Tearing foam... any suggestion?

General Discussion
1

I used to shape with blades on my planer but when Clark shut down, I switched to Burford blanks and they don’t like blades: even if slowing down my passes, it still tears… So I bought a shaper’s barrel and everything was fine again.

Except when I had to shape those Just Foam blanks with a 1" balsa/red cedar T-band… It feels like the planer will burn out… I tried to turn back to blades, but those blanks don’t like them, either…

What’s the solution? Is there a special angle to which blades should be ground to avoid this and still be able to shape at a “normal” speed?

Thanks for any help.

2

two planers, one with blades the other with grit. Keep the blades sharp.

3

gregs right… as a long time user of burford. i use 2 planers a bladed one for bottoms and a grit one for decks…

4

Greg, Dave, thanks for your answers. I do own two planers, too, one with blades and one with grit. With a standard issue blank (i.e. 1/8" or even 1/4" center stringer), I will use the gritted one from start to finish, no problem. But I do many multi-stringered longboards a lot, often with wide center T-bands and those will kill any planer with a grit barrel, even with shallow passes. If I use the one with blades, I will take down stringers all right but then I will spend a lot of time cleaning the foam around because it was just lacerated by the blades. Why can’t we have one tool that would do both?

5

I would try to let the planer turn the other way.

Like I see it, before the planer cuts the foam it starts tearing because of the low cut.

In production techniques it’s called up/down milling.

see: http://machine-tools.netfirms.com/Assets/figs/fig_1_4_1.jpg

When using upmilling with metals it leaves a rougher surface because it doesnt start cutting right away, first it starts pushing down and gliding on it and when forces are high enough is starts cutting. With downmilling it starts cutting right away because the deeper cut to start with (downside of this is that it gives more vibrations).

So I think your problem could be solved by using downmilling. When your blade is sharp enough it should start cutting right away and it wont tear first.

I could be wrong but I think it’s worth to try!

keep us informed, I’m interested in this one.

6

Deeper cuts also tear less. If your using very shallow cuts you’ll rip more so get the contours done and then take a last truing pass deep and slow.

7

i always thought that the foam tears when you run the planer parralell to the stringer.but when your run it at a slight angle it cuts fine. does for me any ways . but thats with u.s. blanks

8

Look at it this way, the tearouts are only going to be half as deep as your cutting depth. Rough out close and do a smaller final pass? Gotta find a positive somewhere, right?

9

Thank you all for your answers. I’ve already tried everything like deep vs shallow, angled vs parallel, etc… I just thought there might be some “secret” device like grinding the blades at a special angle or something… Will keep experimenting…

10

I put in new blades last night.

the other ones were abused

the tear incidence was limited,

my first thought was also get sure sharp blades

and go slower and shallower cuts…

but the value of the line of cutter at 45 degrees or less to the

direction of travel is indeed the answer.

compound this with slower and sharper

and I believe in this holy trinity

sharp slow and respectable angle

this angle reduces width of cut

and rests foot of planer

on the flat of adjacent foam

eliminating the unfortunate dip

and impromptu gouge channel

all things said and done

the sharp guys,you know the ones,

that shave the hair on the backs of their hands to show off

win.

…ambrose…

11

Try getting your blades sharpened to 55 degrees. This eliminates a lot of the tearing.

When possible try gliding the planer base at an angle to the direction of motion.

HTH,

George

12

one other thing i remembered… origional blades that come with the hitachi worked the best and longest. once you had them sharpened them they tore more. also the angle you have the planer helped. . from memory you use a lot of superlight (blue) burfords. they are the toughest, strongest blanks around, but will take some time shaping them… cheers

13

Dave, I use green Burfords, Just Foam and some Walkers that I recently scored. The trouble really is with the wide-stringered Just Foam, otherwise the grit barrel will do the job OK.