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5/8-5 LH Acme tap anybody??

Awleaphart

Aluminum
Joined
Mar 16, 2019
Titles says it.
Got to make a lead screw nut for lathe cross slide. 5/8"-5 left hand Acme. I don't see any taps for sale this size. I can find a lead screw no tap.
A Leaphart
 
I figured.. NO PROBLEM.. highlighted 5/8-5 acme tap.. right click.. Google search... and didn't get back much..

However. You can buy 5/8-5 left hand nuts in several different styles. McMaster
Carr has quite a few from $33. to $68...

Buy the nut, do whatever mods you need to it, and be done, and use your lathe to make more fun things.
 
Yea.
I seen two. One is bronze and I don't think the Dia. is not large as i need. The other is cast iron. I didn't think you could use cast for a lead screw nut? My nut is 1.610 x 1.525 and the acme hole is close to the top of the nut. To the center of the screw from the top is .5205.
A Leaphart
 
For what it's worth, I requested a tap this size from Tapco a week ago, they advised me they cannot make this tap. Something something too coarse for the diameter to make grinding it feasible, said it would likely need to be molded(?). Regal was willing to quote it for me, still waiting on a price. Suggest using a dremel or some other toolpost grinder with a 5TPI acme threadmill on the lathe, cut it like you would any other internal thread. That or, if the application allows for it, upsize your thread to 3/4-5 which is a standard acme size.

Edit: If my previous quotes for special acme taps from Regal are anything to go off... $300-500 range is likely if you only get one.
 
Possible solution
If you have an existing worn out nut, buy the bronze nut, turn it down to a size that you can drill out your existing nut. Sweat solder new nut into hole in existing nut. If it will work on a horizontal mill X feed (and it does), it'll sure be sturdy enough for a lathe.
If need be, you can lock the cross slide by tightening the gibs and use the compound for feed.
 
That thread has a .425" bore diameter, with a thread depth of .110". To single point, you have to grind a tool from a piece of tool steel, the portion entering the bore will have to be ground down to around .300" in diameter neck, with a nose sticking out of around .120". The nose ground to 5 TPI Acme profile. The tip ground to about .070" width. I think I'll pass on this one!!!
 
Look up "This Old Tony" on YouTube.. He has a very good video on making your own tap... Pretty simple process if you have the tools..

Sent from my SM-N950U using Tapatalk

Here you go :)

 
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The lathe is a Breda BRF 150. I have already watched that video and thanks for passing it on. Its interesting. I have spoken to two guys so for that I have got to make Lead screw nuts in the pass and they don't seam to excited about ever trying to make one.
A Leaphart
 
I've replaced two lead screw nuts recently. One, half inch, I bought a bronze cylinder nut, machined some away and silver soldered a chimney on it for the tapped hole and boss that mounts it to the cross slide.

For the other, a 5/8 - 8 acme LH I bought one of the cast iron cylindrical nuts and machined away what wasn't needed. A little drilling and tapping and it's back in the machine.

I can't imagine that with both subtractive and additive processes (turning, milling, brazing) whatever shape you need wouldn't be possible.
 
I think it is worth considering Peter's proposal and going to 5/8-10

for the reason he stated and because 5tpi on a 5/8 diameter is a pretty steep helix angle and seems like it could have a propensity to "unwind" itself under pressure/vibrations unless a positive lock is also untilized.

I say this knowing nothing about the machine in question, so maybe not an issue.

Barring that, modifying an off the shelf nut or grafting it into the original nut body seems like a good option, as already mentioned.
 
a few years ago I did a 3/4 -5 double start in 660 bronze for a lathe tailstock.
I turned a tool for angle and shank clearance heat treated it and ground the back side off free hand. I took quite a while with light cuts and alternating threads til it fit. 1/8 smaller sounds like a lot of passes.

Dave
 
Just a few facts. Standard pitch for a 5/8" ACME thread is 8 TPI. 5 TPI doesn't start until 1".

I suggest that a check is made to be certain it isn't a 2 start thread.

My reference? ANSI/ASME B1.5 - ACME SCREW THREADS

A Stub Acme would give more material and certainly be much more feasible and easier to make.

Stub Acme - ASME/ANSI 1.8

Standard basic thread height of an ACME thread is 0.5P.

For Stub Acme 0.375P, 0.3P (standard Stub Acme) or 0.25P.
 
Just a few facts. Standard pitch for a 5/8" ACME thread is 8 TPI. 5 TPI doesn't start until 1".

I suggest that a check is made to be certain it isn't a 2 start thread.

My reference? ANSI/ASME B1.5 - ACME SCREW THREADS

A Stub Acme would give more material and certainly be much more feasable.

It's not a terribly uncommon thread, but it is a headache. Nordic 15 (SB) and Victor 1640B both use this thread, Nordic is the cross slide while victor is the compound. Technically neither of these are "truly" 5/8-5 as they both have metric diameters. The first time I cut a screw for a Nordic 15 I assumed it was metric and promptly cut a TR16x5L thread while it was actually 16mm - 5tpi (.629-5LH). I'd imagine a lot of Chinese machines use this thread.
 
It's not a terribly uncommon thread, but it is a headache. Nordic 15 (SB) and Victor 1640B both use this thread, Nordic is the cross slide while victor is the compound. Technically neither of these are "truly" 5/8-5 as they both have metric diameters. The first time I cut a screw for a Nordic 15 I assumed it was metric and promptly cut a TR16x5L thread while it was actually 16mm - 5tpi (.629-5LH). I'd imagine a lot of Chinese machines use this thread.

I put the info into ThreadPal and was surprised it was accepted :):cheers:

Acme5.jpg

BTW 5 TPI and 5mm are very close to each other.

5mm = 0.19685"

5 TPI = 5.08mm
 
It was close enough that two worn nut went onto a new 5mm screw, but when you put the 5mm and 5tpi screws next to each other, over around 11” the threads would be aligned at the start and end but they would deviate along the length. That’s when I went back and double checked and sure enough, 5 tpi stayed aligned along the length.

I had been told the thread was a TR16x4L, I don’t know how they came to that conclusion..
 








 
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