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KiddZimaHater
11-25-2012, 11:48 AM
What's a simple trick to stick the 3 wires to the part, when measuring with a mic?
Seeing as I don't have 4 arms.:(

lakeside53
11-25-2012, 11:57 AM
GREASE, grease, grease

BigJohnT
11-25-2012, 12:32 PM
I set the mic a tad bigger than I expect and use my fingers to hold the wires as I slide the mic over them.

John

lazlo
11-25-2012, 12:39 PM
Black (or pink) electrostatic foam works great, and no mess cleaning up the wires.

flylo
11-25-2012, 12:47 PM
Hate to sound(& be) stupid, but can someone explain how this works?:confused: Thanks!

RWO
11-25-2012, 01:18 PM
I use a lump of modeling clay. Pressure from the mic will move the wires into the proper position and give an accurate reading.

RWO

Dr Stan
11-25-2012, 01:19 PM
Hate to sound(& be) stupid, but can someone explain how this works?:confused: Thanks!

the grease or the three wire method?

Here's a site that explains the three wire method: http://www.threadcheck.com/the-three-wire-method-of-measuring-pitch-diameter/technicalinfo/

I remember some thread wires that were called "Flin Wires" (sp?). They were not accurate enough for Mil-Spec parts, but close enough for virtually everything else. Seem to remember a set had fewer wires than usual and it included a chart that made it easy to calculate the PD.

The grease acts as stickum to hold the wires in place. Just hit the part with some electromotive or brake clean to remove the grease.

Mcgyver
11-25-2012, 01:37 PM
Grease to hold the wires on the work....or stick the wires in plasticine (modelling clay) are both things I've used. They reduce the frustration from a 12/10 to about an 8. The wire falls off the grease, the move and shift in the modelling clay..Arrg

we should use thread wires all the time.....its only because they're a 8/10 on the miser scale that we don't

I've got a way to reduce it to a 3. snip two pieces of bicycle inner tube maybe 3/8 wide and an inch long. Punch a 1/4 hole in the centre (mics in my experience are 1/4" anvils). with an exacto knife make two slides at each end.

Slip the wires through the slits, two in one and one in the other and then the whole assemblies on the anvils. It works well. There is a commerical product out plastic that does the same but the price is just plan stupid

J. R. Williams
11-25-2012, 02:08 PM
Empty the chip pan BEFORE using the wires !!

Jaakko Fagerlund
11-25-2012, 02:26 PM
Black (or pink) electrostatic foam works great, and no mess cleaning up the wires.
Probably the best (cheap) solution I've seen yet :) Have to try this next time when I'm making a thread that I have no gauge for.

oldtiffie
11-25-2012, 05:13 PM
The theory of the 3-wire system is fine but the application of it is or can be a PITA.

Using the 3-wire calculations and the known outside diameterof the part being threaded it is quite possible and practical too to get comparable results with either two or one of those wires. It just requires a bit of reasonably easy additional maths.

For those that are "worried" because for some reason I can't fathom or understand they think that "3-wire work" is "tenths work", I can tell you its notso - at all.

The Limits for thread pitch diameters are quite wide apart - see Machinery's Hand Book 27 page 1736 and onward (its a big table) Table 3 "Standard Series Selected Combinations Unified Screw Threads".

You should find most common UNF threads in there as it also includes the upper and lower limits for external and internal pitch diameters for Classes 2A and 2B.

Here is an example of the calculations for a 1/2- 13 - UNC - 3A external thread pitch diameter to be measured with "3-wires":

http://i200.photobucket.com/albums/aa294/oldtiffie/Sketches/3-wirecomps1.jpg

Notice that there is 0.005" (5 thou) difference in the limits ie what you measure with 3-wires and a micrometer - not "tenths" at all - just "thous".

Here it is graphically:
http://i200.photobucket.com/albums/aa294/oldtiffie/Black_book/Black_book_Fasten_P72-73_1.jpg

The best easiest and simplest way to measure external screw thread pitch diameters directly - and almost certainly the most accurate and repeatable way is to use a thread micrometer.

http://www.cdcotools.com/ and look for items 32370 32371 and 32372

firbikrhd1
11-25-2012, 06:23 PM
I use tiny orthodontic rubber bands, one on each end of the wires to hold them in place. No mess, and they stay in place even if bumped accidentally. They come in a couple of sizes and can be had for the asking usually.

rws
11-25-2012, 06:27 PM
I'm in the grease camp. Simple as can be. But I will also agree, that you should put something under them when measuring. Sometimes you bump or move them getting the mic in place and they fall. So to save a lot of headache, place anything, cardboard, newspaper, whatever under the piece when measuring.

polepenhollow
11-25-2012, 08:13 PM
Use grease to stick wires in place. Clean w/ a wiper when done and putting away.. Grease residue on wires is a good thing. Less chance for rust.

chorne27983
11-25-2012, 08:17 PM
I've always used a strip of 2" wide duct tape. Fold it in half while being careful not to completely stick the ends together. Cut one end in half and stick a thread wire in each of the halves and seal the tape around them. Stick the third thread wire in the other end. Then I write the wire size on the tape in permanent marker. Since I have been doing this, I have yet to lose a wire and they are easier to manage.

oldtiffie
11-26-2012, 04:17 AM
To get to the accuracy and consistency required:

a. the wire sizes sshould all be within 0.0001" so that a pitch diameter accuacy of 0.0003" is achievable - which should suit most circumstances.

b. pressure should be consistent.

Read this Machinery's Hand Book 27 page 1897.
http://i200.photobucket.com/albums/aa294/oldtiffie/Machinery_HB27/MHB27_P1897.jpg

Also read MHB27 pages 1893 > 1897 (and onward).

I find that the best micrometer to use is a "disk" micrometer as neither the disk nor spindle rotates:

http://www.machineryhouse.com.au/Q502

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Gear-measure4.jpg

The larger the pitch the more awkward it is to use a standard micrometer as the pitch approaches the diameter of the micrometer spindle (rotating) and anvil (non-rotating).

becksmachine
11-26-2012, 05:28 PM
I've always used a strip of 2" wide duct tape. Fold it in half while being careful not to completely stick the ends together. Cut one end in half and stick a thread wire in each of the halves and seal the tape around them. Stick the third thread wire in the other end. Then I write the wire size on the tape in permanent marker. Since I have been doing this, I have yet to lose a wire and they are easier to manage.

+1 on that.

Masking tape will work also.

Dave