Can anyone with a Fobco and an ok square check something for me, please...?

[Gareth J]

I was about to take a skim off the gnarly, bodged repaired table of a Fobco star. After mounting and aligning as best I could with a dti against the better bits of the table, I thought to check square against the machined surface of the swivel and the lathe faceplate but it was quite significantly off.

Then, thinking I'm better to machine it square, to this, unworn datum, I did so and starting skimming. But its taking material off the front edge of the table, where I would have imagined it would be most worn, rather than the other way around.

Ive not taken off any significant amount so will, I think, realign the table so it's as parallel as possible with as much of the remaining undamaged and un-machined surface as possible. Unless I can confirm that the machined flat of the swivel should indeed be parallel to the table surface. Could anyone check? Does not need to be particularly accurate, this is never going to be perfect.

My only thought now, after typing this, is that welding up the MASSIVE arc of shame may have pulled the front of the table edge up a lot, relative to the swivel mount. In which case, I'm better to carry on lowering the front of the table.

On the table - column mounting bracket, the column hole appears to be 0.09 - 0.1mm out of parallell to the brackets swivel mount face.

 

[Agroshield]

Whatever you come up with, having the front of the table high will be better than having it low.

As the pressure of the drill bit comes onto the table, it will deflect downwards.

If you machine it level under a no-load condition, it will only ever get worse.

Maybe assemble it, hang 5-10kg weight on the front and then sweep it to see what it reads.

The 5-10kg might be too small: I have never seen any numbers for "quill force", whether from a drill or lathe tailstock.

 

[Brad93]

Photos of what you're trying to achieve would help

 

[Agroshield]

In one of Jody's welding videos, he tied a laser pointer to a piece of metal, welded it and showed how much the laser dot moved ten feet away as the metal shrunk.

Maybe you could do the same. Blutack a pointer to the table, shine it at the garage wall and then pull down on the quill handle with normal force to see how much the pointer moves at 3m distance. Then proportionally reduce that amount to the edge of the table.

In some ways, it might be more educational than the weight because not only will the table move downwards under quill pressure, the column will bend backwards and so will the head (so you could move the pointer to the head and see how much it moves). In use, the drill is like a giant G-clamp.

 

[Gareth J]

I said it was bad!

I'm gonna pop up later to check for square against the back of the table, right next to the mounting swivel. It should be more or less unaffected by the welding. It's bound to have pulled significantly.

If that's the case, I might try releasing the tension a bit with a heat and slow cool. Either way, the back of the table, where it won't be too worn or warped is the place to focus for alignment.

I should clarify that I'm not expecting to achieve a high level of precision here. This is only going to be chewing holes through bits of flat or box for very low tolerance cobbling togethers

 

[Brad93]

100% that has warped

 

[Gareth J]

Thanks, it's obvious now I look back.

So, attempt to release a bit of weld tension? Tools at my disposal are a woodburner I could chuck it in at X°C and leave to cool overnight or oxypropane.

Or run some weld along the back?

Or accept that what I have is better left alone and in one piece than warped even more or cracked in half! And skim it flatish now.

 

[Brad93]

Thanks, it's obvious now I look back.

So, attempt to release a bit of weld tension? Tools at my disposal are a woodburner I could chuck it in at X°C and leave to cool overnight or oxypropane.

Or run some weld along the back?

Or accept that what I have is better left alone and in one piece than warped even more or cracked in half! And skim it flatish now.

i wouldn't stick no more weld on it if it's cast iron

 

[Erie Fred]

i wouldn't stick no more weld on it if it's cast iron

I think he missed a spot....right there.....