Unisaw table flatness

[Ron Kellison]

I purchased a 5HP LT Unisaw with a 52" Bies fence a few months back at a price that I couldn't resist. As I haven't gotten around to reworking my shop to install 220V I've taken my time in assembling and adjusting it. It has been an educational experience!

I've learned that the aluminum used in most beer cans is 0.00125 thick and that it's a rough job to move and align extension wings working alone. In the process of aligning the saw, I've discovered that while the wings are absolutely flat the actual top of the table is dished across 0.015, mostly on the right side of the blade. It is also dished 0.008 front to back, mostly near the blade insert.

While I realize that accuracy requirements are really dependent upon the work being done, I would be interested in knowing what tolerances are expected by the other denizens of Sawmill Creek. Do you think my saw will be inaccurate enough to notice?

Regards,

[Mike Marcade]

In my opinion .015" flatness sucks, especially for a saw that demands big money like a Unisaw. My cheap Grizzly jointer tables are flat within .0015". I would expect the big money cabinet saws to have flatness in the ballpark of my jointer. Just my opinion, mind you.

[Rick Lizek]

I know for a fact that Powermatic considers .015" tolerance for the main table of the Model 66. A warm breeze will make your wood move that much. Most woodworking machines don't need the tolerances of metalworking machines. A jointer would be to tighter tolerances. On my older 16" Oliver jointer the old Oliver considered .010" an acceptable flatness for the table. Your saw is fine in my opinion and experience.

Also what are you using for a straight-edge? A level or a real machined straight edge. Companies have to draw the line somewhere on standards. Most saws are pretty flat for the most part.

[Mike Marcade]

I would expect the accuracy of the tool to be an order of magnitude better than the work you are trying to produce.

[glenn bradley]

Steel City and Delta have stated in emails that .01" is within tolerance.

[Ron Kellison]

I'm using a 24" German straight edge acquired from Lee Valley and one of the new 50" Veritas straightedges. I'm also using a set of Mil-spec feeler gauges.

[Bruce Page]

I think we would all love to have dead flat tables. I also think .015 out of flat on a tablesaw is a non-issue. Think about it, what exactly is being affected as you cross-cut or rip?

[Pete Bradley]

In my opinion .015" flatness sucks, especially for a saw that demands big money like a Unisaw. My cheap Grizzly jointer tables are flat within .0015".

What effect do you expect .015 in a table saw to have on the work and why?

Are you saying your griz jointer is good to .0015 over the length?

Pete

[Art Mann]

My guess is if you had never used the straight edge and feeler gauge, you would never have known the difference.

[Cliff Rohrabacher]

I've learned that the aluminum used in most beer cans is 0.00125 thick

I rather suspect that there is one zero too many in there.
It's more like 0.0125" or Twelve Thousandths. The extra zero makes the material lots thinner than aluminum foil.

At any rate I've made the tooling for stamping beer cans.
The material they start with is a flat disk of aluminum. The forming dies are carbide. the upper set drop onto the disk with oodles of force, grab the aluminum and pull it up around the internal die that forms the can shape. It's a fast and hot process. the metal is stretched so that it's lots thicker at the base than the top where the seal is when the can is filled & finished.

[Ron Kellison]

I just remeasured using an electronic caliper and got 0.0020 in my cold shop.. With a 1" micrometer I get 0.0035. Of course, that may be because I cut the these particular shims from an Old Milwaukee can and they may go for the thin stuff to match the quality of their beer!

In any case, I'm inclined to agree that if I didn't have the straight edges and feeler gauges I may not have noticed the dip in the table! After I get power I'll let the quality of the cut determine how happy I am. I'm sure it will be much better than my 30-year old Craftsman!

[Mike Marcade]

What effect do you expect .015 in a table saw to have on the work and why?

Are you saying your griz jointer is good to .0015 over the length?

Pete

I just expect a pretty good flatness on a machine that is quite expensive like a Unisaw. Maybe my expectations are too high.

On my Grizzly jointer, I place a 4 foot precision ground tool steel straight edge along the length of my outfeed or infeed table and can not get a .0015" feeler gauge underneath it anywhere.

[Greg Funk]

I've never put a straightedge on my Unisaw and I don't intend to unless I suspect it is somehow hindering my ability to make straight and square cuts. I don't think it is a critical tolerance.

Greg

[Mike Marcade]

I've never put a straightedge on my Unisaw and I don't intend to unless I suspect it is somehow hindering my ability to make straight and square cuts. I don't think it is a critical tolerance.

Greg

How did you align your wings?

[Gary Keedwell]

How did you align your wings?

Hey....That's what I was thinking...I wish I didn't put a straightedge on my Uni....I lost all respect for it especially after I went to a show and the guy showed me how flat the Steel City TS was.
Gary