Delta DJ-20 Leaving Wood Concave

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Forum topic by BerBer5985 posted 10-04-2012 04:12 AM 1306 views 2 times favorited 9 replies Add to Favorites Watch
View BerBer5985's profile


445 posts in 2388 days

10-04-2012 04:12 AM

I’ve been working on tuning up my DJ-20 jointer that I just got a few days and after getting the knives set and going though one round of making the tables co planar and everything, I finally ran my first board through, which was a junk piece of 4×4 about 36” long. After checking it, it’s leaving the board concave in the middle with about an .011” – .012” dip in the middle. I first though the knives were set to high so I did it again, reset all of them, and tried it again. Seemed to get slightly better, but still about the same. I set the tables with the only straight edge I have which is the veritas 36” aluminum straight edge. I checked the tables again and as far out as the straight edge will go, it seems they are co planar, although they might be off slightly on the far ends, but the straight edge won’t reach? Any suggestions? I thought maybe my technique but with it being a 4×4, I doubt there would be much deflection in the middle. Any other thoughts?

-- Greg, Owner, Quality Carpet One,

9 replies so far

View MedicKen's profile


1612 posts in 3430 days

#1 posted 10-04-2012 04:17 AM

Sounds like you may be applying too much pressure to the board as it passes over the knives. It should onlu take enough to hold the board down to the table, let the machine do the work, not you.

-- My job is to give my kids things to discuss with their

View patron's profile


13600 posts in 3308 days

#2 posted 10-04-2012 04:24 AM

outfeed table might be a tad to low

i adjust by running two boards together on edge
and mating those two edges
if outfeed to low
the ends will touch
but middle don’t

if out feed to high
the middles touch
but not the ends

i don’t have any gauges or ever used one
just different cab shops i’ve worked in
taught me quick ways to adjust tools

like fence parallel to table saw blade
if the board throws sawdust from the fence side
the back of the fence is to loose
if it throws sawdust from the saw side
the back of the fence is to tight

when it quits throwing sawdust
i just go back to work

-- david - only thru kindness can this world be whole . If we don't succeed we run the risk of failure. Dan Quayle

View Roger's profile


20923 posts in 2771 days

#3 posted 10-04-2012 11:59 AM

I agree with MedicKen and Patron. Also, your pressure should be on the outfeed table, past the knives

-- Roger from KY. Work/Play/Travel Safe. Keep your dust collector fed.

View BerBer5985's profile


445 posts in 2388 days

#4 posted 10-04-2012 03:27 PM

I tried a few times changing my technique and was continually getting the exact same results, so then I raised the outgrew table ever so slightly and got to within .004” over 36”. I may play one more time, but if not, I think I can live with the thickness of a sheet of paper over a long span. Plus I have the Byrd on its way, so I doubt it’ll be a problem after that! Thank god!

-- Greg, Owner, Quality Carpet One,

View gfadvm's profile


14940 posts in 2658 days

#5 posted 10-05-2012 02:33 AM

David- Your tips and tricks are always so practical and common sense. Thanks for your contributions!

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View MonteCristo's profile


2099 posts in 2156 days

#6 posted 10-05-2012 03:33 AM

4 thou is pretty well as good as it gets I would say.

-- Dwight - "Free legal advice available - contact Dewey, Cheetam & Howe""

View pintodeluxe's profile


5623 posts in 2781 days

#7 posted 10-05-2012 04:47 AM

Try using a feeler gauge and a little longer straightedge. I shoot for within .002” of coplaner.
Then try another board. I have ran into a couple boards that were so uneven or twisted, that no jointer could fix them.

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

View BerBer5985's profile


445 posts in 2388 days

#8 posted 10-05-2012 11:42 AM

I ordered a lee valley 50” straight edge even thought I have the 36” already, but I’m going to check the tables one more time. But right now, the wood is coming through slightly concave around .003” over a 36” piece. Which I don’t think is too bad. I’d love it to be closer to less than .001” if I can but I may be searching perfection that I can’t find. I’m sure that that could also be cause by the tables not being 100% flat. There’s a .0025” concave area in the middle of the out feed table that is probably the cause of the imperfection. I think it’s livable.

-- Greg, Owner, Quality Carpet One,

View Milo's profile


869 posts in 3287 days

#9 posted 10-05-2012 11:56 AM


I had problems using a jointer forever. One thing that finally helped me out was using two push blocks to move the wood over the blades. For some reason it helped me distribute the pressure properly. You might try that.

-- Beer, Beer, Thank God for Beer. It's my way of keeping my mind fresh and clear...

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