Odd problem- table binds up slightly in middle of travel?

Ok- I am going to start complaining about this before I have enough information but....

I am setting up this Wadkin pattern makers mill and ran into an odd problem on the X table travel.
The table glides like it is on ice when extended to either side.
When brought to center it gradually tightens up- very symmetric binding- not a spot but a smooth symmetric transition from free to binding.
Not extreme- feels like stiction and if on a run you can power right past it but for use about the center of travel it is too much in comparison to how free the table is to each side.

I have the gibs free and if checked when binding they are still loose.
I just tore everything down so all parts are perfectly clean and well lubed.
The table is a bit odd?:
Feed on the X is done by a rack and pinion arrangement with a four start thread on pinion.
The whole machine is closely fitted so my first thought is that with table wear the settled table is binding the rack when in most used portion in center of travel.

I just got this together last night so will investigate today- first thing I will do is look at the rack to see if wheel backlash varies across travel and if so I will pull the pinion and see if that sorts table glide.

I don't have a iron straightedge of correct sort but do have a heavy Starrett precision rule which could be used as a quick check.
The table is a bit heavy so shifting it off machine is a not a casual affair so I think I would wait till I buy a dovetail straightedge before I remove again.

This is the mill:



Thoughts?

Thanks all

Is the rack visible from under the table? You could try putting a bead of grease on the rack (as uniform as you can make it), then run it to one side and check the results from the "squished" grease. It should be much thinner at the center if your guess is correct.

Milland said:

Is the rack visible from under the table? You could try putting a bead of grease on the rack (as uniform as you can make it), then run it to one side and check the results from the "squished" grease. It should be much thinner at the center if your guess is correct.

Click to expand...

The rack is visible and the pinion can be gotten at when the table if full over.
I dimly remember noting that there was no gunk in root of rack towards center and gunk off to each side when I had it in the parts washer.
I am suspicious....

I will check the table- if dead flat I will put an indicator in spindle and see if it floats up as table travels..
I will pull pinion and do the same.

The problem with this theory is that one would think the rack/pinion would have worn in with the table and not be binding.
One thing I failed to do is to index the rack/pinion before I took it apart.

Thanks

I looked at some info in Vintage Machinery.org manuals and it on the ones I looked at used ball bearings on the ways. Is yours that way? Also it talks about a lock screw. It would not take much crud on the ways in the middle that would make it tighten up or if the lock drags tight in the middle. It might be smart to just take it apart and clean it up. Be a detective and look for the problem.