jointer question - thiness of wood?

I recently bought a variable speed benchtop Delta 6" jointer. While reading the instruction book (well - someone has to...) It says that the thinest wood edge that should be jointed is 1/2".
Can anyone explain why? I wouldn't have thought that a board could be too thin. If I have a 4" wide 1/4" thick board against the fence (the 4" against the fence, the 1/4" against the jointer blades) why should that make a difference?
What am I missing here?
www.avercy.com
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Jim K. wrote:>I recently bought a variable speed benchtop Delta 6" jointer. While

I'm bettin' they mean thickness for face-jointing shouldn't be much less than a half-inch. I don't think you're missing anything. Tom Someday, it'll all be over....
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wrote:

Common sense.
If 1/4" is OK, so is 1/8"? So is 1/16"?
Try to imagine (I know it's hard) what might happen if you ran a really thin piece through your jointer.
Dan.
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I can imagine - nothing out of the ordinary. The 1/16" edge is against the knives.

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I have never heard of a 1/2" restriction for edge jointing, but have heard of it for face jointing.
What is the variable speed for?
Bob
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That there is an *error* in the manual. <grin>
I bought the same jointer last summer. I'm infamous, locally, for always reading the entire manual on -everything-. (I don't necessarily -follow- it, but I always read it :) Had to call tech support about something else, and, -- since I was on the line anyway -- *asked* about that very thing. The phone person didn't know; went off and asked a real engineer; came back and said "it's mis-written". 1/2" minimum from the bed to the 'top' (i.e., the 'furthest away from the bed' surface) of the board.
The safety concern -- above and beyond running fingers into the cutters -- is that the board might flex 'into' the cutterhead, with the knife digging in, and snagging the wood. Not kickback, but dragging the wood _down_ into the works, as it breaks above the cutterhead.
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snipped-for-privacy@host122.r-bonomi.com (Robert Bonomi) wrote in

That, and a 1/2 thick board might slid under the guard and get hung up under it, rather than pivoting it aside. Which tempts the user to tie the guard out of the way, and then of course the cutter isn't covered after the board passes by.
John
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You can joint any thickness you want . But what the manufacture is worried about is "tear out". The thinner you go the more you get, if you do not aline the grain. So that is why they have a min thickness.

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wrote:

Are you sure it says "edge"?
Usually, face jointing wood less than 1/2" thick is pointless, as the wood will flex. I don't see why you couldn't clean up a thin edge.
Barry
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The instructions were referring to face jointing a piece, not edge jointing. Personally I'd consider 1/4" the maximum thinness (?) and then only with a feed block, but then I've never used a a bench top jointer.
If they should actually mean edge jointing the only reason I could think of is that after a certain point, when edge jointing, the wood is so thin the cutters just tear the wood off the edge rather then shaving it off. This leads to a messy edge and the possibility of the piece being torn from you hand. Again though I would think 1/2" would be a bit thick for a limit.
Variable speed?
--
Mike G.
snipped-for-privacy@heirloom-woods.net
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Sorry, Mike! (Something's fishy here, your name should be Charlie, for that!)
In two successive paragraphs, they say you should not face joint anything less than 1/2" thick, and then they say you should not edge joint anything less than 1/2" thick.

There's a simpler explanation. Tech support said its a _mistake_ in the writing. :)

Yup. you set it according to the type of wood, and the width of the material hitting the knives. range of speeds is about 3:1.

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On Sat, 03 Apr 2004 02:33:23 +0000, snipped-for-privacy@host122.r-bonomi.com (Robert Bonomi) wrote:

Why?
It's really easy to alter the feed rate on a jointer to vary the cuts per inch. I don't know why you'd change the speed depending on width of material at all. Does you manual give an explanation for different speeds for different material widths?
Barry
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I appreciate the responses - about 1/4 of you understood what I was asking. Not only is my woodworking crappy, so is my writing. However, to the questions:
1. Actually on looking closer at the manual the narrowest edge that can be jointed is 3/4" not 1/2". And yes, that's narrow *edge* down. In other words if I'm jointing a board 8" wide, 4' long and 1/2" thick -- I want to put the 1/2" thick part against the knives.
2. Several people asked about the variable speed. I don't know if it's a marketing gimmick, but there are five settings from 1=6,000 rpm to 5,000 rpm (knive rotation speed.). The chart lists plastic, softwood, and hardwood of widths ranging from 0" to 4". Basically the narrower the material the slower the rpms are supposed to be set.
P.S. And to Robert Bonomi who seems to be the only one who completely understood what I was asking - thanks.
wrote:

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Well, either the rest of the crowd doesn't have _that_ jointer, or doesn't read the manuals. <grin>
i _do_, and I _did_, and encountered -exactly- the same 'confusion'. Thus, when the opportunity presented itself, I queried the manufacturer. I believe that section of the manual is re-written for the next printing.
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