Table Saws: What does flat mean?

[williamebyrd]

1. I just got a new TS, and the top is out of flat by a certain amount (I'll tell you later).  What do you guys think should constitute "low-enough" to expect a replacement under warranty given its intended purpose of general woodworking?

2. I'm new and cannot get my profile set right to send email notifications of responses to my posts. I've tried contacting admin to no avail. Any ideas?

[Aram]

1. I just got a new TS, and the top is out of flat by a certain amount (I'll tell you later).  What do you guys think should constitute "low-enough" to expect a replacement under warranty given its intended purpose of general woodworking?

Here's a suggestion, rather than a hard number.

If the table is humped, and flat boards are rocking, you have a safety issue. Your saw tables are not flat enough. Barring that...

Get your blade set square to the table, by whatever means you trust. Cross cut a short, a medium and a long piece of wood. Check the cut ends with a square, meaning across the thickness of the board. Personally, I would do this on both sides of the blade. Do the same for a few rip cuts. If you are getting square cuts all around, be happy and build something.

Maybe there is another reason to care about flatness. I'm hard-pressed to see it though.

[williamebyrd]

"Maybe there is another reason to care about flatness. I'm hard-pressed to see it though."

I realize that performance is what really matters. But you paid for something that was produced within a certain quality "window". Would you be okay with a dip in the saw that was saw 2 times the spec even if it worked okay? (I'm not saying I have the spec. Can't find one.)

[Phil Thien]

I'm with Aram on this, I wouldn't think to check the table unless I was having a problem.

In terms of spec, my assumption is almost always that if I received it, it was in spec.

[arnman]

I bought my first table saw new, and I was new to woodworking. I don't remember how soon after I bought it that I checked flatness. I discovered that the table was dished about 0.010 inches around the throat and it was not easy to square the blade. It did not seem to affect performance (results of cutting mostly 3/4 thick boards) but I was not happy with knowing it was dished that much.

My new table saw is probably flat to about 0.003 but it is a better saw all around.

As much as I like for everything to be perfect, I have also found that dwelling on perfect can detract from my enjoyment of this hobby.

Ultimately performance for the intended purpose is what counts.

[Ohio Mike]

When I bought my Unisaw over 20 years ago I discovered a 12 thousandths dip in the top. It was right in front of the blade (the area between the throat plate insert and the fence rail).

I loaded it back in the truck and took it back to the dealer.  They fussed a little bit but exchanged it.  The replacement Unisaw is flat to within 6 or 7 thousandths and I consider that acceptable.  It hasn't caused any problems for me.


Mike

[jteneyck]

In my mind, 0.010" is about the maximum tolerable for low spots, and just about 0.0" for a hump. 

John

[Aram]

"Maybe there is another reason to care about flatness. I'm hard-pressed to see it though."

I realize that performance is what really matters. But you paid for something that was produced within a certain quality "window". Would you be okay with a dip in the saw that was saw 2 times the spec even if it worked okay? (I'm not saying I have the spec. Can't find one.)

I might send it back. Might. It would depend on whether it affected the work, my irritation level, and what the spec is. If they spec .003 and I get .006, maybe ok. One supposes that factory specs have head room built in. Maybe.

Another reason it's hard to give definitive numbers: a 0.010 dip 4 inches from the blade will be a lot worse than a 0.010 dip halfway across the table. Another example, a dip in the main table meeting up with a flat extension wing might be just a few thousandth of an inch discontinuity, but if your boards keep getting hung up on it, then it is a problem.

So I mainly look at how well the saw works.

I checked my 2004 Unisaw with a Starrett straightedge and feeler gauges. When I replaced it with a 1084 PM66, I just did a quick visual check. I'm pretty sure it is a lot less less flat than my Uni. I use it and I love it. No ill effects so far. Cut wood is cut wood.

[williamebyrd]

I purposely didn't reveal specifics fearing that it might color your opinion about what flat should mean with regard to table saws. Mine is a brand new R4512 Ridgid. Haven't even plugged it in yet. I hope you can see my drawing. This forum used to let you upload pics directly. The red area is low and maxes out at .023". I'll give 'em a call. I suspect they'll say it's within limits.

image

[Aram]

I purposely didn't reveal specifics fearing that it might color your opinion about what flat should mean with regard to table saws. Mine is a brand new R4512 Ridgid. Haven't even plugged it in yet. I hope you can see my drawing. This forum used to let you upload pics directly. The red area is low and maxes out at .023". I'll give 'em a call. I suspect they'll say it's within limits.

image

Can't see the pic, but yeah, that's a big ol' dip. I'd be looking for a replacement.