threads

[teddy52food]

Gear box on an old machine has timkin bearings with 2 nuts to adjust play and lock
it. Threads were stripped. Couldn't find anything & the threads on the shaft were
damaged too. Put the shaft in the lathe & trued it up. They were 18 TPI & 1 3/8 shaft.
Then I had to cut threads to match the shaft. A lot of trial & error taking my time I
got it done. It has been many years since cutting threads on the lathe.

 

[dr sportster]

Just never disengage the back screw.

 

[Ultradog MN]

Attaboy!
It's kind of like riding a bike.
After not doing it for many years you may be a little rickety at first but you never really forget how.

 

[Janicholson]

Watch that little threading wheel go round and round. Jim

 

[John Garner]

A lot of old lathes didn't have a thread dial.

There are, of course, ways to catch a thread without a thread dial, but simply keeping the half nut engaged with the lead screw and reversing the spindle's direction is a whole lot easier for the guy who isn't in practice.

 

[Janicholson]

True it is. Jim

 

[Butch(OH)]

My Colchester lathe half nuts will pick up an even number pitch at any point on the dial. I actually don't even need the engage the dial for even pitch threading. It is needed for odd pitches and half and quarter pitches. But it also has a separate feed shaft from the threading shaft, I would reakon that makes a difference. A quick trial on some scrap will quickly discern if it works on another machine

 

[Ultradog MN]

''keeping the half nut engaged with the lead screw and reversing the spindle's direction is a whole lot easier for the guy who isn't in practice.''

Unless he doesn't have reverse on his spindle...

 

[Phil Tibbetts]

On a lathe with a threading dial , even threads any line, odd threads numbered lines, half threads every half revolution. quarter threads every full revolution. That's how our lathes were set up .

 

[Harold Hubbard]

I have been reversing the spindle for years. Just found out my ancient Hendey lathe has a reversing lead screw. You just lift a lever at the end of the cut, and the carriage reverses. When it gets back to the beginning, there is a neutral position that holds it while you reset the cutter, then drop the lever into forward and away you go.

 

[MarkB_MI]

Good job, Teddy! I'm not a machinist, but that sounds tricky. And, if I recall correctly, you have some mobility issues that make it difficult to operate a lathe.

 

[4wdtom]

I have repaired a few stripped threads by turning the male down to the next standard size and threading it and usually making the nut. And one or two where I didn't want to reduce the diameter any more than necessary I just trued it and cut a thread, then a nut to match. No standard diameter. Threading is made easier by setting the compound (if your lathe has one) at 29 to 30 degrees so the tool only cuts on one side when fed in with the compound. Chips clear easier, the tool only rubs or, if at 29 deg., cuts nearly nothing on the off side. To get the infeed for the compound at 30 deg. divide the threads per inch into .75 and for 29 deg. .742. Of course sneaking up on a good fit is still required but depending on the thread you are trying to match/fit, tolerance, shaft dia. starting with, etc. it will get you close.

 

[teddy52food]

No reverse.

 

[teddy52food]

Can't do it sitting in a wheel chair. Can't stand up for long either.Make a few cuts & sit down again. Takes twice as long to get only half as much done.

 

[teddy52food]

I had the compound paralell to the bed & used it to line up the bit after engaging the half nut. I guess at an angle would work too. But how do you know how deep the cut is that way?

 

[teddy52food]

I made a mark on it so I engaged it the same every time.

 

[teddy52food]

How does that work with no reverse????????????

 

[wp6529]

(quoted from post at 10:17:08 07/07/23) Can't do it sitting in a wheel chair. Can't stand up for long either.Make a few cuts & sit down again. Takes twice as long to get only half as much done.

One of those fancy power stand-up wheelchairs would probably work. Or loose the deeper chip pan and foot brake if applicable and might get wheelchair clearance under.

 

[dr sportster]

Odd -- no reverse

 

[4wdtom]

With the compound set at an angle, 29 to 30 deg., see my post above for depth of cut using the compound for infeed. Using this method you use the cross feed to withdraw the tool at the end of the cut, returning to the original position for the next pass and advancing the tool with the compound. Some lathes have a stop you can use on the cross feed to return to zero I usually just set the dial on it to zero, back it out one turn at the end of the pass, then return one turn to zero for the next pass, advancing the tool with the compound.