I now have the mill where I can start using it. The last thing done was to fab a mill-head counter-weight. I weighed the head with the motor installed, and it came out to 32#. To make the weight I used an old rusty piece of 3"x3" rectangular tubing I've been saving for just this sort of thing (actually I forgot I had it and almost missed it in my scrap rack). I made an end cap for one side and then proceeded to melt 32# of plumbers lead into it. Then a short length of 1/4" rod was welded across the top to hang the weight from, a few bends were put in the rod to keep the hanging cable centered. A couple of pulleys, a bit of angle, a little band saw work, a length of cable and Viola! I can move the head up and down with one finger on the crank handle, and it stays put once there. I do make it a practice to lock the gibs whenever milling though.
Before I started the project I took some purely subjective benchmarks of the flex of the original column. It was just simply mounting a test indicator and then pushing and pulling on the top of the column and recording the results. When I repeated the test on the new machine (and it does seem like a new machine) flex was reduced by a factor of 4, but the real world test for me was cutting some steel. Before when cutting steel unless I took very small cuts (.010 - .015 doc) it would almost always result in poor cuts and chattering. For a quick test I put in a decidedly worn 3/8 end mill, set up for a cut of 1/4 in wide and started to take progressively deeper cuts, at .040 doc I could feel the motor starting to slow, but it continued to cut easily without any chattering or vibrating. Next I mounted a ½ roughing end mill and set up for a slotting cut. A .050 doc resulted nice cut with only slight slowing of the motor. There was no chattering and only a bit of vibration. After a few cuts the depth was .115". I moved the cutter over 5/16 and made a full depth cut, it cut easy, no problem at all. All test cuts were done dry and at around 1000 rpm.
So all in all I have to say the operation was a complete success. The patient is much bigger and stronger and seems much more capable than before. Ill probably have to be careful not to overtax the motor, as that will now be a limiting factor.
Bill
link to web album: http://picasaweb.google.com/billstupak/X2MillExpansion?authkey=Gv1sRgCKSBivqv_t2ungE&feat=directlink
Before I started the project I took some purely subjective benchmarks of the flex of the original column. It was just simply mounting a test indicator and then pushing and pulling on the top of the column and recording the results. When I repeated the test on the new machine (and it does seem like a new machine) flex was reduced by a factor of 4, but the real world test for me was cutting some steel. Before when cutting steel unless I took very small cuts (.010 - .015 doc) it would almost always result in poor cuts and chattering. For a quick test I put in a decidedly worn 3/8 end mill, set up for a cut of 1/4 in wide and started to take progressively deeper cuts, at .040 doc I could feel the motor starting to slow, but it continued to cut easily without any chattering or vibrating. Next I mounted a ½ roughing end mill and set up for a slotting cut. A .050 doc resulted nice cut with only slight slowing of the motor. There was no chattering and only a bit of vibration. After a few cuts the depth was .115". I moved the cutter over 5/16 and made a full depth cut, it cut easy, no problem at all. All test cuts were done dry and at around 1000 rpm.
So all in all I have to say the operation was a complete success. The patient is much bigger and stronger and seems much more capable than before. Ill probably have to be careful not to overtax the motor, as that will now be a limiting factor.
Bill
link to web album: http://picasaweb.google.com/billstupak/X2MillExpansion?authkey=Gv1sRgCKSBivqv_t2ungE&feat=directlink