Setting up a jointer with a spiral cutter head
Friends –
I just bought a used Ridgid 6″ jointer and swapped out the cutter head for a Lux Cut III. The jointer was moved downstairs to a basement partially disassembled, so I’m in the process of lining everything up. I’m trying to determine how far off the new cutter head is from the outfeed table. In anticipation of using shims, I am attempting to check the level of the cutter head compared to the outfeed table using a magnetic dial indicator. My issue is finding a consistent comparison point across the head. With straight knives, this is pretty simple, as the knives run all the way across the jointer at the same location and I could use either the knife or the body of the head to get a reading straight across. With the new spiral head, I have to find the top of each knive’s rotation and take separate readings on individual knives, OR find a spot on the head itself that is supposedly at the same level on both ends of the head, which doesn’t seem to exist, as the body of the head is also spiraled. My question is this: is the top point of each knife supposed to be the same as I move across the head and rotate? I am getting small (> .002”) variances from knife to knife as I take these “top of the rotation” measurements for each knife, and there doesn’t seem to be a place on the cutter head itself that remains constant from one side to the other. Can you suggest a location or method for determining how much the cutter head is off from side to side? The inherent “twistiness” of the knives and of the body of the cutter head makes this much less straightforward than it would be with straight knives. I have the outfeed table set so that when a straightedge lays over the knives there is a very slight (> 1/16th) movement of the straightedge on both sides. I can hear from the scraping sound that there is a tiny difference in alignment, but I have no way to measure what that translates to in vertical thousandths. Any suggestions?
Replies
>>>>>My issue is finding a consistent comparison point across the head.<<<<
I put a flat tip on my dial indicator.
I positioned it (on the outfield table) over the center of the carbide insert closest to the fence and rotated the cutterhead back and forth to find top dead center. I zeroed the dial indicator on that.
I moved the dial indicator overtop the carbide insert at the other end of the cutterhead and did the same - looking for any deviation from zero at top dead center.
Why position the dial indicator over the center of the insert's cutting edge? Because some have a very slight arc to the edge. I want to measure the highest point.
The link is to a video showing my process of finding T.D.C.
https://flic.kr/p/2ogFnCg
Mike
That is exactly what I did, without the flat tip. I put the tip immediately past the center of the Torx screw holding the insert and then rotated to find the top. I then did the same thing for every insert, working my way away from the fence. I expected to find readings that gradually deviated until I reached the insert farthest from the fence, where I thought I would get the maximum deviation. Instead, I got readings that varied plus or minus some fraction of a thousandth, with the last insert reading an error of .003. I'll try it with a flat tip and see if anything changes. Thanks for the help. At least I feel like I got the methodology correct.
.003 is darn good. Have you checked the cutterhead against the *infeed* table?
When I installed my jointer's cutterhead, I went in this order:
Check infeed table in relation to new cutterhead. If necessary, shim the new cutterhead until they match.
It is preferred that you avoid shimming the infeed table as it gets moved regularly when changing depth of cut. The shims could wear out.
Then check the outfeed in relation to the new cutterhead and shim the dovetails on the outfeed table to match the cutterhead.
In his book Care And Repair Of Shop Machines, John White recommends tuning a jointer to within .005" and then calling it good.
Mike
“[Deleted]”
Is 2 thousandth of an inch a sufficient deviation to affect a piece of wood that will later be surface planed, orbital sanded and then finish applied?
I’m on the cusp of buying a segmented cutter for my 8” jointer and was wondering about aligning it and had this exact question the OP has.
Is .002 an accuracy to truly strive for?
That is 1/500 of an inch.
Mike
IMO, no, especially if it's across a 6" or 8" width. You can work a piece of wood to death to make it flat and come back tomorrow and most wood will have moved that much anyway. Also, more open grain woods like oak probably have at least .001 of variation in them due to pores and grain anyway, even when sanded. This level of variation is something machinists making precision metal parts worry about, not really relevant to woodworking. .002 inches is about the half the thickness of a human hair, btw. That said, we all like to start off with the most accurate cuts we can, so I understand the impulse to check the cutter head and get it as close as possible.
Two thou is about the thickness of a fine hand plane shaving. Can't imagine that would impact just about anything.