table rocks when reversing x travel

[digitalmdj]

I had a friend make me new way strips for me. The old ones were to thin and had to much gap between the table and the strips. Now they just barely fit. I believe that the strips were shifting because of the excessive clearance .

[instructor37]

Originally Posted by digitalmdj I had a friend make me new way strips for me. Now they just barely fit. I believe that the strips were shifting because of the excessive clearance .

Thats a good point. We found one machine that didn't respond to adjustment the way it should. After removing the bed wipers, we could see that the gib strip was a bit too wide and when the adjuster screw was moved in, it moved upward and wanted to raise the carriage off the ways. This may be the problem with the other guy's machine too, as I can't imagine the casting flexing. I let the kids do a brainstorming session just to check their problem solving skills. First, they removed the gib strip and put it on a surface grinder to reduce the width and also to make sure it was completely flat. The raising was caused by the cone point on the adjuster screw not being perfectly on center, so as the screw turned the tip would raise and lower the gib. The dimples in the gibs are done with a drill, and are meant to accept the cone point, but it really doesn't give the proper pressure. I told the guys to devise a solution that could be done with the machine itself. Their idea was simple and clever. They took an 8mm bolt and chucked it up, faced the head and center drilled it. Then they drilled it and reamed it to 3/16". With the gib strip in and held by the other adjusters, they threaded the bolt into one hole and used a 3/16 end mill to make a flat bottom dimple in the gib. Then they turned the original adjuster so it had a 3/16 dog point on the end. The process was repeated until all the gibs and adjusters were done. Now, the adjuster screws fit into the dimples and have a much larger pressure area. The whole process only took a couple of hours once the plan was in place. It was a good exercise in problem solving and the kids met the challenge.

[banctecbobn]

That sounds like a good fix. Never liked all the gib pressure on the points of the adjusting screws. How many adjusting screws does the newer machines have on the X way gib. I have the older Gold series and it has just two adjusting screws. Would it be advisable to drill and tap for additional adjusting screws?

[instructor37]

Originally Posted by banctecbobn That sounds like a good fix. Never liked all the gib pressure on the points of the adjusting screws. How many adjusting screws does the newer machines have on the X way gib. I have the older Gold series and it has just two adjusting screws. Would it be advisable to drill and tap for additional adjusting screws?

The Patriot machines have 4 adjusters and 1 center lock on the Y axis.
X axis and tailstock have 2 adjusters and a center lock
Because the Y table is the longest piece, it is subject to the greatest leverage- adding more screws to the older machines might improve them.

[tsminor]

The best way to fix this is to recut the saddle for a thicker, wedge shaped gib strip, like that of a knee mill. The wedge will maintain a full bearing surface along the whole length of the gib, instead of 2 pressure points under the adjustment screws. Should reduce stiction and force required to move the axis. I have since purchased a Series 1 Bridgeport and will use it to recut my saddle in a couple of months.

[banctecbobn]

I like both ideas from instructor37 and tsminor. I don't have a way to recut the way saddle for a tappered gib so I'm looking into the adjustment screw mod.

Today I adjusted the x gib while I had the dial indicator attached. I was adjusting the gibs too tight before. As I backed off the pressure from the adjusting screws I could make the rocking better or worse. I'm down to .001 when changing directions. If too tight I caused more rotation and too loose I would cause more rotation.

I don't know what the results will be when actual cutting material will be yet.

I always just tightened the gibs until I felt the handle pressure increased but yet not too hard to turn, guess I was wrong to do this. BTW I blued things up and I don't have any high spots other than at the very far right end.