Gib locking & DRO

[petertha]

I just finished installing a DRO on my lathe. It was a bit of a headscratcher & the usual tradeoff's with positioning & mounting, but overall I'm happy with how it came together.

One thing I'm noticing now via the DRO display is how much the cross slide can move simply by tightening down (locking the slide) for final cuts. It can displace several thou, generally in same direction, but not always. The set mechanism is basically a M4? bolt end that contacts the gib strip, The bolt end just has a simple chamfer, makes total sense how it can impart an unwanted push by torquing motion.

What can I do about this? Insert a ball bearing between bolt & gib strip? I re-adjusted the gibs themselves when I had it apart, they are not loose, if anything just a smidge stiff.

[EdK]

(10-29-2012, 01:26 PM)petertha Wrote: I just finished installing a DRO on my lathe. It was a bit of a headscratcher & the usual tradeoff's with positioning & mounting, but overall I'm happy with how it came together.

No pictures, then it didn't happen.

Quote:Insert a ball bearing between bolt & gib strip?

That's what I've done and it works fine.

Ed

[petertha]

EdK> No pictures, then it didn't happen.

You drive a hard bargain, but I like the way you think. Here ya go,

http://www.metalworkingfun.com/showthrea...3#pid13653

[TomG]

You mean the locking screw pushes directly on the angled gib? It's no wonder it moves when tightened. There should be a pin under the screw with an angled end to match the gib, then there is no way the rotating screw can push the gib sideways as it locks. I would not use a ball because that will probably put little dents in the gib where it bears and eventually the problem may return as those dents start overlapping.

Tom

[EdK]

(10-30-2012, 06:37 AM)TomG Wrote: I would not use a ball because that will probably put little dents in the gib where it bears and eventually the problem may return as those dents start overlapping.

Tom

Good point Tom. Maybe a brass ball would be best rather than a ball bearing.

Ed

[TomG]

(10-30-2012, 07:00 AM)EdK Wrote:

(10-30-2012, 06:37 AM)TomG Wrote: I would not use a ball because that will probably put little dents in the gib where it bears and eventually the problem may return as those dents start overlapping.

Tom

Good point Tom. Maybe a brass ball would be best rather than a ball bearing.

Ed

Yeah, those gibs are normally just cast iron. I would skip the ball altogether and just use a pin with an end to match the angle of the dovetail, that's pretty much standard practice. It can be steel as well because there is no point contact or rotation.

Tom

[stevec]

(10-30-2012, 06:37 AM)TomG Wrote: I would not use a ball because that will probably put little dents in the gib where it bears and eventually the problem may return as those dents start overlapping.
Tom

Dent yes but Dents? why would there be more than one dent? Doesn't the gib travel with the cross feed slide and the locking screw?

[EdK]

My mill came with ball bearings that press against the gibs to lock them in place. I guess that doesn't mean that it's a good design though. They do make dents in the gibs, I've seen them on mine. I'll have to consider making some of the tapered rods.

Ed

[TomG]

(10-30-2012, 08:43 AM)stevec Wrote:

(10-30-2012, 06:37 AM)TomG Wrote: I would not use a ball because that will probably put little dents in the gib where it bears and eventually the problem may return as those dents start overlapping.
Tom

Dent yes but Dents? why would there be more than one dent? Doesn't the gib travel with the cross feed slide and the locking screw?

Good point Steve. If the lock moves with the gib it would always bear in the same spot, but I would still recommend a pin over a ball for more contact area on the gib. Maybe if I had a picture...

Tom

[Mayhem]

(10-30-2012, 10:02 AM)TomG Wrote: ...Maybe if I had a picture...