the metric wire sets. It is a pain, though it does work.
You end up measuring slightly above or below the 50% point of the thread, which is where the P.D. is supposed to be read.
I'd post the calculations, but I have to go look them up again, and I'm lazy, and in my garage.
Have fun measuring.
The real Leigh
Diamond
- Joined
- Nov 23, 2005
- Location
- Maryland
Sorry, those aren't even in the right city, much less the right ballpark.
My Van Keuren 60° 20-pitch wires are 0.02887" diameter. The pitch diameter is the measurement over wires minus 0.04331".
The trick is finding a micrometer that will read out in .00001" increments accurately, and which can be held while juggling the wires and the screw simultaneously.
- Leigh
howiesatwork
Aluminum
- Joined
- Apr 22, 2006
- Location
- San Jose, CA
...The trick is finding a micrometer that will read out in .00001" increments accurately, and which can be held while juggling the wires and the screw simultaneously.
- Leigh
That would be a trick, indeed. The best resolution I've seen lately in a hand-held micrometer is .00005"...
A good one with ±.0001" accuracy will do nicely.
WELL. You do have to round off the calculated values toward the middle of the tolerance band.
Once you have the correct size thread wires, you can use them with a regular micrometer. Having them checked is a matter of sending them to a calibration lab so they can use a supermicrometer or UMM or something to check them out.
Once you have the correct size thread wires, you can use them with a regular micrometer. Having them checked is a matter of sending them to a calibration lab so they can use a supermicrometer or UMM or something to check them out.
howiesatwork
Aluminum
- Joined
- Apr 22, 2006
- Location
- San Jose, CA
Yep!
Rounding off to the middle of the tolerance is known as guard banding in Metrology.
Sometimes measurement uncertainties are high enough that sufficient accuracy of measurement isn't going to insure you will be within the tolerance of the parts measured, so you tighten the tolerances you allow, and then you are sure to be in specification.
At higher accuracy measurements, this is done a lot, because the TUR approaches unity.
I sure am glad I do microwave stuff now instead of calibrating gage blocks, or worse... pins gage sets... tedious!
madmachinst
Stainless
- Joined
- Jan 15, 2007
- Location
- Central FL
just to make sure we are on the same page here. I am talking oabout the set that is used to measure pitch diameter. What formula do I use to correct everything? I'll look it up in Machinery's handbook.
howiesatwork
Aluminum
- Joined
- Apr 22, 2006
- Location
- San Jose, CA
Here's one page that shows how:
http://www.precisiontwistdrill.com/techhelp/help_pages/pitch_diameter.asp
http://www.precisiontwistdrill.com/techhelp/help_pages/pitch_diameter.asp
huntinguy
Cast Iron
- Joined
- Dec 17, 2006
- Location
- Washington
don't forget pressure requirements
Supermic (bench mic with digital readout) will also give the required 2.5lbs of pressure to insure correct reading. Aint gonna get a hand mic to do that.
That would be a trick, indeed. The best resolution I've seen lately in a hand-held micrometer is .00005"...
A good one with ±.0001" accuracy will do nicely.
Supermic (bench mic with digital readout) will also give the required 2.5lbs of pressure to insure correct reading. Aint gonna get a hand mic to do that.
FranH
Hot Rolled
- Joined
- Oct 30, 2005
- Location
- Putnam CT USA
threads
If you wish to be serious...this is the way to go.....check ebay for the fixtures then buy the accessories
http://www.johnsongage.com/catalogue.shtml
If you wish to be serious...this is the way to go.....check ebay for the fixtures then buy the accessories
http://www.johnsongage.com/catalogue.shtml
howiesatwork
Aluminum
- Joined
- Apr 22, 2006
- Location
- San Jose, CA
Well, it looks okay for production work, and large rings >2"...
Gonna be a bear to measure a 0-80UNF-2A gage, or smaller, I'd think...
There are a few types of Unified threads: UN, UNC, UNF, UNEF, UNS, UNJ, UNJC, UNJF, UNJEF, UNR, UNRC, UNRF, and UNREF. NC5, NC5HF, NC5CSF, NC5ONF, NC5IF, M, MJ, MJS, UNM, NPT, NPTF, F-PTF, PTF-SAE Short, PTF-SPL Short, PTF-SPL Extra Short, SPL-PTF, ANPT, NPSL, NPSM, NPSC, NPSF, NPSI, NH, NPSH, NFPA, NHR, NGT, NGO, NGS, SGT, R, Rc, Rp, G Series, BSW, BA, ACME –C, ACME –G, Stub ACME, BUTT, PUSH BUTT, AMO, AWWA, DIN, JIS, and ISO standards.
Guess we'll just have to do it the hard way...
Then there's gear measuring...
Gonna be a bear to measure a 0-80UNF-2A gage, or smaller, I'd think...
There are a few types of Unified threads: UN, UNC, UNF, UNEF, UNS, UNJ, UNJC, UNJF, UNJEF, UNR, UNRC, UNRF, and UNREF. NC5, NC5HF, NC5CSF, NC5ONF, NC5IF, M, MJ, MJS, UNM, NPT, NPTF, F-PTF, PTF-SAE Short, PTF-SPL Short, PTF-SPL Extra Short, SPL-PTF, ANPT, NPSL, NPSM, NPSC, NPSF, NPSI, NH, NPSH, NFPA, NHR, NGT, NGO, NGS, SGT, R, Rc, Rp, G Series, BSW, BA, ACME –C, ACME –G, Stub ACME, BUTT, PUSH BUTT, AMO, AWWA, DIN, JIS, and ISO standards.
Guess we'll just have to do it the hard way...
Then there's gear measuring...
67Cuda
Banned
- Joined
- Oct 22, 2008
- Location
- West Coast, CA
This is why they invented thread mics.
GearGeek
Plastic
- Joined
- Dec 15, 2008
- Location
- Vancouver, WA
If you bought thread wires from Enco (or similar) +/- .0025 does not surprise me and should *not* be acceptable. I ordered a set from them just for home project use and was shocked to find them ridiculously loose in the tolerance department. I even found one wire that was not from the proper set. (a .045 should have been a .055) and more than one that were more than a couple thou off. Needless to say I got my money back. I realized Enco wires wouldn't come close to say Van Keuren wires but come on!
I guess when you buy junk you get junk.
~GearGeek
I guess when you buy junk you get junk.
~GearGeek
Forestgnome
Stainless
- Joined
- Aug 2, 2008
- Location
- Californeeeah
I just calculated that the percent error of the wire diameter correlates directly to the percent error of the pitch diameter reading. Of course, since there are two wires in that reading, the tolerances can stack.
Who make a complete set of wires that don't cost an arm and a leg? I went around our shop awhile back checking everyone's wires and pretty much everybody's wires seemed to measure .0001/.0003 under size, these were the standard cheap wire sets you buy for $10-20 of many different brands, even a very old set of real made in USA PEE DEE brand wires were off the same amount.
