View Full Version : Thread measuring tip

12-17-2006, 12:09 PM
I have difficulty trying to manage the 3 wires and mic with only two hands. A piece of shipping foam holds the wires and if positioned carefully I now have both hands to work the mic.http://i48.photobucket.com/albums/f249/deltap/Pic006.jpg

12-17-2006, 12:47 PM
I sure like that idea. I have used masking tape to lock two under the thread and one over but your idea is very good. I always hate to have to use the wires. The problem with them is if they are not held perfectly in the thread you will get a bad measurement. Getting the high center reading with the mic is tricky at best.

I bought a set of triangle thread measuring devices that I like but they are tricky to use too.

12-17-2006, 12:50 PM
I have used plasticine for holding the wires on helps if parts degreased prior to using the plasticine. Also dont let the kids catch you stealing there play doh.

John R
12-17-2006, 02:24 PM
I just bought a set of plastic wire holders. It slips over the anvil on the mic and holds two wires with no hands. So now you have one hand for the single wire and one for the mic. It works
John R

12-17-2006, 03:32 PM
We use electrican's duct seal, to hold the 3 wires, it's like plasticene, but cheaper.

12-18-2006, 09:55 AM
A simple dab of grease on each side will hold the wires in place, then a wipe off and you're done!

12-18-2006, 10:16 AM
I steel the plasticine from the kids so its free sort off.

Dick Plasencia
12-18-2006, 03:09 PM
I may be doing this wrong but it seems to work for me. I use a point micrometer to measure the minor diameter after first having machined the major diameter per the thread tables.
I definitely would like your comments on this.

Paul Alciatore
12-18-2006, 07:49 PM

Minor and major diameter measurements would be OK in theory for perfecty machined, sharp Vee threads. but for standard thread forms with flats and or rounded areas at the tips and roots, it can be misleading unless you also know the exact dimensions and possibly the shapes of those features. It is actually the pitch diameter that is most indictative of the thread's size and that is measuerd at the 50% point of the Vee without the flats or fillets. Wires will measure at a location that is close to that point and with the proper calculations (already done in the tables) will translate exactly to the exact pitch diameter. If you are doing a precision thread, your method will fail.

Thread micrometers, with the proper table, will also give a correct measurement of the pitch diameter. Tips can be made or purchased for standard micrometers to convert them. You do not need individual sized micrometers or tips for every thread as one size will cover a range of pitches. One of my future projects has always been to make several such tips for easy thread measurenent. Some day.....

12-18-2006, 08:28 PM
I pefer thread mikes they are easy to use. thread wires last resort.But I like the idea the stirfome has to be better than tape

12-18-2006, 09:23 PM
Neat idea,good looking threads too BTW.

Dick Plasencia
12-19-2006, 02:29 AM
Paul, I appreciate your instructive reply but it has me a little confused. If the dimensions of a thread as found for example in Machinery's Handbook list the major and minor diameters of a thread would that not take into account the flats and valleys? Otherwise what is it they are measuring when they give these dimensions? The point micrometer should be measuring down to the valley created by the tool.
Seems to me that if the tool is shaped correctly and the major diameter is machined per the dimensions in the thread table all I have to do to get a proper thread is arrive at the correct minor diameter.
I think I need a lot of help with this. Please!

12-19-2006, 03:06 AM
Somewhat OT, but since it came up. How exactly do you use a threar mic? I got a B&S at an auction in a "box lot" of 1" mics of various styles. Got it dirt cheap, but no idea how to use it or calibrate/check it...

12-19-2006, 11:32 PM
Try measuring a 34" pulley over pins.
I gotta tell ya a 34" to 35" mic aint exactly light.
The top pin is not to bad, but holding the bottom pin
and the mic and getting it all aliened to get a good
measurement is tough.
Good tip though