Loose table on Fobco Star

Hi all

I've recently purchased a Fobco Star bench pillar drill which is in very good condition and overall I'm very happy with it. However I've just noticed the large table (which I believe is from the floor standing version) is loose on the column despite me tightening this to the best of my ability! It's only slightly loose and can be tightened sufficiently with the aid of an round tube acting as an extension to the handle on the table.

My question is is there anything which can be done to rectify this or am I stuck with it?

Many thanks

Luke

Mod edit: rotated photo.

Edited By SillyOldDuffer on 11/06/2022 15:00:10

Do be careful not to crack the casting!

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.

I wonder if it could be converted to the superior split cotter clamping?

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.

Thank you all for your suggestions! Some really good ideas here! I'll take some more pictures later today (I'm out of the house at the moment) and will report back. It is the normal clamping mechanism. It will clamp down if I use an extension bar to the table handle, obviously though I'm just a bit concerned the casting would break with too much force applied. 🤔🤔

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

Luke

First thing to do is to verify that there is no build up of workshop dust, cruft or similar in the slot acting to prevent full closure of the tightening slot. I've seen such build ups that were almost as hard as the cast iron and pretty much invisible due to workshop "dust varnish" making everything almost the same colour.

From your description its only a few thou short of clamping using the handle so careful scraping out of the cruft should restore proper operation.

If things really are worn a little more flexibility can be gained by filing shallow grooves down the bore at around ± 120° to the slot using a small round file to avoid stress raisers. Shallow being the operative word. 10 to 20 thou with a 1/4" rat tail file will be more than enough.

Filing grooves really is a last resort tho'. If cleaning the slot improves the nip so its stable in rotation, but not quite enough to hold it up under drill loads it would be better to get creative with something to hlep support the table. Re-purposed car jack or similar perhaps. I always found sliding a heavy cast iron table up and down by hand more work than I cared for. Especially if there was a vice or job on top.

Clive

Edited By Clive Foster on 11/06/2022 11:11:03

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.

With the table loose does it rattle on the column if you move the table front up and down?

Everyone with a industrial bench drill only has a lever 4" long to lock the table, to require the nuclear option gas pipe to come out says you need to apply around 100 ft/lbs. If the split in the clamp is fully closed up at the back when tight then the table needs a bigger column. Widening the split will result in a broken casting.

It may only need a 1.5 or 3thou sacrificial feeler gauge to make the difference.

So I've managed to take a few more photos of the mechanism to secure the table. I cannot see any perceivable gunk clogging up the split

Dave, the table does wobble when wiggled from the front. Using my caliper I measure the column at 54.97mm throughout, indicating no specific wear spots. Looking at the table I believe the hole is probably between 10 -20 thou too big 😪

For that, you need this solution:

http://www.hilarygallo.com/the-zen-shim-question/

Your column is about 83% of a standard can.

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

I see someone on ebay is selling these handles for fobco drills

https://www.ebay.co.uk/itm/174744545764?mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338722076&customid=&toolid=10050&amdata=enc%3AAQAHAAAAkDjN%2BF%2B6IL4L%2Bh%2BIIm%2BRhwx%2FDxeyF6Ta%2BAmHMzZ7DR%2BrvSMzh8E01wiKbRVBfTDFMgdkcoFVfpo9rHJ6xhvZxeO3T6LO5bKRt4JGcSlmZPxCXCu7PJH5evmwErIuawklwL3jjjY7Xx1R2CJp4KVVSdR33eXyDIUJOrNc4WFo2NQa6KE%2BDZ6uUJ%2Bdz47fKlbS7g%3D%3D

If the gap doesn't close all the way when tightened is the casting likely to break? I might just fabricate something like the ebay ad otherwise. I thought the floor standing version was mounted with a 55mm column as well so I can only think this is age related wear?

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.

Like Hopper's idea and it's easy to try. Drink cans are often made from soft Aluminium about 0.14mm aka 5 thou thick and it can be cut with scissors. (Hot tip: don't borrow SWMBO's dressmaking scissors...)

Dave

Thanks all for the help. I've took the table off and measured the gap at the back of the casting. The gap is 1.01mm before being compressed. When compressed around the column it closes to 0.63mm (approx 0.4mm less) at this point the table has started to grip the column somewhat snugly (about enough to hold the table in position without moving due to its own weight). I inserted a peice of paper to act as a shim which was 3.5 thou thick. This worked well and the table was secure with very little force being applied to the handle.

Unfortunately the threads have stripped in the handle which I'm convinced must have happened due to the previous owner using the extension bar

It looks like it's just 3.5 thou too big!

If I made a new handle longer than the original is it likely to break the casing if I tightened it down?

I like the idea of the shim but I'm not sure it wouldn't fall out when moving the table up and down?

Hopper did suggest bending the top and bottom of the shim to retain it in position.

Mike

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

Thanks Mike and Hopper! I did see the post but was just a bit concerned the shim may have still come loose! I've took your advice and ordered a 0.002 thou shim. I'll let you know how I get on!