BU plane sharpening

Re: BU plane sharpening

Derek Cohen (in Perth, Australia)

>Hi Gordon

A small block plane can be used in different ways, all of which determine the cutting angle:

Firstly, for end grain you ideally want the lowest possible cutting angle. Typically this is 37 degrees (12 degree bed + 25 degree bevel). It is possible to go lower than this on the bevel, but endgrain is hard on blades and it will not hold up for long.

Secondly, since you alter the cutting angle by altering the bevel, you could go for a 60 degree cutting angle (by adding a 23 degree microbevel to an existing 25 degree bevelled blade), and this will make a superb mini-smoother for removing small sections of tearout associated with interlinked grain.

Thirdly, a middle path might be to add a 8 degree microbevel to the existing set up and produce a "standard" mini-smoother (same 45 degree cutting angle as a Stanley bench plane). This would be good for most soft woods.

Adding a microbevel ala DC is not indicated. All this will do is increase the cutting angle (I think - I am not sure if it can be done on a bevel up plane). He uses it on bevel down planes to reduce the amount of preparation when sharpening.

If you wish to use these alternatives, just get a couple of extra blades.

Regards from Perth

Derek

HIJACK -bevel vs micro-bevel vs planing angle

Frank D. in Montreal

>HI Derek,

Your post got me thinking about the effectiveness of microbevels at changing the planing angle. I was wondering how big of a microbevel it takes to have any real influence on chip production. I read somewhere (I forget where...) that under 1/16" wide, a microbevel just reinforces the edge, and the primary bevel dictates how the chip is formed and so the effective planing angle; over 1/16" wide, the "micro" or secondary bevel starts to act like a primary bevel, and only then has an influence on chip production (and changing the planing angle).

Now as I said I just read this somewhere (was it Lee?) and I'm not really sure. I'd appreciate your (or anyone's) thoughts on this (not too off-topic after all).

Frank

Size and Effect of Microbevels

Steve Elliott

>I'd consider any bevel 1/16" wide to be a secondary bevel, not a microbevel. But that wasn't your question.

To be effective in changing the cutting angle of a plane, I believe a true microbevel is wide enough. By "true microbevel" I mean only a few thousandths of an inch wide. When the plane is taking a shaving .002" thick (typical for a smoothing plane) only about .003" of the blade actually projects below the sole of the plane. Any cutting geometry happens on this very small scale, and the larger-scale geometry that surrounds it might affect chip clearance, but not the cutting action.

I've been experimenting with setting a chipbreaker very close to the cutting edge, about .005 to .008 inches back. I haven't had any problems with jamming, and the nature of the shaving produced is different compared to a chipbreaker distance of 1/32". I haven't really compared the surfaces produced on the wood, so maybe extremely small chipbreaker distances aren't needed. But they are possible.

The chipbreaker needs to be less than .020" from the edge to have any effect on the cutting action, so a secondary bevel 1/16" wide (= .0625") is more than wide enough.

Re: Size and Effect of Microbevels

Joe Rogers, Northern Virginia

>Hi Steve. What was the mouth opening set to when you set the chipbreaker this close to the arris of the cutter? JR

Mouth Dimension

Steve Elliott

>It was .008". Most of my testing of chipbreakers is being done with a Spiers infill plane that I made a new blade for out of CPM 3V. By the time I was done lapping the blade and working on the blade bed, the mouth was a little bigger than I had hoped for. I think the same chipbreaker setting would probably work with a mouth of .004" but I haven't tried that yet.

Thanks Steve

Frank D. in Montreal

>Very interesting. it makes sense when you think of a back bevel, which definitely has an effect and is usually quite small (thin). Too bad I forget where I read it but I remember seeing a picture of the chip sliding over the microbevel intact and breaking when in contact with the main bevel (so, the theory went, only the main bevel has an effect on chip formation). That would make sense for thick shavings, but now I see how a microbevel would affect the peoduction of a really thin shaving.

Thanks for your thoughts,

Frank

Re: HIJACK -bevel vs micro-bevel vs planing angle

Greg Sloop, Portland Oregon

>My own experience (completely unobjective and unscientific) tends to be that even a tiny "micro-bevel" (a few thousandths) acts as though the primary angle were the same angle.

I found that as I took a regular iron (I always buy the LV 25 deg. irons and just raise the angle, rather than buying a 50 deg. one...) and raised the bevel progressively. it didn't seem to matter how little of a "sub-bevel" or micro bevel I put on it. It performed "better" on the tear out I was testing on regardless of bevel "size."

IMHO, any more than a few strokes is enough to get a decent enough bevel that will perform at the sub or micro bevel angle - not the lower and larger main bevel angle.

My two mites worth. (Literally, ya?!)

Cheers,

Greg

Re: BU plane sharpening

gordon thomas

>Hi Greg:

just wondered if the rear tote on the LV LA planes were an issue for you. The rear adjustment knob seems too close to the tote and would suggest some bruising of the knuckles even for a short period of use. Any thoughts will be appreciated.

cheers,

Gordon

Re: BU plane sharpening

Frank D. in Montreal

>Hi Gordon,

I have a problem with the knob on that plane, Iit gives me blisters on my little finger, but I know it doesn't do this to everyone. I mentioned this on a forum once and Rob Lee explained to me that they designed it this way to maximize blade life; each time you sharpen the blade you have to advance it a little, so the knob advances too. There are 3 solution to this problem (assuming it is a problem for you), as far as I know: grind a little extra off the blade the first time you sharpen it; ask Rob Lee to send you a shorter adjuster (I know that they are available); or wait till June for the new LA heavy smoother. I've seen some pics of this upcoming plane and the adjuster knob doesn't appear (as far as I could see) to be as close to the rear tote. This new plane looks quite impressive, and if it's anything like the LA jack it will surely be a winner.

Frank

Re: BU plane sharpening

gordon thomas

>Hi Frank:

thanks for getting back to me. I tried the LA Jack yesterday and had the same problem with the adjuster, bruising my knuckles. I have small hands and am puzzled why so few people ( with average size hands) have not encountered the same problem.

I do find it interesting that there is available a shorther ajuster knob. Do you have any more information on this accessory?

Sorry for bomabarding you with all these questions but very few seem wiling to discuss these concerns in an open forum.

take care,

Gordon Thomas

Re: BU plane sharpening

Peter Michaux

>There is a great discussion of using back bevels on bevel up planes in Leonard Lee's book. By using a back bevel you can sharpen the main bevel at a lower angle but still maintain a 25 degree included angle. It is in the section on sharpening block planes. He talks about standard angle block planes and low angle block planes for both softwoods and hardwoods.

Re: BU plane sharpening

Greg Sloop, Portland Oregon

>I've never noticed any problem. For the life of me right now, I can't picture where the adjuster is and how I might bang into it.

I'll go out and refresh my memory, but at least as I recall it now, I've never had any problem with it. Ergonomically, I think the LV Jack is better than the LN.

More when I get a chance...

Thanks,

Greg