Chevalier Broken Y axis Ball Screw

I'd like to get pointed in the correct direction for the following problem at my job.

Currently we have an older model Chevalier knee mill that's been converted to 2 axis CNC with Proto-Trak Edge controlling it along with all the hand wheels still.. About 2 months ago the Y axis ball screw snapped at the machined step in the screw for the angular (assuming) bearings at the front of the machine. After contacting Southwestern Industries I was given a part # to order a new ball screw and nut for this machine.

Once it showed up, I spotted quite a few differences that makes my not want to try to use it
-Around 2" too short in the machined end
-The machined bearing area of the shaft is shorter than the original
-The ball screw portion is about .5" shorter
-The ball nut is twice as long (not an issue unless once on the machine it risks coming off of the end of the screw)
-The ball nut flange has two holes within 45* of each other rather than the original with 2 holes 180* from one another.

My next attempt was to contact Chevalier. Due to the machine's age they had to talk to the factory in Taiwan they said. Upon hearing back, I'm told the machine is too old and the ball screw and nut for that model are not available.

So, that puts me to where I'm at now--playing maintenance man and trying to fix rather than ditch a useful machine.

It'd be nice to send back the wrong ball screw to SWI and put $900+ back into the company's pocket. Can this broken ball screw be successfully fixed based upon the location it was broken? I can tig weld it but worry about changing the metal strength and also keeping the two pieces concentric. It obviously broke in a location under a lot of load if the machine is crashed in 1 direction so strength is important.

I'm also told by SWI that sometimes extensions are given for adapting new ball screws to older machines. Taking the broken machined part of the old screw, cutting it down, drilling/tapping, and then adding that to the new screw could possibly re-allow the use of the hand wheel and measuring ring as before. The ball nut flange can have a second mounting hole drilled in it no problem too. Is this extra work worth it though.

Thoughts?

Below are pictures of said ball screws and the machine.
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Since there's no replies, can anyone recommend a reliable custom ball screw supplier to remake this part then?

Here is the first Google hit I got. Looks like they could do it. Ball Screws – Motor City Spindle Repair

If you have a lathe at work, It would be pretty easy just to buy a Thomson ball screw and just make it like you need it. That's what I would do.

http://www.thomsonlinear.com/website...all_screws.php

Just sent the SWI ball screw back today for a refund and will be looking into the options you provided or another provider. I did contact about 3 repair shops/suppliers via their online forms but heard nothing back. From my understanding, once I get through the outer hardened layer then machining should be normal? We do have a Jet 13x40 lathe at work I could put to use for this--need to practice threading first though as I've never done it.

Your 13x40 should work fine. I have a Jet 13x40 also, nice lathes. Threading isn't hard, but it does take some practice to get it right. I have never turned a ball screw before, so I'm not sure what you'll run into. But, I do have a 5/8 Thomson ball screw in the back seat of my truck, and it needs some lathe work on it, so I'll check it out tomorrow and get back to you. I did do some filing on the end of the screw in the thread area and it did not seem all that hard. Worst case, grind through the hardened area.

The other way you could fix the broken screw would be to bore both ends of the broken screw and put in a pin, then TIG weld it. Or make a new end but longer with the pin built in. Then stuff it into the bored end of the screw section and TIG or pin into place.

Given where it broke, I'm going to say somebody forgot to put a radius in the corner, and maybe add in a bit of misalignment, over time you get a broken shaft due fatigue. There is no way that normal radial or axial loads could cause that break. If you look carefully at the broken ends I'm guessing you'll find stress evidence.

Late reply, but I ended up doing the modification you mentioned above--drilled the broken pieces, installed a dowel pin, and welded it back together.

I've had to work on this machine probably 2-3 more times since, most recently drilling out the ballnuts to accept 8mm thread bolts over the standard 5mm thread bolts which kept backing out or snapping. I love and hate this clapped out mill......

Machines are fun :D Happy to hear you got it fixed.