Checking a used jointer

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Forum topic by SeattleD posted 07-11-2013 09:38 PM 1589 views 0 times favorited 6 replies Add to Favorites Watch
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15 posts in 1216 days

07-11-2013 09:38 PM

I’ve owned 2 jointers in the past, a 6” Delta (complete with 2 warped fences) and an 8” Powermatic, which was fine. I’m now setting up a new shop & am looking at used jointers. What is a quick procedure for being sure the machine is straight & true? I understand that the infeed & outfeed tables must be flat & coplanar, and the fence needs to be flat & capable of a true 90 degree angle to both tables at the same time. I have a 50” Veritas aluminum straightedge ( and a good Starret 12” combination square. Is it sufficient to adjust the 2 tables so they are at the same height, then check them with the straightedge to be sure the 2 tables are completely flat in relation to each other across their entire width, then being sure the fence is capable of being set to 90 degrees to both tables at the same time, across the fence’s entire length? My understanding is that if the tables are not coplanar (for example, if the outfeed table “sags” at its far end in relation to the infeed table), that this is pretty much impossible to adjust on most jointers. What deviation from “totally-perfectly flat” in terms of these relationships is acceptable? What checks are good for making sure the blades are true to the tables? Any suggestions appreciated!

-- David

6 replies so far

View mantwi's profile


312 posts in 1313 days

#1 posted 07-12-2013 01:11 AM

Jointers typically have dovetailed ways and adjustable jibs that will allow some adjustment. It really doesn’t matter what brand it is they are all basically very much alike. If one of the tables is sagging use your straight edge and feeler gauges to determine the amount of sag. You can insert metal shims under the sagging table to bring it into alignment. By loosening the jib screws you can get enough play to lift the table for inserting the shims then snug the jibs back up to hold everything in place. The users manual will tell you where the jib screws are located and probably describe the steps for making the adjustment. Honestly i think the best way to determine what is allowable in terms of deviation from perfection can be determined most effectively by edge jointing two boards and seeing if there is a good fit. The wood mag writers love to talk about 1000ths and such but hey, this is woodworking not building rocket engines. Don’t obsess over that stuff, if it looks good it is good.

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312 posts in 1313 days

#2 posted 07-12-2013 10:40 PM

I forgot to say that you should only shim the outfeed table since it is rarely if ever moved you don’t have to be concerned about wear on the shims. Once you determine the thickness needed just use a piece of the feeler gauge under the lower end of the ways that support the table since it will be exactly the right thickness.

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Bill White

4403 posts in 3377 days

#3 posted 07-12-2013 11:08 PM

If the Veritas and Starret tooling is not accurate enough for woodworking, you’re sunk. I can’t imagine needing any finer accuracy. It the machines won’t tune with those devices,.........oh well.
Having said that, “totally” and “perfectly flat” are terms not often used in woodworking. Space ships? YEP!!!
Just remember that the wood you true up today is gonna have some different dimensions tomorrow unless you live in the desert or the arctic. Wood moves, but don’t be intimidated by the .0000…. stuff.
Maybe I need to start a site about WOOD REALITY…..........NOT!
Keep in mind that the classic woodworkers built stuff that has lasted for generations without being able to measure to the nearest gazzilionth (is that a real word) of an inch, meter, micron, etc.
Set ‘er up, and get after the woodworkin’. :)
All comments are meant to be constructive. Same as if you were sittin’ in my shop, and drinkin’ my coffee (or anything else).


View SeattleD's profile


15 posts in 1216 days

#4 posted 07-17-2013 10:58 PM

Thanks for the replies. I agree that woodworking doesn’t require the same tolerances as, say, machining cylinder heads, something I do need to remind myself of now and then. By the same token though, if I’m paying significant $$$ for a machine tool which claims to be able to deliver a certain level of precision, I do expect the tool itself to be accurately constructed. I mentioned I had a 6” Delta jointer about 12 years ago, which came with a very warped fence (middle of the fence was cupped inward more than 1/32”). This is unacceptable, and the replacement Delta sent was even worse. You’re not going to get precision out of the machine which is any better than its own construction tolerances, and things like a fence which is that distorted are not acceptable to me.

-- David

View pintodeluxe's profile


4824 posts in 2230 days

#5 posted 07-17-2013 11:32 PM

I just picked up a Delta DJ-20 8” jointer.
I would take your straightedge to make sure that the infeed table, outfeed table, and fence are flat. Don’t worry about coplanar yet, because that can be adjusted. Hear the motor run, and take a scrap and some push paddles to give it a try.
I hear people say that thousandths of an inch doesn’t apply to woodworking but… the jointer is one tool it does matter. Multiple passes compound any errors, so I shoot for coplanar to within .002”.

Mobile base? Dust Collection? Power? 110 vs 220?
All good questions to answer.

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

View NiteWalker's profile


2735 posts in 1994 days

#6 posted 07-17-2013 11:46 PM

Watch Marc’s video on jointer setup.

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

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