Anyone got a thread micrometer?

That can measure the pitch diameter of a couple O'Donnell plugs?

My toolmaker buddy is away on vacation.

Terry Keeley said:

That can measure the pitch diameter of a couple O'Donnell plugs?

My toolmaker buddy is away on vacation.

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Terry, It should be in the Machinery’s handbook. I can check in awhile. Or are you want some as built numbers as apposed to nominals.

The M8x0.75 turbo plugs?

Thanks guys. Looking for an actual average number from a coupla 1/4-32 plugs.

Hoping to find a class tap to match.

If you've got a regular 0-1 mic you should be able to pick up a fairly inexpensive set of thread measuring wires.

MitchFarabaugh said:

If you've got a regular 0-1 mic you should be able to pick up a fairly inexpensive set of thread measuring wires.

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Fantastic, thanks! I did this sort of thing making gears years ago but didn't know you could measure threads that way.

https://littlemachineshop.com/images/gallery/instructions/ThreeWireMethod.pdf
Gonna p/u a set tomorrow: FISHER MACHINE,FISHER MACHINE THREAD MEASURING WIRE SET,1-811-131,KBC Tools & Machinery

Terry if you need a /4 32 tap I have 1 for you.

Kevin

I have a 0 to 1 inch and a 1 to 2 inch thread mic and I can also use the 3 wire method.

The wire method always makes me wish I had a 3rd hand!

That's were rubber bands come in handy

Kevin Sheren said:

Terry if you need a /4 32 tap I have 1 for you.

Kevin

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I have one, thanks. Trying to find a better fitting one...

My 1/4 32 plug tap cuts a fairly tight thread for glow plugs,,I can't quite remember if it was a bit undersize or I may have used lapping paste and some scrap brass/alum,,might be worth a try or try some different brands of taps,,sometimes the lead isn't ground quite right and they cut oversize or have small burrs,,you could also experiment with a taper tap

Terry, hey might have a much of tools at the end of next week! After 44 years time to move on, maybe back to racing! There is different grades of taps and drill tap hole a couple thousands smaller so you get a 100 % threads most tap holes only get you 80%. If you have a thread grinder in your area, you can take a oversized tap and have them grind it down to what ever you want. I have seen that come in sets of three- rougher, semi finish and finish which end up a nice threaded hole. And as always use a lot of good fluid!

WilliamCummings said:

Terry, hey might have a much of tools at the end of next week! After 44 years time to move on, maybe back to racing! There is different grades of taps and drill tap hole a couple thousands smaller so you get a 100 % threads most tap holes only get you 80%. If you have a thread grinder in your area, you can take a oversized tap and have them grind it down to what ever you want. I have seen that come in sets of three- rougher, semi finish and finish which end up a nice threaded hole. And as always use a lot of good fluid!

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You started all this when you came to look at that Emco C5 with me some thirty years ago in Dearborn! Good for you, I know you had a great career and I've seen some of your work, very meticulous. Will be great to have you back racing!

As mentioned I was hoping to find a smaller H1 or H2 tap but all that's out there is the standard H3, I'm told tightening the threads up is worth a small gain and have been single pointing them but that's a pain. Will know how the glow plugs measure up later today with the wire set and just order a custom tap.

MolyDee's my go to tapping goo, learned that when doing my Ti rudders!

Terry, if I were going to order a custom tap I would seriously consider a roll form tap instead of a cut tap. JM2C
John

John Beardslee said:

Terry, if I were going to order a custom tap I would seriously consider a roll form tap instead of a cut tap. JM2C
John

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I've never used one, what's the deal with them? I've heard Brad recommend them too.

Terry Keeley said:

I've never used one, what's the deal with them? I've heard Brad recommend them too.

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Terry,

Once you use them, you'll never use cutting taps again unless you HAVE to.

They don't cut the threads. They form them. You end up with a far stronger thread with a considerably better surface finish.

They also work very well in Delrin, making tapped holes very much like a nylock nut. Great for motor mounts.

Go HERE for tap drill sizes.

You're welcome.

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC

Wonder if a roll form tap would work on Titanium? Since that material is so hard and brittle??? Or Magnesium? Just thinking out loud... I always shied away from roll form taps. Didn't trust them to form threads/hole large enough. If I needed threads/hole to be tighter, just used a warn tap. Like I said...
Just thinking... Ken Wheeler

K F Wheeler said:

Wonder if a roll form tap would work on Titanium? Since that material is so hard and brittle??? Or Magnesium? Just thinking out loud... I always shied away from roll form taps. Didn't trust them to form threads/hole large enough. If I needed threads/hole to be tighter, just used a warn tap. Like I said...
Just thinking... Ken Wheeler

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Ken,

Don't know about Mg, but form taps will NOT work in Ti. Cutting threads in Ti is bad enough.....

It's not that Ti is that hard or brittle, as it is neither. Ti has a unique tendency to want to gall to steel. The word in familiar circles is "affinity". Ti LIKES steel, so it sticks to it under any real pressure. Even with good lubrication.

440 stainless is the "hard and brittle" one. And, no.... Form taps won't work here, either. Absolutely ZERO ductility. Don't even think about it.

I've used form taps up to 3/8-16 in aluminum and up to 1/4-28 (not 1/4-20) in steels and stainless of most sorts. The key is a good cutting fluid. WD-40 works great in Al, Cu, Delrin and such. I use TapMagic for most steels, leaning more toward MolyDee for the toughter steels and stainless. Getting the pre-tap drill size right really helps, too. I will actually use reamers to establish proper pre-tap hole sizes in some cases. Too big starts to decrease thread engagement. Too small (and I mean just a little) can easily lead to broken taps, especially in the smaller sizes. Go by the Balax numbers and you're good to go.

FWIW, form taps don't make for a "tight" threaded hole. They produce the same threads a cutting tap does, just stronger and no chip, which is REALLY handy for blind holes.

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC

At Logghe Stamping we did many of Chrysler’s tap plates that the door hinge bolt holes thread into, all were roll form taps done on automated equipment. It eliminated using weld nuts which over the years were a quality issue.