Miter Jack Screw

Re: Miter Jack Screw

Greg Deavers in Stillwater

>Hi Frank,

You might be able to use a riffler or triangle file and chase (burnish?) the threads lightly then use some 220-320 sand paper to realy smooth the thread lands with.

The idea is not to remove material but to debur the edges, dings, other gouges in the thread lands, etc.

Hope this helps some.

Greg

I like that idea

jim_reed@marietta

>I would also try an emory board or homemade sanding stick. Do it slowly and check progress often so you don't overdo it. Less is more. Good luck.

Re: Miter Jack Screw

Roy from Cincy

>I just want to point out that any modern tap or die that you might get may or may not have the same pitch, depth and threads per inch as the old threads that you are working on. You need to check that carefully before buying anything.

I'm going to suggest that you look closely at the female threads in the blocks and see if the holes have become egg shaped. I'm going to guess that the shrinkage across the grain in the relatively more massive blocks will have been more than on the smaller threaded jack screw, which may still be nearly round. If this turns out to be true, filing down the male threads may make them very sloppy on the long axis of the hole by the time they are small enough to clear the short axis. If so, chasing out the female threads would be better.

Lots of luck and let us know how it comes out.

Re: Miter Jack Screw

Frank Mutchler in Colorado Springs

>Roy, the jack screw does appear to be almost round. When I roll it on a flat surface it indicates a little eccentricity but not much. I didn't think of the threaded block becomming egg shaped...good point. I'll get an inside caliper and see how the internal threads mike out.

I understand the necessity to match the pitch of the threads should I try to chase them. I have measured the pitch at 5 tpi on the jack screw and the thread shape is a 'v'.

I bought a mini Jet lathe and it's still in the box...this might be a good time to get it out and chuck the jack screw between centers to get an actual run-out. I stated above that the run-out doesn't appear to be too much but it really doesn't take much to act the way it is either.

I don't have proper lighting for the pictures but they do give you an idea of the shape/pitch of the threads.

Re: Miter Jack Screw

Frank Mutchler in Colorado Springs

>Thanks, Greg. As I mentioned to Roy, I think I'll try & get some measurements of the threads and then use your suggestion judiciously ;>)

Re: Miter Jack Screw

Todd Hughes

>I agree with Roy that the base the threaded rod goes though is probably out of round and that is why it sticks. If the threaded shaft is OK I would look for a large wooden clamp that it fits, cut out the threaded hole in the Miter Jack and replace it with the hole which you cut out of the clamp.Could probably use the arm out of the clamp as well if you can't find a clamp the original miter screw fits.Could always go with a iron screw and box as well.....I've seen quite a few of these devices but think this is the first one I believe I have seen where the jaws are in two pieces .....Todd

Re: Miter Jack Screw

Frank Mutchler in Colorado Springs

>Turning a tap on a lathe won't be that much trouble. I'll match the pitch, etc. of the jack screw and run it carefully through the screw block. Probably won't get it done for a month or so...two big projects have to get out first.