Planer Teqnique (powered)

[SteveF]

I seem to have a bit to learn...understatement
when using planer thicknesser I am having issues to get a straight edge
forgetting the odd bit of snipe, I can live with that at the moment
I seem to be getting a "bump" in the middle of the jointed edge (20mm thick boards)
if I try to edge join, the 2 boards are rocking in the centre
flattening seems to go ok, checked with a straight edge
any ideas how to resolve please?

Steve

 

[katellwood]

Is the outfeed table a tad too high. this can force the timber upwards as it exits the cutters.

Also are the tables co-planar I had an issue with this problem on an old Lurem combi machine

 

[SteveF]

I am fairly sure they are coplanar
Is it possible for the outfeed to be too high?
without blades I have tables set level
once blades are fitted, then the infeed is lowered to determing depth of cut
should my hand pressure be on the outfeed or infeed side?
or do you switch mid-pass?
this bump is way less than 0.5mm, but that may as well be a mile when trying to get things right
Steve

 

[Steve Maskery]

Steve
If you ALWAYS get a bump like this, it could be explained by you tables not being perfectly co-planar. If they are V-shaped, you would get a bump.
The other possibility is that your board is a bit spring to start with, and you are just following the existing line of the board edge.
As far as technique is concerned, you should be pressing down on the infeed table to start with, then, as enough board passes over the outfeed, change hands to exert the force over the outfeed table, all the time as close to the cutter head as possible, safely, without being directly over it.
Usual beige stuff, shiny stuff, red stuff caveats apply.

 

[Steve Maskery]

And if you want to try to correct what you have at the moment, try dropping the centre half of the board over the cutters to remove the bump and then try again with the whole edge. If you look down the length with one eye you should be able to see if it is kinky.

 

[katellwood]

The cut on a surface planer is basically lots of parallel scoops (if you catch a planed surface in the right light you will see the scoops) the frequency and depth of the scoops depends on the rpm of the block and the feed speed of the timber.

Because of these scoops the outfeed table should be set very slightly lower than the top dead centre of the blade.

Most planers I have come across have an adjustment on the outfeed table, an exception to this if I recall correctly are sedgewick planer thicknesser's

with regard to feeding the timber, to start maintain pressure on the infeed and as the timber proceeds transfer pressure to the outfeed to finish the cut.

What I would do is feed a straight piece of timber over the cutter for about 18" then turn off the machine. rotate the block so a blade is away from the timber and not fouling it and whilst maintaining pressure on the infeed side examine how the timber meets the outfeed table.

If theres a slight gap and its parallel then the outfeed is too low, if theres a gap at the end of the timber but its touching the outfeed table by the blade creating a slightly tapered gap then the outfeed is too high

You may thick that if the outfeed is too high then as the timber is fed it will catch on the outfeed and stop, this may be so with sharp blades but if the blades are slightly blunt they will cause the timber to bounce and jump onto the outfeed as its fed through

Hope this makes sense

 

[custard]

If it's any consolation I wouldn't worry too much about small inconsistencies in edge planing as personally I always finish edge planing with a few strokes from a hand plane. Even with a high quality professional machine with full adjustability I'll generally get a better glue line from a hand planed edge joint than by working straight from the machine, because even if you get the exact minute hollow you want there's nothing you can do about the inevitable "micro-scalloping" that planer knives always leave. So, if your objective is low volume, fine furniture then use the machine to get your edge joints 90% the way there, and then finish with a bench plane.

 

[Fitzroy]

If you can adjust your outfeed table then micro move it in one direction and see if the situation improves/changes.

I set my blades then drop the outfeed slowly until the board I am planing no longer contacts the edge of the outfeed table.

F.

 

[Neil S]

I think it helps as well if you run the board over the planner with any bend/curve in it facing down. This way the start and end are in contact with the table and any high point is in the middle. Successive passes will eventually remove more and more until there is no high point in the middle.
Conversely if you ran the board across the planer with the high point in the middle of the board facing down onto the table it is too easy to rock the board and successive passes will not straighten it out.

At least that's what I think might happen.

-Neil