Lathe saddle V groove

[kmanuele]

PM1130 lathe, a few years old and only hobbyist use.

Tracking down a long-standing carriage stiction issue, I disassembled the carriage assembly and removed the saddle. Not great machining in there, as expected.

What I noted was a narrow wear mark along the length of the V-groove on both sides. Very narrow is some locations, and a few skipped areas too. About half-way up each face, but this varies also.

You can see the corresponding markings on the ways V also, though this just polishing - no perceptible wear. The ways look good, straight and flat.

Using a straight edge on the faces (perpendicular to the groove), the high spots are obvious.

Info and photos from here and the 'net suggests these surfaces should be flat, 90-degrees, for maximum contact area with the ways. Correct?

I might try to correct this on the mill - an adventure Any suggestions?

Before I mess with this, might see if I can get a replacement saddle from PM -- in case I screw up this one.

K

 

[coolidge]

Look under the flat way at the rear of the lathe for paint. On a brand new lathe I feel some areas of travel are dragging, more difficult to crank through. I found patches of paint gooped up under there, it should be bare metal. The top/bottom of that flat way at the rear is also a pinch point that needs to be adjusted correctly. Not too little or too much but just right.

 

[Huub Buis]

I might try to correct this on the mill - an adventure Any suggestions?

There is a great risk, you do more harm than good and you probably don't wear this lathe down during your lifetime.
Start using the lathe and in time, improve things that really matter.

 

[RaisedByWolves]

Pics if the wear patterns would help greatly.

This could be nothing right up to a poorly manufactured machine.

Most of what the average user would do to correct things will likely make them worse.

 

[C-Bag]

As mentioned by the previous two posts you will likely do more damage than good. IMHO the last thing to use is a mill. If anything a light run of proper scraping would get rid of the stiction and set up the ways to wear in properly. But learning to scrape properly is a very deep and time consuming endeavor. I’m pretty sure pricing a new saddle will cure you from wanting to mess with it.

 

[ddickey]

You could turcite the saddle. You have to mill the surfaces to make up for the thickness of the turcite though.

 

[kmanuele]

Look under the flat way at the rear of the lathe for paint. On a brand new lathe I feel some areas of travel are dragging, more difficult to crank through. I found patches of paint gooped up under there, it should be bare metal. The top/bottom of that flat way at the rear is also a pinch point that needs to be adjusted correctly. Not too little or too much but just right.

Thanks. Been through all the likely cases. The ways are clear of paint, and all surfaces are flat, smooth, and unworn. Also verified that the pinion gear engagement is not too tight (lowered the apron slightly, no change).

 

[kmanuele]

There is a great risk, you do more harm than good and you probably don't wear this lathe down during your lifetime.
Start using the lathe and in time, improve things that really matter.

Thanks. Been using the lathe for a couple years. Happy with it, in general. The aggravation comes with doing a fine z- adjustment from a stationary carriage position. Because of the stiction, a lot of care is needed to avoid overshoot.

A complication with this machine is that the x-axis DRO covers the tailstock-side saddle oilers.

All the comments here have made me re-think my plan.

So thanks to all.

K