Mortice Chisels.......Hollow Grind

[Dave Keay]

I have started hollow grinding all my plane blades and chisels to speed up the sharpening process.

What is the consensus regarding hollow grind and mortice chisels also creating a secondary bevel if one hollow grinds

Thanks.

Dave

[David Weaver]

The process works fine. I think there might be some difference of opinion based on whether you hit a mortise chisel with the bevel toward the waste / open side and drive the chisel straight down, or if you face the back of the chisel toward the waste side.

It works fine for me (hollow grind and secondary bevel) with the bevel toward the waste side.

[george wilson]

I'd just advise against making the bevel too thin or delicate on a mortise chisel. I somehow had the end break off a chisel I was not even especially hitting hard while mortising. I think the chisel might have been tempered too hard,and its hollow grind tipping the scales too much.

[Mike Henderson]

I'd just advise against making the bevel too thin or delicate on a mortise chisel. I somehow had the end break off a chisel I was not even especially hitting hard while mortising. I think the chisel might have been tempered too hard,and its hollow grind tipping the scales too much.
I agree with George. Make sure you're using a grinder with a big wheel so the concave is not too deep. An 8" (or larger) wheel should be okay but I'd be concerned about a 6"

Regarding the secondary bevel, I put a 25* primary bevel on my pigstickers and then a 30 to 35* secondary.

Mike

[Derek Cohen]

Hi Dave

I hollow grind all my blades, both chisel and plane, preferably on a Tormek. The grind on this is shallow (10" wheel) and so I am comfortable including laminated blades as well. However I will not hollow grind mortice chisels. Chopping is one thing, but prying places extra stress on the tip of the blade, and I'd rather keep the primary grind flat for the extra strength it offers. I use a 20 degree primary with a 30-35 degree secondary on my oval bolstered mortice chisels.

Regards from Perth

Derek

[john brenton]

I don't get why one would hollow grind if he had a reliable jig.. I only hollow grind on a new blade that's not worth my stones life, and by the second or third hone the holoow is gone. Is there another reason to do it?

[David Weaver]

Because it's quick to make the grind. In this case, we're talking about doing the grind just to do the grind, not to set up the final bevel angle.

i'll offer the same suggestion derek offered me while ago.

If you're going to make a flat 25 degree primary and a 35 degree secondary bevel, but you want to hollow grind instead, just figure out what increase in bevel angle makes the edge at least as thick as a flat grind over the entire length of the bevel. It's only a few degrees.

[Pam Niedermayer]

I don't get why one would hollow grind if he had a reliable jig.. I only hollow grind on a new blade that's not worth my stones life, and by the second or third hone the holoow is gone. Is there another reason to do it?

I don't understand the passion for hollow grinding either, jig or no jig, except for rationalizing the use of electric grinders (for which no rationalization is necessary); but then I use mostly Japanese edges, wouldn't even think of making back bevels, and so forth. I'd bet if a vendor shipped hollow ground there'd be all sorts of yelling and screaming.

Pam

[Salem Ganzhorn]

I hollow grind my irons and chisels. I don't understand why people would want to remove so much metal with stones :).
Salem

[Pam Niedermayer]

I hollow grind my irons and chisels. I don't understand why people would want to remove so much metal with stones :).

Cute, but perhaps a grinding stone is a stone? :)

Pam

[Frank Drew]

The only tools I hollow ground were lathe chisels and gouges; I don't have a well thought out position against hollow grinding bench tools, just never felt the need. With a well-established flat bevel, I never found that honing back to a keen edge took much time, especially once I switched to water stones.

[Zahid Naqvi]

I guess ever since folks started using round/wheel grinding stones they found the benefits of the hollow grind when doing freehand honing (i.e. in the ease of registering the cutting edge on the stones). In my case if I want a flat primary bevel it will require extra work because my wet grinding stone has an 8" wheel and it creates a hollow grind by default. I also try to free hand the honing on Shaptons and the hollow ground helps a lot in that aspect. As Derek, George and some of the other experienced tool lackys have mentioned if you decide to hollow grind mortise chisels just make sure you use a bigger wheel, if possible just stick with a flat grind.

[Dave Keay]

Thanks for all the replies I recently purchased a Tormek and will try it out with a couple of mortice chisels and see how they perform.

Dave

[Chris Fournier]

I've hollow ground my mortising chisels from day one, on a 7" bench grinder. I have yet to break a cutting edge and no one needs to if they moderate their impact and levering forces (improperly tempered tools aside).

Hollow grinding has plenty of benefits to a tool user, for me it is the time savings that it offers over 100% hand sharpening and when I can save time I am willing to go to the grinding/sharpening room more often because sharpening is quick and effective I tend to have sharp tools all the time.

[Mike Henderson]

Zahid pointed out the advantage of a hollow grind to aid in registering the chisel on your stone when honing. This works fine with ordinary bench chisels but for pigstickers, it limits you. I put a steep primary on my pigstickers, maybe 25*, so that the chisel can penetrate deeper into the wood (it doesn't have to push the wood apart as much) but a 25* bevel won't hold up when pounding out a mortise. So I put a steeper secondary bevel on the chisel, maybe 35*, so that the edge will hold up better. The requirements for the primary bevel and the secondary bevel are at odds, which forces you to hand hone the secondary without registering the primary bevel on your stone.

Mike

[Chris Fournier]

Zahid pointed out the advantage of a hollow grind to aid in registering the chisel on your stone when honing. This works fine with ordinary bench chisels but for pigstickers, it limits you. I put a steep primary on my pigstickers, maybe 25*, so that the chisel can penetrate deeper into the wood (it doesn't have to push the wood apart as much) but a 25* bevel won't hold up when pounding out a mortise. So I put a steeper secondary bevel on the chisel, maybe 35*, so that the edge will hold up better. The requirements for the primary bevel and the secondary bevel are at odds, which forces you to hand hone the secondary without registering the primary bevel on your stone.

Mike

This is no different than putting a micro bevel on a bench chisel is it? Of course the secondary bevel on the pigsticker is likely a bit larger than a bench chisel micro bevel but I have not found it to be too much so. To my way of thinking the secondary pigsticker bevel is really about edge retention against chopping forces rather than "chisel tip" retention against levering forces. As I may have mentioned I don't go overboard with the forces when chopping so my very small secondary bevel suits my dainty style.

[Mike Henderson]

Yes, I didn't mean to imply that the secondary bevel was any larger than normal. My point was that when you do a secondary bevel at a steeper angle than the primary bevel, you have to freehand it (or use a jig) - you can't register the primary bevel on the stone - so the hollow grind doesn't provided that registration advantage that Zahid mentioned.

Mike

[David Weaver]

Who here chops their mortises with the bevel side always pointed toward the wood yet to be cut, vs. the method that is presented in the LN videos (as published by wearing) where the bevel side is always faced away.

I learned to cut mortises doing the latter. The hollow grind exists on the chisel only because a wheel is the fastest and easiest way for me to move the primary back, it's not functional as mike is implying.

I suppose it wouldn't be any harder for me than it would be for anyone else to try the way klausz and a lot of others chop a mortise with the bevel toward the yet-to-be cut part of the mortise, but I don't have any active furniture projects that have M&T joints and maybe someone else can comment on whether not a hollow would cause a problem.

It appears to me from the klausz video on FWW that the mortise chisel FK uses has a steep primary probably for registering with the first method i mentioned above, and a microbevel might cause issues with that.

i can recall having a discussion about this on wood central a year or two ago and there were people who just absolutely couldn't grasp that anyone would use a mortise chisel the way robert wearing describes, and do it fairly quickly with some success.

[Pam Niedermayer]

Who here chops their mortises with the bevel side always pointed toward the wood yet to be cut, vs. the method that is presented in the LN videos (as published by wearing) where the bevel side is always faced away....

I don't know what hollow grinds have to do with how one cuts mortises; but without hollow grinds, I tend to follow Jeff Gorman's advice, cutting from the middle out, flipping the chisel from one end to the other, finally turning the bevel to face the opening when I get near the ends.

Pam

[Mike Brady]

Isn't hollow-gringing a mortise chisel counter to one of the main purposes of the tool? That purpose would be the levering out of chips from the mortise. A hollow grind effectively removes much of the fulcrum for the lever (the bevel of the chisel). This may not make much difference in practice, but in theory, the bevel would be most effective if left flat when the chisel is being used in the bevel down position.

[David Weaver]

That's why I had asked that question. I like the grind off of a 6" wheel, and it doesn't bother anything with the wearing technique, but klausz and others appear to have flat bevels on their chisels (and they're chopping with the bevel into the side yet to be chopped).