need tips on Atlas milling attachment
Hey Guys, got myself a milling attachment for my much-loved Atlas 12x36. Its a proper "Atlas" model...low-mileage! Looking for advice on using the damn thing. Rigged it up today...kind of just "trammed" the vise (graduations were pretty much spot on) and then proceeded to bust every one of my meagre collection of mills...(even more meagre now!!). At the time I was attempting to cut an opening about 1/2 x 2 in the side of some 3/4" mechanical tube. Nothing too extreme. Found it cut best when used conventionally. (i.e. not climb cutting). also noticed some tendency for the entire attachment to "hop" slightly (is this wear or play in the crossfeed causing this???). Also, anyone got any tips/suggestions for adjusting the gib on the attachment itself....seems to "hang" from time to time...had a brief "fiddle" with the adjustments.... Thought I'd maybe ask the board, see if anyone has any experience with these things. First time I've used an attachment to mill. I was using a cutter speed of about 2/3 what you'd noramlly turn that mtl with...maybe a bit faster...and trying to take cuts of about thou & a half or so......too fast/slow....too heavy/light...???? Thanks for the help & take care y'all !!
check your gibs on your crossfeed first,also,did you lock the carriage to the bed? start from the bottom and work your way up,any slack at the mounting point will be greatly exaggerated.mine is a pain in the ass too,mostly because my croosfeed nut is about worn out.i would also take it apart and clean it if i were you,it doesn't take that long-george
"...cuts of a half a thou or so..." may be the problem. You should be able to take .060" or deeper with no problem, with the lathe running in Middle Back Gear or First direct drive speed. As has been suggested, check the snugness of all the gibs.
You might want to take the attachment apart and clean it well. Look for signs of high spots on the gibs and dovetail and stone them out for smoother operation.
It would not hurt to perform the same operation on the lathe cross slide as well. With a milling attachment, everything wants to be as tight as possible, the movements not being used should be locked. Definitely do not climb mill.
The backlash in the feedscrew and nut is not helping either.
I have seen some attachments and lathes that have been modified by drilling and tapping for hold down bolt(s) to provide more rigidity.
Some things I do (and they may be wrong).
You can usually apply a little extra drag by just barely snugging the cross feed lock screw.
Calculate the feed per tooth, too slow is not good either. About .001 for 1/8" cutter, .0015 @ 1/4", .003 at half and above (Tubal Cain). This means .002 - .006" per rev. on 2 flute cutter.
Use your body weight against the direction of feed (lean on or away from cross slide).
All these things are hard on the feed nut and gear train (read abusive)!
NO Climb Milling -- additionally, try to set up so you're only using 1/2 - 2/3 cutter dia. -- so whole of cutting force is against feed. Then none of cutter is "pulling in" the backlash (impossible when slotting - at least at start). 4 flutes may be better here, as next two teeth are engaged against feed when lead tooth goes "Round Center". (Again, not applicable at start of slot)
Also, read on - cuz when I am corrected, we both get to learn something! Best part of this board!
[This message has been edited by uute (edited 12-18-2003).]
I'm not an expert on milling but have already gained some understanding using the attachment I built for the SB9. As JCH says, tighten everything and lock down everything that doesn't need to move. I found the the cross slide gibs tend to loosen from vibration (not chatter) when using the larger end mills. As far as the climb milling you need to take a slightly different view than usual. The problem is worst when a cut tends to lift the saddle off the ways. As far as slots go, a slotting drill works way better than an end mill. An end mill is not intended to cut on both sides at the same time, it is a profile cutter. A slotting drill has asymetrical flutes so they cut one side at a time. I've tried both.
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Thanks for the help & suggestions....nice to know there's others out there with similar problems.....