any experts on planer knives?

sunnybob · 31 Jan 2017

Just taken my JET lunchbox thicknesser apart for the first time to clean and have a nose around. The way I read the manual the knives arent perfectly set.

I cant get a picture from the manual on this page, so if anyone could help you can see what I need on page 7 of this manual;
http://www.jetmachinery.com.au/sites/de ... manual.pdf.
From how I read this section, The guide should rotate over the knife and block without catching. Well it does.
On one knife the blade catches both sides of the guide, and on the other side the blade catches one side of the guide.
I bought this new and have not looked in here before.
The surface finish on planks is not as good as I expected, but never having used one before I dont actually know what to expect.
Opinions gratefully received

RobinBHM · 31 Jan 2017

Its not uncommon for the knives to not be perfectly set, what happens is that the knives move a bit as the bolts are tightened resulting in the cutter diameter not being exact.

It depends how much you are talking about really as to whether it is having an affect on surface finish.

Have you tried machining 2 pieces of wood, one on the left and one the right and comparing both thickness and surface finish.

sunnybob · 31 Jan 2017

No, I want to confirm my thinking and adjust before I put everything back.
When I plane a plank I get lots of small tears in the wood. I have read that this is caused by insufficient extraction of the chips, but theres no sign of that on my machine. There is no build up of chips anywhere around the cutter head that I can see, so thats why I have taken it apart.
I shall surf the tube and see if i can find tutorials.

sunnybob · 31 Jan 2017

Just found a perfect utube by my favourite guy, mathias wendel.
I was right, now I can go ahead and fit them properly.
Thanks

Random Orbital Bob · 31 Jan 2017

My experience of small tearout after a pass is simply that the grain orientation is the wrong way round. When surface planing (& the reverse when thicknessing) I always make sure the grain is oriented so the fibres are supported from behind as they pass over the cutter. I then pencil mark an arrow on the stock to remind me which direction to do future passes. Obviously for thicknessing (if on the same machine) the cutter block is now above the wood so the wood orientation is the exact reverse ie turn through 180 degrees.

If you still experience tearout then either the grain is tricky like in the case of rippled sycamore etc or the blades aren't sharp. But the difference in tear out by orienting the grain correctly is huge.

sunnybob · 31 Jan 2017

I've just fitted the spare set of knives that came with the machine.
WOW! what a difference!

One of the original sets has a very poor edge, and it wasnt me. I have only put through new timber, and not very many foot of that, although admittedly all hard wood.

Just tried it out on a teak plank 10" wide and its come out very smooth.

Tried to upload pics of the old blade but photobucket is down yet again.

mbartlett99 · 31 Jan 2017

Machining teak? Best get another set ready to go then.

sunnybob · 31 Jan 2017

Yes, I realise that was a bit of an extreme test, but it came out very well.I havent found a use for the teak planks yet, just biding my time, but now I now they actually are because they were coated in deep stain.