Thread: Jet 16OS Thicknesser Problems

How sharp are your knives? Dull blades will put greater than usual upward pressure on the head but this still should not happen. I would inspect the lock off clamps and make sure there is no chip buildup or other grime that could be stopping them from locking properly.

How thin is the stock, is it within the guidelines for use with the machine?

Is the Jet160S a fixed table and movable head?
I have a simillar but different problem with my CJT 381 where the table moves, I find that I can get thicker boards at the end of the cut, the table is moving down even with the clamps done up tight, I have a temp fix with a set of chain vise grips around the hieght handwheel shaft to lock it off so it then cant move,
Maybe u could do something simillar?
Peter.

Burnsy

Yes the blades are getting a bit on the dull side, but nothing like I thought should give a problem. In any case I am getting a second set so I can rotate sharp blades. Had a bit of a look around the clamp area but it is difficult to see too much. I have cleaned off the uprights and that all looks OK. The timber is about 3/8" so no problem with being too thin.

PJT

The jet table remains fixed and the motor and cutter head are mounted above. Which makes it even stranger to me that it would lift against not only the clamps but also the weight of the motor. Like you I have started to clamp the handle - but fair dinkum - this is a $1600 machine and I shouldn't have to be doing this.

CliveO

Something has to be moving for u to get thicker boards at the end of a cut, and the only thing that moves is the head, (assuming all else is good) u might still get the problem despite locking the handwheel.

General purpose threads will have clearance between the thread and nut, so if u wound ur head "up" to the set thickness u wanted then locked the handwheel and clamps, the head could still move up by the amount of clearance between the thread and nut (inside the 4 posts) plus any other clearance in the chain/sprockets driving the three other threads, if this is happening I would think that ur board would start at correct thickness then taper up to a thicker thickness then remain at that thickness for the remainder of that board, Is this happening? U might need longish boards to test this. U might also measure from the top of ur post to the head b4 and after a cut, preferably from machined surfaces with a vernier.

With a moving head machine I would move the head up past the thickness I wanted then then bring it back down to the thickness I wanted, I would also nip the clamps up so there is some resistance against the handwheel (so all clearances r taken up) and I am definately driving the head down with the hand wheel then lock the handwheel and clamps at the thickness I want.

Might be what is going on bout the only thing I can think of
Let us know if how u go with it

I do the opposite with a moving table, move it down past the thickness then up to the thickness I want, I know the clearance is taken up with the weight of the table and friction, I'll repeat this even if I go past the thickness setting by a little bit.

Peter

Thanks PJT I have got new blades today and will fit and test. But I like your idea of taking the head up past the thickness and bringing it down with some resistance on the clamps. So will give that a go. In regars to the movement, when it happens I can observe the whole top assembly rise as the board feeds through, and can see the extent of movement on the gauge. I have tried this with feeding the thick end of the board first and separately feeding the thin end - same result. Perhaps it is as simple as having blunt knives, but even so a bit of a surprise on a professional machine.

CliveO

Blunt knives will certainly increase forces on various parts of the machine, one being the clamps to lock the head, the point at which u change ur knives tho I would think would be the unsatisfactory suface finish on the machined board, not when ur head moves up as a result not so sharp knives which to me suggests u might end up changing blades more often than u need to, however, on the upside, sharp knives r a big and if u find u need to keep ur blades sharp sharp to achieve a paralell thickness well that's all good.

The moving down then upto or in ur case up then down is a metal machining thing (fitter machinist in a past life) all ways had to take up clearance when making another cut and be aware of the direction of cutting forces, otherwise it was very easy to get some sort of taper in the job that u didn't want

Hope it resolves the problem and let us know how u go

Peter.

PS When u say u can see the head move up as a board feeds thru,
R u adjusting the hieght b4 u feed the same board thru e.g. taking consecutive cuts?
I was just thinking that if u had set it at a thickness and where feeding multiple boards thru at the same thickness and u where consequently observing this "rising" has me thinking that ur clamps r not holding much at all, In between boards the head falls down (due to gravity and machine vibration) then u feed a board and u see the head rise each time,
R u able to clarify this a bit for for us Clive?

Peter

I have replaced the knives and the problem appears to have resolved - although I haven't had much time to play with it over the last few days - so more experimentation yet to come. As to your PS on the last post, the movement of the head occurred on the first board put through wher I could observe the head rising as shown on the depth gauge, and the head stayed at the new height, so that when I fed the next board through it was thicker. On some occassions the actual wheel used for setting depth was turning at the same time as the head was rising.

Clive

Clive
I'm no expert but something isn't right and I can't imagine dull blades would cause that. I have the same machine and I've given it a hiding with jarrah and marri boards and the machine has been extemely accurate and solid. I can't imagine the forces needed to lift the head the way it tackles taking 1.5mm off 300mm jarrah boards with ease. I've had dull blades on at times but it just make a hell of a noise but still cuts OK although not as good a finish.

Once the 2 clamps are tightened I can't even turn the handwheel on mine.

Just one question... I presume you have a decent dust extractor hooked up? It will clag up pretty quickly without one.

Plunger

I agree - this shouldn't happen and I am not happy so will be taking it up with Jet. As to dust extraction - no I don't have anything, but I can't see any build up so guessing that's not the issue.

Clive

Clive

When you say you've checked for buildup of shavings, did you take the top cover off to look? The only reason I say this that when I first got mine without a dust extractor, apart from making a hell of a mess, it was stuffed full of shavings between the blade assembly and the body. It just couldn't handle large quantities of shavings. I got a Carbatec 2HP dusty and never had a problem since. It also services a 6" buzzer and my new toy which is in the post, a table saw. No more sweeping the floor and a bit healthier.

Garry

Originally Posted by Clive O

but fair dinkum - this is a $1600 machine and I shouldn't have to be doing this.

CliveO

Where do you get it for $1600?
I'm in the market and am in Tassie, this is one place in Vic that lists it at over $2200. Plus freight, of course...
Woodworking Warehouse

Originally Posted by Clive O

The jet table remains fixed and the motor and cutter head are mounted above. Which makes it even stranger to me that it would lift against not only the clamps but also the weight of the motor. Like you I have started to clamp the handle - but fair dinkum - this is a $1600 machine and I shouldn't have to be doing this.

CliveO

They gave you a good deal on that machine but I agree that you should not have that problem.
I wondered of you went ahead and bought it. I was speaking to David some weeks later and asked him if you had settled on that machine and he told me you had.
If you have too many problems, I can always slip over and pick it up and bring it over to my shed and try and solve the problems for you.
Might forget to bring it back though.

Colin who was there on the day.