Reverse rainbow jointing?

[Phil Thien]

you may find it odd then that when I was taught the process above the entire jointer was a mere 42" long  the infeed was 28" of that. I was tasked with flattening stock 8' long for door stiles.  The two things I did not mention was that I could choose the stock for length out of full bunks of lumber and two I bolted the jointer to the floor because the usual hardwoods in 8/4 would tip the jointer at the end of the cuts.  

I am capable of putting straight edges on 10/ stock and flatten 8' + on that short jointer and on a 8" jointer 14' stock and flatten 12' stock if need be I cannot even begin to fathom how to balance stock that long in the middle and end up with workable materials in the required thickness 

Additionally,   Table lengths have little to do with technique if it did you see hand planes in lengths way exceeding the length of a jointer plane   

Joe

I find that using the conventional approach to face-joint a 4-5' long board on this jointer, that I can expect about .01" (or a little more) of crown at the center when done.

So if I place the piece of wood down on my very-flat workbench after jointing it, I can slip a playing card between the board and my bench at about the halfway length of the board.

It isn't much, I can easily press that out with just a little pressure from a finger.  [Therein lies much of the problem, actually.  That little amount IS pressed-out during jointing, only to immediately spring-back.]

And yet, that little amount doesn't typically interfere when it comes to projects.

I was working on a project w/ 8/4 lumber though and thought it would be nice to get it flatter.  That is why I was looking at my technique.

This works (so far), it is fast and doesn't require much thought or any special technique, just a little dexterity to open the guard and hope-past the cutterhead.

Boards face-jointed thusly are straight enough that I can't slip a post-it note between the board, and my workbench.

[JGrout]

It isn't much, I can easily press that out with just a little pressure from a finger.  [Therein lies much of the problem, actually.  That little amount IS pressed-out during jointing, only to immediately spring-back.]

Ok now that I got the rest of the story I can suggest this: work on your technique

once you have about 12" of stock on the outfeed table move _both _ of your hands to the outfeed side of the jointer and continue cutting. 

You cannot push out a bow if the reference surfaces (the stock and the outfeed table) have intimate connection with the outfeed table only. 

I bet your .01  goes away in a pass or two 

Joe

[Phil Thien]

Ok now that I got the rest of the story I can suggest this: work on your technique

once you have about 12" of stock on the outfeed table move _both _ of your hands to the outfeed side of the jointer and continue cutting. 

You cannot push out a bow if the reference surfaces (the stock and the outfeed table) have intimate connection with the outfeed table only. 

I bet your .01  goes away in a pass or two 

Joe

Keep in mind, a 12" segment of a 60" board bowed .01" across the length will likely already be flatter than the specifications for my 12-14" long outfeed table.

That is, for a 60" board with .01" bow in the middle:  (.01 / (60/2)) * (12/2) or .002" would be the bow in the middle of any 12" segment.

So for all intents and purposes, a 30" long jointer will consider a 60" long board with .01" of bow, already flat.

Sure, I can attack it like one would with a hand plane, I plan on continuing with the RR method a while and see if it continues to do better, though.

[JGrout]

Based on your spec then I would say no matter which way you flatten stock you will do no better than your jointer is capable of.

[Tapper]

Personally, I'll stick with the conventional approach. 

John

Dittos! Has worked fine to this point; no reason to change.

Doug