Strange shop made tap

[churchjw]

You must have filed some relief on the tap or it would not have cut.

I make quick taps by some old time tricks. They work perfectly well. When I make parts for antique mechanisms they always need special threads.

A suitable tap can be made by just filing them square or triangular. In the 18th. C.,taps were made that way commercially. They cut very well. I have made taps by filing a tapered flat spot on 1 side of the tap. The flat at the nose is 1/2 the diameter of the tap,tapering out quickly to nothing in about 3/8". The important thing is to then file the threads into a relief so that the foremost cutting edge is higher than the area behind it,or it won't cut. As long as the threads themselves are correct,these quick taps leave a threaded hole just as good as any other tap will. They are not for high production,just for a few special threads. I harden them,and draw to a dark brown color. Some temper to purple,which is just below blue. Blue is 52 Rockwell,and getting too soft to hold up on steel.

George could you post a picture of how you file yours? I'm not sure I did it right with mine and it only worked because it is in brass.

Jeff

 

[FanMan]

I've made emergency taps before by simply cutting grooves in a socket head screw with a Dremel emery wheel and grinding a point on the end. Crude, but works fine in soft materials, aluminum or plastic.

 

[george wilson]

Church: I'll have to dig them out and take pictures. They are so rough and ready I haven't thought about posting them. But,they work very well. Many are left handed. They might not photo well as most of them are black from oil quenching. It might take a while to get them as I am starting a new apprentice tomorrow. Not really new,she worked in the Musical Instrument Sop for 5 years,where I started as Master in 1970. I was asked to be Master Tool(and instrument maker) in 1986.

This woman is now 59 and has been away from me for over 25 years. She made some really great violins,and then would make a fouled up one. Very inconsistent,but very talented. She had better not foul this one up as I gave her over $300.00 worth of German wood to get going. Then,since she had no violin tools any more,I offered her to work here.

 

[LJP]

George and DMS, I would ask that you both post pictures of your homemade taps, please. I find it fascinating, and would like to give it a try. Thanks! Larry

 

[dsh1001]

I've searched in vain for a 9/32=36tpi tap :thinking:

Are you sure it isn't a 7x.75mm? That would be really close to the same. I would guess that is what the nut on the potentiometer is. It would work pretty good for about 5 or six threads depending on the class of fit but a screw of one type in a hole of the other would eventually bind up some number of threads after that.

 

[Dave Smith]

Are you sure it isn't a 7x.75mm? That would be really close to the same. I would guess that is what the nut on the potentiometer is. It would work pretty good for about 5 or six threads depending on the class of fit but a screw of one type in a hole of the other would eventually bind up some number of threads after that.

I measured several of the drill bits thread OD and they are .278-.279 which would be .0025 over 7m but .0030 under 9/32---I measure 36tpi , but I don't have a metric thread gage set---how many tpi is the .75mm? --Has anyone ever heard of a aircraft drill that takes 7x.75mm threaded drill bits?--I do see that MSC does have a 7x.75mm tap--thanks for the reply---Dave

 

[MadTrapper]

My friend Keith was a much better bodger than me. When he had to clean up an external thread he used to cut grooves in a nut using a junior hacksaw then heat to cherry red and drop in a bag of sugar. This seemed to work. I do not know why? Any of you chemists out there explain this method. Nice work on the tap BTW and I am not trying to hijack your thread it just reminded me of an unanswered question about thread cutting that I had.