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Jet 8 inch 3 knife jointer vibrations

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Forum topic by TexanLumber posted 04-20-2018 12:49 PM 415 views 1 time favorited 12 replies Add to Favorites Watch
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TexanLumber

15 posts in 138 days


04-20-2018 12:49 PM

Topic tags/keywords: question tip resource

I just got done setting up my 8 inch jet jointer with the 3 knives and am having chatter while passing boards. I will say that I have room for improvement on my technique, but that is not the cause of this chatter. I can easily feel the vibrations in my arms, but if no wood is on it then its smooth and quite. Pine has some vibration, but it was really bad with hard maple and purple heart. I am a bit hesitant to try the 7 inch board across it right now.
I have the machine calibrated and the knives are all set to the same height. Could the belt not be tight enough?

-- JDH


12 replies so far

View Aj2's profile

Aj2

1386 posts in 1794 days


#1 posted 04-20-2018 01:40 PM

Re check the knife height. It really sounds like you have one or two high. Did you sharpen them?

-- Aj

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TexanLumber

15 posts in 138 days


#2 posted 04-20-2018 03:12 PM

Thanks, I did check the knife height after I first tested it and one was higher than the rest. I reset the knives and still getting excessive chatter. I am feeding slow, and surprisingly the quality isn’t terrible. I’m getting a little bit of chip out. I don’t think this is normal at all for this jointer. I’m going to check the belt tension and hopefully that will fix it, not sure what else it could be. I thought surely the knives would remedy the issue.
Also, I did not sharpen the knives because this jointer is brand new.

-- JDH

View pintodeluxe's profile

pintodeluxe

5654 posts in 2809 days


#3 posted 04-20-2018 03:30 PM

Pass a 4” wide board over the jointer. Make a light cut, and move the board through at a good pace.

Now hold the board up to the light so you can see the surface details. If you see scallops across the board, then the knives aren’t at the perfect height. I use a Snapcheck digital height gauge, and once the gibs are tightened things tend to shift a little. I usually shoot for all three knives to be within .002” of each other. The key is you have to check both ends of each blade.

Setting jointer knives is probably one of the most time consuming things in a shop environment.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View TexanLumber's profile

TexanLumber

15 posts in 138 days


#4 posted 04-20-2018 09:54 PM

Well I worked on the belt, which was a bit of a pain to get tensioned, and that has significantly reduced the chatter. There is still a little more than I would like, but feeling some vibration is normal? The knives are all set the same, so hopefully that was it.

-- JDH

View Loren's profile

Loren

10381 posts in 3644 days


#5 posted 04-20-2018 10:08 PM

Does it have the original motor in it?

I think jointer chatter can result from the cutter
head turning too slowly. If the motor was
replaced it may be running at half speed.

I’ve had a bunch of jointers and while an unpleasant
amount of chatter can occur when facing wide
boards or when the knives are dull, when the
knives are sharp my jointers have cut smoothly.

You can “stone” the knives under power to make
them all the same height. I’ve never done it
but it was recommended at one time in machine
manuals.

The belt may be lumpy or the cutter head bearings
in need of replacement. It’s a bit of voodoo, but
some guys take a screwdriver and put the tip over
the bearings while the machine is running and touch
the other end to their skull behind the ear. Really
the only way to tell for sure if bearings need replacement
is to take them apart, but some guys believe they
can hear something.

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Aj2

1386 posts in 1794 days


#6 posted 04-20-2018 10:31 PM

Brand new out of the box new or new to you. Since your confidant in the knife height then check the pulleys to see if the set screws are tight. Sometimes there are two stacked on top of each other.
Good luck

-- Aj

View Hammerthumb's profile

Hammerthumb

2844 posts in 1971 days


#7 posted 04-20-2018 11:34 PM

I have a friend with a new Jet 8” jointer with a helical head. He also complained of excessive vibration. I found that the lower pulley set screw had not been tightened sufficiently and the keyway had fallen out. This fixed the problem for a while, but he has since told me that it is vibrating again. I have not been up to his house to check yet, but I suspect that I will find a similar problem when I get to it. Check all belts for alignment, and all set screws for tightness. I think they have had a run of equipment that did not get the assemblies torqued properly

-- Paul, Las Vegas

View TexanLumber's profile

TexanLumber

15 posts in 138 days


#8 posted 05-10-2018 03:40 AM

thank you everyone for your help. It seems to be that the jointer is now humming along pretty darn smooth. I believe the problem was two fold. 1) the belt wasn’t tight enough to transfer all the power and 2) the blades were not originally all the same height. I had just gotten a woodpecker straight edge as I found that my previous edge was off slightly. I think that translated into the original setup of the jointer. Either way, this jointer is now awesome!

-- JDH

View BalsaWood's profile

BalsaWood

51 posts in 1154 days


#9 posted 05-10-2018 07:59 PM



thank you everyone for your help. It seems to be that the jointer is now humming along pretty darn smooth. I believe the problem was two fold. 1) the belt wasn t tight enough to transfer all the power and 2) the blades were not originally all the same height. I had just gotten a woodpecker straight edge as I found that my previous edge was off slightly. I think that translated into the original setup of the jointer. Either way, this jointer is now awesome!

- TexanLumber

I just bought an 8” Jet a few weeks ago and it thus far has been great. The only minor problem I’m having is at startup, the motor makes a thump. Are you experiencing the same?

View TexanLumber's profile

TexanLumber

15 posts in 138 days


#10 posted 05-10-2018 08:29 PM

I did! When I first set it up I was getting that thump. Turns out that issue was due to some laxity in the belt. I have the 8” dovetail slide jointer. I opened the cabinet and loosened the 2 bolts under the motor support shelf on the left. Do NOT loosen the ones on the right, I did and it was a pain. Once it was loose I used a spreader clamp to get it as tight as I could then tightened the bolts. When I fired it back up the thump was essentially gone. I believe the belt slips a little when in starts if there is not enough tension. You should only be able to move the belts slightly if you squeeze them together with 2 fingers.

-- JDH

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BalsaWood

51 posts in 1154 days


#11 posted 05-15-2018 10:03 PM



I did! When I first set it up I was getting that thump. Turns out that issue was due to some laxity in the belt. I have the 8” dovetail slide jointer. I opened the cabinet and loosened the 2 bolts under the motor support shelf on the left. Do NOT loosen the ones on the right, I did and it was a pain. Once it was loose I used a spreader clamp to get it as tight as I could then tightened the bolts. When I fired it back up the thump was essentially gone. I believe the belt slips a little when in starts if there is not enough tension. You should only be able to move the belts slightly if you squeeze them together with 2 fingers.

- TexanLumber

Thanks for the info. I lowered the support shelf and there is less of a thump but it seems the jointer is a little louder now. I’m wondering how far down did you go? Also, did you adjust the motor position as well (4 bolts holding it down). If so, how far back did you push the motor? I’m just asking these questions since it is a pain in the butt getting to all those bolts and re-adjusting them all.

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TexanLumber

15 posts in 138 days


#12 posted 05-16-2018 01:07 AM

On the left 2 screws after I loosened them I went as far down as I could before tightening them back up. I did not touch the motor position because that would not really tension the belt, just change the angle. As long as the belt is not rubbing, I believe it should be fine. Your comment made me laugh about it being a pain in the butt…. so true! Imagine unscrewing all 4 on that shelf only to find the right 2 are rigid holes that dont allow for adjusting! I suppose there is a reason those were so impossible to get too lol.
As for the sound, I found that the tune of mine significantly changed. Seemed to be a little louder, but a much smoother hum. I hope that helps, I wish I could have found this info before living it.

-- JDH

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