Long skinny threading

[Illinoyance]

Lee Valley sells the hardware kits.

Acme threads on a handscrew? All I have seen were UNC threads.

[754]

Der erste satz war lustig...

[Dan Krager]

Zu früh alt, zu spät klug. I finally got smart (thanks to advice from above.... ) and mic'd the rod and it shows up at 0.377", i.e. 0.002" oversize. DOH! For the first pass, the die was pressed open by the stock set screw and that allowed me to thread the first pass easily, which was oversized. Today I finished LH threading the material on hand by measuring the at rest gap in the die. Then I put it in the shiny stock with the set screw pressing 90° to the gap and compressed the slot 0.002" using feeler gauges to measure. The set screw was not in a dimple and I fully expected it to spin in the stock, but it held and a second pass on all the oversized LH threads allowed the rod to spin easily in the mating dowel with no noticeable slop.

So, the shiny new stock will get two more set screws machined in to secure the die in the stock and allow easy adjustments when needed. Less than 1/3 of my dies have adjustment slots, but any replacements will definitely have them.

Next up is the RH threaded end which should go quickly now. Then some brass ferrules turned from hex stock and London Pattern Handles machined and turned.

Thanks again for all your help, gentlemen!

DanK

[754]

Dan the good part... is you only have to learn it Once.. well most of us..
not sure if you are referring to it maybe being off size.. but opening it up, then it worked better but was tight... made me think..
Dies dont deal well with oversize barl,

[elf]

An even better option when you don't have a follow rest is to hold the stock in tension instead of compression. A tailstock chuck works well for this. It's also a nice project for the lathe😄😄

[Dan Krager]

Now, why didn't I think of that.


Don't answer that. LOL!

DanK

[754]

Mic the material , if its .375 could be part of problem. .370 be fine.
follow rest , some if us dont have one.. in 30 years I never got to use one.. do i described a work around..
ANOTHER TRICK.. if precision is not required... only have about 4 or 5 inches out of chuck with tailstock support. Cut thread to fit, then advance out ...pick up existing thread .,continue..

[Dan Krager]

RB211, it's not a point of contention as I see it. I just don't have a follower of any sort. I think the lathe threading ion this skinny 3/8 rod 18" long is a good idea...I just am unable to do it at the moment so I'm trying to find another way to do it. And I think I have another way to do it under power now.

By using a different stock I could open the die a couple thousandths and that made all the difference in the world in the forces required to spin the rod through the hand held stock. So, using the setup pictured, the keyed chuck held the rod securely without horsing it down too hard and it took about a minute and half to turn the 9 inches of left hand thread. Lots of oil, chips falling out of the die into a bucket on the floor, and a vice held start before putting it to power works like a charm. The heat build up was significant but not untouchable. I'm impressed with the performance of that ALPs die.

A test fit revealed that the thread is too snug, so I'll repeat the process with the die held to normal size. The hold up to doing that is the old stock that has three set screws to hold the die are all stripped out. The new stock has only one set screw and it's metric, so I'm setting up to drill and tap two more setscrews to match the original set screw. Then it should work to hold the die at finish size.


DanK

[RB211]

In the lathe with a follower rest, single point. Why is this a point of contention?

[elf]

acme are 29, I think you're thinking whitworth which is 55

Sorry, I wasn't paying attention

[mickeyf]

Acme threads have a 55 degree angle between the faces,

55 degrees? This is news to me. Even the link you provided shows different. Only thread I ever heard of that was 55 degree was Withworth, and we don't generally see those on this side of the pond.

[Mcgyver]

Acme threads have a 55 degree angle between the faces, metric trapezoidal threads are 60 degrees. The profiles on each are thicker than UNC or standard metric threads.

https://www.rr-99.top/products.aspx?...e+thread&cid=6

acme are 29, I think you're thinking whitworth which is 55

[elf]

Acme threads have a 55 degree angle between the faces, metric trapezoidal threads are 60 degrees. The profiles on each are thicker than UNC or standard metric threads.

https://www.rr-99.top/products.aspx?cname=acme+thread&cid=6

[Dan Krager]

Thank you all for the greatly helpful posts. I found the McMaster Carr stuff and will strongly consider ordering from them when I get to where I need more material.

I'm confused about the references to ACME threads. I thought, perhaps mistakenly, that ACME threads (in U.S.A) were in the family of square threads. ???? I've never seen square threads on these woodworking hand screws. I must be missing something.

Anyway, I've tried to secure the blank rod in a brand new 6" 3 jaw chuck on my Smithy and spin it slowly in reverse while hand holding the LH die stock. I was excited at first that I could actually hold the stock from turning (I had started it by hand) until I realized that the rod blank was spinning in the chuck! Grrrr.. I horsed the chuck key in all three locations again, gained a pittance, and it still slipped. I didn't mess around with it further even though it would save a LOT of time and seemed to have the power to do the job. Nor did I proceed to set up for "precutting" the threads on the lathe for finishing by hand.

I took the round die out of the nice hex stock with chrome plated (ooooh look at the shiny object) ratcheting handles and put it in the underbuilt cheap round stock with bent handles with three set screws. By putting the middle screw in the V at the split and tightening all screws as far as their stripped threads would allow, I set the adjustable guide firmly to the rod and proceeded to try again, determined to do 32 half rounds before I expired. To my great surprise, it took about half the effort compared to the previous try and the chips peeled out cleanly leaving very adequate threads. I tested the fit and it's a bit tight, but that can be easily fixed with a powered rod holder (lathe or hand drill) to run the die back and forth after a small adjustment. So I was happy with that success and learned something from it. Now that doesn't mean I will never put a round die in a hex stock, but I will be sure to pay attention to how it's done and add set screws if needed.

Some cheater handles ease the pressure on hands and it is going well enough to continue a bit at a time until I can figure out a powered solution.

DanK

[Mcgyver]

Did you notice the oddball threads that it's available in? E.g., 3/8-10 & 12. 'Never heard of 3/8-10 & 12, but they have it in LH !

I didn't. The 10 sounds useful, hundred thou to the revolution. I confess I'm ignorant on acme TPI standards. I mean I've made a number of them, but its always been follow the leader, replacing some existing part vs design. i.e. the tpi was set going in.

Left hand acmes are used on a lot of machine feedscrews (maybe also HD turnbuckles?) so I'm not that surprised there's a lot of LH stuff available