Acorn welding table holes partly clogged

[skogstokig]

I bought a used "acorn" style cast iron table last year. the top is 100mm, square holes. it's obviously been flipped because the bottom side has seen a lot of use, and the holes are partly clogged near the bottom. i don't use traditional dogs but cutoff F-clamps welded to pipe, and in some holes they don't fit well.

anyone got a good tip on how to re-square the holes, so to speak? preferably without flipping it. i'm thinking a file sander / power file would go through A LOT of belts..

 

[Agroshield]

Please clarify/confirm that the holes are 100mm square. That is quite big.

A picture of your own or a typical one from somewhere else would help visualise what you are asking about.

A carbide milling cutter in a wood router might do it. Make a plywood template that fits outside the router to guide it and clamp the template central on the hole on which you are working. Clearly, it could not produce square corners, but that might not matter.

 

[Welderpaul]

Please clarify/confirm that the holes are 100mm square. That is quite big.

I read that as the table is 100mm thick

 

[Welderpaul]

I bought a used "acorn" style cast iron table last year. the top is 100mm, square holes. it's obviously been flipped because the bottom side has seen a lot of use, and the holes are partly clogged near the bottom. i don't use traditional dogs but cutoff F-clamps welded to pipe, and in some holes they don't fit well.

anyone got a good tip on how to re-square the holes, so to speak? preferably without flipping it. i'm thinking a file sander / power file would go through A LOT of belts..

Why not over-drill the holes and change the ends on your clamps to suit round holes rather than square holes?

Would that work?

 

[Agroshield]

Why not over-drill the holes...

Maybe a halfway house: drill with a carbide rotabroach so the diameter is the same as the nominal A/F of the square hole. That leaves a lot less for a sander or file or nothing at all to do and the clamps would fit with no modification.

 

[skogstokig]

Please clarify/confirm that the holes are 100mm square. That is quite big.

A picture of your own or a typical one from somewhere else would help visualise what you are asking about.

A carbide milling cutter in a wood router might do it. Make a plywood template that fits outside the router to guide it and clamp the template central on the hole on which you are working. Clearly, it could not produce square corners, but that might not matter.

no, the top is 100mm thick. holes are about 34mm x 34mm.

 

[skogstokig]

Why not over-drill the holes and change the ends on your clamps to suit round holes rather than square holes?

Would that work?

clamps are already round. with a snug fitting pipe the holes are no problem actually. it's just that some holes are cloggy. table came from a shipyard originally and has seen a lot of use but i like the flatness

drilling with a rotabroch not a bad idea, i don't have a mag drill but could prolly be done with the bosch portable drillpress.

 

[Screwdriver]

Hardened steel, sharpened square chisel and have at it with a BFH.

 

[Maker]

If you could flip it, a carbide burr in a die grinder would probably tidy it up quite easily.

 

[tom2207]

would a power file be the tool to sort it out , and a bit of patience.

 

[Mark 2]

Only spatter surely

 

[DaveB]

Broach the holes out.

If they were initially formed by drilling then they would have been broached out to square.

Otherwise, while labour intensive, a coarse flat file.

 

[Agroshield]

...drilling with a rotabroch not a bad idea

There's two plans in that flaw: the rotabroach machine would need a minimum 100mm stroke and the cutter would need to be 100mm minimum in length.

Broach the holes out.

The dodgy (reduced) part of the hole is now the top. If we assume he does not want to invert the table twice, the broach would have to enter from the bottom and move upwards. Maybe if the table is heavy enough or could be fixed to the floor, the broach could be pushed with a bottle jack.

A slight modification of that idea would be like a square Q-max cutter. Either pull it through the hole with allthread or jack it through the hole with a hollow ram. The challenge might be finding a piece of HSS 34mm square and making a hole in its centre.

 

[Screwdriver]

I would imagine it's probably little more than spatter and flux with the occasional weld nugget. After that, probably just dirt. So I would make a slightly undersized square peg out of hardenable steel, sharpen the end to have a nice square edge and have at it. Literally just a square peg with a flat bottom.

I get the impression you wouldn't need to be too delicate with a monster table top like that!

 

[hotponyshoes]

Do you want some old farriers rasps?
Cut them into strips 34mm wide, tack the strips togeather (might need some grinding or shims) and make one 34mm thick.
Beat them through the hole.
Turn 90deg.
Beat through again.

 

[Erie Fred]

I don't think they were precision broached, the few I have looked at showed an "As cast" hole, with a fair amount
of draft angle as well.
Upper right section of the OP's pix shows a hole (just above the filled in one, and left of that as well) with some waves & fingernail looking defects in it.

 

[skogstokig]

thanks for the ideas. yea i might go with the brute force options and sacrifice a chisel or a rasp and see how it goes

 

[Kram]

Looks as cast if you ask me. Its only cast iron, use a large square file.

 

[DaveB]

The dodgy (reduced) part of the hole is now the top. If we assume he does not want to invert the table twice, the broach would have to enter from the bottom and move upwards. Maybe if the table is heavy enough or could be fixed to the floor, the broach could be pushed with a bottle jack.

For a single hole I'd agree but this has loads of holes so the broach enters one hole and with a pair of suitably long studs and a bridge piece you can pull against adjacent holes.

Looking at teh more recent comments here and looking at the picture - I suspect the holes are just as you'd expect if it were new.
The plate was for blacksmithing things into shape, it's not a precision jig.
Don't places used to have floors like this ?