MetalworkingFun Forum

I am making a custom 1/4" x 40tpi tap for a friend. He had the change gears for his lathe disappear during a move.
I have the threads cut, and a 5 deg taper on the end. I'm getting ready to mill flutes and the square end for the tap wrench. Can I cut the flutes with a regular 1/8 end mill? I don't have a ball end that small. How deep should they be? He'll be cutting threads in cast iron. I have to also make a matching screw, so I will be taping a piece of hex steel stock for a test nut.
I have printed out an article on making custom taps with just a filed obelisk (think Washington Monument) shape for the tapered start and no flutes, but I think flutes would be better.

Chuck

Why wouldn't you just buy one? They are available for as little as $1.62 (plus shipping.)

http://www.amazon.com/s/?ie=UTF8&keyword...fhq0r3rg_e

Well, first cause the guy that needs the tap couldn't afford the prices I found on Amazon. I didn't see the $1.62 price, I saw $15 and up...
Second, I've already made and tested the tap. And I didn't have to spend any money other than the electric to run the lathe, already had some 1/4" drill rod...
Why buy when we can make it? Took me all of 2 hours to make, including heat treat! Noe I know I can make just about any tapI need!

Chuck

Thats the whole point of having machinery, to make things, its a hobby so time shouldn't enter into it.
But curious, if you were tapping the hole and making the bolt why not a standard thread?

I can't make a tap because I'm way too picky about thread geometry, clearance angles, cutting angles, chip flow geometry, and thread tolerances.

picky?

Some would say anal retentive but lets go with picky

Of course, I would never say such a thing - I simply posted in the interest of social commentary!

Now Darren, to suggest I am anal retentive would mean I'm FOS. I am most definitely FOS, but not about most machining oriented stuff.

I am, however, overly critical of things that really don't matter a bit in a home shop. On that list are time (spending too much of it on simple tasks a primary irritant), not using the right tool for a job, and not using the tool correctly for a job.

Could I make a 1/4"-40 UNS tap? Perhaps. I'd be so concerned it wasn't the correct thread form, that it wouldn't curl a chip correctly, might make an out-of-tolerance thread, could bind in a hole, and so on that I just couldn't make one and accept that "It should work fine for this job."

I guess you're right after all. I'm anal retentive.

I've been thinking about this whole "that's good enough" and would like to bring my skill level up a notch to the point of being able to machine something to a known spec rather than to match one piece to another piece. This is purely a hobby for me so I can afford the time necessary to take the time to do that. Pride in workmanship rather than that's good enough. Sorry for the ramblings.

Ed

If you build something from a drawing, do you change specs to what ever you want, or do you make the part to plan? My friend is making an engine to the designers plan. That's why a 1/4-40.
I'll be the first to admit I'm still at the "that's good enough" stage. I'm getting better, and my setups and tooling is improving. I made the tap as close to spec as I could get. I made a nut with it to use as a gage for the screw thread I need to make. The screw will mate with the tapped hole made by the tap I made... Whooh, I'm getting dizzy...

Chuck

(05-29-2014, 07:57 PM)EdK Wrote: [ -> ]This is purely a hobby for me so I can afford the time necessary to take the time to do that.

Ed

I can afford the time as well. My problem (one of many, I know) is I can't afford to buy all of the precision tools that go along with verifying the work that's been done meets those high "standards" in the end.