Anyone actually figure out the table rock issue?

[Fast01]

I've been reviewing all the old posts in regards to this ans was wondering if anyone actually was able to eliminate the table rock issue? I've been playing with my Tri-Power a bunch lately and would like to resolve this problem. I've only been using my machine to polish crankshafts and I'd like to get more use out of it. It's sad, but any small parts I've had to make or modify I've been doing on my X1 with extended X and Y with pretty good results.

[TomB]

I got rid of most of the rocking and I think I know how to get rid of it all but I have not yet got around to it.

I was actually looking for why my table did not crossfeed smoothly so I took the table and casting below the table off. Then I coated the dovetail on the casting with Prussian Blue and manually rubbed the casting against the tabletop dovetail, on the side opposite the gib. I found the contact was bad, i.e. spotty and only happening for about 3/4 of the dovetail length. I took an Arkansas stone that was left over from when I sharpened wood carving chisels and stoned the casting surface. I'd spend about 20 minutes on it then reapply blue and check it again. After most of a full day I had it stoned so about 1/2 of the dovetails made contact. It actually looked like there was two planes machined into the dovetail and I was getting contact on all of one of the planes. (The line of demarcation was too straight to have resulted from my stoning it.) When complete the table moved much better.

Then while I had it all apart I decided to use the bluing to check the casting- to-lathe-way dovetail. It was just about as bad. Basically the dovetail surface on the casting (the side opposite the gib) seemed to be bowed. Depending upon how I held the casting against the ways I could get either the tailstock or headstock end to make sliding contact but not both. I spent the next day with the stone and made the sliding contact much smoother and longer, but not perfect. When I put it all back together again I noticed that the table left/right motion was smoother and that there was less table rocking. That makes sense because as the table-to-lathe-ways dovetail gets straighter there is less opportunity for the table to rock on the high spot in the center of the dovetail.

I have a surface grinder that is not running. As I get time I work on it and it will be running by year end. I now plan to buy a cup wheel for it and then too fully grind both dovetails. I expect that may fully resolve the rocking and stiffen the machine enough to eliminate some of the mill chatter.

While taking things apart I also noticed that there are two socket head cap screws that hold the under-table casting tight to the plates that support the crossfeed lead screw thrust bearings. Those two cap screws were not recessed into the slots designed for them and instead were on washers that bridged the slots. The washers were collapsed into the slots and that allowed the table more motion. I fixed both things at the same time so I don't know how much looseness each contributed.

Tom

[Fast01]

Hmmmm, good stuff! I planned on tearing the whole thing down and checking the mating surfaces. From what I've read on here it seems to me that's where the problem lies. It's nice to have some confirmation from experience, thank you! I guess I'm gonna plan for some long days of stoning over the winter!

[Bell 430]

I had my table rock fixed by a local machine shop. they laid it up on a milling machine, cleaned out both sides of the dove tails, with a dovetail cutter.
They had to take off .006 to clean everything up, now I have .0001 table rock, i think thats acceptable. they charged me $250.
According to the machinist(Who has probably been around since moses) he says when the castings are made, there no allowing them to "AGE". He says they should sit outside in the weather for about 18 months before they are machined.

[ab4td]

I bought one of the Eldrorado Bridgemills in 2003. As a newby machinist I had a lot of difficulty with getting the machine to hold proper dimensions. If I tightened the gib strips tighter, the accuracy improved, but eventually I could barely turn the lead screws. I was attempting to convert to CNC control and this was more than my servo motors could handle. I finally figured out that both gib strips were severely bowed, so both axis were
rocking. So if i changed directions in any direction the table position might be off as much as .010". I ground the strips flat, and I can machine parts with repeatable accuracy.

[terrycan]

I am a new Shopmaster owner. My machine appears to have the table rock issue. Let's talk!

Terry

[mikeamick]

And how about a description of how to tell if my machine has this
dreaded disease ..

[smallblock]

Originally Posted by mikeamick And how about a description of how to tell if my machine has this dreaded disease ..

This was an issue mostly on the older style machines with the X axis leadscrew on the front of the machine. If the gib was warped, then as the table went left and right it would tend to rock on the axis. This would cause it to cut a taper going in and a " drag" cut on the way out. Warped gibs could be from the factory, or as a result of over-tightening the center lock over a period of time. On my old 17-20 XMTC, I flattened the gibs several times over the years. Its pretty easy to do- just remove the gib and lay it on the mill table- you will see any warpage as a gap under the center. If its severe, you can carefully bend it by hand to get close, then use a belt sander to flatten it on both sides.

[mikeamick]

I have the shopmaster 2000 without quadralift ... which I thiiiiink might have
been the 1720 gold ... so I will have to look.

thanks