Planer Thicknesser weirdness

[Zeddedhed]

I'm trying to get a face and edge on some 42 x 170 Euro Oak. The boards have been crosscut to 700mm long.
My PT is a Hammer A3 260 with approx 550mm both before and after the cutters (indeed and outfeed).
I'm using brand new razor sharp blades (three knife head).

The problem is that whilst I can get a very satisfactory Face Side, when planing the edge with the Face Side pushed hard up against the fence I'm ending up with a slight hump in the timber about 2 thirds of the way in from the start. The hump is about the thickness of two sheets of 80gsm paper (not a standard unit of measure I know) but probably enough to give an unsatisfactory glue up when made into the top of the unit it's destined for.

I've tried taking the ends down first to create a convex edge and then with pressure only on the outside side bringing it down to flat but the hump persists.

Any ideas?

 

[Jacob]

Taking the ends down first sounds exactly wrong.
You could try keeping pressure on the near end until the far end has crossed to the out-feed and then put pressure only on the outfeed side.

 

[Andy RV]

Have you always had this problem?

 

[custard]

Taking the ends down first sounds exactly wrong.
You could try keeping pressure on the near end until the far end has crossed to the out-feed and then put pressure only on the outfeed side.

That's what I'd do. Make the edge concave and then run it straight through. If you're fairly new to this operation then after making the edge concave put a scribble of pencil down the edge, that way you can be sure the final cut has removed material all the way along...at which point you should have a straight, true edge. Incidentally, you'll have an even better surface for gluing if you then finish it off with a pass from a hand plane.

 

[James-1986]

Sounds like the outfeed table is a bit high.

 

[Sgian Dubh]

Any ideas?

One cause of this I see quite frequently is for the user to concentrate pressure at the infeed table side, only transferring pressure to the outfeed table as the last 200 or so millimetres of the board approaches the cutters. I don't think creating a convexity is helping you. In fact I suspect this is exacerbating the problem because the piece wants to rock somewhere near the centre point before you start, and passing the piece over the cutters won't necessarily take out the high point because of this tendency to rock, especially if you concentrate pressure on the infeed table for 80 - 90% of the cut. Flattening convex pieces on the surface planer, whether a face or an edge, can be done, but it takes some practice.

The norm is to look for the concave face or edge, and feed this over the cutters, remembering that once the piece has travelled something like 250 - 300 mm past the cutters the downward pressure should be focused on the outfeed table, not the infeed table. The reason for this is the outfeed table determines the flatness, and the infeed table primarily determines the depth of cut, so what's passing over it, once a decent length of flat wood is travelling over the outfeed table, is really only following through.

I admit the above is a relatively simplistic description of what happens, and good technique is most easily demonstrated on shorter pieces of wood, e.g., about the same length, or only 300 - 600 mm longer than the overall length of the machine, and it gets a bit more involved when machining very long stuff, e.g., 3 or 4 times the length of the machine, or is quite severely bowed, or is wavy in the length (multi-bowed), or otherwise warped in complex ways. Slainte.

 

[blackrodd]

Sounds like the outfeed table is a bit high.

+1 For the above, Going for the simplest first, Check the cutters and outfeed table.
Assuming you've had no problems before changing to the new blades, Just a few measly thou will do it.
Regards Rodders

 

[williams1185]

to adjust the outfeed table on a hammer machine is not that easy and with the self setting cutters not a job i would undertake the machine is relatively new im assuming ? have you changed the cutters before ive not had any problems with my hammer they are usually very good , could it be as suggested maybe a technique problem its very easy to plane a board out of true how much cut are you taking off ?

 

[Zeddedhed]

The cutter for the Hammer are self setting - either they are in and therefore right or they are not.
I've been putting the pressure on AFTER the cutters (the outfeed side) rather than the infeed.

So it seems that I need to hand plane some concavity onto the edge and then work it over the PT.
I've always found in the past that that flattening a convex piece is easier because if Concave the ends can ride over the end of the tables thus changing the attack angle mid cut.
However, in the spirit of you learn something new everyday (or you should do) I'll give it a go the other way.
Watch this space..

 

[custard]

So it seems that I need to hand plane some concavity onto the edge and then work it over the PT.

You can get rid of most of the convexity using the machine. As you start feeding in the workpiece keep the pressure over the back of the board on the infeed table, this lifts up the front end and it'll ride above the knives. Then when you're, say, 20% over the knives switch pressure to the outfeed table, then for the last, say 20% of the length of the board apply pressure just on the very front section of the board, if there's any convexity left it'll lift the final part of the board above the knives. Do that two or three times and you're ready to pass the board across normally.

If you're still struggling book yourself in for a couple of days with someone like Peter Sefton and get yourself trained. You've got a nice piece of kit, if it's not producing superb quality then the logical thing to do is invest in your own skills.

Good luck.

 

[Jacob]

Even the best machines perfectly set up require a bit of practice and technique to get them doing what you want. Using a machine is another craft skill, like using a hand tool.

 

[dzj]

Sounds like infeed and outfeed table planes aren't parallel.

 

[Zeddedhed]

Sounds like infeed and outfeed table planes aren't parallel.

I've checked the parallelness (I know thats not a real word - co planarity perhaps?) of the tables and it's spot on as far as I can tell.

I think that the others are probably right when they say that this could be an issue with technique (or lack of)

I'm still not 100% convinced of this as it's not a problem I've noticed before except on long (1.5 metre) boards which by all accounts are challenging at the best of times.

However, like Jacob says the machines are just a tool like a hand plane or plasterers trowel and those are two tools that I'm chuffing useless with.

I'll take a look around for a machining course methinks.

There's a guy local to me called Colin Searle who runs wood machining courses. I'll see if he includes the PT on his course and if so maybe get booked in.

 

[RobinBHM]

Overcoming a convex board that hangs down below the end of the table can be done by pushing the board until about 200mm has been planed, raise off the cutter, remove and turn around. I do it often, however Im not suggesting its safe practice!

Edging a board 170 wide for gluing up is unforgiving and will show up any planing faults -especially in a hard timber.
Sometimes moving the position of the fence, so you are running on a different part of the cutter / beds can work.

Also waxing fence and beds is worth trying. Sharp cutters only need light feed pressure and the boards are only short so you could try a test piece using delicate pressure and compare the result.

Diagnosis is tricky, but given its a quality machine Id start with try differing techniques and if problems still exist then check cutter is correct height above outfeed table, check infeed and outfeed tables are parallel, flatness of tables, flatness of fence.

 

[Zeddedhed]

Overcoming a convex board that hangs down below the end of the table can be done by pushing the board until about 200mm has been planed, raise off the cutter, remove and turn around. I do it often, however Im not suggesting its safe practice!

Thats exactly what I meant by 'taking the ends off' in my opening post

I've already put a good face on the 170mm side of the board - it's the 42mm edge that's troubling me.

What seems odd is that on a wide board I can get a perfectly flat face but the edge causes problems.

Am i mixing up Concave and Convex?

When I said the board was Convex I mean that the board is wider in the middle - for example 169.5 at each end but 170 across the face in the middle?

It could be that I need more than a course in Machining

 

[RobinBHM]

Oops! That should have said concave! -my error (can i blame it on the heat).

 

[Zeddedhed]

After a few experiments this morning and some more checking and head scratching I found this.....

At a point that corresponds exactly with the 'hump' in the workpiece the outfeed table starts to rise, creating the equivalent of a hollow in the table.

Phone calls to Felder are about to happen......

 

[custard]

On my Felder there's a handle underneath the outfeed table, turning it adjusts the "pitch" of the outfeed table so you can ensure it's co-planer with the infeed table. Do you have a similar mechanism on the Hammer?

Also, if there is a problem, why are you getting acceptable results on the face side? It seems odd that the problem only shows itself with edge planing?

 

[Zeddedhed]

On my Felder there's a handle underneath the outfeed table, turning it adjusts the "pitch" of the outfeed table so you can ensure it's co-planer with the infeed table. Do you have a similar mechanism on the Hammer?

Also, if there is a problem, why are you getting acceptable results on the face side? It seems odd that the problem only shows itself with edge planing?

I'm equally confused as to why this only manifests on the edge. Can't explain it to be honest.

Felder are sending an engineer out with a new table next week. Also giving me a full service, belt change, lube job, the works.

They wanted £350 for the visit but I protested loudly. I suspect the fact that their rep is currently trying to flog me a bandsaw and extraction system may have helped.


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[custard]

Felder are sending an engineer out with a new table next week. Also giving me a full service, belt change, lube job, the works.

They wanted £350 for the visit but I protested loudly. I suspect the fact that their rep is currently trying to flog me a bandsaw and extraction system may have helped.

Result!