Sedgwick outfeed table off square?

[Helvetica]

I'm trying to joint the edges of some mahogany, it's 3m long, 350mm wide and 45mm thick. I cut a lovely straight line with my plunge saw, but I want to plane away the saw marks. Problem is the planer is leaving a curve in the inside of the edge, so there's a 2mm gap in the middle of the board - too much to close with clamps & glue.

I can't tell whether the outfeed table isn't square, or it's just down to my control over the board. How would I make an adjustment to the feed tables? Is it even possible on these machines?

Could it be user error? The weight and length makes the boards tricky to move across the tables, and very difficult to put downward pressure on the outfeed side, against the fence, all while moving the board. I have a strip of ply either side of the tables to support, maybe I just need to make this longer.

Other options - glue directly off the plunge saw, or handplane with my record #7 (which I am not too comfortable with)

Any advice appreciated!

 

[memzey]

Did you have adequate in and out feed support? 3m is pretty long. I have a Sedgwick MB and whenever I'm planing something over 5' long I use roller stands set up to the exact heights of the tables and I get none of the problems you describe.

 

[custard]

A 2mm gap over 3 metres is a bit on the high side, but only a bit. Many planers are set by default to machine an "open" or "sprung" joint. For example the factory settings on a Felder planer will give a 0.2-0.5mm gap on a 2 metre long workpiece, leaving you the choice to adjust this out (or accentuate it) if you prefer.

It could just be that the outfeed table is fractionally too high. Obviously if it's substantially too high then the workpiece will catch and not ride over, but if it's just a whisker too high you see a gap opening up between the leading edge of the workpiece and the outfeed table after the workpiece has passed say 300 or 400mm over the cutter block. At some point the workpiece then falls back down on to the outfeed table and the tail end of the workpiece isn't planed as deeply, if you like it's the opposite of snipe.

You can also sometimes get this "over sprung" effect if the knives are well past their sharpening date, what's happening is the knives are tending to lift the workpiece bodily up from the tables and not cutting as deeply, the effect is usually most marked at the two ends of the board.

By the way, I recognise that 2mm is on the gappy side for a sprung joint, but if your sash cramps won't close up a 2mm gap on a 3 metre board then you need bigger sash cramps!

One final point, I almost never joint up boards straight from a machine planer. You can always improve the cut (and therefore the strength of the glue bond) with a hand plane. It takes some practise and persistence to do it accurately, but edge jointing by hand is probably the basic skill in cabinet making and until you've perfected the art you'll always be limited in what you can achieve.

 

[RobinBHM]

A board 3 metres long x 350mm is really a 2 man job to push over a surface planer. With a typical outfeed table of say 600-700mm you are overhanging by over 2 metres by the end of the cut, very difficult to control

It should be possible to get a straight joint, as Custard says if the outfeed table is too high you could be getting an error that is getting big over the 3 metre length.

I cant advise on a hand plane, Im not even sure if I have one!

 

[memzey]

I still think extending the support either side of the tables would be my first thing to try. 3m is a long old board. You will be fighting gravity at the beginning and end of each cut which won't help you at all.

 

[Helvetica]

Thanks for all the advice gents, very informative. Might be a chance to brush up my hand plane skills alright custard. Would you use a #7 jointer or a #4 smoother? Flat blade or camber?

My floor is uneven (rough concrete) and my rollers are cheap! I want to level an area of the floor around the planer but can't find the time. Still I think I have to lengthen the support sheets anyway.

Custard, again I think you are spot on with the reverse snipe scenario. I will inspect that.

 

[Helvetica]

Now that I think of it, I meant to ask if 'spring' will work across 4 boards. I have no problem clamping the 2mm gap when just 2 boards are joined, but will it work when all 4 have that amount of daylight between them?