PDA

View Full Version : mortise chisels



casem
01-22-2004, 06:45 PM
Anyone know a place to order a decent set of mortise chisels? I got a set from GarretWade but they are a little big so I may return them. But I'm having a hard time finding places that carry them. I'd rather not spend more than $20 each.

casem
01-22-2004, 06:45 PM
Anyone know a place to order a decent set of mortise chisels? I got a set from GarretWade but they are a little big so I may return them. But I'm having a hard time finding places that carry them. I'd rather not spend more than $20 each.

casem
01-22-2004, 06:45 PM
Anyone know a place to order a decent set of mortise chisels? I got a set from GarretWade but they are a little big so I may return them. But I'm having a hard time finding places that carry them. I'd rather not spend more than $20 each.

Bruce Hooke
01-22-2004, 07:09 PM
What do you mean when you say they are too big? Are you looking for especially narrow ones, or...?

Bruce Hooke
01-22-2004, 07:09 PM
What do you mean when you say they are too big? Are you looking for especially narrow ones, or...?

Bruce Hooke
01-22-2004, 07:09 PM
What do you mean when you say they are too big? Are you looking for especially narrow ones, or...?

gary porter
01-22-2004, 08:58 PM
You may have ended up with framing chisels which are much bigger than standard mortise chisels.
Highland Hardware has some Crown brand mortise chisels for about $25 avg. Might give them a try.
Gary

gary porter
01-22-2004, 08:58 PM
You may have ended up with framing chisels which are much bigger than standard mortise chisels.
Highland Hardware has some Crown brand mortise chisels for about $25 avg. Might give them a try.
Gary

gary porter
01-22-2004, 08:58 PM
You may have ended up with framing chisels which are much bigger than standard mortise chisels.
Highland Hardware has some Crown brand mortise chisels for about $25 avg. Might give them a try.
Gary

casem
01-23-2004, 11:46 AM
Yes they are fairly heavy duty framing chisels. I've seen Marples mortise chisels that look perfect but cannot find a place that sells them. I'll try highland.

casem
01-23-2004, 11:46 AM
Yes they are fairly heavy duty framing chisels. I've seen Marples mortise chisels that look perfect but cannot find a place that sells them. I'll try highland.

casem
01-23-2004, 11:46 AM
Yes they are fairly heavy duty framing chisels. I've seen Marples mortise chisels that look perfect but cannot find a place that sells them. I'll try highland.

gary porter
01-23-2004, 01:24 PM
Originally posted by casem:
Yes they are fairly heavy duty framing chisels. I've seen Marples mortise chisels that look perfect but cannot find a place that sells them. I'll try highland.Yes, Highland has the Marples and they are good chisels but cost more than the Crown.
Personally I'd go for the more expensive ones maybe even some from Japan Woodworker but they are a good bit more.
Good luck.....
Gary

gary porter
01-23-2004, 01:24 PM
Originally posted by casem:
Yes they are fairly heavy duty framing chisels. I've seen Marples mortise chisels that look perfect but cannot find a place that sells them. I'll try highland.Yes, Highland has the Marples and they are good chisels but cost more than the Crown.
Personally I'd go for the more expensive ones maybe even some from Japan Woodworker but they are a good bit more.
Good luck.....
Gary

gary porter
01-23-2004, 01:24 PM
Originally posted by casem:
Yes they are fairly heavy duty framing chisels. I've seen Marples mortise chisels that look perfect but cannot find a place that sells them. I'll try highland.Yes, Highland has the Marples and they are good chisels but cost more than the Crown.
Personally I'd go for the more expensive ones maybe even some from Japan Woodworker but they are a good bit more.
Good luck.....
Gary

Bob Smalser
01-23-2004, 07:40 PM
Careful...Highland and some others are selling a "Registerd" chisel...I believe it's a Sorby...that they are calling a "mortise" chisel...but it ain't at all, it's a "firmer" chisel.

Mortise chisels are as thick or thicker in depth as they are in width for stength levering out wood.

Bob Smalser
01-23-2004, 07:40 PM
Careful...Highland and some others are selling a "Registerd" chisel...I believe it's a Sorby...that they are calling a "mortise" chisel...but it ain't at all, it's a "firmer" chisel.

Mortise chisels are as thick or thicker in depth as they are in width for stength levering out wood.

Bob Smalser
01-23-2004, 07:40 PM
Careful...Highland and some others are selling a "Registerd" chisel...I believe it's a Sorby...that they are calling a "mortise" chisel...but it ain't at all, it's a "firmer" chisel.

Mortise chisels are as thick or thicker in depth as they are in width for stength levering out wood.

casem
01-24-2004, 10:58 AM
Bob,

Thanks for the warning. This is what I hate about ordering stuff over the web that I can't see before I buy it. But a true "registered" is a mortise chisel, right? Here's what I thought:

joiner's chisel - hardwood

sash chisel - softwood

registered chisel - a heavy duty joiners chisel

casem
01-24-2004, 10:58 AM
Bob,

Thanks for the warning. This is what I hate about ordering stuff over the web that I can't see before I buy it. But a true "registered" is a mortise chisel, right? Here's what I thought:

joiner's chisel - hardwood

sash chisel - softwood

registered chisel - a heavy duty joiners chisel

casem
01-24-2004, 10:58 AM
Bob,

Thanks for the warning. This is what I hate about ordering stuff over the web that I can't see before I buy it. But a true "registered" is a mortise chisel, right? Here's what I thought:

joiner's chisel - hardwood

sash chisel - softwood

registered chisel - a heavy duty joiners chisel

Bob Smalser
01-24-2004, 09:27 PM
Chisel Types as I understand them:

Butt Chisel: Short utility chisel primarily for carrying and hanging doors…works in tight spots and some, like the Stanleys with steel buttons, are designed for striking. Ground at 15-25 degrees.

http://www.tools-for-woodworking.com/images/products/chisels/122362.jpg

Paring or Bench Chisel: Beveled edge blade on a longer chisel for bench use…not to be struck. Ground at 15-20 degrees. Some refer to the straight ones as “bench” chisels and the ones with cranked or offset handles as “paring” chisels.

http://www.tools-for-woodworking.com/images/products/chisels/041110.jpg

http://www.tools-for-woodworking.com/images/products/chisels/122351.jpg

Mortise Chisel: Square blade often thicker in depth then width ground at 30-45 degrees with no secondary bevel….designed to be struck and to break out mortise wood by levering force. Sockets are generally preferred to tangs but well-made tang handles are unlikely to split.

http://www.tools-for-woodworking.com/images/products/chisels/041725.jpg

http://www.tools-for-woodworking.com/images/products/chisels/046400.jpg

http://www.tools-for-woodworking.com/images/products/chisels/049720.jpg

Firmer or Framing Chisel: Often confused…even by vendors…with mortise chisels. Like a bench or paring chisel, but designed to be struck…blades are heavier with square shoulders and sockets are preferred to tangs. Used for heavier work and can also be used, with care, to chop mortises. Ground at 20-25 degrees.

http://www.tools-for-woodworking.com/images/products/chisels/041140.jpg

http://www.tools-for-woodworking.com/images/products/chisels/071147.jpg

[ 01-24-2004, 11:55 PM: Message edited by: Bob Smalser ]

Bob Smalser
01-24-2004, 09:27 PM
Chisel Types as I understand them:

Butt Chisel: Short utility chisel primarily for carrying and hanging doors…works in tight spots and some, like the Stanleys with steel buttons, are designed for striking. Ground at 15-25 degrees.

http://www.tools-for-woodworking.com/images/products/chisels/122362.jpg

Paring or Bench Chisel: Beveled edge blade on a longer chisel for bench use…not to be struck. Ground at 15-20 degrees. Some refer to the straight ones as “bench” chisels and the ones with cranked or offset handles as “paring” chisels.

http://www.tools-for-woodworking.com/images/products/chisels/041110.jpg

http://www.tools-for-woodworking.com/images/products/chisels/122351.jpg

Mortise Chisel: Square blade often thicker in depth then width ground at 30-45 degrees with no secondary bevel….designed to be struck and to break out mortise wood by levering force. Sockets are generally preferred to tangs but well-made tang handles are unlikely to split.

http://www.tools-for-woodworking.com/images/products/chisels/041725.jpg

http://www.tools-for-woodworking.com/images/products/chisels/046400.jpg

http://www.tools-for-woodworking.com/images/products/chisels/049720.jpg

Firmer or Framing Chisel: Often confused…even by vendors…with mortise chisels. Like a bench or paring chisel, but designed to be struck…blades are heavier with square shoulders and sockets are preferred to tangs. Used for heavier work and can also be used, with care, to chop mortises. Ground at 20-25 degrees.

http://www.tools-for-woodworking.com/images/products/chisels/041140.jpg

http://www.tools-for-woodworking.com/images/products/chisels/071147.jpg

[ 01-24-2004, 11:55 PM: Message edited by: Bob Smalser ]

Bob Smalser
01-24-2004, 09:27 PM
Chisel Types as I understand them:

Butt Chisel: Short utility chisel primarily for carrying and hanging doors…works in tight spots and some, like the Stanleys with steel buttons, are designed for striking. Ground at 15-25 degrees.

http://www.tools-for-woodworking.com/images/products/chisels/122362.jpg

Paring or Bench Chisel: Beveled edge blade on a longer chisel for bench use…not to be struck. Ground at 15-20 degrees. Some refer to the straight ones as “bench” chisels and the ones with cranked or offset handles as “paring” chisels.

http://www.tools-for-woodworking.com/images/products/chisels/041110.jpg

http://www.tools-for-woodworking.com/images/products/chisels/122351.jpg

Mortise Chisel: Square blade often thicker in depth then width ground at 30-45 degrees with no secondary bevel….designed to be struck and to break out mortise wood by levering force. Sockets are generally preferred to tangs but well-made tang handles are unlikely to split.

http://www.tools-for-woodworking.com/images/products/chisels/041725.jpg

http://www.tools-for-woodworking.com/images/products/chisels/046400.jpg

http://www.tools-for-woodworking.com/images/products/chisels/049720.jpg

Firmer or Framing Chisel: Often confused…even by vendors…with mortise chisels. Like a bench or paring chisel, but designed to be struck…blades are heavier with square shoulders and sockets are preferred to tangs. Used for heavier work and can also be used, with care, to chop mortises. Ground at 20-25 degrees.

http://www.tools-for-woodworking.com/images/products/chisels/041140.jpg

http://www.tools-for-woodworking.com/images/products/chisels/071147.jpg

[ 01-24-2004, 11:55 PM: Message edited by: Bob Smalser ]

Nicholas Carey
01-24-2004, 09:53 PM
Originally posted by Bob Smalser:
Paring or Bench Chisel: Beveled edge blade on a longer chisel for bench use?not to be struck. Ground at 25-30 degrees.

http://www.tools-for-woodworking.com/images/products/chisels/041110t.jpg
Just to be pedantic, paring chisels, whilst similar to a bench chisel have longer, thinner, flexible blades. Often the handle will be cranked, but not necessarily, as in the image below:

http://www.traditionalwoodworker.com/catalog/images/Paring-Chisels-225-1012.jpg

Paring chisels are used for cleaning up the bottoms of dados and rebates, paring down tenons, etc. (and obviously…never to be struck)

Nicholas Carey
01-24-2004, 09:53 PM
Originally posted by Bob Smalser:
Paring or Bench Chisel: Beveled edge blade on a longer chisel for bench use?not to be struck. Ground at 25-30 degrees.

http://www.tools-for-woodworking.com/images/products/chisels/041110t.jpg
Just to be pedantic, paring chisels, whilst similar to a bench chisel have longer, thinner, flexible blades. Often the handle will be cranked, but not necessarily, as in the image below:

http://www.traditionalwoodworker.com/catalog/images/Paring-Chisels-225-1012.jpg

Paring chisels are used for cleaning up the bottoms of dados and rebates, paring down tenons, etc. (and obviously…never to be struck)

Nicholas Carey
01-24-2004, 09:53 PM
Originally posted by Bob Smalser:
Paring or Bench Chisel: Beveled edge blade on a longer chisel for bench use?not to be struck. Ground at 25-30 degrees.

http://www.tools-for-woodworking.com/images/products/chisels/041110t.jpg
Just to be pedantic, paring chisels, whilst similar to a bench chisel have longer, thinner, flexible blades. Often the handle will be cranked, but not necessarily, as in the image below:

http://www.traditionalwoodworker.com/catalog/images/Paring-Chisels-225-1012.jpg

Paring chisels are used for cleaning up the bottoms of dados and rebates, paring down tenons, etc. (and obviously…never to be struck)

Bob Smalser
01-24-2004, 10:11 PM
Sounds fine with me, Nicholas...we always called them "cranked paring" chisels as opposed to "paring" chisels.

But after looking at the Highland site I borrowed the pics from, I do have some concern they are selling what look like firmer chisels as mortise chisels...which they are not.

I could be wrong, but that sure looks like a 30-degree bevel to me:


http://www.tools-for-woodworking.com/images/products/chisels/041140.jpg


Crown 1" Mortise Chisel 041146

Price Qty Order $34.99

Detailed Description

These "registered" mortise chisels are characterized by heavy blades with unusually thick necks and bolsters, leather shock washers, large ash handles and thick-walled ferrules at both ends of the handle. Sizes to 3/8" have conventional square-section mortising blades, while larger sizes resemble extremely heavy firmer chisels, whose blades are wider than they are thick.

Bob Smalser
01-24-2004, 10:11 PM
Sounds fine with me, Nicholas...we always called them "cranked paring" chisels as opposed to "paring" chisels.

But after looking at the Highland site I borrowed the pics from, I do have some concern they are selling what look like firmer chisels as mortise chisels...which they are not.

I could be wrong, but that sure looks like a 30-degree bevel to me:


http://www.tools-for-woodworking.com/images/products/chisels/041140.jpg


Crown 1" Mortise Chisel 041146

Price Qty Order $34.99

Detailed Description

These "registered" mortise chisels are characterized by heavy blades with unusually thick necks and bolsters, leather shock washers, large ash handles and thick-walled ferrules at both ends of the handle. Sizes to 3/8" have conventional square-section mortising blades, while larger sizes resemble extremely heavy firmer chisels, whose blades are wider than they are thick.

Bob Smalser
01-24-2004, 10:11 PM
Sounds fine with me, Nicholas...we always called them "cranked paring" chisels as opposed to "paring" chisels.

But after looking at the Highland site I borrowed the pics from, I do have some concern they are selling what look like firmer chisels as mortise chisels...which they are not.

I could be wrong, but that sure looks like a 30-degree bevel to me:


http://www.tools-for-woodworking.com/images/products/chisels/041140.jpg


Crown 1" Mortise Chisel 041146

Price Qty Order $34.99

Detailed Description

These "registered" mortise chisels are characterized by heavy blades with unusually thick necks and bolsters, leather shock washers, large ash handles and thick-walled ferrules at both ends of the handle. Sizes to 3/8" have conventional square-section mortising blades, while larger sizes resemble extremely heavy firmer chisels, whose blades are wider than they are thick.

Nicholas Carey
01-24-2004, 11:05 PM
my understanding WRT "registered" chisels was that they were used for cleaning up mortices in timber frames after the mortices were roughed out with a boring machine:

http://www.myoldtools.com/adjust1.jpg http://www.myoldtools.com/adjust2.jpg

Pickup up your bevel, sit on the seat and crank. Fast, quiet and efficient. Some were even two-speed, and I believe some were built with adjustable fences to help you center the mortice in the timber.

Registered chisels were just the ticket for cleaning up the sides of the roughed-out mortice.

Nicholas Carey
01-24-2004, 11:05 PM
my understanding WRT "registered" chisels was that they were used for cleaning up mortices in timber frames after the mortices were roughed out with a boring machine:

http://www.myoldtools.com/adjust1.jpg http://www.myoldtools.com/adjust2.jpg

Pickup up your bevel, sit on the seat and crank. Fast, quiet and efficient. Some were even two-speed, and I believe some were built with adjustable fences to help you center the mortice in the timber.

Registered chisels were just the ticket for cleaning up the sides of the roughed-out mortice.

Nicholas Carey
01-24-2004, 11:05 PM
my understanding WRT "registered" chisels was that they were used for cleaning up mortices in timber frames after the mortices were roughed out with a boring machine:

http://www.myoldtools.com/adjust1.jpg http://www.myoldtools.com/adjust2.jpg

Pickup up your bevel, sit on the seat and crank. Fast, quiet and efficient. Some were even two-speed, and I believe some were built with adjustable fences to help you center the mortice in the timber.

Registered chisels were just the ticket for cleaning up the sides of the roughed-out mortice.

NormMessinger
01-25-2004, 01:44 PM
WOODCRAFT has deep-Mortice Chisels in their latest catalogue, Pg.. 71. Sorby's and only twice what Casem wants to pay, $49.99 each (why don't they just say $50 :rolleyes: )

NormMessinger
01-25-2004, 01:44 PM
WOODCRAFT has deep-Mortice Chisels in their latest catalogue, Pg.. 71. Sorby's and only twice what Casem wants to pay, $49.99 each (why don't they just say $50 :rolleyes: )

NormMessinger
01-25-2004, 01:44 PM
WOODCRAFT has deep-Mortice Chisels in their latest catalogue, Pg.. 71. Sorby's and only twice what Casem wants to pay, $49.99 each (why don't they just say $50 :rolleyes: )

Nicholas Carey
01-25-2004, 05:43 PM
What size(s) mortice chisels are you looking for?

For old tools, you might try any one (or more) of these places:

Patrick Leach (http://www.supertool.com/). Subscribe to his monthly mailing of old tools for sale.

Bob Kaune (http://www.antique-used-tools.com/). Another online dealer in neanderthal equipage.

Also the Inchmartine Tool Bazaar (http://www.toolbazaar.freeserve.co.uk/index.htm), Inchmartine, Perthshire, Scotland. Here's their current list of mortice chisels (http://www.toolbazaar.freeserve.co.uk/TBC/p3.htm#14). (25 January 2004). Lot #388 is a set of 3 pigstickers for 40 quid. Lot #411 is 2 unhafted mortice chisels (1/4" and 1/2") for 10 quid.

Also, the 'Lectronic Neanderthal (http://www-2.cs.cmu.edu/~alf/en/en.html) keeps a list of 'net accessible old tool dealers: http://www-2.cs.cmu.edu/~alf/en/toolframe.html

You can probably save money if you tell the dealers you're looking for an unhafted mortice chisel (and you're willing to put your own haft on it).

Nicholas Carey
01-25-2004, 05:43 PM
What size(s) mortice chisels are you looking for?

For old tools, you might try any one (or more) of these places:

Patrick Leach (http://www.supertool.com/). Subscribe to his monthly mailing of old tools for sale.

Bob Kaune (http://www.antique-used-tools.com/). Another online dealer in neanderthal equipage.

Also the Inchmartine Tool Bazaar (http://www.toolbazaar.freeserve.co.uk/index.htm), Inchmartine, Perthshire, Scotland. Here's their current list of mortice chisels (http://www.toolbazaar.freeserve.co.uk/TBC/p3.htm#14). (25 January 2004). Lot #388 is a set of 3 pigstickers for 40 quid. Lot #411 is 2 unhafted mortice chisels (1/4" and 1/2") for 10 quid.

Also, the 'Lectronic Neanderthal (http://www-2.cs.cmu.edu/~alf/en/en.html) keeps a list of 'net accessible old tool dealers: http://www-2.cs.cmu.edu/~alf/en/toolframe.html

You can probably save money if you tell the dealers you're looking for an unhafted mortice chisel (and you're willing to put your own haft on it).

Nicholas Carey
01-25-2004, 05:43 PM
What size(s) mortice chisels are you looking for?

For old tools, you might try any one (or more) of these places:

Patrick Leach (http://www.supertool.com/). Subscribe to his monthly mailing of old tools for sale.

Bob Kaune (http://www.antique-used-tools.com/). Another online dealer in neanderthal equipage.

Also the Inchmartine Tool Bazaar (http://www.toolbazaar.freeserve.co.uk/index.htm), Inchmartine, Perthshire, Scotland. Here's their current list of mortice chisels (http://www.toolbazaar.freeserve.co.uk/TBC/p3.htm#14). (25 January 2004). Lot #388 is a set of 3 pigstickers for 40 quid. Lot #411 is 2 unhafted mortice chisels (1/4" and 1/2") for 10 quid.

Also, the 'Lectronic Neanderthal (http://www-2.cs.cmu.edu/~alf/en/en.html) keeps a list of 'net accessible old tool dealers: http://www-2.cs.cmu.edu/~alf/en/toolframe.html

You can probably save money if you tell the dealers you're looking for an unhafted mortice chisel (and you're willing to put your own haft on it).

Bob Smalser
01-25-2004, 07:21 PM
Registered chisels were just the ticket for cleaning up the sides of the roughed-out mortice. Have seen boring machines used before, but "registering" the mortise to spec with a firmer chisel is new but rings true to me.

Thanks...so I guess the real answer is that yeah, they are mortise chisels...but ya gotta bore holes forst.

Bob Smalser
01-25-2004, 07:21 PM
Registered chisels were just the ticket for cleaning up the sides of the roughed-out mortice. Have seen boring machines used before, but "registering" the mortise to spec with a firmer chisel is new but rings true to me.

Thanks...so I guess the real answer is that yeah, they are mortise chisels...but ya gotta bore holes forst.

Bob Smalser
01-25-2004, 07:21 PM
Registered chisels were just the ticket for cleaning up the sides of the roughed-out mortice. Have seen boring machines used before, but "registering" the mortise to spec with a firmer chisel is new but rings true to me.

Thanks...so I guess the real answer is that yeah, they are mortise chisels...but ya gotta bore holes forst.

ErikH
01-25-2004, 10:24 PM
I've worked on timber frames as an assistant (my sister-in-law is a master timber framer). Though i don't know squat about tools compared to most here, I can tell you that what people are calling "registered" chisels are used for cleaning up mortises on timber frames. Since few people use hand cranked mortise machines now (either chain or drill type are common) you might have less cleanup than you did 100 years back but there's still cleanup to do.

Having used them myself, I can see one reason why they're not any thicker; they are damn heavy as it is and the thought of using what you call a 'mortise design' 1.5 or 2" chisel (with a nice long handle, naturally) on an above-the-head mortise makes my arms hurt to think about.

Additionally, though the strength per inch doesn't change as they get fatter, the overall strength of the chisel does... if you could somehow carry and use a 8" chisel that was "only" 3/8" thick, I dare say you'd be unable to bend it, try as you might. When you deal with a small chisel like a 1/4", it's easy to exceed the strength and you need the extra thickness if you're goinb to be levering. But in a larger chisel it seems OK to be proportionately thinner; most people understand by nature not to throw 200 pounds of leverage even on a 2" chisel (equivalent to 25 pounds on a 1/4" version).

Not to mention that if you're on mortise cleanup duty (hypothetically speaking, you might not be good enough to cut tenons and do layout ;) you're walking around a building site carrying a chisel which you use for cleaning up shoulders and tenons as well as mortises, on a gazillion beams... You only want to carry one chisel if you can, at least I do at any rate smile.gif

ErikH
01-25-2004, 10:24 PM
I've worked on timber frames as an assistant (my sister-in-law is a master timber framer). Though i don't know squat about tools compared to most here, I can tell you that what people are calling "registered" chisels are used for cleaning up mortises on timber frames. Since few people use hand cranked mortise machines now (either chain or drill type are common) you might have less cleanup than you did 100 years back but there's still cleanup to do.

Having used them myself, I can see one reason why they're not any thicker; they are damn heavy as it is and the thought of using what you call a 'mortise design' 1.5 or 2" chisel (with a nice long handle, naturally) on an above-the-head mortise makes my arms hurt to think about.

Additionally, though the strength per inch doesn't change as they get fatter, the overall strength of the chisel does... if you could somehow carry and use a 8" chisel that was "only" 3/8" thick, I dare say you'd be unable to bend it, try as you might. When you deal with a small chisel like a 1/4", it's easy to exceed the strength and you need the extra thickness if you're goinb to be levering. But in a larger chisel it seems OK to be proportionately thinner; most people understand by nature not to throw 200 pounds of leverage even on a 2" chisel (equivalent to 25 pounds on a 1/4" version).

Not to mention that if you're on mortise cleanup duty (hypothetically speaking, you might not be good enough to cut tenons and do layout ;) you're walking around a building site carrying a chisel which you use for cleaning up shoulders and tenons as well as mortises, on a gazillion beams... You only want to carry one chisel if you can, at least I do at any rate smile.gif

ErikH
01-25-2004, 10:24 PM
I've worked on timber frames as an assistant (my sister-in-law is a master timber framer). Though i don't know squat about tools compared to most here, I can tell you that what people are calling "registered" chisels are used for cleaning up mortises on timber frames. Since few people use hand cranked mortise machines now (either chain or drill type are common) you might have less cleanup than you did 100 years back but there's still cleanup to do.

Having used them myself, I can see one reason why they're not any thicker; they are damn heavy as it is and the thought of using what you call a 'mortise design' 1.5 or 2" chisel (with a nice long handle, naturally) on an above-the-head mortise makes my arms hurt to think about.

Additionally, though the strength per inch doesn't change as they get fatter, the overall strength of the chisel does... if you could somehow carry and use a 8" chisel that was "only" 3/8" thick, I dare say you'd be unable to bend it, try as you might. When you deal with a small chisel like a 1/4", it's easy to exceed the strength and you need the extra thickness if you're goinb to be levering. But in a larger chisel it seems OK to be proportionately thinner; most people understand by nature not to throw 200 pounds of leverage even on a 2" chisel (equivalent to 25 pounds on a 1/4" version).

Not to mention that if you're on mortise cleanup duty (hypothetically speaking, you might not be good enough to cut tenons and do layout ;) you're walking around a building site carrying a chisel which you use for cleaning up shoulders and tenons as well as mortises, on a gazillion beams... You only want to carry one chisel if you can, at least I do at any rate smile.gif