Ideal bed length of jointers

I have been thinking about this for a bit, what is the best ratio of bed length to board? I have been jointing a lot of 8-12 boards for table tops recently and have been getting a concavity in the edge, maybe 1/8-" over 12 feet. I end up cleaning them up with a hand pane and they glue up fine. 4 foot boards come out straight right off the jointer and need no clean up for gluing.

The Jointer I am using is a older 12" Crescent and has (in my mind) short in-feed and out feed tables. This leads me to believe that bed length has a direct relation to how straight you can get a long board. thoughts?

I have a project coming up where I will be gluing up 10 tops that are 4' x 12' and about 30 smaller sized ones. I am thinking of investing in a larger and nicer jointer and wanted to know what this collective knowledge thought about longer bed jointers. my Crescent is works but the short bed and lack of dust collection have me searching for more.

The longer the better! Ideally the board is fully supported on both infeed and outfeed tables. 12' board is hard to get straight with just a jointer unless it's a truly gigantic jointer. You're better off getting them close with a bandsaw, then go to the jointer for finishing. One trick when jointing for edge-gluing is to purposely generate slightly concave edges. Then, when glued up, the ends (which are generally where edge-glued joints start to fail) will be preloaded by the middle. Regards, Mike.

Whetstone, how long is your 12" Crescent? Standard length on later industrial jointers seems to be about 8', but that won't guarantee straightness either, as Finegrain says. I've found it's a matter of technique mostly - figuring out where to press down hard and where to ease up. I also like to create a hollow first and then take light passes til it's atraight, much harder to take a belly out of an edge. But it still requires some finesse to control the amount of spring joint you wind up with. 1/8" is too much, I'd prefer a 1/16" pver that length.

It generally depends on the phase of the moon and alignment of certain planetary bodies. Also there are some incantations to go into, but they are generally not safe to discuss on an open forum , for fear some untrained acolyte will attempt them and knock the universe off it's pivot.

The jointer is a fickle and sensitive machine, demanding constant operator skill.

If the boards are long enough to require lots of pressure at the end of the stroke, just to keep the tail end down on the table, a longer table would be advantageous.
Straightness is more due to table alignment and knife height than length. IMO.
Use a good straight edge to check for parallel tables.

tips-
To set knife height- take a straight jointed board, run it into the cutterhead an inch or so, mark the snipe with a penciled X, turn the board around and joint the full length.You should see what amounts to half the pencil mark -ie, the knife should cut off the top of the mark and leave the rest of the pencil mark in the depression left by the pencil lead.. This means your outfeed table is flush with the cutterhead. Sounds crude, but over the years it has proven in my shop to be a lot faster and more accurate than attempting to use instrumentation. An indicator will tell you how high the knife IS, but it will NOT tell you how high the knife CUTS.

If everything looks fine, but there is still a slight concave in the board, you may be pressing out the bend as it goes through. Hold down the leading end as it starts, ease pressure on the middle of the cut, hold it down on the trailing end.

Also, you can start the cut in the middle of the board to correct a slight concave condition. At the start of the cut, the board being held up by the outfeed table, and at the end the cut is full depth-essentially this is cutting a small taper to get rid of one half of the concave condition. flip the board and repeat, then do one more light full length pass.

I always try to buy my lumber straightlined or s4s, as the time saved in hogging off waste is huge. And emptying the dust... And you start with a reasonably true edge . Obviously this is not applicable if there is little stock to work with.

If the stock is really bowed, use a saw to chop off the bulk of the curve first.

And then there is the Shrine-did I talk about the Shrine?!

Richard, I have not measured the jointer, but I think it is between 5-6 feet OAL. I dont think that the in feed is 3 feet. this is not the best picture, but you can get the idea. It is a good jointer and I would only replace it if I could save time and have glue able joints right off the machine. If I end up having to tune each end on a larger jointer there is no need to replace it. there is a 16" oliver near by that looks nice and I might look into it. the other main issue is this machine is a bear to keep the chips contained and a more sealed machine would be nice.

An addendum- when laying out the boards to dry fit, if I can pull out the concave gap with hand pressure, I figure it is good to glue. 1/8" concave gap over 10 or 12 feet can usually be easily hand sprung.

Whetstone said:

This leads me to believe that bed length has a direct relation to how straight you can get a long board. thoughts?

Click to expand...

The longer the better of course, if for no other reason than to provide as much support as possible for long work. In theory, you can only joint bowed boards that are no longer than the infeed table - if your desire is to simply feed them across the machine without "technique". The longer they are beyond the length of the table, the more "technique" is required to achieve straightness.

I find it much easier to true the edge of long bowed stock by using a straight edge fixture in conjunction with a table saw or router. It's always prudent to employ some form of supplemental support for the portions of long work that project past the end(s) of the machine's table. But even with proper such support, the potential "flop" in overhanging stock has much less opportunity to effect the relationship of the board between the circular saw's blade and fence (or a router bit following a straight-edge guide), than it does the interface of the jointer's cutter head with a board's edge.

Always plenty of discussion on this subject to be found on the woodworker's sites. Here's a link to a recent one:

How to properly joint long boards on short jointer tables?

~TW~

I agree with the longer the better. The machine I currently use has a 7 1/2ft bed, and it does a good job for my purposes. If I had to straighten lots of 12ft lumber, I'd likely take it to someone with a straight line ripsaw or a lumber jointer (chain feed).

Eric

One can get a 12' board closer than 1/8" shooting the edge with a hand plane.
To my mind the bed length can be "ideal" in approaching >50% of stock length on outfeed but shop limitations leave most of us with far lower than that.
I use the short bed MiniMax FS30 and face this all the time. For me the trick is listening to the process as I work along with occasional sight down the length. I will end for end a board a couple of times if needed to pull a sway off each board end as if I were line sawing the edge & will scuff the middle on short passes when chopping down humps just as if I were working the edge by hand.
How wide are your boards- if they are sagging during joining to cause the crown, I would say you are good to go for gluing.

I listen to how the edge is working through each pass as I get towards a true edge. Any lift of the board is apparent and also I am told by the sound of a pass when I have gotten a fair run down the entire length.
Just think of a less than ideal bed length as a hand plane- how would you work to use the tool to fair the edge?
Most of us wouldn't hesitate if we needed to shoot an edge with a plane of 1/4 the length of a board. In machine joining, the issue is stock handling, not bed length per se which causes issues...
Try snapping a fine line back a 1/4" from the edge to help you keep track of progress.

The longer the bed length, the less technique needed & the quicker the work.
I suppose the upgrade question has to be taken on how often you face the limitation of the present gear & who is set to the task.
Do you need to put push labor at this task & expect them the produce fair boards with no fuss?

Lots of great advise here guys! In a way this is like the workmanship or risk vs certainty thread, but without all the philosophy. People think a good jointer should guarantee a straight edge, but it turns out to be all about subtlety and skill. I love Trboatworks remarks about listening to the cut. You gotta use everything you have to get that last little bit of precision.

That being said, if you get that 16" Oliver, I doubt you'd regret it. It would be a significant upgrade in many ways if it's in good shape and you set it up right.

Was it Oliver that made those patternmakers jointers with a 9' or 10' bed?

Eric-
I more or less agree about automating long edge jointing. But it may be worth noting that even Diehl who arguably makes the only "true", and certainly the best "glueline ripsaw" only claims a new one is good for an 8' joint off the machine. Of course they are used for longer joints. I use my Diehl 660 lumber jointer for rough jointing, and for production jointing of all size parts that do not need a glue joint. Although the lumber jointers are specifically designed for making glue joints, I have not yet completely assembled the parts for a knife jointer for it and the lowest feed speed, with 6 knife heads unjointed, leaves a somewhat scalloped edge. It is great for production flooring and moulding blanks, (edges being finished in the planer or shaper). My machine is older, and though the chains, ways, & tables have all been rebuilt to near new condition, the adjustable lead in ramps have not. These are the sections of chainway that one micro-adjusts with a screw to set concave, straight, or convex. At around the straight mark, say for running 12' pieces of flooring, it tends to start wandering back and forth a little. With a helper, we will keep checking each piece and re-cycle maybe 8 - 10%. At that level, operator input, and I don't know how to describe it other than an "awareness", can begin to make similar small effects to what one experiences and others above have described so well for hand fed machines. Some is simply an awareness of what happens in the wood when it is 12' long and maybe only 6" or less wide, as stress is relieved by cutting. The infeed and outfeed tables are each 6-1/2' long with the short factory extensions (long factory extensions took them up to 8.5 ft long at each end!), so eventually the machine may be adaptable to perfect long glue joints, but I don't have the time or job to work that hard (re)fine tuning it yet.

Anyway, I love the machine for rough jointing and basic straightening. Glue joints get finished on the 8' long F & E 12" jointer. Long joints and joints for "important" work get shot with a #8 or #34 stanley hand plane before glue up.

Before the lumber jointer, I used to have a rig for the Advance double spindle shaper that was an offset fence cut from an 8' long piece of plywood. It looked like a section though a jointer, and the area around the spindle (the "lips") was plated with aluminum. I had one with about a 3/16" depth for roughing and straightening, and one with about 1/16" for glue jointing. Set up with a power feeder on the outfeed end only, it was quite effective after it was dialed in, which could take a bit of time an testing.
With a couple tables at either end of the shaper it was relatively effortless to handle long, wide, thick boards on a production basis.
It took too long to set up for less than a few hundred feet, though. I had planned to make a fully adjustable all-steel version with a 10 or 12' fence (5' -6' infeed and outfeed); then the lumber jointer came along.

smt

Thanks for all the info and responses. While I can certainly tune each board through the jointer and hand plane for the odd large top I am hoping to set up where it does not take quite so much skill. There will be 8 of these large tables and about 30 4-6' tops for the rest of the project. I am going to bring in some temporary help on this job and want my process to be as easy as possible. I wont have time to train people on the peculiarity of each tool. I am going to look into the oliver jointer, but I will also look into building a jig for the table saw or router.

One other thing to consider might be lengthening your jointer, as it looks like there may be enough "beef" at the ends of your tables.

I machined a couple of heavy aluminum angles (e.g. 1/2" or so thick at the thing points) to add about 6" to each end of my 14" MiniMax jointer. A couple of tiny and strategically placed brass shims tweaked things flat as I bolted and bondoed them on. After years of use they still maintain near perfect flatness with the tables -- that is, no visible light under a 48" Starrett straightedge. I used aluminum to avoid stressing the existing tables.

The extra foot of length has made it easier to handle long boards, even with rollers (whole 'nuther story) front and back.

Per Pete's suggestion:

My Fay & Egan 506's are both 7' jointers, having 4' infeed tables but only 3' outfeed. (for some counter-intuitive reason this was not uncommon on older jointers). I made this mod adding a little over 12" length to the 12" wide machine and as Pete notes it is an effective accuracy improver as well as back saver.



smt

Yep- my MiniMax is set up for a bolt on extension to the outfeed.
One of these days I will pony up for the plate of make one up...

stephen thomas said:

Per Pete's suggestion:

My Fay & Egan 506's are both 7' jointers, having 4' infeed tables but only 3' outfeed. (for some counter-intuitive reason this was not uncommon on older jointers). I made this mod adding a little over 12" length to the 12" wide machine and as Pete notes it is an effective accuracy improver as well as back saver.

smt

Click to expand...

Steve

That's a nice solution to the problem when jointing very long timbers. I had a similar outfeed table extension that I made for my 12" HD Northfield years ago, but it wasn't as elegant as yours. I layered up melamine coated boards and applied the contraption to my outfeed side just as you did, and I used a single leg with a threaded insert drilled into the bottom to accept a bolt to adjust it to be co-planer. It was 3 feet long and worked very, very well when I was jointing 12' to 16' boards back when I was making a lot of mouldings with my W&H moulder.

I like your solution better. Of course, it's a bit easier when you have a nice metal planer to make everything flat!!

Jeff

If your jointer is out, your 4' lengths are probably no straighter that the 12' pieces, just shorter segments of the same curve, so you don't notice it.
If the curve is constant, you should check to see if the tables are coplanar. If the curve isn't constant, the you should try to be sure you have more support both in and out.
I have a Delta 37-301 8" with 60" bed and routinely joint long stock straight with it, but it does take a little work.
If the Oliver in question has a modern (gibbed) head get it if you can, even if it has babbitt bearings, they're great machines. But be aware, decide where you'll put it and leave it there- they have to be precisely leveled (or precisely straight) upon set-up and they don't put up with being moved around.

I really like the extension Steve made for his F&E too; I'll definitely copy that for the Crescent I'm working on, my back does get tired these days

"But be aware, decide where you'll put it and leave it there- they have to be precisely leveled (or precisely straight) upon set-up and they don't put up with being moved around."

That's the advantage of the "3 toe" jointers - Yates, Northfield, Moak, etc. Wherever they sit there is no torque on the tables.