Some closer pictures of the column clamp would be helpful.

But if it is like most such clamps, there will be a slot that the pinch bolt closes up when tightened. There needs to be a gap still there when the bolt is tightened. If there is not, you can take a hacksaw and open the slot up so it can clamp the column. But as ega says, be careful not to overdo things and crack the clamp.

Have a look at the table and clamping mechanism. Normally the back is slit and the clamp compresses the slit around the column. Make sure there is clearance for the slit to contract (not full of junk or paint). How does the clamp work? If it is a fixed stud with a clamping lever on it, take the lever off and check the threads are not bottoming out (easy fix is to add a thick washer).

Take either the head or the fixed base of the drill off and measure the diameter of the column there and where the table normally goes. Or try to clamp the table in these two places and see if it works better. That will tell you if someone has sanded down the column. It might help to reduce the problem if you invert the column.

If the table is not from the original machine, it may just be an unfortunate stack up of manufacturing tolerances.

A very drastic solution is to add a small slit at the front of the table clamp, but that is a last resort. It would also need a relief hole at the base of the slit so there are no stress raisers. Another drastic solution is to remove the table, heat up the clamping area red hot, squeeze it a little and let it cool down in its compressed state. This requires a lot of thought so that you do not squeeze it too much, and then break it trying to expand it to refit it.

I've owned my bench Fobco for 40+ years, and throughout that time I've done just as you have. The casting is very rigid and it seems that the slightest wear will cause this looseness and the standard ball handle is a puny affair only about 3" long. An easy mod. hasn't suggested itself, there's not really enough metal in the casting to fit a split clamp. To avoid making it any worse I do try to minimise the number of times that I need to adjust the table height by having several pieces of wood of differing thickness to put under the vice/workpiece if safe and appropriate.

Edited By Clive Brown 1 on 11/06/2022 11:09:49

As you have the wrong table you may also have the wrong clamp, perhaps the whole table and clamp assembly was swapped. Undo the clamp completely and see how slack the clamp actually is, could you insert a shim inside the clamp.

Just measured. Clamping my Fobco table closes the slot by 0.008" to 0.010" so if your hole over-size is much above that figure then clamping is going to require a lot of torque on the handle. As said, there is a possibility of fracturing the casting assuming, as probable, it's cast iron and not cast steel..

Although not a simple solution. it might be feasible to put a split-clamp through the casting between the column and the table itself, although the table would tend to interfere with the clamp handle

The easiest solution might be a strip of 5 thou shim or whatever takes up the gap. Make it wider than the clamp so you can cut small cuts top and bottom to bend the ends over to hold it in position when moving up and down.

My Fobco had exactly the same problem, the table would move under the pressure of drilling unless the clamp was really tight, a little too tight for my liking. I used a piece of shim , I believe only about .003" which wraps about 90% around the column and is about 1/4" longer than the height of the table clamping bore, it is then folded over and tapped flat to form a little flange either end of the table bore much as hopper suggested. So it is held captive as the table slides up and down, been like that for years and works fine, small touch up with satin black and you wouldn't know it was there.

My machine was hardly used when Ibought it so don't think it's wear, looks like Fobco's tolerances were a bit wide, otherwise it's been a great machine.

Dave

Just remembered there is a tag on the end of the shim that goes into the clamping slot so the shim turns with the table if it's swiveled. Just looked and the shim is thinner than I remembered , can't meausure it without removing it, but it appears less than .002" We did have some very thin shimstock where I worked at the time so it's probably theirs!

Edited By Dave Wootton on 11/06/2022 18:17:24

Edited By Dave Wootton on 11/06/2022 18:22:01

Hi Luke

The shim is just folded over at 90deg and is flush with the drill table. I just ran a screwdriver around it to fold over a little and tapped it down with a piece of brass as a punch.As the shim is so thin it was easy to tap any crinkle's out, the lip is only about 1/8" wide. I just tried to photograph it but the shim is so thin and painted over it doesn't show in the picture. I originally intended to use a wicking grade Loctite between the shim and the bore of the clamp, but I'm fairly sure I never bothered due to concern it may have wicked into the wrong place! . It's been there since 2004 and been in very regular use and hasn't shifted yet, which is I know tempting fate to say.

Dave

It just occured to me that a little epoxy glue under the lip before tapping down would hold it in place without any getting in the wrong place. JB weld would give plenty of time to work and if the column was given a smear of grease to prevent any excess sticking things up should prove a belt and braces approach.

Edited By Dave Wootton on 12/06/2022 11:13:09