High angle frog vs. back bevel - is one better?

Here is a link *LINK*

Dan Clermont in Burnaby


>The pic was too big. Here is a link to a different forum I polled friends about pulls.

Dan C


Curly Maple

Re: One thing to consider....

Greg Sloop, Portland Oregon


>Dan, I'm simply not going to argue.

I will say that I've played with a host of different cutting angles in a large number of ways, both open and closed mouth.

My observations mirror quite closely the results others here are reporting, so clearly either we're all nuts or perhaps I'm on to something. (Or tagging along perhaps...)

You may not believe it, but both I and DC (I believe), think mouth size has little to do in directly minimizing tear-out. Cutting angle has a much higher degree of impact on tear-out.

If you have success lowering pack weight by removing the handle on your toothbrush and ignoring the case of beer, or removing tearout via mouth size instead of cutting angle then that's great for you.

However, *I* think it's a patently foolish thing to claim as reasonable, that mouth size has anywhere near the magnitude effect as EP, given the evidence I've seen.

HAND

-Greg

Re: One thing to consider....

Dan Clermont in Burnaby


>Hi Greg,

In response to:

If you have success lowering pack weight by removing the handle on your toothbrush and ignoring the case of beer

I drill holes in the handle of my toothbrush which I use on Backpacking trips. Never carry beer. Sorry I ain't that fun

So I taketh you can't make the woodshow to play with Bevel angles, nouth openings and wood? I'll buy you lunch and pay for your admission.

Dan Clermont

Re: One thing to consider....

Greg Sloop, Portland Oregon


>No, afraid not. The drive to BC is a bit much.

Have a nice time.

-Greg

Ditto!

Frank Mutchler in Colorado Springs

Re: Back bevel is much more versatile.

paul womack


>This theory, which works, has been exploited by Lee-Valley with their range of bevel up planes with blades supplied at steeper grind angles. I believe the theory was well known to craftsmen in the past, who might have made wooden planes with steeper pitches as required.

I have a factory made smoother (Griffiths, IIRC) at 55 degrees, so this knowedge wasn't just "craftsman's secrets"

However, it seems to me that a 12 degree bedding angle is rather low to use as a starting point. Karl Holtey's 98 plane with 22.5 deg bed seems better for this function. Philip Marcou seem to be on this track as well.

If you're aiming for a high angle, you're quite right. But if you're trying to sell a super-versatile plane, the low bed allows true "low angle" functionality as well, most useful for end-grain, e.g. using the Lee Valley LA jack on a shooting board.

Some downsides are:

* the need for very high blade angles to get high EP

* thin, hence weak, beds, overcome by material strength

* need for high precision in bed machining - raises cost, although

amortised by the versatility reducing the range of planes needed.

BugBear

Re: One thing to consider... chip breaker

james watriss


>Here's a reply noone probably would expect... who cares about the chip breaker? I've heard Karl holtey invoked in here already, and he doesn't like chip breakers much. (Come to think of it, Clark and Williams don't like them either... I heard Larry Williams say once that he thought they made more problems than they solved) Bevel up planes seem to get by just fine without them. Japanese planes don't require them, and not all of them are even made to use one. Lastly, I have an old mathieson infill that I picked up for (sorta) cheap, and it actually works better if I set the chip breaker back away from the edge by about 1/8" for chip clearance.

From what I've read, been taught, and experienced, the CB has 2 real purposes.

One, to spring the blade, to make sure it's in the plane good and tight, and can't flex very much, if at all. Since the bevel is in the back, the edge can be pushed back a bit, flexing the blade, and making for a chattery cut, if you have a thin, weak(er) iron. This isn't the case with bevel up planes, since the iron is supported all the way down to the wood. This is also one really good reason why the japanese planes don't need them... those irons are HUGE. In this light, I think I'd go bevel up over back-bevel, simply because there's more blade support.

Second, chip breakers were good in old wooden planes once the mouth got wallowed out with time and hard use. If you can't/don't have time to patch a sole, you can at the very least use a chip breaker. I've seen old wooden planes that have solid (ie, non-pierced) irons, from before the days of chip breakers.

If you're going to back-bevel, one thing you may find is that the blade will probably be sharper, on average. With a back-bevel, you're only removing a thin stripe of metal from the edge, and not having to take down the whole back to be in plane. So the edge will sharpen faster, and you're less likely to give in and say you've had enough of trying to get the back flat. Hence, it'll probably be a lot sharper. I've talked to a professional cabinet maker who found this to be true, and while he was initially skeptical, once he gave it a half-hearted try, he was amazed that it made such a difference and was so much easier.

For those of you who don't believe in sharpening jigs, and don't think they could keep a consistent angle when back-beveling by hand, I met one guy who would glue a small block of wood to the other end of the blade to keep the angle consistent when he sharpens. The block elevates the back end of the iron just enough to make a small back bevel when they're sliding it around on the stone, and the angle never changes.

Give it a try, Denis. And just shove that chip-breaker back out of the way so it won't give you any trouble.

Re: One thing to consider... chip breaker

Warren in Lancaster, PA


>James,

You write "Second, chip breakers were good in old wooden planes once the mouth got wallowed out with time and hard use. If you can't/don't have time to patch a sole, you can at the very least use a chip breaker."

Do you really think it was easier to retrofit the plane (many did} and buy a double iron than to patch the sole? Or that somebody would spend the extra money for a double iron plane and the extra assembly time each time they sharpened the iron just to save time patching the sole?

yet another consideration

Larry Williams

>I do agree with James on the dubious value of cap irons. I just don't believe the do anything more than flex the whole double iron assembly for a little better bedding near the mouth and stiffen a thin iron. Generally, I think they cause more problems than they solve.

There's been no discussion of clearance angles in this thread. I first became aware of clearance angles using 55� bedded single iron smooth planes. I grind at 25� and freehand hone to about 30�. At times I've fudged the 30� a little when the honed bevel gets big enough to slow honing. I found that can be a mistake; if I get up to around 35� I start having problems with clearance angle. With inadequate clearance angles surface quality suffers a little but the big problem is with the plane. The ability to control depth of cut goes away that depth of cut can easily become basically self-limiting due to visco-elastic spring back of the wood fibers.

I believe the steeper the effective cutting angle the greater the needed clearance angle. At 55� my experience is that you need around 25� of clearance angle. If you're using a back-beveled common pitch plane to get a 55� effective cutting angle, I think it would be wise to grind the primary bevel and hone at steeper angles.

I've been working on developing some machine cutters that use the same geometry found in planes. These cutters have a steep pitch to enable cutting with, across and against the grain in hardwood. I was having trouble with surface quality--not tear out but tooling signatures in the surface. I had the chip formation where I wanted it and had eliminated tear out but had neglected to consider clearance angles. I couldn't figure out why the signatures didn't change much with changes of rpm or feed speed until I remembered about clearance. I've still got more refining of angles to deal with but these cutters are now doing more than I had originally hoped.

I was using the most recent version today and took a photo of the shavings--I'm not really ready to show the cutters to people. I can say the reason I was making these particular shavings was to remake some parts where I'd forgotten to remove the signatures from the surfaces with a plane. The signatures were fine enough that I had fit all the parts without seeing them. Maybe some day I'll have time to really experiment with clearance angles but right now there's too much other work that needs to be done.

I can't think of an application where a back bevel on a plane iron makes much sense. I'd save back bevels for carving tools where they're an advantage.

Re: yet another consideration

Pam Niedermayer - Austin, TX

>Larry, what is the clearance angle? And how does it relate to the bevel angle? That is, how are the clearance and bevel angles measured? Sorry to be so stupid, but I'm trying to apply these principles generally.

Thanks,

Pam

Re: yet another consideration

Paul Kierstead

>I believe the steeper the effective cutting angle the greater the needed clearance angle. At 55� my experience is that you need around 25� of clearance angle. If you're using a back-beveled common pitch plane to get a 55� effective cutting angle, I think it would be wise to grind the primary bevel and hone at steeper angles.

This would also seem to argue that a BU plane would need to be bedded at 25 degrees if you wanted to use it with an effective angle of 55 degrees, would it not?

Re: One thing to consider... chip breaker

james.watriss

>Well, like I said, most of that is based on what I've read and have been told by various people. It makes sense to me that it'd be easier in the long run to use the second iron than to have to keep patching the mouth. I don't know that doing the retrofit would be necessarily easier, but I can believe that people did it, and that it would become a desirable feature on later planes.

For myself, from the few wooden planes I've made so far, none of them have chip breakers/cap irons, and all of them work very well.

I wasn't trying to raise hell or start an argument. The basic point I was trying to make is this: if the plane is sharp enough, setting the chip breaker back a bit shouldn't be a big deal. So, if the big thing holding you back from trying out a backbevel is what to do with the chipbreaker, that shouldn't be a dealbreaker. And since you're removing less material by honing a backbevel, it should be easier to get the plane that sharp.

Sorry if I come across as a know-it-all or a windbag. I spent too much time in college, learning to vomit out everything I know on command.

Re: yet another consideration

Larry Williams

>Pam,

As someone interested in plane making I think you'd appreciate Richard Newman's article 'Souping up a block plane' in Fine Woodworking issue #39, March/April 1983. It's the earliest information I know of that covers a lot of what some suggest with bevel up planes except that Newman was aware of clearance angles. It's the only place I've seen clearance angles discussed in print. The image is one from that article.

Unfortunately, I invested quite a bit of time figuring out what Newman already knew and explained in the article.

Re: yet another consideration

Larry Williams

>Yeah Paul, that's what my experience says.

If you use a normal bevel down plane bedded at 55� with two different irons, one sharpened at 30� and the other at 35�, you'll find a significant performance difference. With the 35� iron you'll have a plane that balks, is prone to chatter and won't let you take a heavy cut.

I'm not saying you can't take shavings with a BU plane equipped with an obtuse iron bevel. You can and this use may get a woodworker through a difficult situation. You'll be limited to the finest of shavings. I don't see where a plane set up this way would offer anything you couldn't get out of a $7 card scraper.

Re: yet another consideration - BU

Norman (Ottawa, Ont.)

>Good discussion Larry, Paul..

In a typical lo-angle BU plane, the blade is bedded at 12 degrees, this is essentially the clearance angle created. There is,however, at least one plane maker that introduces a more standard bedding angle ( 20 degree+) in his bevel up offering.

In the case of a 25 degree ground BU blade, the clearance angle would be sufficient in a 12 degree bed? In a 38 degree or higher case, the clearance angle now becomes insufficient?

I'm wonderig if the physics of a BU and BD plane differ enough to

not make this an issue with chip clearance, compression, etc.

Has any empirical testing been performed to your knowledge?

Maybe this deserves some testing.

Norman

Re: yet another consideration

Pam Niedermayer - Austin, TX

>Thanks, Larry, I'll try to find #39 at the library. Looks like an interesting article.

Pam

Re: yet another consideration - BU

Larry Williams

>I think there's more difference between bed angles and woods than between the designs of bevel-up or bevel down planes.

I don't know of any studies and even Norman Franz's 1956 thesis and William McKenzie's 1960 thesis seem to ignore clearance angles. I'm not sure, the only information I have is in the back of Leonard Lee's sharpening book. From the photos I'd say they didn't even look at clearance angles. I'm sure some of the tooling manufacturers have studied it and have developed clearance angle specifications for machine tooling.

I got the term visco-elastic deflection from metal working sources. Even metals deform ahead of the cutter and then spring back. It's a pretty major issue in high tolerance metal work.

I do know that acknowledging clearance angles and paying attention to them makes my work easier and better.

Re: yet another consideration

Joe Rogers, Northern Virginia

>Pam you may find a reprint of the article in the early "Best of Fine Woodworking" black and white series. I think the subject is Planes and Chisels. It may be easier to locate on the shelves than a magazine. I will look at my copy and correct the cited title if I was wrong...(perish the thought:-) )JR

I was right...somewhat

Joe Rogers, Northern Virginia

>Pam the series is FineWoodWorking on Planes and Chisels not Best of.

ISBN 0-918804-28-0

I think you would like the selection of articles in it. There is a lot of wooden plane info including Japanese and Vietnamese planes.

It was instrumental in my stepping over the edge of the woodworking slope.JR

Re: yet another consideration

Pam Niedermayer - Austin, TX

>Thanks, Joe, but a search of the Taunton site for "Newman" only returns the original article in #39. Maybe they don't have the Best of .... black and white books online? A search on Amazon doesn't show any such animal. I thought perhaps it was the Bench Tools best of, but nothing by Newman there, just an article by Maurice Fraser on Block Planes.

Pqm

Re: I was right...somewhat

Pam Niedermayer - Austin, TX

>Thanks, Joe, that did it, don't know why my previous searches didn't uncover it. The library didn't have it, but there are some cheap copies on Amazon.

Pam

Steve Elliott's work

Wiley Horne

>Larry,

Further to your point....Steve Elliott is doing systematic testing of plane blades and bevel angles. See attached link. Although his work in this area is still at an early point (he has been perfecting his methods), his experiments to date indicate that for planes attacking at the same cutting angle (47.5 degrees), blades with less included angle and more clearance angle started sharper and stayed sharper through hundreds of lineal feet planed, subject to the steel being able to take the load. Looking forward to more of Steve's tests.

Wiley

Re: yet another consideration - BU

Norman (Ottawa, Ont.)

>Thx for the info and references Larry.

I looked through my collection of old FWW mags. and of course, issue #39 is not there.

My understanding is that a 25 degree angle would be the minimum acceptable angle on a plane iron for reasons such as strength, less brittleness, edge retention, etc..

I also read that 12 degrees is the bare minimum clearance angle for a blade angle either in a bevel up or bevel down configuration. To acquire cutting action, there must be enough of a clearance angle underneath the blade, otherwise the blade slides over the wood surface and polishes the wood.

These two criteria are combined in the lo-angle BU configuration and it works. Higher effective angles can be created with use of secondary bevels and back bevels.

Just my .02

Norman

Re: yet another consideration

GolfSteve in Calgary

>Hi Larry. I've ran across brief references to clearance angle before on Woodcentral, but never really understood what was happening until I just couldn't get my planes to work no matter how sharp I got the blades.

What happened to me was exactly what you described - my secondary bevel got wide and freehand sharpening was taking a long time (and I'm not some monkish super-Zen sharpening expert, so keeping a consistent bevel angle while sharpening a blade for a long time is difficult). I cheated a bit by raising up the blade to increase the bevel angle. I found that above a 35� bevel I started to run into clearance angle issues. It was very frustrating because the iron was sharp but it seemed like the blade would dull extremely quickly and I had to resharpen after a minute or two of planing. I had to extend the blade depth to get it to cut, but then it would grab. Very frustrating. My troubles co-incided with a project that used a lot of Maple instead of my regular Cherry, so I initially put a lot of the blame on the Maple.

What I found is that I had trouble with planes that have blades bedded at 45�, but I had less trouble with my 4-1/2 smoother with a high angle frog (50�).

So now any time I run into problems with the blade seeming to dull very quickly, or when sharpening starts to take too long, I run over to the grinder and put a new hollow grind onto the blade. This is a pain because I hate getting grinding dust all over the shop, but the next sharpening is a real pleasure and the plane performance is 5x what is was before the hollow grind. I also try and concentrate on keeping my bevel angles low when I'm freehand sharpening.