How to acheiving a straight edge on a jointer?

[lucky9cat]

Hi, I'm new to the group and been have woodworking for quite a while but still have problems . More often than not the jointer appears to take more wood off at the ends leaving the middle proud. It's a real pain jointing boards to glue up for table tops and such like.

I've got a Jet JPT-310 planer/thicknesser that's about eight months old and have just spent a day following the jointer tune up steps outlined in the Aug/Sept American Woodworker but still have the problem.

It really baffles me and it may be my technique. Does anyone else have this problem and more importantly have they overcome it?

Regards
l9c

 

[johnelliott]

Welcome to the forum, Lucky

It sounds like the two tables are not in the same plane, or that the cutters are describing a circle which is higher than the outfeed table. Have you checked both of these?

Another thing I've noticed with some planers is that the more passes you take trying to get the timber straight, the worse it gets

John

 

[Pecker]

and been have woodworking for quite a while but still have problems .
Regards
l9c

hey, I'm a chippie with 20+ years of experience and still have problems! Dont worry about it

Seriously, a big warm welcome to the group. I'm very poor on workshop techniques but I'm sure someone will come along shortly and help you out!

mark

 

[DaveL]

Hi Lucky9cat,

Welcome to the forum.

I think John has hit on your problem, the blades are a fraction higher than the out feed table at the top of the rotation of the cutter block.
You ether need to raise the out feed table or if that is fixed then lower the blades into the cutter block. It may only be 1/32" or 1/16" thats all it takes. :x

 

[lucky9cat]

Hi Guys and thanks for the warm welcome and ideas.

I'm pretty sure that the outfeed table is set high enough for the blade sweep at the top of the arc for it not to be a problem. I've set the blades as per the manual so that it moves an aluminuin block by a tenth of an inch and I don't appear to get any snipe at the tail end of the edge. Nevertheless, I'll give the idea a go tomorrow.

As John says, the more you try to plane out the high spot in the middle, the more pronouced it seems to get. I'm glad someone else has experienced this too

Regards

lucky

 

[engineer one]

have you checked the levels though.

put the blade at top dead centre, then run a level across is to the
outfeed, that should show you for sure. are you sure the outfeed
table is actually level itself?

the question is maybe techinque. how do you start your jointing
at the beginning of the wood, or at the highest points?

are you keeping the same pressure all the way along, or
should a feather board be used, to ensure that the wood
is having the same depth of shaving taken off all the length?

paul :wink:

 

[Simoli]

Something not mentioned yet is that you need to put pressure on the part of the board which is on the outfeed table. If you put pressure on the infeed side you will get that convex curve. If a board is fairly long relative to the jointer then it will take several passes in order to get the board edge flat.

 

[Scrit]

Hi L9C

Assuming from what you've written that your fence is true and the infeed/outfeed tables are coplanar I think your problem could be one of two things:

My experience is that if the cutters are too high you will get tail-end snipe only - where the material drops onto the outfeed table. Snipe is very visible as a straight line "step" across the workpiece. Do you then turn the timber round so that the sniped tail becomes the leading edge? That could result in snipe fore and aft. I'm afraid that a small amount of snipe is almost inevitable - all you can do is fine-tune your knife settings to minimise it.

At what point do you transfer downwards pressure from the rear table to the front of the work? Ideally you need to transfer pressure onto the outfeed (front) table as soon as you have enough reference surface to support the workpiece - if you don't then there is a slight tendency to keep pressing down towards the rear of the workpiece. This means that if the workpiece already has a bowed edge it can continue to have one (useful technique sometimes - coopers use this to their advantage). Is there a gap under the leading edge of the timber as you plane? As Simoli says this can be significant.

Another point I was wondering about is how square is that shot edge? Have you checked? There is a possibility that the planer fence is flexing causing you to produce an out of square edge at the start and end of the cut under side pressure which might seem like a bellied edge when you came to glue-up.

Are you keeping the same pressure all the way along, or should a feather board be used, to ensure that the wood
is having the same depth of shaving taken off all the length?

Sorry, Paul, but I don't think a feather board will work - I reckon that it would simply get in the way of jointing and would make planing followed by edge jointing a nightmare of taking it off and putting it on. Interesting thought, though.

Scrit

 

[engineer one]

scrit you may be right,but it is a different answer to the same question,
is the loading on the wood the same all the way through the machine.

i found when i started using my ad160 mafell, i got a kind of lifting
if i did not put the same pressure all the way along, so i was
thinking that a hold down on either side would, be valuable, and
make sense.

paul :wink:

 

[Scrit]

I suppose it depends on whether or not your boards aren't too wide. I just couldn't see how you'd attach a featherboard to handle say a 12inch board on edge. Or have I got the wrong end of the stick here?

Scrit

 

[Newbie_Neil]

Hi Lucky

Welcome to the forum.

Cheers
Neil

 

[lucky9cat]

Right, Sorted

It was mainly my technique. Once I started transferring the pressure to the outfeed table as soon as enough wood was on it to take it, there was a big improvement. I started to get consistent results unlike before where the convex curve just got worse. I can now see what you mean about barrel makers using pressure on the infeed table to get a nice convex curve!

Once I had sorted my technique out I could then adjust the outfeed table in a more controlled manner as the results were consistent.

Now I can get a perfect edge!!

Thanks very much Guys, and I hope I can help someone in return.

Regards

Lucky

 

[DaveL]

Right, Sorted

Well done, glad the problem is solved. \/

So what (apart from dust and shavings) or you making? :^o

Any chance of a few pictures of the progress and the finished item. :roll: :wink:

 

[Losos]

Lucky - Thanks for posting this prob. I've had it on odd occassions, sometimes it came out OK other times not, seeing how you've solved it (With help from people ) makes me certain now that it's my 'technique' as well - I must try to put the pressure down on the outfeed asap after piece starts to go thru'

 

[engineer one]

glad that we all helped to solve the problem,
but i do think it confirms the rule to check your
tools before using so that you can discount that,
then look for techniques as the answer.

paul :wink: