Bevel angles for dummies...

[Eric The Viking]

... well this particular dummy.

I'm struggling with an ill-chosen purchase - some slabs of purpleheart. Originally I had designs on a bandsawn box for the Domestic Controller, which mutated into a heart-shaped design with a lid for earrings, etc. Looked do-able on paper, but then the 'fun' started.

I'm not really having fun.

In order to achieve what I wanted, shapewise, I intended to bandsaw a heart'shaped body and lid from the fairly rough stock, before sculpting the exterior shape and making recesses for the contents. In order to do that, I've been trying to flatten four faces, about 200mmx200mm.

In 'full' sizes I've only got bevel-up planes - 4, 4 1/2, 5, 5 1/2 and 7. I'm getting best results with my 4 1/2, with a bog-standard Stanley blade, although I have a Japanese laminated one I've yet to try.

"Best results" gives the wrong impression though: the edges last around 10 minutes and tear-out is extreme and horrible. Part of the problem, I think, is that the grain, such as it is, is pretty much parallel to the surface.

Anyway, I've been grinding to 25, honing to around 40 (scary sharp to 2500 grit - I can shave with the results - they're not bunt). The frogs are all Common Pitch (45). I don't think it's steep enough, so a micro-back-bevel is called for.

The question is, given I can't change my planes to BU, what should I be going for on the angles, mainly to avoid the tearout, and does anyone have any tips, apart from keep the sharpening table nearby, to save the legs?

Cheers, E.

PS: Haven't been around here for a while - good to hear DC's getting better!

 

[LuptonM]

You could always used a toothed blade for initial flattening

 

[Harbo]

Scraper and ROS


Rod

 

[Jacob]

OK it's a challenge to do it with a plane (if you want a challenge) but could be time consuming and expensive.
If you just want to get it done then do what a woodworker would do; belt sander and ROS.
I wouldn't use a 4 1/2 though. I've never seen the point. I'd try the 4 with a good camber to the blade so you only use a bit of the blade and then tilt it first left and then right to use 2 more bits before resharpening.

 

[dunbarhamlin]

the edges last around 10 minutes

Anyway, I've been grinding to 25, honing to around 40

Here's a couple.
10 mins much too long between touch ups if you're having trouble. The number one weapon again tearout is sharp
Honing to around 40° is probably too obtuse, leaving only 5° clearance angle.

Skewing across the grain with a well cambered jack (and not too heavy a cut) may help initial flattening.

In summary, your anti-tearout regime (in almost commonly accepted order) is:
1) Sharp irons - frequent honing required.
2) Light cut - reduce the blade projection to a whisper.
3) High angle - a back bevel worth a shot - might as well add 10°-15° straight off. Note this does shorten effective edge life (back to point 1), and is harder to push - most would probably suggest using a narrower plane for this.
4) narrow mouth - provides support to help prevent the shaving (split) propogating ahead of the cutter.
and finally, I think largely discredited
5) moving the cap iron very close to the cutting edge to act as a "chip breaker"

An extra tip - do wax your sole - this will effectively reduce the depth of cut a little, and help maintain a steady stroke with that high angle iron, reducing the chances of skipping and juddering.

Oh - nearly forgot -
Hone frequently.


[Edit - the aforementioned toothing blades, and powered apprentices all make lots of sense - especially since this phase is turning into a chore]

 

[Eric The Viking]

@Jacob: For normal use (sensible wood!), I rather like the #4 1/2 - the extra mass is nice. I'm indifferent to the width, as I've only recently acquired the 2 3/8" planes - I used the #4 and #5 for years without anything much bigger - I can flatten, square and true surfaces with the #5 quite nicely and it was my only Bailey for many years. I'm used to getting the camber just so, for best effect. Coincidentally, I've just splashed out on a Makita 1/2 sheet orbital, which should arrive tomorrow or Wednesday, so worst-case I will have a decent quality 'little electric friend'.

10 mins much too long between touch ups if you're having trouble. The number one weapon again tearout is sharp

Righto. I've a chunky glass plate for SS so it's a moment's work to whip the iron out and touch it up.

Honing to around 40 is probably too obtuse, leaving only 5° clearance angle.

I did wonder if sticking to around 30° and a micro back-bevel might be better.

Skewing across the grain with a well cambered jack (and not too heavy a cut) may help initial flattening

I ended up doing that by default.

The irons aren't as good as I've had them in the past (although pretty sharp nonetheless), and I found any straight stroke, at any angle along or across the grain, would dig in and/or cause tearing. I've got the mouth set very fine (frog well forward), and the cap iron as close to the edge as I dare, and hardly any projection.

I ground the primary bevels on my Dakota wet wheel (Tormek-like), and I wonder if I should also have honed 25° before the secondary bevel, to get an initial camber (I like an Eclipse guide for plane irons). The Dakota tends to leave too straight an edge - you can take off the corners, but that's not the same as a proper camber.

In summary, your anti-tearout regime (in almost commonly accepted order) is:
1) Sharp irons - frequent honing required.
2) Light cut - reduce the blade projection to a whisper.
3) High angle - a back bevel worth a shot - might as well add 10°-15° straight off. Note this does shorten effective edge life (back to point 1), and is harder to push - most would probably suggest using a narrower plane for this.
4) narrow mouth - provides support to help prevent the shaving (split) propogating ahead of the cutter.
and finally, I think largely discredited
5) moving the cap iron very close to the cutting edge to act as a "chip breaker"

Yup, apart from probably not honing enough I've been doing most of those. I will try the #4 or #5 in preference to the 1/2 sizes though - I understand what you mean about blade support, and in the past the narrower two have had quite a bit of work on both cap irons and lever caps to ensure good even pressure.

An extra tip - do wax your sole - this will effectively reduce the depth of cut a little, and help maintain a steady stroke with that high angle iron, reducing the chances of skipping and juddering.

Yup, always do. I haven't worked on the soles of the 1/2 sizes, but the other two have a near mirror finish. Point being that wax both lubricates and lifts those slightly, whereas it tends to settle in the depressions of the castings of the others much more (I've been putting off fettling the #7 until I feel strong enough!).

[Edit - the aforementioned toothing blades, and powered apprentices all make lots of sense - especially since this phase is turning into a chore]

I'll skip the toothed blades this time, as it's beyond that stage really. I've got about 0.75mm of cupping to deal with across 20mm width. For this purpose, flat is OK (don't need absolutely parallel). Provided I can stick the surfaces together with DS tape, I can still bandsaw the shape successfully.

I do appreciate all the advice. I may yet resort to sanding , but I'm not quitting yet!

Cheers,

E.

 

[Corneel]

For flattening, work across the grain, then a bit more diagonally. That leaves a flat but rough surface, but without the deep tearout (when you are not too unlucky).

After that you want to smooth it. A high angle is really helpfull here (when the super sharp blade AND the light setting AND the cap close to the edge don't help enough). When even the high angle fails , it's a scraper and/or sanding job.

 

[andy king]

An age old solution for dealing with end grain to prevent splitting that can work equally well with wild and interlocked grain is to work it in small circular motions with the plane, and from all around the stock, so from outer edges inwards to the centre.
It skews the cut and slices rather than lifting and tearing. A fine set iron and narrow mouth opening help as well.
HTH.

Cheers,
Andy