Acme Threads

[dallen]

Why sorry I got a lot out of the discussion. I don't care how mundain the task different people have different idea's and ways of doing the same thing. And this is one I didn't have any thoughts on until now.

and I can say yep I been there and done that, I cut acme threads and still make a mess of it

[Tony Wells]

I rarely use the compound method of feeding into the thread, and have no complaints. I get acceptable results based on the theory that the support given by cutting on both sides of the tool prevents any pushoff . I don't use HSS tooling for threading, so perhaps I would take a different approach, but I've had no problems using the straight in method. I cut UN, Acme, Stub Acme, and a few API tapered threads, and once in a long while, a square thread or a buttress, two of my least favorite threads. Oh, and an occasional Metric thread. And some weird specials like double lead and threads that are proprietary. I normally cut to factory gages.

[dallen]

I did a little of both with the feeding of the tool bit, by that I mean I fed it straight in with the cross slide and at the 14.5 angle of the compound and didn't really see that the lathe was being over worked, anyway it handled the cut both ways.

I know that it really shouldn't matter if the bit is sharp, a thought that popped up while reading Tony's post was if it would help the cut if guy way to take a rotary tool with a stone and put a radius between the edges of the bit to help relieve the square edge??

I got sidetracked yesterday and didn't do anything with trying to cut the acme thread hopefully today I will be able to get something done with it. One reason I am wanting to do this not because I have a money making part to make, but I am fixing to take a short gunsmithing class at a local Votech and I know some Barrels were put in with Acme and Square threads 1885 Remington Rolling Block for one. And I have plans for a 1895 Winchester High Wall I want to do some day.

[Tony Wells]

Dallen, I'm not sure not sure I follow. Are you talking about grinding groove long the top of the tool? As far as the edges are concerned, they need to stay sharp, as they are cutting too. There shouldn't be any square edges on the tool. It will have a small clearance to accommodate the helix angle of the cut, but nothing more.

[dallen]

Thanks Tony you answered my question about what I was thinking about doing, don't do it, besides on the smaller pitches I wouldn't be able to do it anyway because of the narrowness of the bit point.

gotta find something to make that nut out of for John, no sense in making the bolt if you don't have something to screw onto it.

[ScrapMetal]

Just a little more detail on the Acme thread from an old copy of "How to Run a Lathe" -



-Ron

[TomG]

(09-30-2012, 10:08 AM)ScrapMetal Wrote: Just a little more detail on the Acme thread from an old copy of "How to Run a Lathe" -

Good info Ron.

Those Acme thread gauges are indispensable when cutting Acme threads. It's very difficult to get the flat on the tool the proper width without one, unless you happen to have an optical comparator kicking around.

Tom

[dallen]

I got me one of the cheap chinese gauges, don't have a comparator and my eyes ain't what they was yesterday so this is going to be fun trying to get it right.

I want to thank all of the guys that have posted encourgement and tips to help me with this. please continue if you can think of something like don't use carbide you will break it like I already did this morning on a UNF thread another ten bucks down the chip pan

[PixMan]

I have one of those gauges, and I even looked at it once right after I bought it!

When I make threads, I'm more often than not using pitch-specific full-form inserts. With those, I just have to align the QCTP to be perfectly square, and away we go!

If you are grinding an ACME tool by hand, I find it easier to make a nearly sharp point tool with the 29º included angle first, then carefully grind the tip a tiny bit at a time (no pun intended) until the tip fits into it's proper notch in the gauge.

[big job]

I dont know if this helps at all but Wholesale Tool has pre-ground tools in all sizes.
all size lf & rt taps too. Guess I got luckey on flea bay a new Starrett Acme gauge
5 bucks. Origional package, looks like in the 1940s