Lapping the X-Axis

First, a couple of things:

1. Don't do this unless you are prepared to take the time to clean all the grit away properly when the lapping has been finished. The clean up can take as long or longer than the lapping itself.

2. If it ain't broke don't fix it.

Materials needed:

Lapping compound:

I made up a lapping compound using 1000 silicon carbide grit, machine oil, and a slight amount of mineral spirits to thin the slurry out. If you can't find silicon carbide grit then you could use a commercial lapping compound. I decided on 1000 as I did not think I needed to remove very much material. If the bed was worn more I probably would have started slightly courser at first.

Tony Jeffree has pointed out that the Silicon Carbide might be a problem as it could become imbedded in the softer materials. I did not experience this but would be amiss not to mention the possibility of this happening. If this worries you then I would suggest that you use as Taig recommends for their lathe bed a soft scouring powder. Since this is a much less aggressive abrasive the lapping could take considerable time. One compound I would be wary of are those made from diamond grit. 

Miscellaneous:

 
A small brush, I used a small metal handled acid brush.
Lots of absorbent paper towels and some cotton rags.
Mineral spirits (kerosene would do)
Assorted Allen keys

Procedure:

Move the table to the far left by jogging to the right.
Unscrew the lead screw supporting bracket on the right (two cap screws)
Using a slow jog start to unscrew the lead screw assembly. I usually use a G1 -04.0 and then just support the screw and stepper assembly as it unscrews itself from the mill. Use a rag in your left hand to support the screw, it should be quite oily.

Put the lead screw assembly away from the mill to avoid the chance of contamination with grit.

Slide the table off.

Clean the table with mineral spirits. I stood the table in a bowl of mineral spirits and used first the brush then rags to clean it.

Clean the X-axis mill ways again using a brush and rags limiting the amount of mineral spirits to keep from contaminating the Y-axis.

Once clean you now have a choice of either removing the saddle nut, or stuffing it with paper toweling. YOU DO NOT WANT TO GET ANY GRIT IN THE THREADS. If you do remove the nut then stuff some towel in the hole it came out of.

Dry the ways and the table with towels.

Apply a very light coating of machine oil on the ways (just a few drops will do) and put the table back on the mill. Now slide the table back and forth over the ways to test for any stiffness. In the case of my mill there was quite strong resistance at each end. Find the stiffest part of the travel and loosen the gib until there is only slight resistance at that point.

Note: Although this has been mentioned before it's worth repeating, the X-axis gib screws on the Taig mill are not as they appear to be. The center screw is in fact a gib screw, but the right and left screws are lock screws that must be removed completely in order to access the real gib screws. These are a real PITB to get to, and I believe the factory uses loctite on them, at least on my mill it took a fair bit of "convincing" to loosen them.

Move the table so that one of the ends is in the middle of the bed and apply a light amount of lapping compound on the front ways, top and gib face, apply the compound also to the top of the rear ways. Move the table to the opposite side and apply the compound the same way.

Now move the table back and forth over the bed, at first there may be some resistance as the compound settles in, but try and reach a point where you can move the table from side to side the full travel distance (or about 1 inch past the side of the bed). At this point you can give extra attention to the areas that were stiff in the first place, but always finish off with full-length strokes.

Once you feel that the resistance is equal along the length of the table tighten both right and left gib screws slightly and repeat the above procedure. Keep doing this until the gib is seated properly and there are no stiff areas.

Remove the table, and clean both it and the ways as above. Again apply a light coating of oil and slide the table onto the ways. Test out the movement and readjust the gib to give you no side-to-side play, but also make sure that the table can still move freely. Hopefully at this stage you'll find a marked improvement and it will give you the impetus to repeat the whole procedure again (in spite of the stiffness that may now be developing in your arms and shoulders) in order to get the lapping as close as possible.

I did mine twice and the final results were amazing. I can now tighten the gib with the table in the middle and then run the table right though and out either side of the bed using constant finger pressure.

Now comes the fun part, all the grit that is on the bed and table ways needs to be completely eliminated.

The first step is to do the same cleaning procedure as outlined above. For the table I took it outside and used some water and dish detergent in a pail to thoroughly clean it, then hosed it down. For the mill bed I it cleaned it again a few times, each time switching to a clean paper towel. Check the towel each time and look for any traces of the dark grit. Continue this until the towel comes away clean. I then ran liberal quantities of machine oil over the ways and bed again using towels to soak up the access and wiped them down with a succession of fresh towels, again checking for any telltale signs of gray coloration. 

When all this is complete, put a final thin coat of oil on the ways and check the table motion again.

Since the lead screw is out it's a great opportunity to clean and inspect it as well, I used the same mineral spirits in a bowl routine I had used with the table. Dry the lead screw completely using rags and time, then apply a light coating of oil.

Move the table to the left far enough to expose the saddle nut and screw the lead screw in by hand until it is just starting to come out the other side. From here you can jog the screw over until it's about an inch from the right hand side. Move the table over to the right and refasten the lead screw bracket with the two cap screws.

Now run some jogging tests to make sure that there are no stiff points remaining. What I did was to write a small gcode file that simply run the table back and forth 10 times along the full length. Keep increasing the default speed until you reach a satisfactory level. In my case I was able to get rapids up the 35IPM. Taig does not recommend going beyond 30 simply because it will cause faster wear on the lead screw and saddle nut.

I hope the above helps, and that it gives you even more pleasure out of using the mill.