Thread: Jointer knife balance

I think the answer is that it will affect balance, but probably only slightly and maybe not enough to notice. I would weigh the blades individually. A digital set of kitchen scales should be adequate for this purpose. I am assuming that the knives are 150mm or 200mm. This will give some idea of the relative difference.

If it seems within reason try the blades in the machine. Again assess vibration levels. If the thinner blade was a significant amount lighter try having the other two blades shapened again (assuming they have similar weights and possibly not by your previous sharpener ). You mght have to explain why they are being sharpened and what you hope to achieve.

Hopefully one way or another the blades will be of a similar weight. Did you notice excessive vibration before the blades were sharpened?

Regards
Paul

Ah yes...they're 150mm knives.

Unfortunately I don't have a decent set of scales that I can use but I should be able to compare them to each other with a jury rigged tilting scale. And prior to their "sharpening" the jointer ran quite smoothly. I guess I could chuck them in the machine and see what happens...it couldn't be much worse than what it was like before.

It's been a good exercise so far, but now I'm in two minds as to whether to keep working on them or lash out on a new tungsten set. The amount of sandpaper I've gone through already is approaching the cost of a couple of new knives and by the time I'm finished...who knows...but they would be handy to keep as a trashy set for rough work.

Knife weight will definitely affect balance - and it has a bigger effect than you might think. A 2 gram difference in weight can translate to as much as 12 kilograms of force on the spindle at 8000 rpm (was taught that when i was learning to use a 4-sider). Obviously a 6" jointer isn't spinning that fast and has a smaller cutter block so the knives are closer to the centre, but there's still going to be a significant amount of force from out of balance knives which will result in a poor finish and excess wear on the shaft bearings.