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Posted: Sun Sep 25, 2011 10:57 pm
by JPG
algale wrote:Great catch, JPG. I did miss that, in paragraph 7 of his write up,
http://www.woodcentral.com/bparticles/knife_adjustment.shtml, he does in fact actually state that one must reset the outfeed level with the knives after all the adjustments are made with moving ruler:[INDENT]All that remains is to set the outfeed table level with the knives. If you don't, then you will gouge board ends or taper the edges. Worse, you may get convex or concave profiles. Use the ruler for this. Adjust the outfeed table until it just barely contacts each knife across its length. [/INDENT]So the one inch movement of the ruler was simply a convenient unit of measure and was used (as I used my measuring stick) to ensure that all knives were at the same height and were also level.
On the other hand, unless I have missed it, the web resource I cited http://woodgears.ca/jointer/knives.html does not contemplate a further adjustment to the outfeed table after adjusting the knives slightly proud of the outfeed table using the moving ruler trick.
Correct it does not! That is IMHO a good example of misguided mis-information. Even the 1" procedure did the same thing with its ending advice re fixed outfeed table jointers.
I consider setting knives above the outfeed table bad advice. Now it may compensate for some faulty technique but that is two wrongs!
Posted: Mon Sep 26, 2011 8:08 am
by dusty
beeg wrote:I have that book and never found a use for it. 
I've been sorta like beeg on this book. I have a copy of the 5th edition but I have hardly ever referred to it. I don't even know where I got it. Copyrighted in 1967, it is illustrated with a lot of older furniture and older tools but the text is still all valid today.
I've moved it to the shelf with my copy of PTWFE. Another older book that should be readily available is the Band Saw Handbook by Mark Duginske.
Of course, these are all located right along side a collection of smaller books (smaller because they are specialized) written by Nick Engler. These books are also becoming somewhat dated by the illustrations contained within.
Does anyone have a copy of Units in Hand Woodworking by J.H. Douglas and R.H. Roberts. The copyright date is 1946. This was my text, for three years, in high school wood working. It is still a go-to manual for many shop tasks. The only power tool illustrated is a power grinder.
Posted: Mon Sep 26, 2011 9:17 am
by mountainbreeze
pennview wrote:In another reference I have, a book that was sort of the bible for woodworkers before there were thousands and thousands of books on the subject, "Cabinetmaking and Millwork" by John L. Feirer, on page 371 it states that "for accurate cutting, the rear table must be exactly the same height as the knives at their highest point." It goes on to explain that if the outfeed table is too low or cutter head too high, you get snipe. If outfeed table is too high or cutter head too low, you get a taper.
This seems to support my experience. After raising the knives, the taper issue went away for me. Maybe it simply compensated for my poor technique.
One reason that it may be better for the knives to be slightly above the outfeed table would be to compensate for "springback" in the wood. I've seen this mentioned relative to a planer. I don't know if this applies to a jointer or not.
Posted: Mon Sep 26, 2011 9:43 am
by JPG
MB:
I am glad you have reached a tolerable situation with the jointer.
I thank you for starting this thread.
The discussion that has occurred here hss I am sure been a thought provoking experience for many.
I believe we firmly established the proper blade height setting.
However we skimmed the surface regarding 'technique'.
I think that is not easy to put into words. A better subject for show rather then tell.
I suggest you do some self examination regarding 'technique' and maybe gain more insight into the way a jointer works, or more importantly how it does not work.
I do not think 'springback' is a significant jointer issue since it is not cutting to thickness. In any event it is quite small dimensionally.
Keep the faith!:)
Posted: Mon Sep 26, 2011 10:18 am
by pennview
Either of the two books I mentioned earlier -- "Power Tool Woodworking for Everyone" and "Cabinetmaking and Millwork" -- describe proper technique and use diagrams and photographs to show how this is done. The Jointer Owner's Manual also covers proper procedure. See:
http://www.shopsmith.com/academy/jointers/index.htm.
How much pressure to use is simply a matter of keeping the wood firmly against the the tables and fence without deflecting them. If you don't overdo the pressure, you shouldn't have problems. It isn't likely you'll move the tables, but the fence is another issue.
I'd expect if you took a 2x4 and cut it into four 2' lengths and then jointed the edges and surfaces, you'd get the procedure down pat at the cost of a couple of bucks. Read the instructions carefully about when to use push sticks or blocks.
Jointing long boards can be a problem on the Shopsmith jointer because of it's small size. But, infeed and outfeed support with something like roller stands can help if they're adjusted accurately.
Posted: Mon Sep 26, 2011 11:40 am
by dlbristol
JPG40504 wrote:The opposite happens.
When the infeed end is pressed against the infeed table, the registration to the outfeed table is lost. The leading end can float above the outfeed table. This causes the blades to take too deep a cut, but at some point the workpiece will 'rock' and cause the trailing end to rise thus cutting a thinner cut at the trailing end. You end up using the infeed table as a reference at the leading end, and the outfeed table at the trailing edge.
Now if the blades are raised above the outfeed table and the infeed is set to the desired depth of cut on the leading end, the leading end will rise even further above the outfeed table. With the blades raised higher the ciut after the workpiece 'rocks' will be deeper than before and will probably reduce the amount of tapering.
Keep in mind that the 'rock' I alluded to will raise the trailing end off the infeed table, thus it cannot 'fall' off the end of the infeed table and cause snipe.
I believe the absence of snipe with the blades raised above the outfeed table asserts the existence to the rocking movement.
It should prove interesting to determine if the jointed edge is straight and not bowed out in between the ends.(tapered at both ends)
I am going to mess around with this as soon as I can. It has given me a lot to play with. I have some things to get ready for Christmas and some jointing to do.