How Flat is Flat Enough?

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Forum topic by Chris_Tx posted 04-24-2019 09:32 PM 706 views 0 times favorited 13 replies Add to Favorites Watch
View Chris_Tx's profile


30 posts in 507 days

04-24-2019 09:32 PM

Topic tags/keywords: question tablesaw refurbishing

Hello all,
It seems that the cast iron table on my vintage table saw, is not quite flat. Laying a straightedge along it, I can slip a .01in feeler gauge under the straightedge in the center of the table, like so:

So my question is, should I be concerned about this issue? Should I take it to a machine shop and try to get it ground flat? Or is .01in not to bad? As you can see, I don’t have an elaborate setup to check flatness, so I don’t really know exactly how off it is. Any advice would be appreciated.

13 replies so far

View JayT's profile


6402 posts in 2987 days

#1 posted 04-24-2019 09:39 PM

Don’t fuss over it. Wood will move more than .01” over the course of a day of temperature changes. Square up the blade and fence to the miter slots and start cutting. The only time I’d even check is if everything was set dead on and cuts were coming out wonky.

Add in the fact that you don’t know if it’s the table or the measuring stick. Unless you are using a machinist’s straight edge, then you can’t know that the edge you are referencing off of is actually true.

-- - In theory, there is no difference between theory and practice. In practice, there is.

View Aj2's profile


3087 posts in 2574 days

#2 posted 04-24-2019 10:39 PM

Check closer to the throat plate with a shorter straight edge. Then you can get a better idea how to square the blade from the table.
The proof will be in the cut you get.
Wood doesn’t move .01 daily unless it’s still drying.
Report back Captain:)
Good luck

-- Aj

View fivecodys's profile


1637 posts in 2412 days

#3 posted 04-24-2019 10:44 PM

I’d call it good enough and go.
If you start making wooden parts for NASA then you might spend some more time fussin’ with it.

-- A bad day woodworking is still better than a good day working.

View John Smith's profile

John Smith

2440 posts in 938 days

#4 posted 04-24-2019 11:10 PM

I d call it good enough and go.
If you start making wooden parts for NASA then you might spend some more time fussin with it.
- fivecodys

if you start making things for NASA, you will have to send that straightedge to the Cal Lab
to be calibrated.



-- there is no educational alternative to having a front row seat in the School of Hard Knocks. --

View tomsteve's profile


1038 posts in 1995 days

#5 posted 04-24-2019 11:12 PM

Hello all,

, so I don’t really know exactly how off it is. Any advice would be appreciated.

- Chris_Tx

you dont know exactly how off it is so leave it be or find out exactly how flat it is before thinking about machining

View SMP's profile


2125 posts in 681 days

#6 posted 04-24-2019 11:15 PM

Looks like there is paint/stain on your ruler? What I do time to time is take a paint scraper and scrape my top as if I was a Benihana chef scraping the teppan. This gets the spots of glue, dried oil, metal ridges from scratches, etc down. That stuff can skew straight edges.

Not a big deal for woodworking, simce there are so many variables,but as many variables as you can remove will make it easier, less frustrating, and better results in the long run.

View Wookie519's profile


2 posts in 443 days

#7 posted 04-24-2019 11:40 PM

Dimensional stability to that magnitude isn’t something i’d worry about in my shop. You could probably straighten that table out with body heat by leaving your hand in the right spot long enough.

View AlaskaGuy's profile


5806 posts in 3085 days

#8 posted 04-24-2019 11:46 PM

I’m one of those nuts that like everything as close to true as possible. That being said the real test is how it cuts.

-- Alaskan's for Global warming!

View ruger's profile


142 posts in 871 days

#9 posted 04-25-2019 12:34 AM

LOL I wish I knew where I could buy some magical wood that never moved .

View Chris_Tx's profile


30 posts in 507 days

#10 posted 04-25-2019 05:19 AM

Hi again,
Thanks everyone for the input, I am glad to know that it should not be a problem to me, unless of course I can land that contract with NASA, but then I will probably want a better saw:)
Aj2, I did what you said, and checked closer to the throat plate, and the gap is certainly less there.
When I get the saw all back together, I will try the test cuts.
SMP, you’re right, I need to clean my ruler, it got to close to a stain-job a while back.
I am just like you AlaskaGuy, having something just a little out of whack really bugs me for some reason :)
Thanks again.

View Richard Lee's profile

Richard Lee

298 posts in 1551 days

#11 posted 04-25-2019 11:10 AM

As stated thats not a straightedge, you dont actually know whats out.

View dbw's profile


414 posts in 2412 days

#12 posted 04-25-2019 11:50 AM

As stated thats not a straightedge, you dont actually know whats out.

- Richard Lee


-- measure 3 times, cut once

View wingless's profile


77 posts in 518 days

#13 posted 04-26-2019 02:27 AM

Try using a Craftsman model 1019 Laboratory edition, signature series torque wrench. The kind used by Cal Tech High Energy physicists, and NASA engineers to adjust the bed.

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