How flat is your table saw top?

[Matt Allan]

Setting up my saw now and curious as to how flat you guys get your tops. Setting up a PM66 and aren't overly thrilled with its flatness from the factory. Having to adjust part of the stand and still need to shim a few places to get even better, slight cutting in the front and back.

How flat do you guys get your tops?

[lou sansone]

Setting up my saw now and curious as to how flat you guys get your tops. Setting up a PM66 and aren't overly thrilled with its flatness from the factory. Having to adjust part of the stand and still need to shim a few places to get even better, slight cutting in the front and back.

How flat do you guys get your tops?



I try to get them pretty flat, but I don't have a 6 foot machinist straight edge to check it with. I would say that it was within maybe 0.01, but that is just a guess. With the size of the saw that I have it took a little fooling around to get it flat within reason.
This link will explain what I am talking about.
http://www.sawmillcreek.org/showthread.php?t=18836

lou

[Derek Arita]

Had a Jet and the top was dead flat. Have a PM66 and I had to shim the top to get it flat to within .002. I know there are those that will say as long as your top is within .008, you're OK. However, once you've had a table saw with a top within .001 of flat, you can't help but feel every top should be that way. Wish my PM had a Jet table top.

[Matt Allan]

Had a Jet and the top was dead flat. Have a PM66 and I had to shim the top to get it flat to within .002. I know there are those that will say as long as your top is within .008, you're OK. However, once you've had a table saw with a top within .001 of flat, you can't help but feel every top should be that way. Wish my PM had a Jet table top.

Yep, my last saws top was dead flat. Ironically it was a PM 64a, and now that I have upgraded to a PM66 I need to screw with the top more. It was really bad in the back when I got it, big cup because one corner of the stand was up too much and the bolt in the back was just pulling the center down. After fixing that high spot on the stand the top is relatively flat but not perfect yet.

I have a very slight bit of cupping in the front center, which is harder since shimming there isn't as easy and will require a bigger shim.

Any tips getting the 66 top flat?

[scott spencer]

Hi Matt - My GI is pretty flat. I've never measured it, but using up to a 4' straight edge there wasn't enough variation to raise any concern, although I did need to shim one of the wings.

[Dave Wright #2]

Here are the factory specifications that came with my saw:

Table Flatness Measured Diagonally: 0.010" Maximum Gap
Overall Table and Extension Wing Flatness: 0.025" Maximum Gap

I believe those are typical specs, though most manufacturers don't publish them. Flatter is better, for sure, but tops that as flat as the above specs will perform well for woodworking applications.

Worrying over getting the top flatter has diminishing returns. My previous saw had a top that was crowned and well outside of the spec. It bothered me to cut on this potato chip of a top, but I must admit that it didn't seem to reduce the saw's performance.

FWIW my saw seems to have come much flatter then the specs. I don't see light below an engineering straightedge moved around the top.

Good luck setting up the saw!

Dave

[John Hart]

I got pretty anal with my saw's flatness and made sure that I couldn't see light in a straight edge across the main surface and to the wings. I figure I'm well below .010. Now I need to find some flat wood!:)

[Kelly C. Hanna]

I couldn't get a dollar bill under the gap I saw under the straightedge on my 1023s top...good enough for me.

[Jim Becker]

I had to slightly shim the wings on my Jet LT cabinet saw with some foil, but otherwise, the top is dead flat...at least with anything I own to measure it. For metal-working, I'd be more concerned about verifying it, but for woodworking, I have other things more deserving of my mental processing...such as getting more shop time and not making the same mistakes more than three times! ;)

My fence is a different story...I need to replace those plastic faces "real soon now"...

[Derek Arita]

Matt,
You sound a lot like me. Flat, to me, means dead flat. I was advised to use brass shims. I was using cheap feeler guauges to shim, but found that tightened down, the top would slide around on the shims. The brass is soft enough to grab, but hard enough to maintain thickness.
I used the brass for shimming around the bolts. Shimming at various points around the mounting bolts, I could "tweak" the top quite a bit. I also used brass to shim the extension wing mounting surfaces, so that the wings were flat. That's where a lot of slippage occurs unless you use a material that can get a bite, like the soft brass.
For the center-front of the table, I did use a stack of feeler guages to raise a dip in the middle of the table. Slippage wasn't a factor there.
With all of the variances in woodworking materials, I like to at least know that my machines are as close to perfect as I can get them, so that they are not adding to the problems. Good luck. Let me know how it works out.

[Kent Cori]

I've had about the same experience as Kelly. My Griz 1023SL top is flat enough that I can't get a piece of paper underneath my 4' straight edge.

[Dev Emch]

I have not seen any published specs on my two saws but I did come across a wallace jointer publication from about 1925 which listed this jointer to have a table within +/- 0.002 inches or 2 thousandths.

I did put a 36 inch brown and sharpe machinists reference straight edge known as a camel back on my martin and I was not able to get a 2 thou feeler gage under it. There was the area covered by the throat plate but the throat plate is homemade from 1/2 inch birch ply. I used several positions with the camel back and was not able to get this 2 thou feeler gage to go under. I guess if I were to go with a 6 footer, I might be able to get a bit more light to show through and who knows, maybe even get the 2 thou feeler gage to wiggle under.

I am about the 4th or 5th owner of this martin T-17 which was made during the early 70s. It is solid cast iron to the floor and does not use the newer composit steel and concrete construction. But regardless of how you feel, the new fit and finish with this concrete steel sandwich construction is out of this world. They know how to build machines over there.

For the most part, standard blanchard grinding which leaves those large swirls will often have a flatness within about 8 to 10 thou max. If you can get to within 5 thou, I would say forget about it. But machines done with metal planers (the old way & what many germans and some itallians are using today), you should not be surprised to find flatness within 1 to 2 thou!