Need help adjusting jointer

[James Malcolm]

Trying to straighten the edges of some boards on my jointer prior to glueing them up. For a majority of the length, they match up great, but there is a small gap along 1st and last 3" of each board. Unfortunately I've already rough cut them to length such that I can't just cut those 3" off each end. Looking for advice on what may be wrong with the adjustment of my jointer so I don't throw it all out of whack. Thanks.

[Mel Fulks]

How long are the boards?

[James Malcolm]

30" on a Grizzly GO490 (76" long bed)

[Mel Fulks]

If you were holding the material down on the out feed table ,which is proper, the out feed table needs to be a couple thousandths higher .If you think you might have been holding down on infeed side too much ,you could re joint.Small adjustments with the modern stick type adj (instead of the wheel type ) I find more difficult.

[James Malcolm]

Yeah, I thought the parallelogram beds would be better but I think I would like the dovetail better. I'll try adjusting the outfeed as I think I'm doing it right. Always fun trying to teach yourself

[David Kumm]

Parallelogram are better than the new dovetail beds for adjustability so you just need to work with them. verify the outfeed is set right and check it on both ends of the knife, then check that it is parallel to the infeed on both sides. Dave

[Jim Andrew]

I find when jointing boards for glue joints, that I try not to move my hands to new positions while running the board through. If I move a hand to a different place seems to affect the joint.

[rick sawyers]

majority of the length, they match up great, but there is a small gap along 1st and last 3" of each board. .

If you are getting what they call snipe it is because your outfeed table is below the height of your blades at top dead center. Raise the outfeed table just a little and it will work better for you.

[Richard Coers]

Mel is right on the mark. The infeed table is only there to set how much material will be removed. All hand pressure should be moved to the out feed table as soon as you can control the board, and stay on that side of the cutter with a hand over hand motion. Also, you need a two point contact when starting. That means the edge bow must be hollow so only the ends touch when you start. Normally, you should only get snipe at the end, at the end if the out feed is too low, and if it is too high, the cut will run out and not dress the entire board. I always start with the out feed low, then raise it ever so little until the snipe disappears.

[glenn bradley]

As stated, the snipe you are getting is usually from the outfeed being too low. Fortunately the parallelogram beds move up and down very easily and remain . . . well, parallel. Your manual (pages 43-44) will tell you how to unlock the bed and how to back off the stops so you can move freely till properly adjusted. Reset your stops (or not) and lock down the bed. Presto.

[Lee Schierer]

To save some wood, take the blade out of your combination square and stand it on end on the out feed table with a couple of inches hanging over the top center of the cutter head. With the power disconnected, rotate the cutter head in the direction it normally travels (blade moving toward the infeed). As the cutter approaches the straight edge it should just touch the straight edge and move it less than 1/8". That should get your table height set pretty close.

[ian maybury]

I'm mid jointer sort out, and although its a different maker's combination machine the principles are the same. Follow the safety procedures in the manual carefully, as it's easy to get injured messing with a jointer.

+1 on using the old reliable 'carry forward' or stick test Lee describes above to set knife heights relative to the outfeed table. (much easier than messing with a dial gauge) All three knife heights need to have been set to be the same, and the outfeed table set parallel to the knives across its width first - but I've found a piece of aluminium (make sure it's straight and has no burrs) works well.

There's a definite sweet spot to knife height versus the outfeed table - a little too low and you feel resistance as a result of the piece dragging on the leading edge of the outfeed table. Keep on very gradually (a thou or two in height, or a couple of mm change in the carry forward in the stick test makes a noticeable difference) reducing the outfeed table height, and it eventually feeds easily and smoothly.

Some of this has already been said, but for completeness....

Drop the outfeed table more than this and the chances are that snipe will start to develop on the end of the work that's last to pass over the cutter - when it drops down on the cutter for the last inch or two as a result of no longer being supported on the infeed table. Severe snipe tends to have a characteristic form - a couple of inches or so of run of increased depth of cut, then an abrupt step up to shallower depth of cut. If the outfeed table is too high it may produce snipe on the leading end of the workpiece - the workpiece gets lifted up off the infeed table by the leading edge of the outfeed table when it reaches it. Creeping into a snipe situation by gradually adjusting the table heights in small amounts means that the work needs careful checking as at first as it won't be obvious. Slight snipe may just seem much like a very slightly convex/bellied jointed edge.

One test taken from a piece on the web which worked quite well for me was to take an already jointed piece and feed it forward on the infeed table and over the cutter for say two inches, and lift off. To leave a clearly defined short jointed section or 'land' with a step at the end where the cutter stopped removing material. (much like a snipe) Scribble with a soft pencil on the resulting land, then turn the piece 180 deg and feed the full length of it over the jointer so that the marked land is last to pass over the knives. If there is no visible snipe at either end and the pencil mark is mostly removed but some of the deeper marks are still faintly visible then the knife height is about right relative to the outfeed table.

Extra knife height relative to the outfeed table tends towards producing a concave jointed edge, and the opposite reduces this.

Table parallelism is the other basic (both in the same plane) - it's checked with a reliable straight edge (maybe a high quality level?) the length of the two tables end to end. With the knives rotated out of the way rest the edge firmly on the outfeed table (make sure there's no dust, debris or tipping going on, and that it's pressed down on the outfeed table), and check the gap underneath along the length of the infeed table with a feeler gauge at maybe three points across its width. If the two tables are high at the outboard ends relative to parallel the machine will tend to joint convex, if drooping the opposite. Both tables also need to be parallel across their width.

There's a lot of talk about adjustments, but I seem to find that in the end the tables basically need to be set parallel (it's not all that realistic as an option to adjust the jointing for a straight cut), and the knife heights within a thou or two of the 'sweet spot' height relative to the outfeed table. That there's scope for very small adjustments beyond that to correct convex/concave jointing - but that if this doesn't correct the its quite likely that table flatness is worth checking as it may be a factor.

The great unspoken in all of this may be table flatness and other alignments. The manuals don't seem to really engage on (beyond generic flatness tolerances set nice and wide to protect themselves against claims for table replacement) infeed and especially outfeed table flatness. If there's a hump of even only say 0.005in in the out feed table it'll joint straight until the piece is kicked up by it. If the hump is e.g. toward the end of the outfeed table the result may look very like snipe. If the area of the tables near to the knives is not accurately flat (to within a thou or two) it makes a mockery of talking of setting knife heights relative to the tables to within the commonly recommended thou or two - and the resulting variable knife heights may make results all very unpredictable. Hollows if local/of small area and unless right beside the knives (especially on the outfeed) may be less of an issue...

No doubt there's experts who have no trouble (and lots more that don't worry about a bit of inaccuracy in their jointing), but I've found that when it gets down to fine adjustments (and if jointing an edge then only straight is straight - anything else is not) that it can be quite difficult to separate the effects of knife height, table parallelism and out of flatness (even slight amounts) in the tables. Also that e.g. differing lengths of workpiece placed at differeing points across the width of the table may behave a bit differently.

There's inevitably (i guess) a zone beyond which a given machine simply isn't accurate enough to go. The size of this zone/band is determined by the accuracy of its manufacturing and set up, and tends to define (with good user practices) just how accurate an predictable performance of the jointer is. The bad news seems to be that even a couple of thou in the wrong place can matter quite a lot. That seems to be what i've found so far anyway, but all input appreciated....

ian

[Jim Matthews]

The last time I set a jointer involved the basic knife setting mentioned above (1/8" travel).

Set the infeed table to the average depth of cut you like to use (more passes, less material each time).
Using a straight piece of clean grained stock that won't deflect after the test cut - remove 3-4" with at least half the length of the INfeed table still covered by the stock.

Turn off the jointer and allow the blades to stop spinning.
Disconnect the jointer from mains power to make any table adjustments.

Rotate the head so that it no longer contacts the stock under the jointed section.

Advance the stock over the outfeed bed and clamp in place.

Place a piece of standard A4 paper (4 thousandths thickness) on the outfeed table.
Raise the outfeed table until the paper won't slide under the trimmed stock piece.

If you're still getting snipe at this setting, raise the outfeed table to slightly less clearance.
(4 thousandths was adequate for my needs.)

You can check for co-planarity using the same sheet of paper and stock clamped at different places on the infeed table.

If you find that your stock won't slide easily across the outfeed table, try a spray lubricant. I use Bostik Topcote.
The natural tendency with jointers is to push down hard over the cutterhead, where I concentrate on pressure against the fence.

You needn't take off a great deal of material, but you don need to keep things square to your reference planed face.

[Mel Fulks]

Ian, you said "extra knife height relative to out feed tends to produce concave edge, and the opposite the reverse effect". The first statement is possible since the table wil not ' be there' for its buddy , and so the operator can make your predicted result happen. But it is not possible for knives lower than out feed table to produce a convex edge. Elevating the out feed table ,in the range of 2 to 4 thousandths (depending on the length of the material) produces a concave edge,AKA a "sprung joint" for edge gluing. If the material is held to the out feed table ,the table will make the material "climb " and produce a long slightly concave arc. As written before by several of us,the best way to adjust out feed table is to joint two pieces of wood 3 or 4 feet long ,with table intentionally too low,and alternately raise table and put the two edges together until they touch along entire length.TASTUM SOUPO!. It is a delicate adjustment and IMO much easier on the older "wheel type" machines. A slight dulling of the knives , or a nick in them , can make the out feed table "too high" even though it has not been moved.

[J.R. Rutter]

OP - If I were you, I would just run the edges on the table saw and shave them down to be flat. After they are gluing, go back and play around with the outfeed table per the advice above. Trying to troubleshoot a jointer with project parts is no fun...