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fobco drill

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Philip Burley14/05/2019 14:19:33
130 forum posts
3 photos

I have a Fobco drill . The table won't clamp up securely , I have a scissor jack under it . I notice that the split in the rear if the clamp doesn't go right to the bottom or the casting . If I cut through this last bit will it clamp better or could it be a disaster . Anyone had similar problem ?

Phil

Clive Foster14/05/2019 14:51:17
1835 forum posts
59 photos

Pretty sure that the slit doesn't go right to the bottom on Fobco drills. For example see the lower picture of the restored one on this page :- **LINK**

Had similar issues with poor grip of cast iron ring clamps on high quality machines (albeit not drill tables) a couple of times before.

First one went away after disassembly, careful inspection and clean up. Can't recall exactly what the problem was but it may have been a raised thread stopping the slit closing. That one had a thread one side of the clamp not a simple through bolt. Dunno what the Fobco has.

Second one was a fracture in the clamp region. Nicely filled and painted over by previous owner! Welding sorted that one.

Time to take it apart and get the magnifying glass out. Fobco drills are generally considered very good so having the casting split for only part of its depth is unlikely to be the true cause. There are engineering reasons why it was done that way. Whether it actually makes any difference when compared to an equally well engineered fully split system I know not.

Clive

ega14/05/2019 16:16:24
1262 forum posts
108 photos

Could the slit be left incomplete to prevent the casting closing up too much due to released stresses?

Ian Parkin14/05/2019 16:49:37
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651 forum posts
174 photos

take the clamping mechanism out and look at it

its a bolt with a collar ( loose) that has a piece machined out of it to fit round the shaft

and a nut at the other end with a similar part machined out.

when you tighten the 2 pieces pull together and grip the shaft

theres no moving of the casting

David George 114/05/2019 17:53:02
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906 forum posts
297 photos

I have had to repair a similar problem with a Fobco bench drill it had been used in a toolroom to drill graphite and the graphite was abrasive so that the clamp wouldn't lock but the and of the ring closed when tightened. I just had a larger slot cut with a wider slitting wheel to allow it to clamp.

David

Clive Foster14/05/2019 18:04:01
1835 forum posts
59 photos

Ah! What Ian says sounds familiar.

I now recall a friend saying many years ago that he found a similar problem on "something" caused by "someone" fitting oversize washers under either, or both, bolt head and nut so the two collars couldn't pull together and grip the shaft. Basically converting it from something that used two loose collars provide the grip, as Ian described, into a simple close up the slit system.

Dunno whether such an error is possible with the Fobco arrangement but if it is it's awfully easy for someone not up on the twin collar system to make. Hafta say I've personally never seen the two collar arrangement used with a slit in the housing. The half dozen ones I've encountered all sat in solid bores leaving me wondering how it all worked. I think frustration got the better of me the second or third time and the offending article dismantled for a look-see!

Clive

Ian Hewson14/05/2019 18:32:41
259 forum posts
24 photos

Just had a look at my Star, and the table is clamped by a bolt straight through to the locking handle, no collars.

The split is not the whole length of the collar.

The head casting is locked via two clamps pulling on to the column.

Peter Spink14/05/2019 19:21:57
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62 forum posts
14 photos

I had the same problem which drove me mad for ages, probably caused by slight wear on top part of column.

Fobco handle.jpeg

Replaced original small handle with much larger one. Handle boss has blind tapped hole. Long spacer keeps handle away from column. Thrust bearing between handle and spacer.

Replaced bolt with piece of studding running through square spacer with nut on left.

Fobco nut.jpeg

Square spacer has corner cut away to engage with cut-out on column clamp and stops it rotating.

Studding has part of thread machined away to allow cap screw to lock position of studding when nut has been tightened to set handle throw.

It all works so well that the handle could be a bit shorter but haven't got round to it yet.

A lot of faff but works a treat!

Philip Burley14/05/2019 19:23:12
130 forum posts
3 photos

Ian points out that there is a loose collar that clamps on the column. There is just a through bolt on mine , not original just a hex head that locates on the one side and a nut on the other . Is there somthing missing ? I have to really tighten the nut hard to get it to hold and a bit frightened of breaking the casting

Phil

Peter Spink14/05/2019 19:43:36
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62 forum posts
14 photos

I think the loose clamp should be just below the top assembly and used to stop it descending rapidly if you slacken off the locking handle. It's bl**dy heavy!

Ian P14/05/2019 19:55:56
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2171 forum posts
90 photos
Posted by Philip Burley on 14/05/2019 19:23:12:

Ian points out that there is a loose collar that clamps on the column. There is just a through bolt on mine , not original just a hex head that locates on the one side and a nut on the other . Is there somthing missing ? I have to really tighten the nut hard to get it to hold and a bit frightened of breaking the casting

Phil

I have the same Fobco and although its quite elderly the fit of the column in the table casting is still good enough for the clamp to work. To make operating the clamp handle easier I have a slightly longer (but a bushed plastic) lever about 100mm long and have fitted an M10 bolt. What helps greatly is the fitting of a cheap a ball thrust race which is something I have done to several other machine clamps.

On the Fobco I certainly do not need to apply excessive force for the clamp to grip so suggest that there maybe something preventing the casting closing up on the column. Extending the slit would be a last ditch resort so suggest you investigate further.

Ian P

Clive Foster14/05/2019 20:04:31
1835 forum posts
59 photos

Phillip

If yours doesn't have the internal collar clamp system and if there is enough metal around the the bolt holes to allow them to be enlarged a little I'd seriously consider retrofitting a collar style. Collars don't have to be very big to be extremely effective.

(OT example :- Back in working days we had some Thor labs 2" diameter vertical column style optical mounts in the lab using similar collars in brass to hold the attachments in place. Itty bitty 6 mm socket head clamp screws. Let the boss in for a play once and he, ignoring my advice, leant hard on the standard key. Major, major battle to get it off again. Once my temper had subsided I set up a demo getting him to balance on it via a right angle bracket after doing the screw up with a screwdriver handle type key, not the usual L thing. Much to his amazement it didn't move. Big lad too, 12 or 13 stone. )

I've heard say that brass on steel gives more grip than steel on steel.

Clive

Ian Parkin15/05/2019 08:08:37
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651 forum posts
174 photos

This is how they work on most fobco’s I’ve had both stars and larger

e71069d1-3f35-4071-90f2-918724b9f6c9.jpeg

5154641a-eb19-4b09-a069-ce965e84e751.jpeg

Ian Hewson15/05/2019 09:07:42
259 forum posts
24 photos

Just to make my earlier post clearer, the table is locked with the nut and bolt arrangement, no inserts, whilst the head uses the arrangement shown above with the internal clamps.

The support collar fitted under the head to support it whilst moving is also a nut and bolt arrangement.

My table locks with the handle shown in Ian Parkins post without any undue force.

Old Crock15/05/2019 23:13:46
24 forum posts
5 photos

I have had three Fobco drills and a friend has another. All of them have the same table clamping arrangement. The slot in the casting in all of them did not extend the full height, it was closed at the bottom.

I think there may be some confusion. There are two clamps of the type Ian Parkinson refers to on a Fobco. One provides a clamp for the quill, the second provides a clamp for the head assembly on the column (note it does not “support” the head but prevents – or allows - the head to swivel clear of the table and base).

There is a collar under the head which clamps to the column to support the head itself, and as Peter Spink says it prevents the heavy head falling and smashing into you, or worse the table! This collar is clamped by a through bolt with the chrome handle as the nut.

The table is also clamped to the column by a through bolt in the same way. Both through bolts mentioned probably had square heads originally as the castings have a square to fit the head and prevent it turning.

I have had the same problem as Phil and others have mentioned in getting the table to clamp firmly on all the Fobcos I have encountered. It appears to be the Achilles Heel of an otherwise excellent drill and like others I have resorted to a longer lever. The original 2.5 inch handle just does not do it so I use a stout tube spanner giving me a lever 6 inches long but it still requires some effort to avoid movement. Incidentally when the clamp is relaxed I can get a 0.080” feller in the slot and when it is securely clamped only a 0.030” feeler will fit so it is not closing the gap completely. The gap is clean by the way!

John

Philip Burley16/05/2019 07:16:30
130 forum posts
3 photos

not just me then !! I will make up a new bolt and I have a small thrust bearing to try , I will see how a longer arm works out The scissor jack holds the table up but have been getting some sideways movement , when clamped

Regards

Clive Brown 116/05/2019 08:38:43
262 forum posts
7 photos

My Fobco Star is as others say. The Table is clamped by  a through bolt and short ball handle. The slot is closed off at the bottom. I too use a piece of tubing to get more leverage. I put this need down to 50+ years of wear causing a slight increase in clearance on the column. In use I try to minimise the number of times I move the table with an array of wood packing kept by the machine.

The head is clamped by a two-piece clamp, also shown above. It's more effective than the split clamp but there is not enough metal in the table casting to modify it to that type.

Edited By Clive Brown 1 on 16/05/2019 08:39:22

Edited By Clive Brown 1 on 16/05/2019 08:40:31

Ian P16/05/2019 12:25:58
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2171 forum posts
90 photos
Posted by Clive Brown 1 on 16/05/2019 08:38:43:

My Fobco Star is as others say. The Table is clamped by a through bolt and short ball handle. The slot is closed off at the bottom. I too use a piece of tubing to get more leverage. I put this need down to 50+ years of wear causing a slight increase in clearance on the column. In use I try to minimise the number of times I move the table with an array of wood packing kept by the machine.

The head is clamped by a two-piece clamp, also shown above. It's more effective than the split clamp but there is not enough metal in the table casting to modify it to that type.

Edited By Clive Brown 1 on 16/05/2019 08:39:22

Edited By Clive Brown 1 on 16/05/2019 08:40:31

If one is not bothered about originality then I think there would be enough metal in the table casting to install a split-cotter type clamp (like the one that locks the head from rotating). There would only be enough metal if the centreline of the new hole for the two halves of the clamp was offset so it was nearer to the column. Ideally this would have to be done by boring so you would need access to another machine.

Ian P

Nigel McBurney 117/05/2019 20:00:49
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591 forum posts
3 photos

I purchased my Fobco ,star brand new,in 1968 ,and only used by myself, and still all original ,my table lock bolt is hex headed and the hex engages with a step in the casting,and it still clamps the table securely. The slot in the table is the same as others have stated ,about one inch of of the slot is not cut through,My thoughts are that the designer wanted some of the bore for the column to remain solid and improve the fit of the table,particularly over a long life,a full slot could easily distort with a lot of use and the table become out of square to the column. I still find the table locking lever adequate without any extension and I am no gorilla. My main gripes with the drill are spindle speed,as a production drill speeds are adequate,for model work,and experimental workshops a lower spindle speed of say 250/300 would have been better for reaming and large countersinks, and the column would have been more usefull if it had been about 2 iches longer. both irritations were resolved when I bought a 10 speed 3 mt floor standing Meddings drill, though I still prefer the Fobco for very light precise drilling.

Ian P17/05/2019 20:42:28
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2171 forum posts
90 photos

Nigel, your Fobco speed problem will disappear in a trice if you fit a VFD. It was the best thing I ever did to mine when I swapped the original single phase motor for an elderly 'square' Hoover motors. I mounted a speed pot and three position (Fwd/Off/Rev) on the wiring access panel (the Fobco label plate) which I can reach while operating the quill lever. No belt changing as I use 5 to 150 Hz and its brilliant for tapping, M2 to M10, and countersinking. I have even counterbored a 1" hole to 2" diameter by 1" deep with in aluminium.

For the naysayers who recommend fitting an extra fan for slow motor speed, I have never had any motor heating problems. A fan might be needed if the motor was heavily loaded for long periods but I doubt many drilling operations are done continuously for hour after hour.

Ian P

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