A little Cast Iron info Please? RE: TS tables in particular.........

[Mark Rios]

I'm starting to put my Unisaw back together (it's in 14 pieces right now) and after checking my table for flatness I noticed something strange.

When I first checked it, with the wings off but the main table still bolted to the cabinet, the table was dead flat (< .0015) on the diagonal, from my near left to the far right (standing on the infeed side). However, from my near right to the far left it had a dip with the lowest point at the insert cut-out. The dip was .017. I will assume that it was just bolted down out of the box and the original owner never checked it or adjusted it.

About an hour after I unbolted it and took it inside my house I checked it again and the dip was only .014. This was two days ago.

This morning I just checked it again and the dip is .009. The other diagonal direction is still dead flat.

Is the cast iron moving to flatten itself out? Does it have a memory? A memory that would last four years?

The table has a .005 dip at the insert cut-out when the straightedge is placed front to back. When the straightedge is placed side to side, it has a consistant dip from front to back of .003

What tolerences are acceptable?

Is there anything wrong at all?


I am using a 35" Snap-On precision straightedge (used for checking engine blocks and cylinder heads and such) and Snap-On feeler gauges.


Any info, help and/or advice is welcome and appreciated.

Thanks very much.

[tod evans]

mark, it`s a tablesaw for heavens sake! put the poor thing back together and cut wood. leave the .000002 stuff to the engineers. that saw table is going to be much flatter than any board you`ll pass across it and even then the board will start moving as soon as it`s cut....02 tod

[Mike Spanbauer]

Hi Mark,

On my 66, I had a similar situation when I purchased it years ago. It had been sitting in a shop unused for the prior 5 (poor thing ;). The top was dished from front to back around the throat and the wings crowned to the outside edge. During the rehab, I removed the top / wings and placed them on a piece of MDF I had on a spare bench (w/ torsion box top). Over the 2 weekends the rehab took me the crown nearly disappeared and the wings became almost perfectly flat.

So, I don't know if it moves slowly or not, but I experienced something similar w/ my saw and all I can think of is that the mounting bolts were too tight and the stresses relieved themselves?

Mike

[Jim Becker]

When you removed the top from the cabinet did you carefully note the location of each of shims (they look like washers, but are NOT washers) so that you could reinstall them in exactly the same position? Was the cabinet on a flat and stable surface when you reinstalled the top? (Cast iron BENDS...)

[Mark Rios]

When you removed the top from the cabinet did you carefully note the location of each of shims (they look like washers, but are NOT washers) so that you could reinstall them in exactly the same position? Was the cabinet on a flat and stable surface when you reinstalled the top? (Cast iron BENDS...)


There were no shims ( I did check) and I haven't reinstalled the top yet.


I got another "emergency" house fix up call this morning from the realtor I work for so it will be another couple of days before I can get back to it.

[rodney mitchell]

I wholeheartedly agree with Tod.

[glenn bradley]

If my math is right .003" is about 1/64" deviation over a four foot length; close enough for me.

[Kyle Kraft]

Cast Iron can be deformed over time due to uneven mounting surfaces, etc. I never set anything on my CI surfaces, except my workpieces while being machined. I always, in the case of a milling machine, return the table to a centered position with the vise over the saddle. This is also why it is so important to level a precision metalworking machine, because the machine can actually conform to the unevenness of the floor.

I heard a story once about a high school shop where a student set a heavy object on the end of a jointer table and it temporarily deformed the table in the direction of the floor a considerable amount. The question you have to ask is "Will it return to its original state?".

But I concur with the others, it's just a tablesaw. You're not making space shuttle parts on it.

[Jeff Horton]

The real question is how does it cut the wood? I have never had anyone take a dial indicator to my wood and thats what matters. Don't create a problem that is not there.

Dial indicators have their place in the shop but seems to me they cause more worry and concern than help.

[Bruce Page]

Mark, it sounds like the table had some stress induced during the previous setup. When you go to remount the table onto the base, take your feeler gages and check how it is sitting on the pads in a “free state” and shim accordingly. Use a torque wrench when putting her back together.