Can a linear slide be rigid enough?

[offabit2001]

Hi, was going to look into constructing a cnc mill. I have a complete bridgeport j head spindle assembly with bearings. My question is do you guys think a large linear slide would be rigid enough for the x and y table. Seems to me it would shake it to death if you were taking anything larger than say
.050 at a time (1018 or 1045, not aluminum). Would love to hear some input on this. Don't want to use a Chinese compund slide. Don't think it would be precise enough. Thanks

[elmerfud]

interesting, i have bunch of old ball rails but all are short stroke.
in the full size stuff at work these are used in gangs, but not singularly.
should be ok for a small hobbie set up, 2mm cuts max i guess??

[RICHARD ZASTROW]

Early Cintimatics and Pratt & Whitney Vertical N/C machines used round linear ball ways. They were the low end machines and weren't all that rigid.

There are linear bearings available that run on flat rails without rollers. They are filled with epoxy stuff like "Moglice". Pretty rigid if specified tight clearances. You could possibly use inexpensive/used flat rails.

Depending on what you intend to do with this machine, both solutions may work.

Dick Z

[neilw20]

I have a Pratt & Whitney Model B (circa 1975 I think).
It has round linear ball ways.
Repeatability is good but for the size of the machine and weight, can only take mousey cuts.
Because the spindle has only a cam-lock on an NT30 holder, it is a pain to make adapt new holders.
Good base for a CNC machine and adapted for servo Z on the quill including encoder. 30-6000 RPM fully variable. 3HP
Steppers and ball screws in X Y. 1 Ton. Add drivers and Mach3 to make a machine. about 500mm x 300mm Y
I used it manually for years, but never added the PC

Any offers? Not the right forum, but was on topic before I drifted.

[offabit2001]

Thanks for the replies. I'm justed bumed with the prices of these linear systems people build on here. I'm a true working man, and don't have $400 or $500 to spend on each axis, before I buy the other parts. I have about $1500 to spend before my wife gets real abusive. Looked at the linear bushings blocks that run on supported rails. Might be an option. Not looking to build aerospace parts, just want have fun. I might try loading up one of the Mazaks from work into my truck and bring it home with me. I guess thoses little cnc'd x2's are looking a little better about now to me.

[neilw20]

You've been spoiled by using real machines. There are really a lot of of 25 and 30 year old machines you can pick up for scrap value.
Throw some time at them and you can stay in budget.
The Pratt and Whitney Model 'B' is a perfect candidate and example.
You should find something for under $500 that just need lots of time.

[offabit2001]

Good advice neilw20. I believe that's the way I'll go. I'd rather put my blood, sweat and tears into fixing something up than to just bolt something together anyways. Well maybe I'll just convince myself of that, seeing I have no other real options.