Used Table Saw... if the table is not dead flat should I move on? What else to check?

[Nick Sorenson]

I am considering buying used for a heavy duty cabinet table saw. What should I look for? If the table is not absolutely flat should I move on? Also what about the fence?

I'm curious. I would think that over time steel will bow a little bit and move from perfectly flat. So if I do buy used should I move on from saws that don't have a dead flat table?

Accuracy is important to me.

thanks!

[Simon Dupay]

You don't need a very flat table on table saw, it won't effect accuracy if the table is out less then .02-.03. Unless it was in a fire a cast iron top shouldn't warp-so don't be so picky.

[Nick Sorenson]

Originally Posted by Simon Dupay

You don't need a very flat table on table saw, it won't effect accuracy if the table is out less then .02-.03. Unless it was in a fire a cast iron top shouldn't warp-so don't be so picky.

I'm not sure that's true... I don't know all of course. But if the table is wavy the edge cut would be a perfect 90 in some spots and off in others as the board follows the error in the table. That could make for a bad joint I would think.

[John Downey]

Originally Posted by Nick Sorenson

I'm not sure that's true... I don't know all of course. But if the table is wavy the edge cut would be a perfect 90 in some spots and off in others as the board follows the error in the table. That could make for a bad joint I would think.

You'd be absolutely amazed the kind of bad joints you can make work if you want to. I wouldn't bother worrying about how flat a top is, any more than I worry if the jointer table has old rust pits (mine does). Learn to work around the imperfections in your work and you might just have something to show for your efforts, but obsess about making the "perfect" joint every time and you'll spend years getting nothing done. Just my opinion, worth what you paid.

[scott spencer]

Blade and fence alignment, setup, arbor runout, blade runout, throat insert, etc., are very important to accuracy. Table top deviations would have to be pretty significant to effect the cut...depending on where they are. Keep in mind that we're dealing with wood, and by it's very nature it can move quite a bit from day to day. You'll want your TS top to be visibly flat, but I wouldn't lament over that aspect. The vast majority of tops should be suitable.

[glenn bradley]

Manufacturers who have stated tolerances to me via response to my requests were .008" and .01" variation across the table. A variation of .004 on my saw caused me to inquire. It has been a non-issue in practice.

[lou sansone]

as others have said, the top should be flat, but don't obsess when it comes to thousands of an inch.

lou

[Caspar Hauser]

It's Wood, Wood I tell you, Wood, wood, wood ...hahahahahahahahahaha wood wood wood wood wood wood

[Nick Sorenson]

It is wood. I could definitely be wrong here. I looked at a local cab shops 1970 or so Unisaw and I have another local cabinet friend whos also considering a sawstop and mentioned selling me his powermatic. The first one I saw had about a .050" arch in the center. In all directions it dropped toward the edges. It's hard for me to immagine that this wouldn't cause an edge to be angled a bit almost as if the blade were tilted. Seems like this would cause the joint to be tight on say the bottom but wide open by whatever the deviance was times two since two cuts were made to get two edges to joint. But I could be wrong. I just don't see how it couldn't effect it. I know on my radial arm saw, the manual and Mr.Sawdust book both said (and Jon Eake's book) all said, make sure that that radial table is dead flat and straight in every direction. They all seemed to make a big deal out of it.

[glenn bradley]

Originally Posted by Nick Sorenson

In all directions it dropped toward the edges. It's hard for me to immagine that this wouldn't cause an edge to be angled a bit almost as if the blade were tilted

The significance of that effect would vary with the size pieces being run and how the support beyond that point is. Making guitar parts I could see your pieces being of a size where this could be of concern. this is where most folks use a jointer to prepare the glue joint.

The deviation in the top can be dealt with to some degree. I was able to minimize mine (accidentally) while re-aligning the top. Cast iron is quite flexible and my rearrangement of the corner shims (cabinet mounted trunnions) gained me a greater degree of 'flatness'. This made me curious so I experimented and ended up better off than when I started.

I think if you search under 'glue line rip' or 'glue ready joint' around the web you will find a few of us who are lucky enough to go straight from the tablesaw to the glue up but, many folks joint or handplane to prepare. As to the deviation or 'tilt' you refer to, IMHO there can be more deviation than that in the stresses released from the material as a reaction to the cut. HTH.

[Mike Cruz]

Ha, dead flat. I can only imagine the general population they are addressing when they say that. We are woodworkers. We care about things like .05 of an inch. Pardon me, in advance, to everyone that I offend, BUT, they are putting that in a RAS book. How accurate is a RAS when you pull it out 16-20 inches? If it were 1/32" off, I think that would be pretty good!

My brother has a RAS. He is not a "woodworker". He uses it. It works. His table is as "dead flat" as he needs it to be.

[John Thompson]

Move on from saws that don't have "dead flat" tables.... Nick

If that is a must for you Nick, you're going to do a lot of moving! Put a straight edge on the saw to see that is is realitively flat on the center table that the blade is housed in. Make sure the wings are adjusted properly so they are not higher than the center table. It doesn't matter if there is a dip 1" deep in the center of a wing... that will not matter what-so-ever. But a large bow up would with long stock. Also be sure the outer perimeter of the wing is not raised above center table height when the extention is mated or just a hair below the main table. That alsowould affect a cross-cut with long stock that extends over the outer edge of the wing. Not much but it would cant the cut slightly if the blade is vertical to the center wing.

I notice from your other thread you have concluded a machine must have a dead accurate flat fence and now a dead flat table from this thread. With no offense intended that is a "tell" you are not yet an experienced WW that understands what is important and what is not at this point. When working with wood you are not going to purchase dead on precision you are looking for with the purchase of a TS alone.

Good luck in your instrument making...

[Ken Fitzgerald]

Wood is a dynamic material. It is not metal which can be dynamic too.

When you cut or machine wood you will see variations ....some quite extreme because of the conditions under which the wood grew .....was it a limb...did it grow vertical....did it grow horizontal......if horizontal was it on top the limb or the bottom of the limb......did it grow in a dry climate .....was it grown in an extremely wet climate.........was it cut during the spring and summer......was it cut during the winter..... All of these factors affect the internal tensions and humidity within a given piece of wood. Kiln drying may ....MAY help decrease the effect of the moisture content of the wood but....the internal stresses can still be released when cutting.

When you cut or machine wood you are cutting a dynamic material.

The material will change after you have cut it and it has absolutely nothing to do with the tool you used. It's wood. That's it's nature.

1/64 of an inch equates to 0.0156.......I personally wouldn't fret over any variance less than 0.015.

[Don Jarvie]

As long as the fence and blade are square to each other then the flatness of the table shouldn't be an issue as long as it's relatively flat.

Even if you push down on the wood it wouldn't effect the wood unless the blade or fence isn't square to the table.

It would effect the crosscuts if it was way out but cast iron on the big saws is so thick it shouldn't dip unless it was damaged over the years.

[Pete Bradley]

Table flatness is way down the list. Some things to consider:

1. Are there missing or broken parts? Look carefully at the raise and tilt mechanisms expecially. Are replacements available for whatever you find? What haven't you found (there's always something)?

2. Is the arbor in decent condition? Contrary to the advice you'll usually get here, bearings are cheap and relatively unimportant. A chewed up arbor is a problem.

3. Do you have suitable power for the motor? If not, factor the cost of a VFD or new motor in your offer price.

4. Does it have a serviceable fence and a blade guard?

5. Is the table way out of flat? There's no such thing as "dead flat", only differing degrees of flatness.