Is There a Max Board Length for Jointer?

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Is there a rule-of-thumb for the maximum length of a board to be run across a jointer? Is there a ratio of bed length to board length or something like hat?
The manual for my 6" Delta has *minimum* requirement, but nothing about maximum.
I know technically, if you have out feed rollers/support, there would be no maximum length, but I'm guessing there might be a point of diminished returns, per se.
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-MIKE- wrote:

Generally, once you get over twice the length of the outfeed table the force to keep the work on the table will be sufficient you'll distort the cut. That said, w/ practice and care, one can manage pieces longer than that...how's that for waffling??? :)
The possibility of using external support on a jointer is minimal at best--it's essentially impossible to get them adjusted to the precision required to actually be so well in line that relying on them for support won't distort the edge. Having one is a certain safety feature in knowing nothing drastic is going to happen to the work if you do need to let it drop, but thinking can rely on one for the root operation of the jointer for truly straightly joined edge is false hope imo.
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dpb wrote:

You mean the entire jointer bed or just the outfeed half?
My jointer table is 36" total, with each bed being half of that. I've been running 4' boards with no problem, but I anticipate anything longer than that would be pretty unstable.

I was thinking the same thing.
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-MIKE- wrote:

Infeed plus outfeed x 2.
It's a ballpark rule, but generally gives satisfactory results. It takes a good deal of technique and practice to exceed it by much, but it can be done.
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Swingman wrote:

So, twice the length of the jointer?....
...or in equation form, "Infeed + [(outfeed)2]"
Infeed 18" Outfeed 18" Max board 72"? or max board 54"?
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-MIKE- wrote:

As I attempted to say, there is no fixed formula.
If it's a 1x3 piece of pine, you can joint quite a long piece satisfactorily--replace it w/ a 3x12 piece of oak and the overhanging weight will be a major issue far short of that.
All you can do is work with what you have and see whether what you're trying to accomplish works or not.
The key thing is to give up when you require so much downward force you're losing easy control of the workpiece -- it's in those extreme cases where you're trying to push the limits that I allowed as how there's a point in a support simply to give you that safety back up of being able to let the end fall on the support instead of trying to keep it on the bed and risk an injury. You're much more likely to do that when you know your workpiece isn't going to go crashing on the floor.
When work pieces get to be unwieldy w/ the equipment you have you either need one of three options --
a) figure out how to do the operation on smaller pieces which are later joined (admittedly hard on length sometimes),
b) get larger equipment (or go to commercial shop) if not sufficient to justify the outlay,
c) do the operation w/ the workpiece stationary and a hand operation (be that hand plane, router w/ guide, whatever...
Whatever, if it feels uncomfortable, it's probably also unsafe.
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dpb wrote:

I appreciate you taking the time to write all that... however, my reason for asking has nothing to do with safe handling or being able to handle the lumber. I see that I didn't make this clear in my first post.
I'm looking to see where the limit is for an accurate cut. I'm wondering if there is a limit in length at which you can no longer expect perfectly straight results.
Setting aside all other factors.... assume everything else is covered: safety, machine set-up, proper operator technique.
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-MIKE- wrote: ...

And after all that, obviously "we have a failure to communicate" :(
There _IS_ no such magic limit; it's dependent on the particular piece owing to the size effect already expounded upon and probably even more importantly, the expertise of the operator (that is, after you've been using a jointer (and even more so, the same jointer) for 30+ years, you'll undoubtedly be able to do work far in excess of what you were able to do with it after only the first few weekends).
IOW, quit worrying over it, try whatever it is you have to try and see if you can get a good edge(+) (again staying within comfort zones for safety, obviously).
I don't know what else there is to say.
(+) Assuming you have the jointer set up so that you can take a 2-3' piece and create a tight joint to demonstrate there's not a setup issue, after that wherever you run into a problem it's an operator problem, not that of the jointer.
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On Thu, 05 Nov 2009 15:27:59 -0600, the infamous -MIKE-

Then the limit is human error coupled with lumber error. How big can you handle safely and precisely? A few interrupted passes can take down a bowed board, but you have to be able to manipulate it during those passes without error. Got twist, or both? Forget it.
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-MIKE- wrote:

In the example it would be 72" ... but, once again, that is just a ball park estimate for what is a comfortable length to joint on that particular jointer, so DON'T take it as a hard and fast rule.
There are other factors besides table length, material and technique being two equally important.
As a general rule, the longer the jointer tables the longer the board that can be jointed.
IOW, if you're shopping for a jointer, use an overall longer table length as a desirable feature.
This is one of the reasons the Powermatic 6" jointer has historically been such a popular machine ... being only a 6" capacity, the tables on it were as long as what came on many 8" jointers.
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The number you are looking for is 72", how did you arrive at 54"? The shorter the board from that point the more consistant your results will turn out as you want.
Now if you object is to straighten a board, that board clamped down to a 3/4" x 96" piece of plywood and run through your TS works nicely on boards 8' long.
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Leon wrote:

"Infeed plus outfeed x 2. "
Infeed 18" + (outfeed 18" x2) = 54. I was just making sure he didn't mean that.

That's how I didn't it before I had a jointer, but with a router. :-)
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I see. I must have just visualized (Infeed + Outfeed)x2 ;!)

I typically can straighten on the TS good enough for glue ups and am currently looking to get rid of my 6" jointer, although not trying very hard. ;~)
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6" jointer some years ago. It was not something I missed. When I recently decided to get a thicknesser (planer) I opted for a combination machine because the price was attractive and resale is better if I want to upgrade. Although the jointer gives excellent results, (I recently jointed some 8' boards for a bookcase to see what results I could produce,) it is no better than the TS. Both methods seem to give me flat boards for thickness planing and straight edges for glue-ups. For me, the TS is very much faster for truing up significantly distorted boards, even it it requires more than one pass for wider boards.
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diggerop wrote:

Well, I'm diggin all this talk about table saws, now that I have a good one.
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Best tool in the shed from my point of view. .... To Samuel Miller (1777, ) I dips me lid
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wrote:

my rule is twice the length of the bed. sometimes I need support or help depending on the species. it gets hairy at the end of the cut! :-]
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On 11/05/2009 11:47 AM, -MIKE- wrote:

You can go as long as you can hold the board on the bed. However, as it gets longer, accuracy can be compromised, especially at the ends of the board.
As dpb mentioned, you need to be able to hold it down. Edge jointing an 8-foot 1x6 is one thing, jointing half of a benchtop is another thing entirely.
Once it gets too unwieldy or if accuracy is paramount, I'll turn to my hand planes.
Chris
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Chris Friesen wrote:

Yes, accuracy is what I'm concerned with. And I generally make sure my boards are at least a couple inches longer than finished size to account for any snipe(?) on the ends.

I'm talking about edging, in this instance.

I'd have to sharpen them... and learn what all those knobs and levers are for. :-)
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On Thu, 05 Nov 2009 15:40:06 -0600, the infamous -MIKE-

Good.
One doesn't "joint half of a benchtop", suh.

Then you'd have to train your hands to feel precisely 90 degrees (though there are training wheels for that.) It's a skillset which can be learned, but it takes lots of practice for it to be maintained.
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