Hydrashift crossfeed nut specs

Hello,

I am working to get my 10x60 3hp Hydrashift lathe in shape. I had some pretty horrendous (150 thousands) backlash in the crossfeed and have been trying to get down to a minimum. In the process I discovered that the crossfeed taper pin was sheared off by a prior &%&*bag operator in what way I have no idea since there was no evidence of trauma to the handwheel. The handwheel was still turning the screw until I started to tighten nut at dial per the manual to take out backlash. I had to drill out pin in handle and drift out remainder in screw. I then put in a broken drill I happened to have that closely approximated the size to see if I could take out the backlash by tightening the nut at the dial. Lo and behold I got down to 12 thousands backlash. I also was tightening the crossfeed nut setscrew and top screw to accomplish this. When I got the backlash down to .0012 I decided to run the auto feed at low speed to check the function and along the way it seems I locked up and the crossfeed nut seems to have stretched above the cut and will not run the screw now. There was already a crack in the nut and wear in the threads, but I think I exacerbated it.

Sorry for the lengthy intro, but my question is does someone have specs on this part. I believe it is bronze as most are, but it seems to have an 8 pitch acme thread, which is a real bas##rd to find. I am not even considering calling Cincinnati to source part, and now I need to make one. I do not have a mill yet, so I am trying to find some specs for this part. Any and all help is appreciated.

Thank you

What's the readings on your micrometer dial? If .200 or .400, then it's 10TPI (200 being direct, 400 being diametral). If it's .125 or .250, it's 8tpi (.125 being 1/8"). Might want to replace the screw while you are at it, sounds like it has pretty severe wear if it locked up at one end or the other of the travel. Also, never use a piece of drill rod for a pin like that. Those pins are very soft and designed to shear before it breaks anything important, as you just discovered. Try Mcmaster-Carr for the replacement nut.

As for backlash, backlash on a lathe is not nearly as big a deal as on a mill. Lathe operations are one direction or the other. You are working outside or inside. As long as you make sure to only approach the work from the same direction, backlash is not really a problem. If you overshoot your number when setting up a cut, don't just back off, back off a full turn and try again, to keep the screw and nut loaded the same direction.

Thanks Mike C. You know, I was working around the backlash and it was cutting great, but I guess I got greedy and was just trying to tighten the whole system up. I was aware that the nut had a crack in it (seems like a goofy design with a slit more than half way thru part) It looks like it is a 5/8-8 LH Acme thread. My dial is 250 diametral. Looks like Mcmaster Carr has the bronze nut in the correct size. I was using the drill bit just as a temporary pin to try to work on the backlash while I looked for a new taper pin. I just ordered the nut and the taper pins from mcmaster carr. I agree about replacing the whole screw. I am going to have to hand file the bronze nut to size, so it may come out looking like an egg. I am going to start with these 2 parts and see where it gets me. Thanks for the supplier source!

Nobody cares if it looks like an egg of you put it all back together and it works right. McMaster-Carr has EVERYTHING!

Success! Unbelievably, the order from McMaster Carr came on Saturday, and I just ordered Friday, so they have a new customer for sure. I was able to get the taper pin installed and the crossfeed handle is back to right. I trimmed up the nut and threaded it for 3/8-24 and now the crossfeed is back in action. It seems pretty evident that the crossfeed screw will also need to be replaced. There is not a ton of slop and the threads look clean, but it does seem to have a slight wobble or runout. Once I get a mill, hopefully soon, I will take on this project and put a more professional looking nut back in the system. Thanks again for great info!

I don't have a lot of time to get out in my metal workshop, but the crossfeed slop in my Hydrashift 10x36 is on my list to address. I looked at my at bit, and think it's related to the attachment to the taper attachment, but that's just a guess at this time.
Jack