Modifiying the edge of LV chip breakers for use on cambered blades

[Mike Holbrook]

I posted a thread recently in an attempt to get more specific information on specifically how to modify chip breakers. The thread went off on a discussion of whether or not to camber the edge of the CB or not and neglected to discuss any other aspects of modifying CBs.

I bought a number of LV double irons and two new LV Custom planes in the last year or so. I am specifically interested in how to improve those edges. I have read a few different posts, and Derek's site regarding how to modify these CBs. These double blades are not made like Stanley double blades. The CBs on the LV blades do not have the hump near the edge of the blade. The angle of the LV CBs is less than the 30 degrees I hone my blade bevels at. Other posts I have read suggest a steeper angle. Instead of the hump in the edge of the LV blades, there is an approximately 1/4" raised area on the bottom of the CBs.

My question becomes whether to do a micro bevel, change the entire bevel to X different angle, or maybe a steeper hollow grind. I am wondering if anyone has tried hollow grinding a CB edge? Maybe hollow grind the entire bevel then grind a steep micro bevel in the edge of the hollow?

Certainly a hollow grind makes the surface the chip hits concave vs the convex surface Stanley planes have. I have read some information that seems to prefer that the chip ejects straight up instead of curling. I am wondering if the chip makes contact with a concave vs convex surface if the chip might eject straighter? Those who hate the idea of a hollow ground CB, please post what kind/angle bevel you would suggest. It might be harder to do but the CB edge could be modified to be convex, more like a Stanley CB.

[steven c newman]

Maybe a show&tell about where you are planning on grinding? When I "mate" chipbreakers to the iron, I grind a knife edge. The area right behind the edge, that rests on the iron is flat. The idea being that as I tighten the two blades together, the knife edge will deform just enough to sit gap-free on the iron. I also polish the top, even to the point of a strop. Of course, mine were made my Stanley, Millers Falls, Sargent, and the like. Shavings will come up out of the plane enough that they tend to wrap around the wrist of the hand on the front knob.

Not sure IF you could call mine hollow-ground. They are at a slight angle of maybe 5 degrees that points down to the knife edge. Usually, I work a cb at the side of the beltsander. Just the edge. The rest of the cb is angled down, below the edge of the sandpaper going by. Since most of the chipbreakers that come through my shop are......UGLY, and barely mated to the irons.....I wind up doing about everyone that shows up. After the ride on the sander, then a few rides on the oilstones. Then a few swipes on the strop, to polish the hump part, not the underside.

Main results from this? Iron does not chatter, no shavings get stuck between the two. On a cambered iron, I will set the cb to the corners, since there is usually not much steel beyond it, in the middle. Straight edged irons...1mm set back from the edge. Also, all the chipbreakers and irons I use in the shop are what came with those 60-110 year old planes. Haven't seen any need to buy the latest thick irons.

[Jim Koepke]

+1 on what Steven said.

My vote in this would be for a flat or convex bevel on the CB. The shavings will likely not cooperate by faithfully hitting a micro bevel on the CB. Of course if your main metal removal equipment is a standard grinder, then having a hollow ground bevel may be your only option.

jtk

[Reinis Kanders]

45 - 50 degree bevel, maybe 1 mm or so in size seems to work for me.