Replies

1. 
   roc | Apr 12, 2010 10:33pm | #1

   Under magnification is it grainy and matt or shiny and blunt ?

   Broke or did the edge get accordioned back/dented in ?  Under magnification is it grainy and matt looking ( broke ) or is it shiny and blunt (too thin to hold up )?   I have had shiny and blunt even with a three hundred dollar Japanese chisel.  Chisels don't get any harder than that.

   I made the bevel angle more obtuse ( 35° or so ) and all was well.

   I really like the old box wood ! ! !  Just don't see box wood any more;  at least not around here for sale.

1. 
   Jammersix | Apr 12, 2010 11:12pm | #3

   Obtuse

   When they used the word "obtuse" in The Shawshank Redemption, I had to look it up. (It was a semi-minor plot device)

   You're using it differently, I bet...

2. 
   gdblake | Apr 12, 2010 10:34pm | #2

   Mortise chisels need a bevel of 30 degrees

   While the edge should have held up to more than one or two strikes, you typically want to give a mortise chisel an initial bevel angle of 30 degrees to put more steel behind the cutting edge.  If you still get a broken edge I would guess that the chisel wasn't properly tempered and the edge is too hard/brittle.  A few of the folks here can walk you through tempering the chisel if it comes to that, it's not that difficult.  I've done a little bit of metal work (fashioned a couple of knives and successfully hardened a too soft chisel) but don't believe I have enough expertise in heat treating to walk somebody else through the steps.  There is also plenty of information about the process available on the internet.

   gdblake

3. 
   hammer1 | Apr 13, 2010 10:43am | #4

   If you contact Sorby, they will tell you, the chisel is ground at 25 degrees. You should hone it with a secondary bevel of 30 for softwoods and 35 for hardwoods, otherwise the edge will fail. Lie Neilsen also makes the same recommendation on their new chisels. That stouter angle may not be what you would prefer but it makes a night and day difference on old and new chisels.

   Pic 1 is the one I sent Sorby after dissapointment with new chisels. Pic 2 is the same chisel with a secondary bevel after much use.

   
1. 
   dwmmd213 | Apr 13, 2010 07:02pm | #5

   Thanks, guys, for the responses. The broken edge does not appear bent or accordianed, but chipped or broken. My thought was to regrind the bevel to something less acute, but the original bevel was 25° and I didn't want to go through the trouble of metal-removal if this turned out to be a common problem with old Sorbys.

   I really like the boxwood, too, and I hope this chisel can be turned into a reliable user. Has anyone tried these heavy-duty traditional English mortise chisels by Ray Iles, available from Tools for Working Wood? They seem to come highly touted:

   http://www.toolsforworkingwood.com/Merchant/merchant.mvc?Screen=PROD&Store_Code=toolshop&Product_Code=MS-MORT.XX&Category_Code=TBMC

1. 
   derekcohen | Apr 15, 2010 09:44am | #6

   There are two bits of information that stand out for me: (1) this is a vintage chisel, and (2) the edges chipped, and did not bend.

   I would interpret this to mean that the blade has been re-hardened at some point in the past 50 or 100 years .... perhaps because poor grinding destroyed the temper of the steel in the first place .... and the steel was left over-hard.

   If so, regrinding the edge to a higher angle will not have any benefit. The steel will still be overhard and chip. Altering the bevel angle is of greater help when the steel is too soft to cope at lower cutting angles.

   You need to (1) re-temper the steel, and (2) grind a 20 degree primary bevel with a 30-35 degree secondary microbevel to finish. That is the traditional set up for a mortice chisel.

   Regards from Perth

   Derek

2. 
   davidah | Apr 19, 2010 01:52pm | #7

   Bevel angle of a Lie Nielsen mortise chisel

   Am I confused? The chisel shown in the pictures looks more like a bench chisel to me since it has beveled sides. According to the Lie Nielsen catalog the primary bevel of their mortise chisel is flat ground at 30 degrees with a secondary bevel of 35 degrees recommended. I find that the 30 degree bevel on my Lie Nielsen does make it difficult to cut a 1/2" mortise in maple but I assume that that is the nature of the beast, 25 degrees being insufficient to support the cutting edge for this application. Now for a bench chisel 25 degrees seems fine.

4. 
   hammer1 | Apr 19, 2010 07:59pm | #8

   My picture is of a Sorby bench chisel but as far as I know, the mortice chisels are the same steel and the same bevels. Lie Neilsens are ground at 30 degrees, recommended honing at 35 degrees. I posted the picture to illustrate what happens to the edge at a low bevel to see if that was what the original poster was talking about.