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How do you edge joint a convex edge on a jointer?

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Forum topic by SMP posted 08-14-2020 04:33 PM 793 views 0 times favorited 14 replies Add to Favorites Watch
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SMP

2446 posts in 753 days


08-14-2020 04:33 PM

I have always had difficulty edge jointing boards that are convex. Concave seems to be not a problem, but when i do convex edge jointing I seem to make it worse. I am guessing its my technique so I am wondering what fellow LJers do. Its a 6” benchtop so i don’t have a lot of infeed table to make a jig or anything.


14 replies so far

View John Smith's profile

John Smith

2651 posts in 1010 days


#1 posted 08-14-2020 04:45 PM

I am thinking that you want to take the “crook” out of a board for jointing ?
I would fasten it to a known straight board and run it through the table saw
to get a true edge on it. you can use any number of clamps, screws or hold-downs
to keep the crooked board held securely to the straight board.
(you will get satisfactory results if your table saw fence is set up properly).

.

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

View cmacnaughton's profile (online now)

cmacnaughton

218 posts in 492 days


#2 posted 08-14-2020 05:25 PM



I am thinking that you want to take the “crook” out of a board for jointing ?
I would fasten it to a known straight board and run it through the table saw
to get a true edge on it. you can use any number of clamps, screws or hold-downs
to keep the crooked board held securely to the straight board.
(you will get satisfactory results if your table saw fence is set up properly).

.

- John Smith


I have a sled very similar to the 2nd photo. Works like a charm.

-- –Chuck M. Nutmegger by choice

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AlaskaGuy

5984 posts in 3157 days


#3 posted 08-14-2020 05:35 PM

What machine you using? Why you say joint I think of a jointer. If you’re talking jointer I always joint the concave side and then rip the convex side straight on the table saw. Depending on what I’m doing I may run it through the planer to finial size and remove any saw marks.

It you are using a table saw the pictures already posted above work well.

If it really a pronounced curve straight line it with something like circular saw and straight edge first.

-- Alaskan's for Global warming!

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Aj2

3323 posts in 2645 days


#4 posted 08-14-2020 07:59 PM

Sometimes I want a straight edge on a board that’s convex shaped. Or shaped like a football
First you will need a jointer that’s setup right. The first few cuts are key to get a flat spot in the middle that works out evenly as possible to the ends of the board.
That’s all to it start your flat in the middle. I start all my boards on my jointer with the convex side down. Sometimes it will release tension in favor of saving some thickness in wood.
If you jointer has short tables then it much more difficult to straighten long boards.
Good Luck SMP

-- Aj

View Rich's profile (online now)

Rich

5865 posts in 1437 days


#5 posted 08-15-2020 12:45 AM


The first few cuts are key to get a flat spot in the middle that works out evenly as possible to the ends of the board.

- Aj2

+1. That’s exactly what I was going to write. Just hold it steady and it’s easy to get that flat spot to work from. It might help to set the jointer for a deeper cut on the first pass or two to establish the flat area, then set it back for finer cuts and go from there.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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ibewjon

1934 posts in 3641 days


#6 posted 08-15-2020 12:58 AM

I vote for the straight edge and circular saw or table saw. Much easier than fumbling around on any jointer. Get it close, then joint away.

View Lazyman's profile

Lazyman

5794 posts in 2235 days


#7 posted 08-15-2020 02:29 AM

Table saw jigs above are the quickest way and you can usually just skip the jointer completely, especially if you have a bunch of long boards to joint.

I am surprised that no one mentioned using a hand plane. Even if you don’t want to hand joint the entire edge, you can always start with a well tuned jack plane to work the hump down to get it close and you can then move to the jointer.

And if you are eventually going to cut the board shorter anyway, shorten them first and you may eliminate most of the problem.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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Rich

5865 posts in 1437 days


#8 posted 08-15-2020 03:47 AM

This is a good example of the fact that any operation can be accomplished in many ways. Is one right versus another? Nope. Not if you get acceptable results. Who cares how you got there?

The OP specifically asked about jointing convex edges. There’s a technique to that that works. Aj2 and I addressed it.

Yet, as is typical for LJ, everyone jumps in with a better way to do it. Yes, a table saw jig works. We all know that. But the fact remains that the OP asked for help for a specific thing—how to do it on a jointer.

So is the OP wrong if he ignores the jig suggestions and does it on his jointer? Nope. Not if he gets a board with a straight edge.

The moral of the story? If you achieve what you wanted to do, it doesn’t matter how you did it.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View SMP's profile (online now)

SMP

2446 posts in 753 days


#9 posted 08-15-2020 04:38 AM

Ok thanks all. My table saw blade is kind of tore up right now and can’t afford a new one at the moment. So trying to use my jointer. I got the tables shimmed level so i think its my technique. So its a benchtop jointer, and the boards are 4 feet long . If i apply pressure down as it hits the blade it basically just rides the hump. If I understand what you guys are saying, do I need to kind of float the leading edge so it doesn’t contact the blade and the blade doesn’t contact until further in closer to the hump?

View MPython's profile

MPython

298 posts in 660 days


#10 posted 08-15-2020 04:42 PM

If I understand what you guys are saying, do I need to kind of float the leading edge so it doesn’t contact the blade and the blade doesn’t contact until further in closer to the hump?

- SMP

SMP, yes, you’ve got the idea. Start by lowering the convex board onto the jointer table a few inches ahead of the middle and run it across the jointer for a few inches, say six or eight inches, then pick up the rear of the board so the jointer stops cutting and remove the board from the jointer table. Repeat several times, lengthening the cut each time. This will procedure will joint off the crown of the convex edge and give you a flat which will support the board as you run it full length across the jointer. When you begin jointing the board full length, the cutters will not contact the leading edge or the trailing edge of the board. Don’t force the front or the back of the board down onto the cutters. Keep running it through the jointer, resting it on the flat. Each cut will make the flat longer until the flat extends the full length of the board. Then you’re done.
Hope this makes sense.

View pintodeluxe's profile

pintodeluxe

6204 posts in 3661 days


#11 posted 08-15-2020 04:52 PM

If one edge is convex, then the other edge is usually concave. Joint concave side down when you can.

In the rare instance when I can’t, I strike a straight line with a sharpie pen and cut a straight edge at the bandsaw. Then the board can be milled at the jointer as usual.

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

View Lazyman's profile

Lazyman

5794 posts in 2235 days


#12 posted 08-15-2020 07:06 PM



If one edge is convex, then the other edge is usually concave. Joint concave side down when you can.

- pintodeluxe

With a 4’ board on a benchtop jointer, that may actually be more difficult than a convex side because you will only have one end on the jointer at a time. Depending upon how badly it is warped , you might have to work down the leading edge to get it close, spin it around to do the other end and then run the entire length through the jointer.


Ok thanks all. My table saw blade is kind of tore up right now and can’t afford a new one at the moment. So trying to use my jointer…
- SMP

Without a working table saw, getting the other side parallel to the first one is going to be tricky. Generally, the jointer is used to get one face flat and one edge straight and perpendicular to that face. The other face is usually made parallel on a planer and the other edge parallel on the table saw. To get the other edge parallel without a table saw, you may have to draw a parallel line and make short passes to sneak up on the line until you can make a few final full length passes being careful not to taper that edge. I’ve used a similar technique to make a tapered leg but I have never tried to make the second edge parallel that way. Getting the other face flat and the board a consistent thickness would be even harder.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View ibewjon's profile

ibewjon

1934 posts in 3641 days


#13 posted 08-15-2020 09:42 PM

You can use a handsaw or a jig saw or a circular saw and a straight edge to get the edge straight enough to run through the jointer. Less work and safer to start with a straighter edge.

View AndyJ1s's profile

AndyJ1s

414 posts in 603 days


#14 posted 08-16-2020 02:33 AM

I was taught to joint the concave edge first, if you have a long enough jointer table. If not, then the following is how I was taught to do it, on the convex edge first:

Assuming the crook is centered on the length of the board, put the center of the board edge down on the infeed table (power off), and slide it toward the cutter head until it almost contacts the cutter head.

Now clamp a shorter, straight board to the face of the board to be jointed, with the straight board’s edge down flat on the outfeed table. This will hold the board steady lengthwise for you while you make the first jointing pass, to create a flat spot. Start this first pass with the cutter head between the end of the short, straight board, and the peak of the convex edge of your board, such that the cutter is not contacting the bottom of your board until you slide it further over the jointer. If the resulting flat spot is not long enough for you to hold the board steady on it without the clamped board, run the entire length of the clamped assembly over the jointer again, until the flat spot is long enough that you no longer need the straight board for support.

Now you should have a flat spot on your not-yet-straight board, long enough to allow you to joint the rest of the board straight. Remove the other straight board, and finish jointing, keeping the flat spot down on the infeed table (and outfeed table as it passes over the cutter head). The flat spot should keep getting longer until it covers the whole length of the board, then you are done.

It may help to draw a straight line along the face of the board, next to the convex edge, especially if the peak of the crook is not centered on the board. This can be used as a guide for clamping the straight board, such that this straight line is parallel to the jointer tables.

-- Andy - Arlington TX

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