I need help getting a flat board with my jointer

Hello all. I have not posted in years, nor have I had a chance to use my shop in years. But recently I embarked on a new project and I needed to square up some stock. I am building using douglas fir 2x4's. My jointer is a Grizzly GO490.

I flattened the face and edge of several pieces, and then I started getting boards that would get rounder and rounder. I tried different boards, but the same thing happened. At that point, I stopped everything and began to check the setup of the jointer.

I set the blades using a One Way. All the blades are the same height and are all same height as outfield table. I used a long 50" straight edge from Lee Valley to check coplanarity of the two tables and the infeed was currently not coplaner to the outfield. The furthest point from the blade was high. After many hours, I got the infeed table to be within 0.001 at four points on the table and felt this was great.

Another session with the jointer and the same thing is happening. I am now suspecting technique, but I have jointed hundreds of board feet on other jointers without ever having this kind of problem. After a few passes, as the board passes the blade it has to drop a noticeable amount to get to the outfieed table. It is as if the infeed table is sagging. I can raise it to 0 height and it lines up well with a straight edge across both tables. It is as if the parallel adjustment of the infeed changes its coplanarity as the table is raised or lowered, but I don't have a way to measure the distance to the straight edge when the table is down in cutting position.

Have watched countless you tube videos and I think I am doing things right. Can anyone offer any suggestions as to what to check, or what to try next?

Thanks!

Put the straightedge on the outfeed table and use feeler gauges to measure the gap between it and the infeed table.

John

That is how I set the infeed table. Now my suspicion is that when I change the height of the infeed table, it goes out of coplanarity. I am going to get another set of feeler gauges so that I can make the measurements near 1/32".

Does this sound like the infeed is sagging?

You want your infeed to be slightly below your outfeed.
You want the knives to be a gnats hair above the outfeed (just enough that you can feed across).

Feed with concave side down, focusing on any extremely high spots.
Don't apply so much pressure that you are causing the board to deflect when you still have significant concavity.
When you get to the point that you need to run the entire board across, focus your pressure on the outfeed side.

When my jointer starts cutting funny it's usually the knives are getting dull and the outfeed table needs to be lowered.Because they are starting to be at the same plane as the table.
I have one of those Aluminum straight edges for my jointers it's not accurate enough to dial in the tables.Too much sag.
Maybe try lowering the outfeed till you get snipe then bring it up little bit at a time till its gone.
Good luck

I was going to say what Andrew said.

My advice is to sharpen the knives. Dull knives will push the work up which throws everything off.

I don't know that jointer and the pictures I just looked at don't help but I think you've got multiple adjustment points out of whack. IIRC jointer tables are normally shimmed and adjusted in more than one spot to get them in the correct plane. Check under each table and see if you can see tensioning screws that might have loosened.

Recently - I was forever getting a snipe on the ends of every board - no matter how I fed or pushed my boards into the jointer. As I tried to perfect my work method, the snipe would travel down the length of the board deeper into the in feed side. The final solution was sharpening the knives and lowering the knives just a hair below the out feed table.

All,
I double checked my beds for flatness and coplanarity. I still think they are about as close to perfect as I can do.

i took the blades (knives?) out and took them to a sharpener. They did need sharpening, but rather than sharpen these, I decided to buy some better blades. I will put those in tomorrow and adjust them.

i will report back. I hope this helps, but if nothing else it will have eliminated one potential source of trouble. Thanks to everyone for their suggestions.

Bill

Sometimes concave, sometimes convex; depending on what will yield the most out of the board.

A while back I had the same problem while jointing long boards. I spent hours ensuring the jointer was properly set up. It turned out to be glaringly simple. My shop made extension table on the infeed side was higher than the jointer infeed table. It was lower where the shop made attached to the cast iron as it should be. The high point was far enough from my work area that it took me a while to catch on. Not saying this is your problem, just saying check for simple things first! Would have saved me much time and lumber.

Quote:

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You want the knives to be a gnats hair above the outfeed

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I agree setting the knives slightly above the outfeed table may solve your problem