Delta DJ-15 jointer bed length ...........

Hi All,

I have a Delta DJ-15 jointer and have always wondered why the in feed table is much longer than the out feed. I came up with a way to lengthen the out feed side with out making it a hack job, but was wondering if the tables could be interchanged or if they were assembled wrong from the start.

Thanks ! Brian

Toolznthings said:

Hi All,

I have a Delta DJ-15 jointer and have always wondered why the in feed table is much longer than the out feed. I came up with a way to lengthen the out feed side with out making it a hack job, but was wondering if the tables could be interchanged or if they were assembled wrong from the start.

Thanks ! Brian

Click to expand...

I have a DJ-20 that has the same long infeed. I like it like that. If you have a crowned board, place it on the long infeed so that it touches in only 2 places. The board doesn't rock and will get more flat with each pass. After having this jointer for 20+ years, I've never wished that I had a longer outfeed table.

Toolznthings said:

Hi All,

I have a Delta DJ-15 jointer and have always wondered why the in feed table is much longer than the out feed.

Thanks ! Brian

Click to expand...

I understand the reasoning to be just as crashtest described. I think of it this way: one basic purpose of a jointer is to shape a plane surface from one that is irregular by removing material incrementally from the high spots. Having a long infeed table allows the maximum contact (within reason) of the high spots of the irregular surface. As the stock goes over the cutter the outfeed table basically serves simply to provide stability for the newly formed planar surface. The longer the infeed table, the more irregular surface it contacts, which serves to reduce the number of cycles of jointing that are needed to achieve a complete plane. A short outfeed table is fully adequate for its purpose because its surface is tangential with the cutterhead circle and the wood surface leaving the cutter is ostensibly a plane, if not in the first cycle, it should be in subsequent cycles.

In use, the "long" infeed table is used to support the irregular stock, say the flat side of a rough sawn board, on as much of its length as is feasible with as little downward pressure as is consistent with maintaining stability and control (so as not to deflect the stock). As it slides over the cutter, the newly formed plane makes contact with the outfeed table and downward pressure is established and gradually increased so as to maintain solid contact with the outfeed table. A key technique is to gradually shift downward pressure from the infeed table to the outfeed table as the stock progress through the cut - timing of the shift varies with length of stock and degree of distortion in the original stock.

In my experience, the long infeed table is most important when jointing longish rough stock. It is of marginal benefit when jointing finished and relatively straight stock.
Jim

Jim S. said:

I understand the reasoning to be just as crashtest described. I think of it this way: one basic purpose of a jointer is to shape a plane surface from one that is irregular by removing material incrementally from the high spots. Having a long infeed table allows the maximum contact (within reason) of the high spots of the irregular surface. As the stock goes over the cutter the outfeed table basically serves simply to provide stability for the newly formed planar surface. The longer the infeed table, the more irregular surface it contacts, which serves to reduce the number of cycles of jointing that are needed to achieve a complete plane. A short outfeed table is fully adequate for its purpose because its surface is tangential with the cutterhead circle and the wood surface leaving the cutter is ostensibly a plane, if not in the first cycle, it should be in subsequent cycles.

In use, the "long" infeed table is used to support the irregular stock, say the flat side of a rough sawn board, on as much of its length as is feasible with as little downward pressure as is consistent with maintaining stability and control (so as not to deflect the stock). As it slides over the cutter, the newly formed plane makes contact with the outfeed table and downward pressure is established and gradually increased so as to maintain solid contact with the outfeed table. A key technique is to gradually shift downward pressure from the infeed table to the outfeed table as the stock progress through the cut - timing of the shift varies with length of stock and degree of distortion in the original stock.

In my experience, the long infeed table is most important when jointing longish rough stock. It is of marginal benefit when jointing finished and relatively straight stock.
Jim

Click to expand...

You explained that much more clearly than that guy before you did.

Thanks for the great reply. Will leave well enough alone and improve my methods of feeding the stock. Thanks for all the tips !!

Brian

The problem is that a long infeed tempts people to face joint long boards incorrectly. The bass-ackwards reasoning is further supported by shop teachers who think it is safer. Not that I'm opinionated or anything.

Actually, I have spent my professional life getting the best yield and flattest lumber possible out of a given stick. From time to time I resaw large quantities of lumber for yield. It only works if it is face jointed correctly. Otherwise the result is 2 bowed sticks, neither of which is thick enough.

If you have the luxury to work only very aged lumber that was long airdried, the following does not apply or at least does not apply as strongly. But for recently KD hardwood lumber, planing off the hump causes the wood to curve in that direction. So if the hollow side is put down on the jointer and made flat, then run through the planer cutting the hump off, the board will bow in that direction (go concave where it was previously convex). Often significantly. If instead the hump is placed down on the infeed table, and the board started with the leading edge just on the outfeed table (for the first pass at least & until the cut nears the trailing edge of the board in multiple passes); as the hump is planed off, the board will relax and curve the other direction (in your favor) If the 8' stick of 4/4 had a 1/4" hollow end to end, after planing a 1/8" off the hump, it will probably be either flat, or starting to curve the other direction. So it won't actually be necessary to remove 1/4" of material, as would be necessary with the hollow down. Furthermore, when planed in the planer, it will remain closer to flat so long as the hump side is always planed off each pass, when working down to thickness after the board has cleaned up.

The last time this came up I took a bunch of photos to demonstrate how much (several random boards right off a pile) react after re-sawing, and after a hump is planed off each. But my son hooked up a new computor for me last birthday (last spring), and I have lost a couple years photos.

smt

Stephen -

DUH - your timing is perfect. Did just what you said NOT to do yesterday on the cabinet I ma currently building. Piece ended up too thin.

Now that you explain it and I put my brain in gear as to the forces in the board it makes perfect sense. So tomorrow's efforts will be better!

Thanks.

Dale

Hi,
I'm paying attention ! Thanks for the lessons !

Brian

"In my experience, the long infeed table is most important when jointing longish rough stock."

Agreed. I have a DJ-20 and have used it to prepare stock of all kinds with uniformly perfect results.

The extra-long infeed table is particularly useful when preparing rough stock. I prefer to start with rough, where 4/4 is really 1" and not 3/4; where 5/4 is really 1-1/4" and not 1-1/16" and 8/4 is really 2" and not 1-1/2".

A lot of sugar maple went through my DJ-20 and my Unisaw in order to make to Scandinavian-pattern workbenches with all-wood vises.

Boy, you should see the truly "heroic" finger jointing jig which I use to form the joints for the tail vise and the shoulder vise ... I use a 10" dia. Forrest Dado-King. Perfect finger joints every time.

stephen thomas said:

But my son hooked up a new computor for me last birthday (last spring), and I have lost a couple years photos.

smt

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Stephen, is the old box still around? I have dismounted an old hard drive and installed it into a external hard drive accessory case that can be USB'd to the new computer. May be possible to save the photos if they aren't integrated into a Korean metrocar...or a Chinese bridge.
Joe

"A lot of sugar maple went through my DJ-20 and my Unisaw in order to make to Scandinavian-pattern workbenches with all-wood vises.

Boy, you should see the truly "heroic" finger jointing jig which I use to form the joints for the tail vise and the shoulder vise ... I use a 10" dia. Forrest Dado-King. Perfect finger joints every time."

Sounds interesting Peter, show us some pix.

Stephen, I'm still trying to recover from the humiliation of jointing the wrong face on my lumber for the last 45 years! Your technique makes so much sense - taking the first cut on the hump removes some of the compressed wood on that face and allows the board to relax a bit and un-cup, more after each cut. Then when you plane the formerly concave face you have to take less material off to get it flat.

Does this still work on material that has been properly stress relieved? Seems like you're relying on a sophisticated manipulation of the stress in the board.

Joe-

The problem is that I sort of understand what you said, but it is close to Chinese or Korean to me! Seriously, the other box is still here on the desk. "Most" of the photos were downloaded after I kept at Jr. for a bit. But aprox 3 years seem to have now disappeared, as well as "many" photos taken between April '12, and about Aug or Sept '12. I'm aggravated about that because I photo-documented a major job during that period. The photos were here, now they are not, except the few emailed to others at the time. I'm hoping that for next B-day coming up, maybe he will come back up here and show poor dear old dad how to clear things up. There was a time when I could learn to do this stuff. Now I can't afford to get lost in it for 2 or 3 days (daze?)

Richard- Even if the material has been stress relieved, it tends to be the better approach, IME. Some of the effect is due to how wood grows, besides the poor kiln drying effect. However, well stress relieved material, including either well AD material, or "formerly" KD material that has lain in the loft for 15 or 20 years behaves a lot differently. It (old rested, many thermal and humidity cycles) tends to resaw without cupping or bowing, and does not spring so noticeably when when the hump is taken off. I gather (& have rarely experienced) that some softwoods can behave the opposite, due to tension wood; completely as a separate issue from kiln effects. I hardly ever work with softwoods, so have less experience there.

Does this still work on material that has been properly stress relieved? Seems like you're relying on a sophisticated manipulation of the stress in the board.

Click to expand...

Good analysis. But it is real, can't be ignored, and begs the question: Isn't most craft about the sophisticated manipulation of stress?

smt

"Isn't most craft about the sophisticated manipulation of stress?"

Absolutely!

Don't loose the old box. If the photos weren't deleted accidently they can be recovered. They probably reside in some obscure file on the hard drive. Depending on the need and what they mean to you there are layers of data recovery available...
Joe

Stephen, thanks for explaining the, " I just flattened the stock, why is it curved again?" conundrum. I have tried and tried to tell the guys that and was never clear. Or they didn't listen. Hmmmmmm......