Tapping Essentials from Hass Automation Good info for manual and CNC machinists

[WmRMeyers]

Good info on how and WHY to select various types of taps both in manual machining, and in CNC systems. Been playing with taps and dies for at least 50 years, still learned some stuff, and got good explanations for some old rules of thumb for mechanics and machinists.

NOT my content.

Bill

[Moldyjim]

Now explain why anyone would ever use a 6-32 tap in steel.

I HATE 6-32 TAPS.
They are the worst designed thread form of all. IMHO.

I've tried to teach people that coarse thread pitches are for threads in aluminum, copper etc. Fine pitch is for steel etc.

Am I wrong? If so Why?

[jdurand]

I would use it when I have to use 6-32 screws. Now that I'm moving to metric-land I'll have to learn all new threads.

I'm currently hanging out in Alabama waiting to draw the card that lets me pass "go".

[WmRMeyers]

Now explain why anyone would ever use a 6-32 tap in steel.

I HATE 6-32 TAPS.
They are the worst designed thread form of all. IMHO.

I've tried to teach people that coarse thread pitches are for threads in aluminum, copper etc. Fine pitch is for steel etc.

Am I wrong? If so Why?

In 1914 or 1915, 6-40 was the standard thread for #6 machine screws, according to my pdf of the 5th Edition Machinery's Handbook. Special machine screws were 36 or 32 TPI for the #6 size. 32TPI IS the coarse thread. And the place I see it most is in electrical outlets and boxes. I'm only 66, and really only been playing with machining for 13 or 14 years, but I've been a mechanic of one sort or another for about 40 more years. I don't believe I've every run into anything but 6-32 machine screws in that time, with one possible exception. I have here on my desk a Bausch & Lomb student microscope that may use other than 6-32 screws. They seem to be too coarse. The screws that hold the body of the microscope to the focusing mechanism may be 6-36 or 6-40. I've not been able to find anything but 6-32 screws. McMaster-Carr and Brownell's are two companies that apparently carry them, and I've not taken the thing to my local Ace hardware yet. They have #8-40 screws, so they may have some of the other sizes in the sets of gray boxes.

[Frank S]

In 1914 or 1915, 6-40 was the standard thread for #6 machine screws, according to my pdf of the 5th Edition Machinery's Handbook. Special machine screws were 36 or 32 TPI for the #6 size. 32TPI IS the coarse thread. And the place I see it most is in electrical outlets and boxes. I'm only 66, and really only been playing with machining for 13 or 14 years, but I've been a mechanic of one sort or another for about 40 more years. I don't believe I've every run into anything but 6-32 machine screws in that time, with one possible exception. I have here on my desk a Bausch & Lomb student microscope that may use other than 6-32 screws. They seem to be too coarse. The screws that hold the body of the microscope to the focusing mechanism may be 6-36 or 6-40. I've not been able to find anything but 6-32 screws. McMaster-Carr and Brownell's are two companies that apparently carry them, and I've not taken the thing to my local Ace hardware yet. They have #8-40 screws, so they may have some of the other sizes in the sets of gray boxes.

You might try typing gun screws or instrument screws into your search when looking for a thread you are having difficulty locating
Clock maker is another term but usually for the very small screws

[Nick79]

Wow, this explains why I sometimes break taps. Of course it might help if I purchased BETTER taps to begin with. I watched the entire post and learned quite a bit - Thank you.

[WmRMeyers]

You might try typing gun screws or instrument screws into your search when looking for a thread you are having difficulty locating
Clock maker is another term but usually for the very small screws

Brownell's does gun screws, and McMaster-Carr seems to have about everything, but I really need to find a place that has what I need in stock so I can go there with the microscope parts and find out what fits. Or buy assortments. A dozen of each size from 1-12 machine screws from Brownell's is around $20, which isn't bad, but money is kind of tight here. I've spent quite a chunk on medical stuff SWMBO and me in the past year. Somewhere in all this stuff I have a small package of tiny taps we got for something SWMBO wanted to try years ago. I want to find them and add them to my collection, and then maybe I can make my own screws, if push comes to shove. And before I can go to Ace, I need to find the microscope body. It's here under one of the piles, somewhere...

Bill

[WmRMeyers]

Wow, this explains why I sometimes break taps. Of course it might help if I purchased BETTER taps to begin with. I watched the entire post and learned quite a bit - Thank you.

I've not broken one lately, but I also haven't done much tapping, lately, either. I've got a couple of little projects where I'm going to be doing tapping in very small sizes in the near future, I hope. Thought it would be a good thing to share for that very reason. I've mostly been buying Vermont-American taps and dies, since that what my local wholesale tool supply was carrying, but they're moving to Bosch. What I did was buy cheap Chinese tap & die sets some years ago, and as I've used them (and mostly found them about useless), I've been buying V-A taps and dies to replace the original not-so-good taps and dies. I figured $5 for a tap and die case wasn't a bad price. A couple of the taps have actually been usable. Most needed a bit of honing to work. Not sure why they left flashing/burrs on the taps, for example. But the cases are decent.

Bill

[old kodger]

If you are looking at very old equipment, it's possible that you've run across BA(i think it stands for British Association) taps and dies 9and 10 BA would be about 40 thou dia.or so, and insane tpi.

[Floradawg]

I've never heard that explanation for fine vs. coarse. Fine threaded holes and fasteners provide more holding strength.