Lapping a cast iron surface

[woodchucker]

No to a camelback for a tablesaw. Guys, this is a contractor saw. No need to go to those lengths. A level would be good enough.

 

[MikeInOr]

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.

 

[Dabbler]

@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)

 

[woodchucker]

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.

 

[Alcap]

Any ideas on how the top got low in the middle ?

 

[MikeInOr]

Any ideas on how the top got low in the middle ?

I would bet it came that way from the factory.

 

[woodchucker]

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.

 

[mac1911]

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.

Is the table worn or poorly supported and the cast is sagging?

 

[MikeInOr]

I agree with @MikeInOr, it's probably in their seasoning, and then milling

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.

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.

I love the corrugated top on my Italian sliding table saw!



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.

 

[mac1911]

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.

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?