Jointer Knife "Hills and Valleys"(?)

[Lonnie in Orlando]

I just installed a newly sharpened set of knives in my Rigid 6" jointer. During the initial setup, dial indicator showed that the edge of one knife has almost 4-thou valley vs the ends, relative to the outfeed table. The middle of the other two are +/- one-thou vs the ends.

The sharpening shop says that 4thou is about as good as they can do.

It's obviouosly a little hard to set them uniformly at +2thou above the outfeed table.

> Is 4thou varience normal/acceptable?

> Any suggestions on how to best set them? ( I averaged the difference across the knives: some higher than +2thou; some lower than +2thou.)

> I never checked for hills/valleys before so I don't know if previous knives were similar. Am I being too anal?

Thanks for your advice,

- Lonnie

[Tom Miller]

> I never checked for hills/valleys before so I don't know if previous knives were similar. Am I being too anal?

Hmmm, not sure if I'm under- or over-qualified to answer that. I did stop worrying about a little "scalloping" of the jointed edge from my power jointer (less anal), once I took to making a final pass with a hand plane to get a glassy-smooth surface (more anal?).

I measured the amount of "scalloping" to be ~1mil hill to valley -- not noticeable when edge jointing for glue-up. But it would be noticeable if you were to apply a finish directly after surface jointing (which you wouldn't be doing). I can decrease this scalloping quite a bit just by feeding slower, too.

I think one should expect to be able to set the knives within a couple mils of each other, but it does take a little fiddling.

Regards,
Tom

[cgallery]

A common complaint I read when researching knife sharpening. Some shops seem to be able to do better than others. I don't know if it is technique or if they have better holders for the knife to prevent them from deflecting or what.

I know my little Woodcraft wet grinder will allow me to get a knife to +/- .001" on my 8-5/8" long knives w/o too much trouble.

[LCHIEN]

if two knives are +/- .001 and one knife is +/-.002 (that's what .004 from ends to center is, really)
I'd set the two better knives as closely as possible and the third knife so that the ends were at the right height and the center a little lower.

[Lonnie in Orlando]

Thanks guys. I guess the bottom line is that my first test cut after installing the knives was smooth, clean, and quiet. Moisture swelling/contracting is probably greater then the varience in the height of the knives. That "anal" gene reared its ugly head when I discovered the hills and valleys!

Tom -
> I move slowly across the knives on my final pass for a clean cut. I used my jack plane before I bought the Rigid and got pretty good results. But I would probably bugger up the edge if I used it now. Need practice.

cgallery -
> I was surprised when the shop mgr told me that they use the back edge of the knife to reference the grind of the sharp edge.

Loring -
> Maybe I should have set the ends equally at +.002. The middle would be below the outfeed table, but would be above the infeed table, so it would still cut. However, I seldom cut at the ends of the knives, except on 5-6" face-jointing.
> I'll run the "average" setting for now. Perhaps I'll readjust to be closer to +.002 on the ends later of I'm not happy with the results.

- Lonnie

[Garasaki]

This issue is addressed in the famous jointer knife setting goggle video.

You can actually get the knives to bend inside their holders enough to eliminate the variance, or so the guy in the video says.

I've never tried or had to do it. Probably one of the advantages of a tiny lil baby jointer (4").

I will say, that even 0.004" of an inch is a prettttttty darn small amount.

[LCHIEN]

Loring -
> Maybe I should have set the ends equally at +.002. The middle would be below the outfeed table, but would be above the infeed table, so it would still cut. However, I seldom cut at the ends of the knives, except on 5-6" face-jointing.
> I'll run the "average" setting for now. Perhaps I'll readjust to be closer to +.002 on the ends later of I'm not happy with the results.

- Lonnie

The reason why i suggested making the ends at the right height (and the middle .002 too low) was that in most cases you'll be taking way more than .002" cut so the knives will be doing an appreciable amount of cutting all the way across the width. And the other two knives will have to take a .002 additional cut in the middle., just a real small amount, to finsh up what that blade "left".
But on the ends, you won't have an "overcut". - the cut depth will be at whichever blade is set the highest.

[Lonnie in Orlando]

Loring -

You're right. I'll lower the "valley" knife ... if I can bear the 95deg heat, 200% humidity, and a shop full of hungry Florida skeeters.

Thanks again to all for your advice.

- Lonnie

[Bruce Cohen]

Before I switched to a Sunhill Spiral Cutterhead, $150.00, I spent way too much time futzing with the knives of my Rigid Jointer. I did find that Ridge Carbide does an excellent and cheap sharpening (not to mention FAST) job.

I would try them if you dont want to shell out the bucks for a priral cutterhead. At least you'll no longer have to mess with each blade's setting.

Bruce

[Lonnie in Orlando]

Thanks Bruce,

The key phrase is "way too much time futzing with the knives". Like I said earlier - I let my anal gene take over the knife setting process this time.

I adjusted the knives so that the highest point on each knife is 2-thou above the outfeed table.

I won't sharpen the knives that I took off until I have some miles on the set that I just installed. If the knives have substantial hills and valleys the next time I have them sharpened, I'll check with Ridge Carbide. (Not ready to shell out for a spiral cutter yet!)

- Lonnie