Damaged spindle threads, what to do?

[Dan Forman]

I was trying to get rid of some persistent tear out, and had the bright idea to put the lathe in reverse, and use my scraper on the far side of the bowl. I'm not in the habit of using the set screw to hold the chuck on the spindle, as I'm forever going back and forth between chucks and face plates... I bet some of you can see where this is going.

So I'm scraping on the far side of the bowl at a pretty slow speed, and the next thing I know the bowl stops moving and the chuck is spinning off the spindle. It was going so slow that it didn't fly off, just sat there bouncing around a bit, but it did damage the threads enough that I can't screw it or anything else on the spindle. It doesn't look all that bad, just the first thread is a little rough, the rest are fine. Can I use a die to clean up the threads? I would imagine a new spindle would be expensive. I won't know if I need a new chuck adapter until the spindle threads are fixed. Any ideas? Thanks.

Dan

[Jeff Nicol]

Dan, You could take a small file shaped like a triangle for sharpening saw blades and file thebad parts by hand until you can get a chuck or faceplate to thread on. Just take your time and remove the dented in places that keep the threads from starting. What are the threads? 1 1/4" or 1", you could get a die, but some times are worse if you get it started wrong. Take a pic and send it to me and I can give you more trouble shooting on it.

Jeff

[Mike Minto]

there is also a tool called a 'thread file' - do a search, they're not expensive. you just lay the proper face of the thread file on your damaged threads, and move it back and forth, restoring the threads. hope you get it fixed. mike

[Dustin Lorenz]

Dan, You could take a small file shaped like a triangle
Jeff

That is going to be your best bet. I have a cheap little set I picked up in the bargain bin area at a local hardware store. The files I bought were labeled as jewelers files. I have had to fix up some very fine threads here at work on a CNC Turret Punch Press for the main ball screw very expensive to replace. It can be done rather easily just don't rush it, and if you have a rather long section of threads to work with and only the first full turn of threads are bad the end could always be ground a little, but you would probably still want to clean them up a little after that. Your starting thread should have a decling taper for easier starting.

[Steve Schlumpf]

I use a set of jewelers files and they work great. They come in a variety of profiles and should be easy to find at any hardware/home improvement store.

[Ken Glass]

Dan,
I concur with all the above. Most of the time just removing the top and sides of the boogers on the damaged threads will allow you to repair it enough to resume work. You can tell by the responses we have all been there.

[Jim Underwood]

You can probably pick up a thread file from your local auto parts store. This may work better than a triangular file in that the angle of the cutting teeth are correct. A triangular file is 60 degrees, which tends to take off more than you want off the top of the thread. The other reason the thread file may work better is that it has more than the one tooth across the file to keep the correct pitch (tpi) on your threaded workpiece.

I've used both, an they'll both work for small dings. From your description, it sounds like you just need to file it a bit and you'll be good to go. Having the first thread a little dinged up won't hurt anything.

[Kyle Iwamoto]

Boogered up threads? I've NEVER done that...

Don't feel alone....... Even the local *marts have those triangle files. Chase from the good threads and follow the contour to the damaged section, it will be fine. Only 1 side of the thread should be damaged, you can use the good side to guide you too. As you can tell, I've personally never done that....

[curtis rosche]

the other thing you could try if you dont have a file or a die, take a cold chisel and grind the edge to a point that is close to what the threads should be, and carefully tap it into the threads.

[Dan Forman]

Thanks for the information, sounds like it should be relatively easy to fix. I was thinking that even a tap that large would be hard to find and quite expensive. I'm glad that you all have good memories to be able to access such tips without having any personal experience in the matter. I feel better now.

Dan

[Dan Forman]

A little judicious use of the file and I'm back in business. Needed to order a new adapter for the chuck though. Other chucks and faceplate work fine now.

Dan