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Sophiedoc
12-23-2010, 10:26 AM
I have a mill with4 1/2 inch round column with 2 jam bolts which I have even used a breaker bar on,cleaned the column with ether and tightened the Gibbs and still the head will rotate on heavy cuts.Other than lighter cuts and sharper mills are there any other solutions than getting a square column mill?

terry_g
12-23-2010, 10:34 AM
I was considering buying a round column mill. After a bit of research I was advised one of the first things to do was to replace most of the
threaded fasteners with quality grade eight fasteners. Apparently this makes a big difference.

Terry

Lew Hartswick
12-23-2010, 11:08 AM
:-) Put a key way in the column and key the head. :-)
...lew...

BillTodd
12-23-2010, 11:17 AM
I have a mill with4 1/2 inch round column with 2 jam bolts which I have even used a breaker bar on,cleaned the column with ether and tightened the Gibbs and still the head will rotate on heavy cuts.Other than lighter cuts and sharper mills are there any other solutions than getting a square column mill?

Are you sure the bolts are actually squeezing the head clamps not bottoming in their threads? (i.e. try spacers on the bolts)

I'm very surprised that you can move the head with even the heaviest cut. The only problem with mine is loosing position when moving the head up or down. Perhaps a heavy duty version of my wishbone (http://billtodd.dyndns.org/drillmill)fix would do it?

Bill

lazlo
12-23-2010, 11:21 AM
I was considering buying a round column mill. After a bit of research I was advised one of the first things to do was to replace most of the
threaded fasteners with quality grade eight fasteners. Apparently this makes a big difference.

It does make a huge difference. I replaced my Chinese cheese bolts with ASTM hanger bolts, and it completely eliminated head slip. If you search for "Robert" on the Yahoo Mill/Drill group, I posted the size and thread I used.

You have to be careful though -- you can easily crack the cast iron clamping slot if you torque the ASTM bolts too much.

darryl
12-23-2010, 05:49 PM
Be sure the slot is not closing up all the way before enough clamping force is generated on the column. Could be paint build-up there, preventing the bolts from transferring enough pressure to the column. On my RCM, I don't need much force at all on those bolts- the supplied wrench with its fairly short handle allows for more than enough torque on the nuts. Once you get the problem figured out, consider also putting some lube on the threads- or lets back up here and first put some good bolts in there. The nuts will run easier on them to begin with. Some of that supplied hardware is crap-

Then again, there could be a fair amount of cosmoline trapped between the upper and lower bosses on the head, where it rides the column. To clean mine, I used something like WD and sprayed above and below the head. Ran the head up and down and wiped away everything off the column, top and bottom. Did this several times until there was nothing left to wipe away when I cranked the head up and down. I let it go dry for the last few travels, just to see when no more junk was coming out, then gave the whole column a wipedown with a clean oiled rag. Some may have better advice for this lube, but I just use a light oil. What they call turbine oil or hydraulic oil- either is fine I think. It's not there for lube really, more for rust protection.

wooleybooger
12-23-2010, 08:43 PM
the bolts on mine seemed to stretch-set head,torque bolts,cut; re-torque bolts,cut again,re-torque again. junk-box bolts fixed that.

Sophiedoc
12-24-2010, 10:28 AM
Didn't think of the bolts being inferior.Will get some good bolts and go from there-thanks all.

terry_g
12-24-2010, 10:52 AM
A demonstration of bolt torque I once saw was put on by a service rep from the Kenworth Truck Company. The rep took a new 16mm 10.9 frame bolt the same ones that held the Kenworth frames together. He passed it through a strain gauge of some sort that had a digital readout in PSI. The he got a couple of mechanics to torque the bolt to maximum spec.
200ftlbs if I remember right. then Loosen the bolt and re-torque it to the same spec again. the PSI reading dropped to about 70% the second time. He repeated the test again with another new bolt with the exact same result.
He informed us that the drop inholding pressure when re-tightening a lower grade bolt is much larger.

I don't think you can rely on the bolts in these Asian machines being of any kind of quality regardless of what it says on the bolt head.

Terry

gnm109
12-24-2010, 11:02 AM
I owned a Harbor Freight Mill-Drill for about ten years. It got me started in milling and was actually a pretty good mill and a terrific drill press.

It had two bolts that came through the back of the head and which were clamped with nuts. It came with a wrench that was used to loosen and tighten the nuts to clamp the head.

I never had a problem with it slipping when making a cut, although I tended to stay away from heavy cuts. The only problem that I had was having to re-tram back to the center point when raising or lowering the head. That got to be a hassle.

In order to make it a little easier to loosen/tighten the head, I made two handles out of rod that were threaded in the ends and drilled for handles. That made it easier to get some torque on the bolts.

Sadly, the tram issue is the main problem with round column Mill-Drills. In my case, I dealt with it as long as I could and then changed to a BP style Webb clone.

Here are pictures. I also removed the large plastic cover over the belts and replaced it with a guard so that I could access the belts for speed changes more easily.

Good luck.

Overall view:

http://i144.photobucket.com/albums/r188/gnm109/Machinery/HFMill-Drill1.jpg

Closeup showing the handles. The upper and lower handles tightened the clamp on the head and the center one was used to move the motor for belt speed changes.

http://i144.photobucket.com/albums/r188/gnm109/Machinery/HFMill-Drill3.jpg