Jointer Setup: How straight should my straight edge be?

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Forum topic by John146 posted 04-11-2017 01:06 AM 645 views 0 times favorited 5 replies Add to Favorites Watch
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90 posts in 650 days

04-11-2017 01:06 AM

So I recently scored a very good deal on a Ridgid 6” jointer.. however, the knives were not set straight, and I’m also wondering whether the tables are coplanar.

I’m now in need of a straight edge, but don’t have any good reference point to start with. I got a 8’x1” tube aluminum which I subsequently cut in half (8’ is too tall) and then proceeded to butt the halves against each other. There are some hills and valleys, and it seems that the biggest gap is 0.006”.

I’m not sure what else to test it against. I’m not entirely sure my table saw’s surface is perfectly flat, and the clamping ‘straight edge’ has a visible crook in it as well (when put on the table saw, and my square aluminum). The local store doesn’t have straight edges either.

Should I go the box level route? order one from Amazon? Is the gap I have good enough? I’m not good at math, so I’m not sure what that measurement means in terms of jointer set-up.

-- John 14:6

5 replies so far

View Redoak49's profile


3672 posts in 2194 days

#1 posted 04-11-2017 01:37 AM

I have the Lee Valley 38” straight edge that I use for alignment. It is flat to within .003” .

View mahdee's profile


4025 posts in 1973 days

#2 posted 04-11-2017 01:50 AM

You can use a simple jig for the knife adjustment. Piece of wood with 4 magnets in it; two 2” from each end. Put it on the fixed side and slide it over until the other two reach the blades. You have to eye where the center shaft is in reference to the blade tips to make an accurate adjustment. As it relate to adjusting the other side, once you level both sides to the fixed table, you are good to go. There should be two adjusting bolts underneath that are designed to level it to the fixed table.


View Markmh1's profile


92 posts in 649 days

#3 posted 04-12-2017 12:50 AM

My 24” Starrett rule (for a combination square) is straight to within .002. I’ve checked this a number of times using it when I worked in the tool shop.

I would consider that pretty flat/straight. You could try to get something cast iron and hand scraped but we’re only woodworking, right? I’d say leave the magic stuff to the toolmakers.


View Aj2's profile


1886 posts in 2003 days

#4 posted 04-12-2017 02:06 AM

I think should just get the knives set and run some boards if you get two edges jointed with out any gaps on the ends or middle it’s good.
Your probably not going to even be able to adjust them other then moving them up and down.
Good Luck

-- Aj

View John146's profile


90 posts in 650 days

#5 posted 04-12-2017 04:37 AM

I painstakingly adjusted the knives and from what I’ve measured, they are all 0.002” from each other. I tried with a test board and it worked well.

My issue so far has been with face jointing, not edge jointing. Maybe I’m not doing something else right, or maybe my push blocks are not gripping enough.

-- John 14:6

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