clean cuts = curved edge

mark yundt · #1 01-30-2008, 12:15 PM

This tip is in response to questions about getting clean cuts,,eliminating or cutting down on the tearouts and fibers left at the bottom of stop cuts and grounding type cuts. That area is where the majority of problems exists,,lets face it. And as we all know that's the hardest area to reach . Various techniques have been posted on how to get rid of them ranging from riffler files,,to sandpaper folded up a certain way,,to gluing it onto popsicle sticks of various shapes and emery boards.Using a dremel or micro motor with small bits to try and clean it up.Getting really small chisels to poke around and try and get them out or doglegs and what not.
These are all fine,,and do work to some degree.But not one of them adresses solving the problem in the first place.What keeps causing it?

I had recently said somewhere on here that I purchased some new chisels/gouges.And I said they weren't bad out of the box,,I could have sort of used them,,but would prefer not to,,,because they were not really great.So I modified basically the entire chisel to make them what I would consider useable.

The one thing that really struck me was that I could not get a decent stop and clearance cut out of a single one of them! I reground the angles to what I like,,tapered the corners back into the sides and then stoned them before buffing.
Now this part might raise some eyebrows but I don't keep the cutting edge of my gouges straight and perpendicular to the shaft itself. I would imagine many try very hard to keep that edge straight and square as they are sharpening,,but I can't find any compelling reason to do so.The reasons not to keep it square ,,to me ,,far outweigh any reason to keep it square. Once I made the adjustments to my new gouges I could not help but make perfectly clean stop cuts each and every time. The project I am currently working on is nothing but hundreds of stop cuts and clearancing them.The all have to be clean,,and I have no intention of going back a second time with something trying to clean them up.I've got better things to do with my time and patience.

Out in the wide open,,these edges serve no real purpose,,besides that's not where those pesky little fibers show up is it? It's in the bottom valleys and creases that they show up. If you stop for a moment and think about what's happening in those bottom stop cuts you'll quickly discover that the shape of the chisel is what's causing this to happen. The entire edge of the chisel cannot meet the verticle stop cut....it can't. So when you go to pop the chip out,,little fibers remain or are torn off instead of cut and low and behold you have fuzzies in there that you now have to find a way to get out. You're defeating the purpose of the chisel to make a clean cut.And that's what it was intended to do.

Why try to go back in there with a knife or any of the other "solutions" when you had a chisel in there in the first place? Get it to do it's job then you don't have to bother with the unsatisfactory multiple steps.Cut once and you're done.

Now I don't make a radical sweep to this edge as if it were a spoon or something,,but just a gentle arc which will by necessity increase with the greater depth of the chisel. I generally keep this to chisels numbered less than 5..once you go over this ,,say into the 7's it's not really necessary as those chisels aren't used in this fashion..so it's basically 2,3 5's that I do this to. The sweep tend to be a bit more pronounced with the wider the chisel ,,as well as the greater the number.
The possibility of unsevered fibers increases with the greater the angle you are driving the chisel at,,so to get around this problem,,if you are trying to take big chunks out quickly using a 7 or 8 is to then go back and simply do the final paring cuts with a shallower chisel.
One other "trick" to getting clean,smooth stop cuts is to not use a flat chisel as the tool of choice to shear the sides of a deep cut.Again,,on my current job there are hundreds of these as well.Dosn't work,,and in most cases will cause more problems to solve. Virtually ALL the straight cuts I'm making are being done with a curved gouge ,be it ever so slight.A flat chisel though can and does make very nice crisp lines as a final pass at that bottom line. That area and line is the only one your eye catches making you think the cut is arrow straight and perfectly clean.

doris · #2 01-30-2008, 04:33 PM

just to put a second voice for this odd sounding truth...yes, i can say this is right...i did not know the explanation, and it is nice to understand now, but as i said in another thread, i had my gouges always slightly bullnosed, and with thinner at the sides, so with a belly so to say, and i did resharpen them after reading recommendation of the straight front edge, and geometry of the bevel...no, now my gouges did no longer cut so easily and clean as i was used to...so, i did resharpen them back, to be very slightly bullnosed, and with belly, again...i did not know why it works better, but i saw it does, at least with the way i carve.....so to me this proves it true :-)

cats pa · #3 01-30-2008, 04:36 PM

Listen here, mister. Are you one of those tool-modifying yahoos? Who jest ain't satisfied with the manufacturer's wisdom on how a tool should be shaped? You think you know better than the big-aff corporation and all their beancounters? And I bet you're thinking that here in America, each citizen has the right to his own special tools, set up the way he wants them, huh? Is that what you're gettin' at, bunkie?

Me, too.

Parker

mark yundt · #4 01-30-2008, 05:11 PM

HA HA HA,,,LOL,,YUP,,guilty as charged,,,just a rabel rouser,,a real anarchist in the midst...LOL LOL
So nice to know I'm not alone!!!

Revlis · #5 02-07-2008, 02:30 PM

Mark, I understood a tiny little bit of what you are on about...

It's shear madness all this talk about modifying tools, from a rookie's point of view it's quite an unspeakable notion, re-grinding these expensive tools you just bought to suit your own needs? Madness...

I don't weld up custom hex keys, oh wait... yeah I do, I don't weld 90deg angles onto wrenches or grind them to a particular thickness... Oh yeah I guess I've done that too... Screwdrivers, hammers, vices, all have at one time or another found themselves remade to something I needed at the time. For whatever reason though modifying my carving tools sounds really spooky, has to be because I'm new to it and I don't know better than the designers at the companies yet.

Interesting.

Amazing work BTW Mark, just checked out your website, fantastic stuff...

ChrisS · #6 02-07-2008, 03:02 PM

If I understand you properly changing the angle of the edges makes the end cut at the same time when you put a little levrage on it. That would make sense to me. I have had every drafting class known to man. When you lay out duct work or design parts that have a curve they meet at points you would never guess they would. If you have a sweeping curve it would not make contact at all points the way it is made. I can see that from my years as a machinest.

Am I right in thing thinking? I can see I am going to learn a lot on this site about carving.

Thank you for the information. I will experment with it later today.

mark yundt · #7 02-07-2008, 03:14 PM

I think you're understanding me correctly. Using only words can be tricky,,I think a quick demo might be in order.
I would hesitate to use the word,,,Leverage. You generally do not want to use a chisel as a pry bar to pop out a chip. But the slight change I am using on my chisels makes a cleaner cut at the bottom of a stop and clearancing cut.

Revlis,,,AHHH a man after my own heart! Can't even begin to guess how many tools I've taken a torch to,,,literally,,just to get the right angles,,chisels,,wrenches,, adding extensions to screwdrivers to get a 2 1/2 ft reach ( don't ask) car parts..you name it. Give me a blue flame and a grinder and I'm 'gonna have a ball! No tool is safe.

ChrisS · #8 02-07-2008, 04:11 PM

Quote:

Originally Posted by mark yundt

I think you're understanding me correctly. Using only words can be tricky,,I think a quick demo might be in order.
I would hesitate to use the word,,,Leverage. You generally do not want to use a chisel as a pry bar to pop out a chip. But the slight change I am using on my chisels makes a cleaner cut at the bottom of a stop and clearancing cut.

Revlis,,,AHHH a man after my own heart! Can't even begin to guess how many tools I've taken a torch to,,,literally,,just to get the right angles,,chisels,,wrenches,, adding extensions to screwdrivers to get a 2 1/2 ft reach ( don't ask) car parts..you name it. Give me a blue flame and a grinder and I'm 'gonna have a ball! No tool is safe.

I knew I should have not use the word leverage. I was thinking about that. I have only done repair and repalcement carving for furniture I have been restoring and selling through the years. When I come to the end of the cut I very often seem to give it a little extra push at the same time putting a little pressure down to lift out the chip. I have never had lessons or had carving demonstrated but have alway done a good job on what I have done. I have always used jewlers or diemakers files to clean up. I have a lot to learn about doing it with one final cut. I learned how to carve molds in steel. I even worked on molds for transmissions all the way down to molds for small parts. It is no different in wood except you do not need to be so exact. Thanks for the reply. I am with you when it comes to making a tool that meets the job. I have cut many a wrench and welded it at a different angle. etc. I have changed screwdrivers into eveythig you can think of. I just use Craftsman and when I am done they give me a new one. Shame on me. LOL

mark yundt · #9 02-07-2008, 09:30 PM

O.K.,,just for clarity sake I used a section of PVC pipe to make for a more visual demo here..It's silly but you can photograph it easier and actually see what is going on in a better scale.
In the first shot you can see a "chisel" with a typical square end. In the second you can see how the corners are laid back. And just for the demo I am using a scaled up stop cut and the relief or clearance cut to see just what happens as the chisels are used for clearancing these cuts. In the fourth you can see how the edges get in the way of the bottom of the chisel being able to hit the bottom of the stop cut to make a clean cut...whereas the final pic you can see how the laid back edges allow the chisel to make full contact across the entire width of the chisel as well as at the very bottom where the fuzzies live.
Not being able to hit the bottom like the second last shot is what causes fibers not to be cut,,,and if you forced the square edge chisel to reach this spot the corners would out of necessity dig into the stop cut and leave marks which don't look good on a sheared surface. When you go to pop out that chip,,if ALL fibers arent cut,,,well,,you leave a mess that you have to clean up. A knife won't work too well simply because the fibers aren't on the sheared side,,but on the waste cut side,,poking with a knife makes the matter worse.

mark yundt · #10 02-07-2008, 09:36 PM

Here you can see a top view of what's happening,,from the laid back edge to the square edge. I also included a shot of a fairly deep chisel to see what happens in an extreme condition as well as showing what happens when a grounding chisel of the same shape is used and why this chisel can work so well in addition to the shaft being at a better angle to use in this position of clearing a waste cut. Full contact of the cutting edge.