How flat is flat enough for a straight edge?

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Forum topic by Sirgreggins posted 08-11-2013 12:41 AM 2113 views 0 times favorited 15 replies Add to Favorites Watch
View Sirgreggins's profile


299 posts in 2259 days

08-11-2013 12:41 AM

I’m looking to add a jointer to my shop soon. I’m a recent college grad so i dont have much money. I saw an iGaging straight edge at Grizzly for $50 and a Veritas one from Highland woodworking for $65 (both 36-38”). I know that these are relatively inexpensive for the kind of accuracy they claim but like i said i dont have much money. otherwise i’d be going with Starret. I have a decent carpenters level that stays in the case so it doesnt get dinged, but i doubt its flat enough to set up. Of course if you guys think this is accurate enough then i’ll use that. Both of these straight edges claim to be within .003” but ive read mixed reviews on both. What are your thoughts? Thanks as always

15 replies so far

View Dallas's profile


3599 posts in 2511 days

#1 posted 08-11-2013 12:51 AM

An old guitar string will be more accurate than anything you could by with a straight edge.

Consider this:
Beautiful wood work and furniture was created thousands of years ago with nothing as close as a .003” tolerance. Wood moves. Even if it’s dead, it moves.

-- Improvise.... Adapt...... Overcome!

View HorizontalMike's profile


7758 posts in 2937 days

#2 posted 08-11-2013 12:53 AM

To be honest, I just use the 3ft, 4ft, and 5ft versions from HD. The 5ftr is just $11, and I have had good luck with them for years. I am about to replace the 3ftr because of wearing it out after making repeated cuts/marks with a razor. Why spend a fortune…

-- HorizontalMike -- "Woodpeckers understand..."

View firefighterontheside's profile


18351 posts in 1880 days

#3 posted 08-11-2013 01:15 AM

I’m happy to hear you guys saying that. I use a straight edge like Mike mentioned. Seems straight enough to me. My joints close up.

-- Bill M. "People change, walnut doesn't" by Gene.

View Loren's profile


10476 posts in 3671 days

#4 posted 08-11-2013 02:12 AM

I use a level. I have a couple of expensive 24” straight edges
but for jointer setups… meh. Not needed.

View NiteWalker's profile


2737 posts in 2600 days

#5 posted 08-11-2013 08:54 AM

I have 24” and 38” veritas aluminum straight edges and they’re great. Plenty accurate for setting up woodworking machines. I though I’d have buyer’s remorse for not buying a steel starrett, but the aluminum veritas are great.

You can get them cheaper direct from Lee Valley.

You always hear about how wood moves, so accuracy to .003 or whatever isn’t needed. The thing is you’re not setting up wood; you’re setting up your machines, where that .003 can make a difference.

-- He who dies with the most tools... dies with the emptiest wallet.

View JoeinGa's profile


7736 posts in 2030 days

#6 posted 08-11-2013 01:11 PM

.003??? REALLY? What are you building? medical equipment? or airplanes to government specs?

Geeze, if anybody thinks wood that is within .003 out-of-flat wont clamp up and the joint be invisible is WAAAY more anal than I am :-)

-- Perform A Random Act Of Kindness Today ... Pay It Forward

View Sirgreggins's profile


299 posts in 2259 days

#7 posted 08-11-2013 02:14 PM

i’m never concerned with wood being within .003”, ive just heard that one might want to set their machines up to be within that tolerance. I will use my level. Thanks for all the great feedback. LJ’s is the best place for WW info around.

View RobsonValley's profile


31 posts in 1787 days

#8 posted 08-11-2013 02:29 PM

There’s a great advantage in being able to align machinery to that sort of tolerance.
You can never blame your golf clubs for your lousy play.

View BJODay's profile


526 posts in 1966 days

#9 posted 08-11-2013 02:34 PM

I was using the “5 cuts to perfect cross-cut sled” to square up my sled fence. I was getting frustrated because I kept adjusting it back and forth and couldn’t get closer than o.003” over the length of the fence. Then I woke up and thought 0.003 ” is a pretty small margin. A sheet of paper is typically 0.004”.

Cut yourself some slack. I would purchase a level. Then you have a tool that can be used for more than one job.


View Bogeyguy's profile


548 posts in 2091 days

#10 posted 08-11-2013 02:57 PM

Amen!! Not meant to be a religious statement. LOL!

-- Art, Pittsburgh.

View darthford's profile


608 posts in 1947 days

#11 posted 08-11-2013 06:59 PM

I don’t have the time or patience for frustration, these are my frustration fighters -

Starrett combination square with 12” and 24” satin chrome finish blades. Your average HD square isn’t square.

Mitutoyo coolant proof digital calipers, 6” or 8”. In addition to using them in the shop I almost always takes these to the stores and lumber suppliers.

Dial indicator with magnetic base and T slot jig for setting up tools.

Incra MITER5000 Table Saw Miter Gauge with Sled and Telescoping Fence.

Sharp blades and bits of good quality.

These shop lights with daylight bulbs

You can do some fine work even with less expensive power tools if you have the tools to dial them in accurate.

View Sirgreggins's profile


299 posts in 2259 days

#12 posted 08-11-2013 08:28 PM

How do i use a guitar string for determining flatness? I understand that under tension the string straightens out but is there a jig you can point me to? thanks

View Dallas's profile


3599 posts in 2511 days

#13 posted 08-11-2013 08:34 PM

Clamp guitar string to one far end of piece to be checked, clamp other end of string to other end of piece to be checked under tension.
Anyplace with daylight under it is not flat.

-- Improvise.... Adapt...... Overcome!

View pintodeluxe's profile


5702 posts in 2837 days

#14 posted 08-12-2013 06:27 AM

A Veritas straightedge would be great.

A cheap check for your builders level is to lay it on a jointer bed (a known flat surface). Use feeler gauges to check for gaps at each end, and in the middle of the level. Then flip the level over to the other edge and recheck. If the gap remains consistent, and is less than .002” it is accurate to set up a jointer. If the gap changed, your level is not perfectly straight.

Good luck.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View Sirgreggins's profile


299 posts in 2259 days

#15 posted 08-12-2013 01:39 PM

Thanks pinto. Another great tip to stow away

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