View Full Version : Mill/Drill Twisting

06-08-2004, 10:05 AM
I have the small Jet Mill with the round shaft. It seems like no matter how tight I crank the shaft there is still some twisting when I'm milling sideways. The only thing I use it for is to cut slots in square tube. Lately I've just resorted to turning the tube on it's side and using a slitting saw. Does anyone have any ideas of how to stop the twisting short of drilling a hole through through the head and and threading the shaft at intervals and bolting it anytime I raise or lower the head. I'm kind of convinced that the only good mill/drills are the ones with the square shaft. I haven't tried cranking the shaft bolts down with my air wrench yet, but maybe that's the next option.

06-08-2004, 10:08 AM
I drilled dimples in my similar mill. I had the head off and drilled dimples radially. It'd lock into them pretty good.

I sold that mill and upgraded to a old bridgeport.


Mike W
06-08-2004, 12:42 PM
Do this mod and it won't move:


06-08-2004, 02:03 PM
Try to load the cutting pressure toward and away from the column whenever the forces are high, and it is practical to do so.

I had a slight problem with it slipping once, and found out that the nuts had started to gall the threads. I replaced the bolts and nuts with SAE grade 8, and put a hardened washer underneath the nut. I also used high-pressure grease on the threads and washer. I haven’t had any problems since.
Oh yeah - To make the smaller nut head fit into the recess in the mill head, I wrapped it with thin bar stock, and brazed the ends together. The nut side fit the factory wrench better than the original nut. I can post a picture if you like.

06-08-2004, 02:43 PM
Great photos, but can you help out with an explanation of your modification
Many thanks

Mike W
06-08-2004, 05:41 PM
Sure, a 4 by 4 inch plate will fit inside the head. A nut is welded to it which holds up the 1/2" plate. The angle brackets on the plate go against the head to make sure the plate does not shift. I added some 1/8 metal to locate on the machined bottom of the head at the column and the spindle hole.

The tube in the back is hard chrome. The part that slids on it with the head has a bronze bushing inside. Everything bolts on, no holes required. http://bbs.homeshopmachinist.net//biggrin.gif

Dave Opincarne
06-08-2004, 06:23 PM
Great idea Mike! I've been thinking about adding a square way to the column itself and trying to cut in a slot in the head but I like this better.

06-08-2004, 07:35 PM
Take a look at John's post #8595 at http://groups.yahoo.com/group/mill_drill/

I don't know if you need to be a member or not.

He describes what looks like a nice method of keeping the head registered when moving it.

He also has some good pictures in
folder "Guide Bar" located in the photos section.

Tom M.

06-09-2004, 11:00 AM
[QUOTE]Originally posted by Mike W:
Do this mod and it won't move:

http://img36.photobucket.com/albums/v110/tek798/Mill/?action=view¤t=cd2cde69.jpg[/QU OTE]

06-09-2004, 11:04 AM
Is that an Enco 91000? I have what appears to be an older version of that, it only has twp through bolts on the head for tightening it to the column, it moves drastically when called on for slotting type procedures. I really like the mods you made, I know what my next project will be.
Whats with the modified feed nuts? Looks like a good idea, but what problems were you trying to overcome?
Robert in Aptos

Mike W
06-09-2004, 01:47 PM
It is an RF-30. One of the table nuts was bad because the feedscrew had burrs on it. New nuts were $45 each so I decided to make my own. I just added another pic. This was my first attempt to keep the head from losing zero when I raised it. The tubes telescope and can then be locked with the clamp. I wasn't getting the results I wanted so I went to the rear support.

I decided that they would add support to the head so I left them in. They are easy to take out by pulling the pins. The bottom of the table is beefed up with 3" channel.


06-09-2004, 04:05 PM
I have the smaller RF-20, bought in 1992 as the Grizzly G1005. The two head-to-column clamp bolts were cheese, replaced them with good bolts and haven't had a problem since. Once you get past the "it's a kit" part, it's a great machine, has worked far beyond what I thought were reasonable limits.


06-15-2004, 01:17 PM
<font face="Verdana, Arial" size="2">Originally posted by wirewrkr:
[QUOTE]Originally posted by Mike W:
Do this mod and it won't move:

http://img36.photobucket.com/albums/v110/tek798/Mill/?action=view¤t=cd2cde69.jpg[/QU OTE]

That looks like a lot of work!! I thing I'll try some grade 8 nuts and bolts and the air wrench first.

Mike W
06-15-2004, 05:30 PM
The rear support didn't take that long once I figured out what I was doing. http://bbs.homeshopmachinist.net//biggrin.gif

It will also allow you to maintain alignment when you move the head.