For the second time in a month I have broken off a corner of my 1″ chisel. I was cutting a mortise and it broke when I levered.
The chisel was freshly honed and cutting well. It is a Footprint chisel bought around 1982.
Is this a normal occurrence or could I be doing something wrong? I recently bought a proper 6″ bench grinder. Previously I used a “mastersharp” which is a little low speed single wheel grinder (2″ wheel) with a set of sharpening guides.
When grinding I dip the tool in water to cool it down. An engineer colleague says that by doing that I am harming the metal by making it brittle.
Advice will be greatly appreciated as regrinding is not my favourite pastime and cuts into my limited woodworking time.
Thanks
Replies
If the chisel is getting too warm to hold it next to the end of the chisel where you are grinding, it is overheating and by quenching you are hardening the steel.
Norton 3X wheels from Tools for Working Wood will help alleviate that as they do run cooler. But no matter what the wheel, to warm to hold next to where you are grinding is too hot. Quench more often.
Take care, Mike
You'd have to get your chisel pretty hot to harden it. Depending on the steel, you would need 1350F +. More likely you are drawing the temper, softening the chisel. High carbon steels could have temper temperatures of 350-400F. You can easily hit that with a grinder. The blue colors don't come until you get beyond 500F. I think the problem is the levering. No edge, "pigsticker" or otherwise, can withstand that. Bevel angles sound okay. Your secondary bevel might actually be helping you. Adam
"I think the problem is the levering. No edge, "pigsticker" or otherwise, can withstand that."
Dunno what you think of that guy, Chris Schwarz, but he wrote an article on "Mortising by Hand" in the Spring 2007 issue of Woodworking magazine, a sister publication to a little magazine called Popular Woodworking, if I am recalling correctly. It begins on page 16 and continues through 19. He recounts a method developed by a fellow named Maynard. See how many times the word "lever" (or variations such as "levering") appears in the article and accompanying step by step captions.
How do you make mortises? If you use a "pigsticker," how to do remove the waste?
Edited 11/4/2008 4:53 pm ET by Samson
"Dunno what you think of that guy, Chris Schwarz..."Never heard of him. What magazine? I thought they went out of business.AdamP.S. I pare out my mortises. No levering, no chipped chisels.
FWIW, I have actually used my vintage pigstickers and Isles new versions on many projects over several years (using all sorts of wood from maple to cherry to poplar etc). Never had a chip.
Naw, they're still in business although they may have to pare down their staff..
but seriously, Adam, I was taught to use mortise chisels and lever out the bulk of the waste...also saw Jim Kingshott's videa and he does the same thing...I know there's usally more than one way toget to a goal but I'm curious as to how you "pare"out say, a 1/4" wide1 1/2 ' deep mortise...could you give us a description..
eager tto learn more Neil
Pretty sure this technique was described and illustrated in some magazine that is either in your bathroom or in your mailbox. Hunt around. It's worth considering. When you make chairs by hand, you have to make these wacky angled mortises. I don't know how you do that with the bash and lever technique.
Adam
It's not in the bathroom but I'll search some other areas where I stash my WW periodicals...haven't made any chairs of yet, but the bash and lever technique worked great for the asian style garden bench I've been working on...chairs seem to be a level or two above my skill set but eventually....
Neil
Adam, you sly dog, it was in my mailbox afterall...the illustration of you paring out the waste with your mortice chisel cleared up my clouded conception of what you were telling me...somehow I had the impression you were creating the waste by paring but it appears that you are still pounding the pigsticker to create the waste..indeed, a picture IS worth a thousand words...see you in Berea
Neil
You have to chop the end grain at the end. But from the other side to that chop, you can just pare that material away- no prying- or at least not much.
I find that chopping compresses the wood, making it harder to chop and harder to lever out. If you do this job a little more gently, the wood is easier to work, the chisel stays sharp longer, and the job gets done quicker.
Remember, mortises are like termites. There's never just one.
adam
Ask me when I see you. Tell me who you are and I'll be sure to do this for you and make you try it. I may be difficult to find though.
Edited 11/7/2008 3:31 pm ET by AdamCherubini
Adam;
It is far easier than you may think to overheat an edge while grinding. The thin edges can quite easily reach full cherry red and that is good hardening color. Of course the edge is the very place that is critical too.
If grinding with a grindstone that came with the grinder you are almost guaranteed a sad result. Good quality stones are expensive but well worth the price. It still requires care to avoid overheating the steel. A belt sander is a much more forgiving alternative and of course the wet grinders very rarely burn steels.
Thin pieces of steel are rather easily heated to high temperatures. It's an old blacksmiths demo trick to cold forge a small steel rod until they can light a scrap of paper with it and then use that to start the forge fire.
What comes to my mind is that the bevel angle you are sharpening your chisels to is not appropriate for the type of work you are using them for. For paring with or across the grain, taking fine cuts, a 20-25-degree bevel is ideal. For chopping mortises you want a steeper angle like 30-degrees, which makes the edge stronger and less succeptable to breakage. For harder woods, a steeper bevel is in order as well.
When levering to clean up your mortises, is the "top" bevelled side that is leading or the "bottom" flat side?
By heating your chisel up and quenching it in water, you are shocking it, which can cause fine cracks in the steel. It's better to not let the tool get that hot by either using a different method of sharpening or taking more breaks to let the tool cool down.
Chris @ www.flairwoodwork.spaces.live.com
- Success is not the key to happines. Happiness is the key to success. If you love what you are doing, you will be successful. - Albert Schweitzer
My general advice would be that aside from "pigstickers" (actual mortising chisels), you never want to "lever" with a chisel.
I wonder if I'm doing anything right.Obviously the chisel is getting too hot because it tends to hiss when I place it in water. I am grinding to 25 deg and honing to 30 deg and mortising in beech.Thanks people. Operating procedure review coming up :-)
Just a thought - 5 degrees sounds like quite the micro-bevel. I'd stick to a degree or two.Chris @ http://www.flairwoodwork.spaces.live.com
- Success is not the key to happines. Happiness is the key to success. If you love what you are doing, you will be successful. - Albert Schweitzer
I grind at 25 deg by measuring 53mm on the chisel, drawing a line and resting this line on the tool rest. Dimensions derived using AutoCAD.I then hone freehand using a 30 deg set-square to guide the tool angle.Are you suggesting that I lower the tool handle as much as possible?Would this not lead to a more fragile (although sharper) edge?
For your application, I am recommending that you grind the chisel to about 28 degrees and use a two degree microbevel. This is based on theory I have read and practiced. From my personal experience, I do not know if the 5 degree microbevel is hurting you or merely overkill.Chris @ http://www.flairwoodwork.spaces.live.com
- Success is not the key to happines. Happiness is the key to success. If you love what you are doing, you will be successful. - Albert Schweitzer
I am here to learn so I will certainly try this. I've just come in from the shop to rest my back, having finished this set of cuts but there are more due soon.From various articles I've read I got the impression that, as a general rule, one grinds to 25 deg and then hones to 30 deg. If I understand you correctly, when doing things like cutting mortises, I should go for 28/30 which will give me a stronger edge.Question: should I aim for 28/30 all the time or only for this application? I only have one set of chisels but have no problem with buying another set so that I can have different angles on them.Thanks.
My take is that there is some extremely complicated physics involved here. I think Leonard Lee did some testing to arrive at his micro bevel angles. That would be a good place to start. Let your own experience be your guide from there.
Personally, I think you are better off with the lower primary. But I'd have difficulty prooving why it would be better (i have my theories) and I suspect you would be hard pressed to tell the difference. What I think you really need is a mortise chisel and a little practice. I really enjoy working with chisels. I hope this has been a fun experience for you. You can do a lot with a chisel.
Adam
The simple solution would be to buy one or two proper mortice chisels. Some firmer chisels are thick and strong enough to take the pounding, but their lack of thickness (compared to a proper mortice chisel) means less sidewall registration, and this makes it more difficult to keep a straight line or lever out chips.
The primary bevel is ground at 20 degrees for better penetration, with a small secondary bevel of 35 degrees for strength.
Here is a vintage 1/2" Oval Bolstered Mortice Chisel by Ward (top) with a modern 1/4" Ray Iles (lower) ..
View Image
Regards from Perth
Derek
I have a couple of those which belonged to my father. I remember (mis)using them 45 years ago and have only a few days ago dug them out, de-rusted and sharpened them.OK, summary of the results of this thread:Don't quench blades when grinding.
Grind more gently.
Go for a smaller microbevel.
Use mortise chisels for work involving levering.Hey 2" beechwood plank - here I come!Thanks
Derek:
Thank you! You are correct using the correct tool in the proper way will resolve this fellows blade breaking dilemma. Possibly smaller bites might help too.
Madison
I would only use that steep of an angle for chisels that requre it - ones that are used for tough tasks such as chopping out mortises. That being said, I have my Irwin Blue Chip chisels ground to 25 degrees with a couple degrees for a microbevel and they have held an edge startling well throughout my recent dovetail chopping. I mean, I am amazed that they are still as sharp as they are. I've cut dovetails for eight drawers in soft maple without any noticable degradation of the edge.
If you do a lot of mortising, follow Derek's advise and spring for a mortising chisel. The straight sides make it harder for the chisel to twist in the mortise as you drive it in.Chris @ http://www.flairwoodwork.spaces.live.com
- Success is not the key to happines. Happiness is the key to success. If you love what you are doing, you will be successful. - Albert Schweitzer
Hey some body has a chisel hard enough to chip? Can I buy it? Most of the junk out there is way under "hardened".
Good advice on bevel angle. That is probably it. Too shallow.
Interesting fact : the japanese have the hardest chisels. They don't lever. They have another "chisel" tool to remove the waste
http://www.japanwoodworker.com/product.asp?s=JapanWoodworker&pf_id=17%2E120%2E3&dept_id=12800
and yet another to clean the bottom.
http://www.japanwoodworker.com/product.asp?s=JapanWoodworker&pf_id=17%2E120%2E1&dept_id=12800
In closing I must say you will not harden the steel by quenching unless you take it past the "critical" temp which will be a dull red. Then in a quantum leap be in the water to quench.
This is the point where the body centered Alpha Iron becomes face centered Gama Iron. (sounds technical doesn't it?)
The damage you will be doing is only if you get some blue and then you are way softer than before (less hard). To harden it you would have to have the body of the chisel near red so the edge stays red while you move it to the water. Other wise the cold body will suck the heat out of the edge before you can quench it but too slowly to lock in the hard state.
Here are two more Japanese stories:
One master said if a plane Iron was a tweek too hard he would put it on a tin roof during one of the hotest days of the year and it would aneal the edge just right.
Others said most blades when brand new from the master blade maker were prone to chip and just the heat generated from fast planing would aneal the edge just right.
We are talking Rockwell C 66 or a tweek more. 68 is max. I would be surprised if your chisel was above 62
enjoy !
Edited 11/6/2008 2:47 am by roc
I pretty much follow this guy's procedure. He seems to know what he's doing - lots of levering going on.
http://www.taunton.com/finewoodworking/SkillsAndTechniques/SkillsAndTechniquesArticle.aspx?id=26994
"lots of levering going on."Yes. With a mortising chisel, not a bevel-edged chisel.
Alan,
Yes, definitely only with a mortising chisel. I think by now Mr. Davcefai realizes that he didn't have the best tool for the job.
-Chuck
"I think by now Mr. Davcefai realizes that he didn't have the best tool for the job."And a lot of other things too!This weekend I shall be mortising my Record vise into the worktop of the new workbench I am building. I confidently expect not to break any more chisels.Sunday morning I'm off to the weekly fleamarket to look for old mortising chisels :-)
chuck,Thanks for that reality check.Up to this point in the thread I was becoming a bit disoriented with the advice not to lever out waste in a mortise. (HUH?). Also the acceptance of anything but a mortise chisel to cut a mortise.I use paring chisels (and yes, firmers are really only beefy pairing chesels) only to slice down the walls of mortises that have been wasted with a drill bit first. And to clean up ends and corners. Pairing chisels just don't chop mortises very well.Adam, I have no intention of starting an argument, but you have given some very strange advice here in the last several days. Advising against levering out mortise waste in this thread and previous advice that shellac should "never" be sanded as a means of leveling before rubbing out. Are you deliberately trying to mislead?Rich
Rich,When I come back from KY, I'll see if I can shoot some video of my mortising technique.Adam
Regardless of how you use your chisels , when using the grinder the type of wheel is paramount , as Mike Wenzel stated . I use White sugar wheels for grinding steel shaper knives and they work well for most any chisel shaping and hollow grinds too . I do quench to keep cool , but never let them get real hot in the first place , don't rush it .
dusty
So, to recapitulate:
1)You need to use a mortice chisel which is suited to the job of chopping levering and paring-all three. The shape of this chisel at the sharp end is distinctive in that the bevel should be rounded at the back-facilitates levering the waste out. Think about it.Most new chisels do not have this and you should do it-it takes a few seconds to do on your grinder. The cross section profile of a decent mortice chisel is also not square....
2) When grinding chisels, plane blades or any hardened high carbon steel like O1 cease warming them so much that you can't hold them near the end or need to literally quench them . Sizzling spit or water means serious damage is imminent. Repeated dunking in water may cause hairline stress fractures which you can't see with naked eye but....
3)What wheels are running on your grinder- grey things? If so take them off and put them away. You need a couple of softish Aluminium Oxide wheels-the white ones. One can be coarser than the other.
A good one to have is a Norton 38 A 60 H. These wheels have codes on them with lots of figures and letters, but there are four things to note, apart from correct diameter, width and bore:
38 = Nortons AO wheel type
A= Aloominoom Oxide
60= grit size like in "sand" paper. You could have a 60 grit on one side and an 80 grit on the other where 60grit is the coarser one.
H= hardness of the wheel . A is the softest-for grinding very hard tool steels ranging to Z being the hardest. H is a good one-not too hard or soft.
4)You need a wheel dresser. I advise either a multi diamond or a single point diamond. Not expensive considering the pain they prevent and the fact that they outlast you.
Contrary to what Adam says the white wheels are not expensive at all. A 180mm by 13mm white Norton for my surface grinder costs NZ$28.
The expensive ones are the Seeded Gel ones (SG) and an average woodworm does not use those.
philip,"3)What wheels are running on your grinder- grey things? If so take them off and put them away. You need a couple of softish Aluminium Oxide wheels-the white ones. One can be coarser than the other."I agree, and that's what I routinely use.However, the very hard silicon carbide gray wheels have gotten a bad rap. They can be used perfectly well. It's all about technique.I think the major problem with them is that they are the only type supplied on all the cheap, poorly-made grinders that are sold by the millions and wind up in cluttered garage work shops, metal working shops and auto repair places. They are unbalanced, have irregular surfaces and the "tool rests" supplied with these machines are terrible. They typically get used to true up screw driver tips that have had their blades damaged by use as a prying device or from taking an electric arc which has chewed out a good piece of metal. Actual grinding of tools is sent out to a pro by such places.With all of their pre-existing faults, when such equipment is used to grind chisels, the results are usually very poor and overheating is the most common problem and is often unavoidable to the inexperienced wood worker.But if such a wheel is properly balanced and dressed and the chisel is held in a decent tool rest, excellent results can be obtained. The "secret" is a VERY light touch. That's all. And monitoring the temperature of the tip with one's finger, not to get too hot to touch just as you have advised. Low speed (1750 rpm) is also a good idea.Professional shops use gray wheels all the time. White or pink wheels are simply too slow-cutting when there is high volume to be done.Rich
I think the gray wheels clog very easily. SiC seems to have very large pores. And the old fashioned machine shop wheels were really designed for long life, cutting HSS lathe tools etc, which don't really have the low temp tempers our tools do. So they aren't particularly friable.So I guess there are 2 issues. One is the porous nature of SiC wheels (and whetstones) in general. The other is their friability. If you keep these stones very clean, dressing after each use, they will probably work okay. The white and pink aluminum oxide wheels (Al2O3) are a little easier to use and are better suited to ww hand tools. Better still are the SG wheels, but these wear very quickly and make a huge mess.Adam
Adam,As I said I use a white Aluminum wheel.But I had an 8" gray wheel for a while that I trued up with a diamond dressing tool. I could easily re-grind grind the hollow bevel on many chisels (assorted 1/2", 3/4", 1") when honing had grown the flats large enough. (assorted 1/2", 3/4", 1") before the wheel needed redressing. I don't know how long the wheel stood up to more serious grinding needs. But re-dressing it only took a minute or so when needed. Easy enough to do. No burned chisels. Very usable results.Rich
I went to a flea market yesterday to look for chisels. Overall very disappointing but I got hold of two unused ones. They are 10mm and and 13mm, 7mm thick and flat ground at 25 degrees.I've no idea what brand they are, the only identifier is the "England" stamped on the metal. The handles are also an unknown, they are "padded" plastic. Encouragingly the 13 mm one raised a wire while I was flattening the back on a 180 grit diamond stone. The chisels each cost the equivalent of $1.00 but if they don't work out I will grudge the time spent prepping them.Thanks to all for the help and advice. Up to now I had rather taken chisels for granted.
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