Why do board sometimes "catch" on my first jointer pass?

[Sam Shankar]

I have a relatively recently made 8" Jet jointer with a spiral cutterhead. When I run stock through it, sometimes the leading edge of the piece will bonk the front end of the outfeed table and just stop.

I deal with this by backing the piece off an inch and then pushing the piece in again faster. Kind of a head start. That seems to "jump" the piece up onto the outfeed table.

You're thinking: "obviously, this guy's outfeed table is too high." But it's set so that a steel rule pushed from the outfeed table back into the cutterhead grazes a tooth on the cutterhead enough to rotate the cutterhead a wee bit. And it's even all the way across. Moreover, if I lower the outfeed table I start getting the usual problems with that--snipe and some bowing.

The saving grace is that this problem only happens on the first pass of a piece, and only on about 50% of pieces. By the second pass, everything is fine.

Does this happen to others? Should I just ignore it?

[Aaron Inami]

I think this is normal behavior if your piece has a pretty drastic concave underneath. The material will actually drop down as you move across the cutterhead because the infeed table is lower than the outfeed. If you don't like this behavior, maybe reduce the amount of "jointing" by raising up the infeed table somewhat and making shallower cuts.

[Andrew Hughes]

You don’t have to outfeed set as good as it can be.
To set outfeed height lower outfeed below the infeed side. Take a cut on a board until 5 or 6 inches over hangs the outfeed side. Raise outfeed to just barely touch bottom of board.
This is called let the cut determine the height.
Good Luck

[Kevin Jenness]

If you get this when feeding in a flat piece and your machine cuts a concave edge or snipes on the trailing end, then your outfeed table is low. If the jointer cuts straight edges then it's happening because you are feeding bowed boards in crown up. You can continue with repetitive initial cuts or put the crown down. I find I get better results that way on average, facing the convex side first .

[Mel Fulks]

Agree with Kevin , and facing convex side first often makes the OTHER side wake up and stretch out !

[Carl Beckett]

I dont know if this is recommended - but if concave and the front edge drops I pull it back and go again. This cuts the front edge back until some other part of the board is supported by the infeed and the front no longer catches.

Safe? Others can advise...

[Sam Shankar]

I’ll try the other method for setting out feed height and see what flipping boards does. I was always taught to joint with the concave down…

[Mark Hennebury]

Depends on a few things, jointer set-up, lumber condition (flat, twisted, bent, concave, convex,) the length of the board relative to the infeed table, if any of the board hangs over the end of the infeed table and below it, it will rise up as the board is fed tipping the leading edge down, also depends on the person doing the pushing, and if they know what they are doing.

I should mention if the board is concave, I work a few passes from the outfeed table, pulling the last foot of wood across the cutter, the turning the board around and doing the other end, flattens it out a bit first.

[Marc Rochkind]

Yes, exactly that happens to me when board is way off. I back it out and then go again, as you said. After jointing, the bad start is milled away.

[Kevin Jenness]

I’ll try the other method for setting out feed height and see what flipping boards does. I was always taught to joint with the concave down…

Leave the outfeed alone if this is your only complaint. You can easily bump the front of a concave board into a correctly adjusted outfeed.
If you can joint the edges of two boards as long as the outfeed table and mate them with no significant gap and no snipe, the outfeed height is fine. Otherwise. adjust in small increments until you can get that result.

Usually it's safe to pull the board back and go again if you don't lift the tail end up, but if you do or the board is severely bowed the nose can dig in and kick back on the back stroke. Safer to lift the nose free with your fingers well away from the action, or take the first passes off the tails as Mark described above.

[Andrew Hughes]

I forgot to mention the method I described to set the outfeed height is done on the edge of the board. One that’s fairly straight.
If your insert head is in plane with the outfeed width you should be set. If not you’ll have one side cutting more then other side. A whole new discussion
Good Luck

[Tom M King]

Sight each board, and sometimes before each pass, and develop a strategy. After a while, it only takes a couple of seconds.

[Wes Grass]

Concave boards I sometimes start in the 'middle' and get a decent flat at the end to reference from.

Twisted, I rock it to find the middle and run my thumb on the table to steady it on the first pass.

[Kent A Bathurst]

Concave boards I sometimes start in the 'middle' and get a decent flat at the end to reference from.

Yeah. Wes is on it.

Or - my version of reality - when I bump against the edge of the outfeed table, back up the board by 3" and go again. In effect, you "nibble" the offending wood off the board, until you get a clean pass. Basically Kevin's version without the fine-tuning.

[Derek Cohen]

I have a relatively recently made 8" Jet jointer with a spiral cutterhead. When I run stock through it, sometimes the leading edge of the piece will bonk the front end of the outfeed table and just stop.

I deal with this by backing the piece off an inch and then pushing the piece in again faster. Kind of a head start. That seems to "jump" the piece up onto the outfeed table.

You're thinking: "obviously, this guy's outfeed table is too high." But it's set so that a steel rule pushed from the outfeed table back into the cutterhead grazes a tooth on the cutterhead enough to rotate the cutterhead a wee bit. And it's even all the way across. Moreover, if I lower the outfeed table I start getting the usual problems with that--snipe and some bowing.

The saving grace is that this problem only happens on the first pass of a piece, and only on about 50% of pieces. By the second pass, everything is fine.

Does this happen to others? Should I just ignore it?

It will do this if the board is bowed - which is expected as we joint with the hollow in the centre and facing down.

It may also do this if you do not place the downforce on the infeed table before the blades.

Regards from Perth

Derek

[glenn bradley]

I think this is normal behavior if your piece has a pretty drastic concave underneath. The material will actually drop down as you move across the cutterhead because the infeed table is lower than the outfeed. If you don't like this behavior, maybe reduce the amount of "jointing" by raising up the infeed table somewhat and making shallower cuts.

As folks have observed this is the leading edge dropping into the gap between TDC of the cutterhead and the lip of the outfeed table. This is minimized somewhat on parallelogram jointers but can still happen if the face against the table is severely concave. It is easy enough to carefully start in the middle and knock the tail end down. Then rotate ends and proceed as usual.


I dont know if this is recommended - but if concave and the front edge drops I pull it back and go again. This cuts the front edge back until some other part of the board is supported by the infeed and the front no longer catches.

Safe? Others can advise...

I do mostly back out when this occurs. There is certainly the possibility of kickback if the situation is severe enough. I have a p-bed jointer so the table adjusts in an arc that follows the cutterhead. Although this makes the gap between table and cutter less for a given height the difference is not terribly significant. As mentioned above, if I get a catch that is minor I will back out and re-feed. This is NOT a recommendation it is just something I have learned to determine based on experience and feel. If the catch is significant I will control the stock and power down the machine before I move / remove the material.

[andy bessette]

I use the track saw to straighten the edge first. :)

[Prashun Patel]

This happens to me - even if the board is not "severely" concave.

I back the board out, flip the board front-to-back, and joint from the other side if this happens. After a pass or two, enough of the concavity is jointed away that it will be eliminated.

If the concavity is more pronounced, I start in the middle and again, flip end for end until there's a smooth pass happening.

[lou Brava]

This post got me thinking about jointer use instruction & I remember an article in Fine Woodworking that really covers the machine and how to use it. So i googled it and here it is.
https://www.finewoodworking.com/project-guides/shop-machines/master-the-jointer