Subtleties of climb milling

No, it was not. Maybe not being locked with gibs being out that much did it?
 
That would be my first thought. I'm definitely guilty of that.
I'm in the habit of locking my lathe carriage when necessary but haven't developed the habit on the mill. Yet :D
 
LOL, I don't lock anything on my lathe other than the tailstock. I guess I'm guilty on all machining tools.
 
Do the numbers I gave for backlash and gibs (after adjustment) sound correct?
 
No idea to be honest, I don't have that make of mill so best someone who does chime in on the numbers.
 
How are you securing your work? I'm assuming you don't have a milling vise with 12" wide jaws (I shudder to think how much THAT would weigh). Perhaps your problem has to do with how you're securing it? If it's just captured on the ends the center can flex.

Or maybe you have some sort of resonance condition. Check that by changing the RPMs a little.
 
Think it through: what's special about the middle of the table? It's the balance point. Either side of that you've got more weight of the table on one side than the other, which pulls against the ways making the assembly more rigid and introducing a little extra friction. Hit that balance point and all that goes away.
I climb cut a lot on my old bridgeport. I know tons of people will tell you the sky will fall on your head if you do, but I've learned when I can and genuinely can't. Keeping on top of the gibs and backlash adjusters and using just a little bit of drag on the lock of the active axis, while making sure the rest are locked up tight seems to do the trick.
 
If the gibs are not a good fit (assuming tapered gibs) or poorly adjusted you could have play on one side of the saddle and none on the other. I found this on my Rockwell mill, needed to spend some time fitting them better to get more play out of the system. Still need to lock axis that are not in immediate use too.
 
I'm not sure how to adjust backlash on this mill. The handles and dials are keyed. And the balance point statement does make since especially if my Y gibs were too loose.

It was on four 1-2-3 blocks with four adjustable clamps. It was pretty darned solid.

Thanks everyone!
 
When I have to mill a rectangular slot that's wider than the end mill I go around the perimeter so I'm either climb milling or conventional milling for the entire 4 sides. I get a slightly better finish climbing but as far as the mechanics of the cut it doesn't make much difference which way I go as long as I don't mix the two. If I turn a corner that switches from climb to conventional the backlash immediately switches to the other extreme and I get a divot sticking out of my corner. If it's something important and I have to make multiple passes I draw a picture with arrows and leave it on the mill table. It really pisses my off when I have a half dozen perfect passes under my belt and make a divot on the last one! This is the crap you have to put up with when you're an old dog learning new tricks!
 
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