cutter head stress

[william watts]

It's past time that I change my jointer knives. It's a 6 in. Jet and I would like to remove all 3 knives at once and take them to my local saw shop to get them sharpened. Searching the web I find a site that says removing all knives will "stress" the clutter head and a site that says remove all three knives at once. I know I can purchase new knives cheaply and change them one at a time, but I like my local saw shop. Does anyone know if it's ok to remove them all? Has anyone ever stressed a cutter head? Am stressing to much?

[Mel Fulks]

When there is more than one set Ive always just replaced one knife at a time. Manufacturers always put their liability as their first priority when writing directions, but when that machine was new the knives went in to empty spaces one at a
time. With one set it is perfectly safe to take them all out. Just tighten each just a little as you install and after all are in ,go around a couple of times gradually bringing all up to equal torque. Oh, tighten knives working from center out alternately. Heads are always under stress, on a shaper a four knife head sometimes won't fit on the spindle if only two
knives are being used,so a couple of narrow blanks have to be used to stop the distortion. Obviously you will not be taking the cutter head off the machine.

[ron david]

It's past time that I change my jointer knives. It's a 6 in. Jet and I would like to remove all 3 knives at once and take them to my local saw shop to get them sharpened. Searching the web I find a site that says removing all knives will "stress" the clutter head and a site that says remove all three knives at once. I know I can purchase new knives cheaply and change them one at a time, but I like my local saw shop. Does anyone know if it's ok to remove them all? Has anyone ever stressed a cutter head? Am stressing to much?
nothing like having a spare st of blades. eliminates any down time esp when you need them. I keep at least 6 spare sets of both jointer and planer blades. i don't like my local saw shops
ron

[Jerry Miner]

FWIW, I've been changing jointer knives for 30 years---6 in., 8 in. and 12 in.--- I have always pulled them all at once and replaced all three. Have never experienced any stress-related issues. Don't worry. Be happy.

[Lee Schierer]

Searching the web I find a site that says removing all knives will "stress" the clutter head and a site that says remove all three knives at once.

What is the web site's basis for their statement that it will stress the cutter head. Stress is created any time you put metal under pressure. The reason we use steel is that it can be designed in a way to take acceptable levels of stress. Removing one or all of the knives will relieve existing stress that was created when the cutters were inserted in the first place and the bolts were tightened. When you put in the new or resharpened cutters you will once again stress the cutter head. Use the approach recommended in your owners manual for changing the knives and if you are really worried use a torque wrench to measure the torque on each screw as you tighten them.

Remember "everything on the internet is true" :rolleyes:

[Mark Bolton]

I have a hard time seeing it on a small head, or even perhaps a three knife head, but my understanding was always the concern with torquing one knife position with nothing in the other positions and the possibility of stressing or even distorting the head. Tightening that one position with the other two empty could in theory close those two empty glands slightly I suppose but it would seem a stretch.

I always remove all the knives but then when I re-install the new knives I install them one at a time, setting them, and just snugging them. Once all the knives are in the head I tighten each knife in a round or two (usually one) and then do my final tightening. My feeling is that the knives are evenly tight around the head but I know full well its an over-think. Im not 50 year veteran but Ive been swapping knives for a long while and every single time I hit the switch after swapping out a set Im always thinking of how nasty it would be for one of those knives to fly out of the head.

[Peter Quinn]

When I set knives i do so in a circle with all three knives in place and under torque, then set one knife at a time. This way any stress is present so I have a real read on the head. Once I've done the whe head and everything is checked I go through and recheck. But will pulling all the knives from a head do damage? I can't see how.

[william watts]

Thanks to all. I have removed all 3 knives and taken them to the saw shop. Sounds like removing all 3 knives is standard practice. I am no longer stressed and all is well. Its great to have this site where all is good and true :).

[Matt Day]

That just seems silly. If you're going to worry about anything, worry that you'll forget to tighten them up before you turn it on. ;-).

[wayne forsyth]

You would strip the gib bolt threads before you will stress the cutter head.