Lapping a cast iron surface

I think your best bet by far is to get a straight edge that will allow you to measure to the tolerance you need and then go table saw shopping. I think this will save you a lot of money and a lot of grief.

It might take looking at a few contractors saws to find one that will suit your flatness requirements but used contractor saws can usually be picked up for quite cheap... a lot cheaper than paying a machinist to blanchard grind your current top and it will also probably take less time to find the new saw.

I would guess that trying to grind the top yourself with a hand held tool will result in a wavey top instead of just a concave top.
 
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@woodchucker, I agree. A decent level would be fine. The original question was asked in relation to how to straighten cast iron surfaces, so I tried to give a complete answer. I did mention about a milled surface being good enough - the idea of a level is a *really* great one!!

Funny, I haven't seen a cast iron Delta saw so far out... My General 12" is almost as flat as my surface plate! - well, easily within a thou everywhere. (It was blanchard ground)
 
Unfortunately contractor saws are not as beefy as Cabinet saws, and a 12" saw will have a beefier top than a 10" saw.
I looked up the OPS saw, and what he paid for his, back in 2000 you could have bought a Unisaw brand new, a Jet, and almost a PM66.

:rolleyes:
 
Any ideas on how the top got low in the middle ?
 
I agree with @MikeInOr, it's probably in their seasoning, and then milling ... I don't know if they blanchard grind, mine seemed to have deep swirls, I am not sure if it were milled (fly cut) or ground. Mine was rough enough to say it was milled, not ground, but I am not certain.
There's an advantage to having a corrugated plane (although many dispute that), I think it breaks the sticktion... but in a tablesaw, the lines would need to go parallel to the blade, and my swirls were mostly 90 to the blade. I sanded it smooth to my liking and use butchers wax to keep the table smooth as silk.
 
vulrath said:
I'm not sure how far out it is right this second, but I can say it's out enough that I suspect it's messing with the cut. It's been...painful...to get the blade dialed in. I too have a Delta saw (36-725).


I'd like to use it for both a saw and as a reference surface. I looked into getting it milled and/or ground, and it would cost almost as much in labor as the saw itself. It'd be one thing if I had the machines to do it myself, but I don't.

ETA: When I say reference surface I'm talking about woodworking, not metalworking. I'm not building rockets here, just furniture and some occasional weld art.
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Is the table worn or poorly supported and the cast is sagging?
 
woodchucker said:
I agree with @MikeInOr, it's probably in their seasoning, and then milling
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Is seasoning cast iron just letting it sit (sometimes for years) before milling it? To let it shift to a stable form so it doesn't shift in the future after machining?

According to Google seasoning cast iron is baking a layer of oil on the surface to keep food from sticking to it. ;)

woodchucker said:
There's an advantage to having a corrugated plane (although many dispute that), I think it breaks the sticktion... but in a tablesaw, the lines would need to go parallel to the blade, and my swirls were mostly 90 to the blade. I sanded it smooth to my liking and use butchers wax to keep the table smooth as silk.
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I love the corrugated top on my Italian sliding table saw!

MPS00845.JPG

There is a lot less friction when pushing a piece over the corrugated top. The moving table has a flat finish which is great for extra friction keeping the work piece from moving.
 
vulrath said:
I'm not sure how far out it is right this second, but I can say it's out enough that I suspect it's messing with the cut. It's been...painful...to get the blade dialed in. I too have a Delta saw (36-725).


I'd like to use it for both a saw and as a reference surface. I looked into getting it milled and/or ground, and it would cost almost as much in labor as the saw itself. It'd be one thing if I had the machines to do it myself, but I don't.

ETA: When I say reference surface I'm talking about woodworking, not metalworking. I'm not building rockets here, just furniture and some occasional weld art.
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Are you having a hard time getting blade 90’ to the table?
Have you checked to make sure all the motor/housing/ brackets bolts are tight.

I struggled getting my Dewalt 10” running true to the miter slots.
Took me a good while to fund 2 hidden screws that got me that last bit.

This might be a bit of a hack.
Have you considered epoxy on the low spot? Like body filler?
 
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