I just don't get it

[James Pallas]

I read all the things about "Don't scrape the bottom of mortises with your chisels", "You need 35* bevels on chisels" and so on. Yet we take a plane iron with a 25* bevel and shove it with both legs into wood, knots, edge grain, and some very hard wood at a 45* angle and expect it to keep performing. I do get the thing about more brittle steels chipping if you pry with them, that goes for screwdrivers with hard tips too. I also understand there may be issues if you use a 2 lb. hammer like Thor in a fight. But just using your chisel with normal hits with a mallet in a straight manner or scrapping a little is going to ruin the edge.
Tell me what I'm missing here.
Jim

[Stanley Covington]

I read all the things about "Don't scrape the bottom of mortises with your chisels", "You need 35* bevels on chisels" and so on. Yet we take a plane iron with a 25* bevel and shove it with both legs into wood, knots, edge grain, and some very hard wood at a 45* angle and expect it to keep performing. I do get the thing about more brittle steels chipping if you pry with them, that goes for screwdrivers with hard tips too. I also understand there may be issues if you use a 2 lb. hammer like Thor in a fight. But just using your chisel with normal hits with a mallet in a straight manner or scrapping a little is going to ruin the edge.
Tell me what I'm missing here.
Jim

If you aren't experiencing chipped/rolled/dulled edges with the methods you are using now, then the solutions to these problems others have suggested are irrelevant. That explains why you "don't get it."

For others, they are real problems, right now. They do "get it."

These problems have been around as long as humans have been using steel chisel and plane blades. They are not new solutions. Chances are you may need to apply these solutions to your work in the future. Maybe not. It all pays the same.

[Prashun Patel]

I always thought it was the depth of cut and levering the tip that was detrimental to the edge of the mortise chisel. That applies a lot of force across instead of into the tip.

When planing, the tip is never levered.

This being said, I tend to scrape the bottoms as you do, and it works ok for me. But I hop mortises by hand infrequently.

[ernest dubois]

I read all the things about "Don't scrape the bottom of mortises with your chisels", "You need 35* bevels on chisels" and so on. Yet we take a plane iron with a 25* bevel and shove it with both legs into wood, knots, edge grain, and some very hard wood at a 45* angle and expect it to keep performing. I do get the thing about more brittle steels chipping if you pry with them, that goes for screwdrivers with hard tips too. I also understand there may be issues if you use a 2 lb. hammer like Thor in a fight. But just using your chisel with normal hits with a mallet in a straight manner or scrapping a little is going to ruin the edge.
Tell me what I'm missing here.
Jim

James, I think you have to dial in on the question or problem as you see it like a laser or it will be asking for trouble. For example, there is no problem in, "just using your chisel with normal hits" and "scraping a little" will never "ruin the edge". In your question as posed, there are no problems despite the conclusions and assumptions other readers will be prone to draw and then carry on about page after page. For example, I would ask one thing, did you ever have a problem using your chisel and mallet normally?

[Stewie Simpson]

I always thought it was the depth of cut and levering the tip that was detrimental to the edge of the mortise chisel. That applies a lot of force across instead of into the tip.

When planing, the tip is never levered.

This being said, I tend to scrape the bottoms as you do, and it works ok for me. But I hop mortises by hand infrequently.

Prashun; have a listen to what Frank Klaus says at 1min in the following video about prying the waste free with a mortise chisel. https://www.youtube.com/watch?v=PQ6vBrqHH3A

[Matt Evans]

When planing, the tip is never levered.

That is the main difference.

If you don't have the issues with your mortise chisels chipping, cracking, or dulling quickly, then you may just have some chisels that have more forgiving steel than some others. It also sounds like you may simply have found your own natural "chip Limit" and "Mallet force" which means you likely aren't overtaxing your chisels in the first place. (I do a lot of larger scale mortises, and tend to go a bit overboard on occasion, and that is where I run into the most issues)

The Narex set that I have is great, but it definitely a little more brittle than the older chisels I've used. I've taken to using a cranked neck chisel to clean the bottoms of smaller deep mortises to help conserve the Narexs tips.

One other note: The deeper the mortise, the more straight line force you put on the tip of a chisel when levering. So, the bottom of a mortise on a deep mortise is going to see the greatest chance of a tip breaking off or chipping. To illustrate this you can draw an arc with a set of dividers with the depth of the mortise being the circles radius. Please excuse the poor upside-down illusration .

[Warren Mickley]

Without watching you work it is tough to know whether you are being rough with your chisel. If you need a 35 degree bevel or some weird steel for a mortise chisel, then these are clues that your mortising technique is none to clean. When I read about whacking or bashing or a chisel that must stand up to abuse, I am thinking that the writer is hard on his tool.

If a mortise is just a little shallow for the length of tenon, I usually make a series of shallow cuts along the bottom so that each cut pushes the waste toward the previous cut. That way everything down there is already loose if you want to lever it out. I generally mortise to within 5/16 of the far side of the stile, which leaves a little cushion for the chisel to avoid breaking out the back. Scraping the bottom strikes me not so much as abusive, but as a slow way to extend the depth.

[Jeff Heath]

Not all chisel steels are created equally, and not all people use/abuse/whack them the same way. These angles that always talked about should be used as a guideline as a place to start. Once you've done some work, you'll be able to hone in on what works best for you, based on the species of wood you use, and how hard you're hitting your chisel with a mallet. Big bites, and a lot of prying, are going to be harder on an edge. I have learned, over the years, how hard I can push my tools without damaging them. My sharpening station is 10 feet from my bench, so if I sense a chisel or plane iron is dulling, I either pick up another chisel in the same size (I have many) or go sharpen it again. There's a trade-off between a sharp edge and a steeper bevel angle. You'll figure out what works best for your situation, and your style of work.

[Jim Koepke]

I read all the things about "Don't scrape the bottom of mortises with your chisels", "You need 35* bevels on chisels" and so on. Yet we take a plane iron with a 25* bevel and shove it with both legs into wood, knots, edge grain, and some very hard wood at a 45* angle and expect it to keep performing. I do get the thing about more brittle steels chipping if you pry with them, that goes for screwdrivers with hard tips too. I also understand there may be issues if you use a 2 lb. hammer like Thor in a fight. But just using your chisel with normal hits with a mallet in a straight manner or scrapping a little is going to ruin the edge.
Tell me what I'm missing here.
Jim

One thing to remember when it comes to a plane blade is its support system. A thin blade, compared to a mortise chisel or just about any other chisel for that matter, has a frog under it and cap iron and lever cap on top of it. In a plane the blade is usually limited to taking a shaving less than a 1/16". A mortise chisel may be moving a chip four or five times that in a single whack.

The force of my mallet blow for mortising is the hardest whacking any of my in shop wood working tools receive. The really hard whacks are saved for splitting wedges and usually outside with extra room to swing a sledge.

At the end of the video Stewie linked Mr. Klaus shows a rather large lock mortise or swan neck mortise chisel that is made to get down into a mortise and clear the bottom of a mortise. Another method is to make the mortise a little deeper than the length of the tenon. That provides a little space for any extra glue. The bottom of a mortise doesn't have to be pretty.

jtk

[James Pallas]

I really don't think I'm having problems with chisels. I do wonder about all of the different opinions. I don't own any expensive chisels. I did at one time buy some chisels from a popular tool maker and ended up giving them away. They were nice chisels felt good in use. They were harder to sharpen and supposedly needed a different bevel angle. I have what I call inside and outside chisels. The inside ones I use at the bench and the outside ones I use for rougher work such as repair work or working on wood that is very dirty like my deck or something. I have owned chisels that were just no good, would not hold an edge cutting bass wood or something such as that. Would not even be good paint can openers. I have for years sharpened at 25* or a little more for bench chisels and 20* or so for paring. I've never felt that I had to sharpen more than necessary. More often in harder wood for sure and I expect that. If I have a chisel that folds I believe something is wrong, if it chips maybe I hit something or could be the steel. I can usually hear with the first hit if the wood is harder than I expect it to be and can adjust my technique for that work. I was just wondering about all of the comments that I read about it. Mortise chisels I try to keep at 30* +. Good comments here about the subject.
Jim

[Jim Koepke]

I really don't think I'm having problems with chisels. I do wonder about all of the different opinions.

Hopefully all of the different opinions circle back to people expressing what is working for them in their work.

What actually works for you in your work environment is reality. Everyone knows, or should know, one reality is worth more than an infinite number of opinions.

jtk

[Patrick Chase]

Prashun; have a listen to what Frank Klaus says at 1min in the following video about prying the waste free with a mortise chisel. https://www.youtube.com/watch?v=PQ6vBrqHH3A

Like many such rules, the prohibition from prying seems to be frequently broken by those with enough skill (not me). Obviously Klaus has a sense of just how hard he can lever his chisel without chipping or folding the tip, so he takes advantage of that to accelerate the waste removal process a bit.

[Jim Koepke]

Like many such rules, the prohibition from prying seems to be frequently broken by those with enough skill (not me). Obviously Klaus has a sense of just how hard he can lever his chisel without chipping or folding the tip, so he takes advantage of that to accelerate the waste removal process a bit.

What sharpness can't fix must be left to experience.

jtk

[ernest dubois]

I do wonder about all of the different opinions.

And the tool flippers, advertisers and the huge racket around them all know it, want you to be just curious enough to spend your money to see if what they all say just might be so. They will be wooing you with the newest gimmick, mystifying you with the numbers and the jargon and most of all belittle you for not having the latest.

[James Pallas]

And the tool flippers, advertisers and the huge racket around them all know it, want you to be just curious enough to spend your money to see if what they all say just might be so. They will be wooing you with the newest gimmick, mystifying you with the numbers and the jargon and most of all belittle you for not having the latest.

Nice one Ernest. There is that saying, "Believe none of what you hear and only half of what you see." I stopped going to that dance about 60 years ago when I got my first paying job. I'm not buying it unless I put it in my own hands. Same thing for trying things, I only believe it after I have done it.
Jim