gib screw adjustment on mill drill

[jwoitasek]

Hey Folks,
Thanks for all the help and responces on my posts!

I Have a few questions.

#1. How tight should the X and Y table gibs be?
Is there a good way to adjust them?

#2. Working with 4140 steel and using different mill bits, To me the finish is not what I would like to expect. ( Lots of circular patterns that are not consistant.)
Like a dull bit but this is on more than one.
even on light finish cuts the pattern is still there.
Head spindle has no play with a dial indicator.either in run out or end play.
Can I get this machine to give me finishes comparable to a bridgeport or am I expecting to much?

#3. going to look at a bridgeport here at work for-sale.
Any pointers to look for??

Thanks and have a great holiday.
JRW

[bdarin]

OK, one at a time. I have a Jet mill drill not too different from yours. The gibs should be just tight enough so there's some "drag" on the table as you move it (either way, X and Y). Then it's tight enough to not move during cuts and cause roughness. #2: you're expecting too much. m/d heads are on a column like a drill press and this is a section prone to movement. A knee mill is much, much more solid. This movement causes uneven cutting.....not much, but visible. Also, if you're moving the table by hand, uneven speed by human power will cause an uneven looking pattern. #3: Can't help you there, but if it's a real Bridgeport, buy it.

[Thrud]

Spindle may not be perpindicular to the table. Get a large Timken cup and set it on your clean table, put a dial indicator in the spindle and sweep it around the cup top. You should get even movement 360* - otherwise adjust the head until it does.

Way lubricant is very important - Sympathetic Vibration can set up if inadequate lube is present (it dampens them) in the ways. ISO 68 is commonly used.

To measure the spindle slop put a straight 6" round bar in your biggest collet, set up a .0001 indicator at the tip of the bar , grab the spindle (manly like) and shake the crap out of it. When the indicator moves, note how much - you would be surprised how much slop you really do have.

If the bridgeport is in good condition for cheap, pay yer money and throw that baby in back of the 'ol VW.

NOTE: Your better half will be pissed when you displace her car from garage for said Mill - it is tough to be a man, and man has to do what a man has to do. Explain to her that it is better that the Mill is in the garage, than you taking apart Harleys all winter on the living room rug (the white rug) like you did last year...

Have fun, play safe

Dave

[martin_vanmeter]

Try this site for a document on inspecting a mill

http://www.mermac.com/freemill2.html

[Thrud]

Martin

That is a very good article. I like the part about anoying the seller by bringing inspection tools - I would still do it.

Dave