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[Kerry Verne]

Now that I have my garage cleaned, I started work on my sled. Cutting into $60/slab of this phenolic coated BalticBirch, I take my 20x20" piece and set it on the top of my saw to see how it fits.

Then I notice that it's not flat, and rocks diagonally about 1/16+. Possibly warped?

So I rotate it 90 and try again... it still rocks diagonally in the same spot.. which means that its not the plywood.   

After I'd bought the saw off Craigslist, I noticed someone had managed to deform the case, like it had been dropped on it's head. No cracks in the cast iron, so I figured it just needed shimming. Now I'm not so sure. It's not just one corner higher, but a slight bulge on the right side of the blade.

For now, I'm hoping I just shimmed it wrong and I can straighten it out.  I've got $400 in the saw, another $350 in the 50" fence, and gobs of time that I'm not keen on repeating. A new tabletop is $200 +S&H, and the case is still bent. Maybe a hand built cabinet would fix it, but maybe not.

The upside is that tax season has started, and the woodworking itch is helping everyone else upgrade their tools with their refund/rebate checks, leaving their old saws on CL for me to pick through. I'm due one too, but a jointer and planer were the only items on the list.  I could do a CL swap and sell mine to someone else, buying some other guys old saw.

Or sell it for $500, and upgrade to a real cabinet saw with cast iron wings.

[Scott Peterson]

That is a bum deal!

Just a thought - could you take your table top to a machinist and have them grind it flat again?  Might be a stretch, and I would also make sure the blade can still be set right (parallel to the miter slots and perp to the table).

Another thought is to use some rods and linear bearings up off of the table surface to support the sled - much like Lee K's setup.  Might be a lot of monkeying around every time you set it up again to be sure both rails are in the same plane, and the blade is set right wit respect to the sled...

I hope something works out for you!

[Kerry Verne]

Thinking on it during the day, I'm really hoping it's just shimmed too high in the front right corner.

[Kerry Verne]

Once again, no beer before shop time, and make sure you're not tired.

Saw is fine, though not perfect. Plywood was warped and I feel like a tool.

[Scott Peterson]

Glad to hear the tabletop is in good shape.  I thought about it more during the day also and wondered if it is possible to warp a cast iron (?) table by dropping it...  I remembered a smash lab session where we did a tension test on a cast iron coupon - it doesn't extend or flex much before simply fracturing.

After testing against a straightedge - I found my tablesaw top is not perfect either, but OK.  With the MIC-6 sled, I can find small gaps as the sled is slid across the table.  However, I think it's relatively minor.  The art in all of this is that NOTHING is perfect, and the task is to work around the imperfections and not let them multiply.  I scrutinize for so long, but after I have a bunch of pieces cut and find a tiny error - then the task is to put the error in a place where it won't be seen or won't matter much.  Seems a little dishonest if I get too hung up on perfection, but realistic after I remind myself nothing is perfect.  So goes all of woodworking, I suppose.

I have not found phenolic to be real flat (I bought a 1/2" phenolic plate before turning to the MIC-6 aluminum), and haven't worked with Baltic Birch plywood much.  I think MDF is about as stable as manufactured wood can get, but maybe that is more opinion than fact. 

[Canuck]

Just a thought Kerry, a long straight edge might be a good investment.  Lee Valley's Veritas line sells one that would be perfect for setting up the offset on your jointer once you get it up and running.  I should be one to talk I don't even have one, but have pined for one for a while now, it's next on my list of must buy items.

[Kerry Verne]

That's not a bad idea at all.

[Scott Peterson]

Good suggestion, John!  I actually bought the 24" aluminum straightedge from Lee Valley last summer when I was building my sled.  I think they are a good value - maybe not as permenant as a stainless straightedge, but about 1/2 to 1/3 the cost - and not a tool I use very often.

By the way, I use my granite surface plate a lot more than the straightedge for making puzzles.  Surprisingly, these are not as exotic nor expensive as you might think before tuning into the availability and realizing how common they are.  I got mine from Woodcraft (about 2" x 8" x 12" or so) for about $30 if I remember correctly - they sell them for sharpening.  I use it to make sure all the polyhedral building blocks are glued together nice and flush - as well as checking flatness.

[Canuck]

Yeah those granite surface plates sound like the ideal thing, I currently use a glass 'breadboard' which is actuall really flat although probably not as flat as the granite plate would be.  I've yet to find a supplier here in Canada for them

[Scott Peterson]

Looks like Lee Valley carries the granite surface plates too...

http://www.leevalley.com/wood/page.aspx?c=2&p=32526&cat=1,43513,51657

These are also common for machinist work.  You might check machinist supply shops, or maybe the store you mentioned a while ago which is the Canadian equivalent of Grizzly?

[Canuck]

Thanks for that link Scott, man I swear I've never seen that in their catalog before and i've looked through it a million times!

[Kerry Verne]

Grade B from Enco is $15.
 http://www.use-enco.com/CGI/INSRIT?PMAKA=640-0100&PMPXNO=947969&PARTPG=INLMK3

[Canuck]

I've seen guys mention 'Enco' quite a bit on the pen boards, their prices are really low!

[Phil Tomlinson]

I've gotten several items from Enco--you can't beat the prices for the "B" line items, which are usually plenty accurate for woodworking tolerances.  The granite slab is a great deal.  Plus they send you one of those monster catalogs.

[Kerry Verne]

I saw this on the SawStop article:

At the insert opening, the tabletop had a crown of 0.011 in. when I first examined it. (Hybrid saws and cabinet saws tested recently all had suitably flat tables.) Rather surprisingly, when I rechecked the table's flatness after we had run test cuts and fired off the brake mechanism two times, the top had settled down to a much more reasonable crown of only 0.005 in. A sharp blow can sometimes snap warped cast iron back into flatness, and I suspect that firing the brake cartridge did exactly that.

Update: Table Flatness

When the SawStop manufacturer read our original review, the company president did some investigating. Here's what he said about the table:
I don't think it is likely that firing the brake would change the table flatness. There just isn't that much force imparted to the table. I think it is more likely that the change might have come from different pressure on the tilt limit stop. We surprised to see that you had a table crown of 0.011 in. We played with a saw here and found that if you apply much force after you reach either of the tilt limit stops, you can easily crown the table.

Considering that I usually set my alignment to my square, I'm tempted to back the positive stops out further than 90, and avoid any undue pressure from underneath.