[iandh]

My X3 has a bunch of slop in the column, I've already tried adjusting the Gib to my heart's content, and found that it seems the dovetail in the head is misground (it has a hump in it, so no matter how perfect the gib is, the head will still rock). I have .005" + of tilt in the head, which makes my plans to CNC the machine basically worthless unless I do something.

At this point I feel I only have a few choices:

- Have the dovetails properly reground ($$$$)
- Sell the machine and buy a G0704 ($$$)
- Buy a decent linear rail set and convert the column ($$)

I am thinking the linear rail option is the best. I'm planning to CNC anyways, and it will make life WAY easier for the steppers or servos, as well as giving me a MUCH more accurate z-axis. I would venture to say that it would also be more accurate than the stock z-axis on the G0704, so I think it is a better option than switching to that machine as well.

Also, until I complete the CNC conversion, it will make the z-axis crank about 10 times easier to operate.

Thoughts?

[pete from TN]

If I were you and had a problem with a hump in the ways I would maybe first try the lapping method IH shows on their website where you take the column off the machine, lay it on something solid and then using some media lap the Z slide into the column carefully. This takes some time and a lot of work but it should make the ways straight if you are careful. Problem with linear guideways is that while they are real nice and super slick if you put them on something that is already warped you will warp them as well. If you take the Column off the machine and take it to a local machine shop that has a large surface grinder they should be able to knock it down flat pretty easily and you might be surprised at how cheap it costs. You need to first determine exactly where the problem is and without taking the machine apart and measuring against known flat references that is difficult. I would try to find that lapping procedure IH recommended on their early non-ground way machines and see if that sounds like it would work for you. Might take a little time and some elbow grease but it would not cost much to do and if it fixes the problem you are good. If it does not you have not really lost anything and can then work out a way to accurately apply the linear guideways to the column. Someone with a nice VMC could probably machine your column on both sides and drill all the holes and tap them for the guideways pretty easily if you decide to go that route. Cruiser on the IH forum used the travel of the Z slide to control a wood router to machine some slots for the linear guideways on his machine and it apparently worked but I do not think his problem was that the ways were not ground straight. I do not remember for sure tho... Good luck and let us know what you wind up doing and how it goes...peace

Pete

[cornbinder23]

I like the linear rail idea, for those of us that love more projects!!!
I am planning something similar to mine eventually, but I don't have as much of a z issue though.
Boxing the column in the rear would add an immense amount of strength IMHO
You could mill the ears of the dovetail on the column and mill a slot through to have a way of attaching the ball nut to the ballscrew similar to the G0704, the column itself is pretty beefy on these mills just not executed right.

Anyway looking forward to a build thread if you do choose the linear rails

JTCUSTOMS

[iandh]

I couldn't help it, I went ahead and pulled the trigger on these:

IKO 16.5" Linear Slide Rails w/4 LWHD15 Bearings cg - eBay (item 390325949460 end time Jun-29-11 13:43:55 PDT)




I was cruising around and they just jumped out at me. They're the perfect length, the perfect form factor (rail size), and they are a pair with two saddles each, which is super rare by itself. Most ebay auctions are either for a single rail with two saddles, or for two rails with one saddle each.

On top of that, this place sells high tech surplus, so chances are these rails have seen a pretty easy life.

Obviously buying used linear bearings is always a risk, but the way I look at it is that even if these have .001" of slop, they are still 5x better than what I have right now. If I am careful about how I build things, I can probably take some of the play out also.



The bottom line is that I knew there was no way I was going to get this mill converted to CNC with the z-axis in its current state, and for $100, this pair of linear bearings is my safest bet. I could spend weeks screwing with the factory dovetail, only to get a minimal improvement, or I could do this and actually improve upon the machine.



Worst case scenario, I've been planning on a small tabletop CNC router, and these would work great for that also... either way I think they're a pretty safe buy.

[rwskinner]

I'm with you. I've been debating this same thing for some time. I have scrapped and lapped until I can't see straight and this head still rocks. I can loosen the gib and get rid of most of the rock but then I have a poor finish.

In manual mode I could live with it because I locked the head down, then used my quill for depth and everything was fine, but in CNC mode it's not so good.

The rest of the SX3 is pretty solid, but that head drove me nuts. I surely hope my RF45 is better that that SX3 I own.

Richard

[SmoggyTurnip]

I'll be watching this thread with great intrest. Where do you plan on mounting the rails, front back or sides? Are you going to have some machining done on the column to mount the rails.