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 (http://cdn0.grizzly.com/manuals/g0490_m.pdf) (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...

[Myk Rian]

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.
Check all the knives like that end-center-end.

[ian maybury]

Hi Mel. Think maybe we're at cross purposes, or else I've missed something. If so please pardon me.

The manual I have talks about reducing the knife height above the outfeed table/raising the outfeed table to reduce concavity, and that seems to happen in practice - and was what I meant by 'reverse effect'.

My machine has a tendency to cut slightly convex, and seems (unless I'm missing something?) almost impossible to get cutting concave at all within any reasonable range of knife height (before snipe sets in) with the tables set flat - but I think it's (a) not normal, and (b) probably caused by the tables being in spec but a bit out of flat in places. (humped slightly at about 3/4 distance down the outfeed table, and with a slight dip in the edge of the infeed table beside the cutter. Dropping the infeed tends to improve the situation, but is likely to cause other issues. The plan is to flatten them, as unless there's an adjustment I've missed it seems like there's no other way to fix it.

It's a bit of a mind bender to figure exactly what the combined effect of all the possible adjustments and inaccuracies is...

ian

[rick sawyers]

My machine has a tendency to cut slightly convex, and seems (unless I'm missing something?) almost impossible to get cutting concave at all within any reasonable range of knife height (before snipe sets in) with the tables set flat - but I think it's (a) not normal, and (b) probably caused by the tables being in spec but a bit out of flat in places.ian

If you want a concave or "spring" joint the best way is to lower the far end of the outfeed table a tiny amount. And when I say tiny amount I mean tiny. If you put a long straight-edge in the middle of the jointer with the machine off and you have were to loosen the gib screws you can see the back end of the outfeed table drop. For a concave cut let the outfeed table drop just a hair at the far end and you'll have it.

[Mel Fulks]

Ian,my comments assume that the tables are parallel and flat. I have used a number of the older beefier jointers extremely well made but out of adjustment. They are out of adjustment because someone misguided tried to "adjust" them. Once they are restored to parallel etc.fine adjustments to out feed table are still necessary when knives are changed,nicked,slightly dulled,or one needs sprung joint. Tips like the straight edge 1/8 inch forward are good but there is nothing as accurate as putting two jointed edges together to see if the machine is right. If one starts that adjustment,sure that the table is low and alternately raises and checks ,no thread slop will be involved ,and the correct height will be reached. Lets hope our combined epistles are of some help to James.

[Clay Fails]

My best advice is to use a #7 or #8 jointer plane for jointing the edges. Follow David Charlesworth's (and others) advice to plane a hollow on each edge before glue-up. I have a well tuned Delta DJ 20, and under the best of conditions it cannot produce a glue joint anywhere near what a good hand plane can. The machined surface will always have small imperfections that the hand plane won't, and you can't get the hollowing effect from a jointer. That's my 2 cents.

[Mel Fulks]

Of course you can get good glue joints with a machine .My guess is your machine has low quality steel and might need adjustment .Handplanes are wonderful things ,but James has a jointer and wants to use it.I have machine jointed thousands of exterior panels ,glued them ,ganranteed them against ends popping open and never had a single failure. Commercial work can be of high quality .

[Stephen Cherry]

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.

That's a nice tip- basically it tells you that the outfeed table is too low- and as the table is set more precisely, the strait edge moves less.

If the outfeed is way too high, as you joint a board you won't make it onto the outfeed table because the edge will stop it. If the outfeed is just a little too high, you will get a perceptible step in a jointed board at about the first .75 inch of the cut, just as the board raises up to the too high outfeed table.

Your finger is very sensitive to this step.

Ideally, you can set the outfeed table so that the strait edge does not move, and you do not get the little step on the wood.

[ian maybury]

Pardon if its hijacking the thread, but hopefully it's been relevant to you James. There's probably a lot of sense in JR's advice to if possible find another way around the problem to get the project done before going back to putting in the time and care that's needed to get the jointer set up. It's turned into several weeks of trials and detective work in my case, and it looks like my tables need some flattening and/or i have to accept a slight tendency to joint convex. (which won't do)

Thanks Mel and Rick, that fits. The suggestion to drop the end of the out feed table a whisker (so that its not quite parallel with the infeed table) to get it cutting concave gels with the suspicion that it's as above the slight hump in my outfeed (and a low area to the front of the infeed table adjacent to the knives which presumably has a similar effect) both of the order of 0.008in that's causing it to tend to cut slightly convex.

Knife heights are at this stage very unlikely to be the issue - it's been through all of the options. For sure getting the right knife height at a given time is a matter of very fine adjustment of the height of the outfeed table.

I guess in theory it should joint straight with the knife heights tuned correctly, and the tables parallel - that dropping tables has to be compensating for something. I'll report in due course on the effect of flattening the tables.....

ian

[Mel Fulks]

When I have have worked with jointers that have that drop down out feed table (commonly referred to as pattern makers jointers) I have experimented with them to try to make a sprung joint by dropping the table. Was not able to do it. I of course do not say you can't ,but I think any success must involve some manipulation beyond just running the board,such as varying pressure,dropping some part over the head etc. The method we used for sprung joints was to raise out feed table ,the amount varies according to the length of the material. A piece 6 or 7 feet long needs only a thousandth or two ,a piece only 30 inches long will need at least 4 thousandths and you will have to bang the corner on the table to get it to clear out feed table and hold down pretty hard,and you do get that little bump in the edge mentioned earlier.We always cut the material about 3 inches over finished size and that removes it. Here is how I use the drop down .When glue jointing the material climbs ,more wood is removed at the start of the cut than at the end,so you have to set cut depth pretty deep.On material over 7 feet long that loses more wood than is practical .By dropping the out feed table end,AND elevating entire table a couple of thousandths I can cut a perfect arc on pieces 12 feet and more. The work climbs but the dropped table end makes for easier adjustment and less waste of wood.Sprung joints are best done on stuff pre 'standard way' jointed and ripped. In the following 'glue jointing ' work remains parallel by flipping boards end over end before second edge is cut. I think the problems some members have comes from tables not parallel ,according to what I read here some of the brand new ones are off! 20 years ago I made a straight edge 8 feet long just for realigning jointers.I used white Formica glued to both sides of tempered Masonite with plastic resin glue .After ripping ,beveling,and much filing it was accurate and is accurate .I have never let anyone else use it and keep it hanging vertically. A good machinists level would be helpful too if working on machines on a good concrete floor.

[ian maybury]

Thanks for that Mel. I'm going to lie low pending another session with my machine, as there's a risk I could mislead.

It's interesting to see you talking in terms of thou when discussing table heights and the like in the context of fine jointer tuning - that's what i seem (despite the inference of the manual) to be finding too.

It means that by extension the tables need also to be very close to perfectly flat, although clearly humps will be more problematical than localised hollows.

As above and as i've posted before the bugbear that seems to arise in all of this is that there are many machines the tables of which are not this flat. (this applies to more than just jointers) Most makers (and writers on the web and in the mags) either ignore the issue, or list much wider tolerances for acceptable flatness in their specs. There's those too that feel that fine tolerances should not be discussed in the same room as woodworking machines.

Whatever the reason there's then typically this happy little (but idealised) discussion of set up that gets rolled out. This based on getting the tables set up to be coplanar, and the knife heights to be right - but the elephant in the room that is potentially out of flat tables typically doesn't get a mention as likely cause of jointer problems. (can't imagine why that might be - but the business of looking past the nitty gritty fine detail that determines the reality of using a bit of kit in favour of an idealised discussion seems to arise all the time in mag reviews and the like when woodworking equipment is discussed)

The other factor that comes to mind is that this stuff is mind bendingly difficult to visualise - it requires figuring out exactly what's going on, and where the support to the piece is at every point in its transit over the knives. It strikes me that a video animation showing (in exaggerated form) the effect of what happens when the tables are re-aligned from dropping slightly at their outer ends to being very slightly raised, with the associated effect of varying the knife height would be such a useful training aid. A video could avoid the complications inherent in fingering any specific maker as having issues too...

Even a video may not be simple, in that it seems likely that the effects of misalignments in table coplanarity and knife height changes to some degree overlap - in some situations. Technique plays a part too in that wood is flexible to a degree, and because it determines which table is supporting the workpiece at a given time - so there's potentially more than one (or indeed many ways) the cut can be influenced by this.

Over to the combo of an expert on jointer set up, and another on making simple animation videos. 'Jointer Set-Up and Beyond - the Forbidden Knowledge'. Maybe the idea of treating the issue of machine and tool alignments and set up 'warts and all' could even be extended to cover other machine types and be the basis of a series - even if it did amount to washing the underwear in public/spilling the beans on the guild secrets... :)

ian

[Mel Fulks]

Ian ,you may be wondering where I got those "thousandths" table measurements. In a thread called JOINTER FRUSTRATION in the Gen Wdwrk and Powr Tools forum I have a post describing how to retrofit any jointer that uses hand wheels to make table adjustments with a position pointer. By using a pointer and marked increments I have been able to tell how much I'm moving the table, so over time I have gotten a feel for how much does what. I sure some are skeptical about the home made straightedge mentioned yesterday , but it is certainly more accurate than the plywood rippings and extruded metal pcs. I've see some attempt to use! The post was ,I think,in August. Keep us posted about your progress.