I quit! That's enough. Never again........

[Captain Jerry]

... will I put a #2-56 HSS tap into brass or aluminum. It's just asking for trouble. And I don't need to. I'll use this:

That is a piece of #2-56 all thread turned into a thread forming tap. I just grind a flat on the end like making a D-bit. It may cut a little bit but it doesn't make chips, so I think it is forming the threads. On this version, the threads go all the way to the end so it is like a bottoming tap. For a tapered version, just grand a very small taper on the end before grinding the flat. I used a very fine grit sanding disk an did not bother to hone it. I used it by hand and power driven in the mill on both aluminum and brass, on blind holes and through holes with good results. I finally broke it by intentionally bottoming in a 1/2" deep hole in aluminum under power. There was no 'SNAP'. It kind of wrung off and left a 1/8" stub that I was able to grab with pliers. I don't know how many holes you could tap before it wears out but if needed, a quick touch on the sander and it's good for more, and If it breaks, you are out about ten cents.

Never again will I turn the air blue because a tap. It should work for #4 as well.

Jerry

 

[steamer]

Step away from the ledge Capt! ;D


I know I hate small taps too! :big:


Dave

 

[AussieJimG]

That looks great! And so simple!
You say that you ground a flat on the end like a D bit; but it looks like a simple flat rather than the usual D bit cut which (as I understand it) is a flat along the axis. Could you tell me which it is please?
Jim

 

[Captain Jerry]

Jim

It is a fairly shallow angle, to a depth of just over 1/2 the diameter at the tip. I'm no expert, but that's the way I make D-bit reamer too.

Jerry

 

[cfellows]

Nice tip, worth trying. I wonder if a stainless steel allthread or screw world last longer?

Chuck

 

[lumie]

Hi captain

great idea but what size do you drill the tapping hole, I must try it out.

Lumie :bow:

 

[Captain Jerry]

Chuck

I don't know about stainless for wear but I don't think its as tough. I'm not sure but I think the all thread has rolled thread and is a little harder. I used a 2 inch length which is pretty long for a screw. The 2 inch let me get a good grip on it with the salvaged chuck that I use for hand tapping.

Lumie

I used a 5/64" drill bit in brass and aluminum. I don't think it will work in anything harder.

Jerry

 

[AussieJimG]

Thanks Jerry, now I think of it, I have seen D bits made that way.

I might try one of your taps using a cap screw; they seem to be hard as well as high tensile.

Jim

 

[Florian]

I wouldn't try it with stainless steel as it tends to gall (at least this is a problem with v2a screws when you assemble them dry...)

To get it lasting longer, I propose to use some silversteel and cut a thread with the lathe on it. Then "polish" the thread by using a slotted brass nut, putting the nut in the vice and applying some oil. You may also use some polishing compound.

Then harden the selfmade threadformer and finally prepare it to use (grinding the flat)

Or, maybe it is possible to harden a normal thread rod / screw by using hardening compound...?

Cheers Florian

 

[Maryak]

I used a 5/64" drill bit in brass and aluminum. I don't think it will work in anything harder.

Jerry

You might get a couple on a harder metal, if you heat it cherry red and quench it in water. From memory the steel used has a reasonable amount of carbon in it. Try it on some scrap as it may just end up too brittle.

Best Regards
Bob

 

[Captain Jerry]

I don't think I want it very hard. Every time i have broken a HSS tap, it broke right at the surface and gave me fits extracting it. (Yes, I know about Alum) I like that the allthread was flexible enough to twist and break off above the surface where I could get hold of it. And since it will probably disappear into the 4th dimension before its worn out, I don't want to spend too much time on it. If it makes a half dozen holes, its served its purpose.

Jerry