Need help with Y-axis taper gib

[AndrewH]

I recently purchased and took delivery of a PM-30MV, last night I was finally able to get it reassembled on the stand.

The problem is, the Y-axis is very tight, so I went to adjust the gibs and even when it’s set at the loosest it can go it’s still not enough. The rear set screw is bottomed out so it can’t push it in any further and the other side is only hanging on by a couple threads.

If I take the gib completely out it moves smooth as silk but as soon as I put it back in it gets really tight and with both screws at their maximum adjustment it’s still not enough. It will be smooth moving towards the column and then suck the gib in when going back out and get tight again.

Not exactly sure what to do, I don’t have much experience with tapered gibs as most
Of my machining experience lies in large CNC machines.

Any help would be appreciated!

 

[T Bredehoft]

Contact Matt, he'll make it right. Three year guarantee, right?

 

[AndrewH]

Contact Matt, he'll make it right. Three year guarantee, right?

Yes, but I posted just to check and see if there’s something I may be doing wrong. I don’t think so because I did the X-axis first and it’s feeling smooth and easy to move.

 

[HBilly1022]

I could be wrong, but it sounds like you have the 2 adjusting screws adjusted so that they are not both snug to the gib. ie one is too loose and won't hold the gib from sliding back when you reverse direction. Try snugging up the one that is only held on by a few threads

 

[AndrewH]

I could be wrong, but it sounds like you have the 2 adjusting screws adjusted so that they are not both snug to the gib. ie one is too loose and won't hold the gib from sliding back when you reverse direction. Try snugging up the one that is only held on by a few threads

No, that’s the problem.

There’s two screws, one of them is the retaining screw that fits into a notch in the gib and the second one in the back is the one that holds it in place/pushes the gib forward into the retaining screw (which loosens the fit and makes the table easier to move).

Hopefully that makes sense, with that said even with the pusher screwed bottomed out in the hole and the retaining screw snugged down the table is too way too tight. Since the screw that pushes the gib forward to loosen the fit is bottomed out in the hole there is no more adjustment possible.

So in conclusion I feel like maybe the gib is either the wrong length or the taper on it is incorrect.

 

[Bob Korves]

The screw that fits in the notch is the one that adjusts the gib. It both pushes and pulls the gib. The other screw is to lock the setting when completed. Tightening the lock screw can change the gib fit slightly and so might require more fine tweaking of the adjusting screw. Do not over tighten the locking screw. That can warp the gib, making the setting tight.

 

[AndrewH]

FYI guys, after more tinkering and a lot of experimentation I have figured out the problem. Either the base is warped or the stand that came with it isn’t flat. When I loosened up the bolts holding the machine down all of a sudden it started traveling smooth as silk with the gib installed. Looks like I’ll need to shim one corner of the machine .05 or so. At the moment I’m able to have 3 of the 4 bolts tightened down and the 4th one just snugged so I don’t think it’s going anywhere!

Thanks for the suggestions everyone!

 

[HBilly1022]

Congratulations on finding the problem. Now it's time to play.

Enjoy your new mill.

 

[AndrewH]

Congratulations on finding the problem. Now it's time to play.

Enjoy your new mill.

I wish! I ran 240v to it today and cleaned off the cosmoline but since I had to disassemble it to carry it downstairs I now have to square the column and tram the head. The new problem is that I don’t have a cylindrical square nor a lathe to make one and even tiny ones are pretty expensive.

Any ideas?

 

[HBilly1022]

Do a search for tramming a mill. I'm new at this stuff too but have not heard of using a cylindical square to tram a mill. The way I have seen it suggested, just involved using a dial indicator attached to the mill spindle. Lots of youtube videos showing this.