Skew chisel – flat or hollow ground
DennisS
| Posted in Power Tools and Machinery on
Question from the newbie corner …..
I read in one of my intro books on turning that the skew should be flat ground rather than hollow ground. The Tormek jig for holding the skew puts a definite hollow grind on the tool.
What say ye, turners?
Dennis in Bellevue WA
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[email protected]
Replies
Ye old sharp part runs right against the wood.
If you hollow grind you will experience the wonderful world of catches and hurls.
In other words, this is about the toughest tool to master and the hollow grind leaves less tool touching and more chance to catch the edge.
Richard Raffin does a a good demo if you can find his tape.
Bob
Intuitively this stands to reason. I bought the Delta sharpening center (bad choice) thinking I could wet grind a flat bevel on my skews. I think it would be acceptable if I could find a good alum. oxide wheel to replace the piece of soap Delta provides.
Dennis in Bellevue WA
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Bob,
I still experience a fair share of catches using a skew, but I'm afraid I can't blame them on the hollow grind. I tried a flat bevel when I first started out, based on Ernie Conover's suggestion (probably the same author Dennis is refering to), but found that I always ended up with a slightly convex bevel after several honings. I think we can all agree that a convex bevel is very hard to control- I experienced a lot of bad catches then.
So I switched to grinding the bevel on a 6" grinder and found that it's much easier to hone to a sharp edge without rounding the bevel. (The only reason for the 6" grinder is that's all I have- $10 at a garage sale- unlike Dennis who has all the nice toys :). And if I do get a catch, it's just me not having a firm grip on the tool or carelessly dragging it back over the work instead of lifting it off after making a cut. It's all about riding the bevel- doesn't matter whether the bevel is flat or hollow, just make sure it's not convex.
Rick
I've seen several illustrations showing beautiful planing cuts with the skew edge practically parallel to the lathe axis. That's a sure invitation for me to catch. I seem to do fairly well keeping the tool edge at a considerable degree off the axis of the lathe.
Tried both flat and hollow ground (off my nice toy -grin-) but in the end I think it's just practice, practice, practice.
I'm doing mostly hollow stuff right now so don't get the needed practice.
Dennis in Bellevue WA
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I have to agree with you Rick.
Practise takes a lot of the errors out of the process.
I don't skew as much as I should because I have not mastered the tool.
I figure a guy should run a series of figures on a piece of stock before tackleing a project to make sure the angle and bevel and brain are all sharp.
Do you give the blade a curve or to you use it straight?
Bob
Bob,
I have both. My current favorites are two skews, both 1/2" wide, one with a straight edge and the other with a slight curve. I can't really say that I prefer one over the other. I just pick up whichever one happens to be the sharpest at the moment. Like you said, the most important thing is practice. The skew is a beautifully simple tool- as long as it's sharp and the bevel isn't convex, it's up to the operator to do the rest. Happy turning... I know I will be doing a bunch of turning this weekend.
Rick
try the del stubbs "trial video" on this forum, the last 20 seconds or so of the demo shows why a tool cuts and how you can experience the same in your own shop. highly recomended for doffers ( anti - skew ers)
What "trial video" are referring to, and where is it?
Peace,
kevin
http://www.taunton.com/store/pages/060007.asp
this is under the store, videos for turning, and select del stubbs video, there is a short clip.
It here on this site Kevin.
Go back to the main screen and pick it out from one of the side bars.
I could get it for you but this forum dosen't like excursions fromthe topics.
Bob
Thanks, found it.
Dennis -
I agree with the others. Don't think you would want hollow ground for a skew. But, as you know, I just made my first one.
I use a 2" vertical belt sander to sharpen all my chisels. I can set the tool rest to any angle and can sweep and rotate the tool easily to get the shape needed. I can also easily switch to different grits.
Hollow grinding - i.e. grinding against a rotating round surface for most part came into vogue with the advent of electric motors. The old timers used a foot powered stone that was circular but was so large that they essentially got a flat grind. Is hollow grinding really preferred anywhere? Or, is it just a convenient method of sharpening?
PlaneWood by Mike_in_Katy
PlaneWood
"The old timers used a foot powered stone that was circular but was so large that they essentially got a flat grind."
Mike,
This is a good point you made, I have been using the Tormek for my skews only because I have trouble holding the skew flat to the stone, the Tormek treatment works better than my own hand but I have always wonder about the hollow grind on the skew. As far as the other edge cutting tools, no problem with the Tormek. That belt sander idea works great with turning tools, I just found out, but need to make some more jigs to hold the skews.
Paul
Well, Mike, I just picked up a 6x48/12" sander at the ww show today so getting a decent flat grind is only a jig away. With a pail of icewater close at hand to be sure. I remember when I worked in an office across the street from our Pike Place Farmer's Market years ago watching the guy come around with his mobile sharpening truck affair to sharpen up the butchers' knives. Those guys, the butchers, could whack off a side of ribs with one slice. So there must be something to this sandpaper sharpening thing!
Gotta wait 'til next week to pick up the sander, though. The truck was full of 'Yota Land Cruiser parts I forgot to unload last night.
Dennis in Bellevue WA
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Dennis: when you get that new sander home and fired up you will indeed see a big diffrence in your sharpening skills..way to go buddy.. I have a lathe and have only used it for limited spindle turning use,Im thinking of trying my hand at some bowl turning any tips you might pass on to me???
ToolDoc
Actually, not to be a name dropper, but since I didn't have anything at all to start with for sharpening tools, period, I bought the Tormek machine. Pricey but with the proper jigs and all I can get a consistent edge on things like fingernail gouges and so forth. The only thing is the skew chisel which, as we've been discussing, should benefit from a flat ground edge.
Again (SysOp - are you paying any attention) since there's no turning forum, we'll migrate to the topic of bowl turning here instead...(grin)
Suggestions for turning bowls? Well, consider it the blind leading the blind if you will (I'm far from the definitive source of turning info, you see) but I'd suggest working with green wood especially to start with. It cuts so much easier, there's lest dust, at least at the outset, and the "potato peelings", as they were called by another poster, that come flying over your shoulder is a complete trip! Doesn't matter if you end up with anything worthwhile, the process is the thrill!! (grin)
The frustrating part of turning green wood is figuring out how to turn into the blank in such a way to plan for shrinkage as the piece dries out. Planning in such a way to minimise cracking. Or, also frustrating, is to rough out a piece leaving it, say, 3/4 or 1" thick, coat it inside and out with diluted end grain sealer, then having the patience to set it aside for a few months or however long it takes to get dried out enough to work with minimal dimensional change. I just don't have that patience. I'll grab a roughed out blank that's sat for a two or three weeks and go at it. I guess the secret is to build up a big stock and backlog of rough blanks so you'll have stuff to work on down the road.
Like any other aspect of woodworking, perhaps even moreso, a sharp tool makes for a pleasant session at the lathe. You can thurn stuff with a screwdriver but you'll get a much better finish with a sharp tool!
As if there weren't enough frustrations, getting a nice flowing form free of tool marks takes, evidently, years of practice. I cheat and sand my pieces along the axis of the lathe (with it not running, of course)to smooth out the tool marks before I start the finish sanding with the lathe running.
Other than the fact that these frustrations sometimes drive me nuts, I find it a very pleasant experience 'unwrapping' something inside a block of wood. You never know what you'll find in there!!
Dennis in Bellevue WA
[email protected]
Dennis: thanks for the quick bowl turning lesson,your the man... Im going to give it a whirl and see what happens..
ToolDoc
Doin' is better than tellin/ that's fer sure.
May your bevel always be rubbing!
Dennis in Bellevue WA
[email protected]
DENNIS: "May your bevel always be rubbing" is that like "Dont let your Tool Loaf" ??
Take Care My Friend. ToolDoc
And...
I'll have my router guide show you around my shop! <vbg>
bob
I can't see that a hollow grind creates any problems. Mine is not hollow ground as I keep it sharp on sandpaper on flat steel, but the best article I have seen on the skew is by Mike Darlow FWW Sept. 1982. There is a diagram of a hollow grind with a secondary "micro-bevel". I turn only occasionally as most of my stuff doesn't have turned parts, but when I do, I find the skew the tool of choice as it leaves an almost finished surface requiring little if any sanding and thus keeps the edges of the turning sharp. My advice would be, take the time to learn the skew and it will become your turning tool of choice most of the time.
Wayne
I agree, Wayne, that the skew leaves the finest finish. I've been practicing and experimenting with different techniques and found that I've been having the tool rest too low. A recent essay I read (mentioned earlier) says it should be 1/4" or so above center. That's worked a lot better but - me being somewhat vertically challenged means I'm working with the tool handle at or often above my elbow ht. Lowering the lathe isn't an option with the cast iron legs. I'm thinking in my future dedicated shop I'll build a little platform like 4-6" high to remedy this. It's a good bit easier to control the tool when it's braced against my side or, with the case of most gouge work, against my hip, leaving the body to control direction.
Hard, dense woods are more problematic, too.
Dennis in Bellevue WA
[email protected]
Hi Dennis,
Great to see a turning discussion. Have you tried choking up on the skew handle? I used to grip the skew like a bowl gouge, with the dominant hand near the end of the handle, handle braced against the leg or hip. But since you don't need the leverage with skew like you do with a bowl gouge, I found it works much better if I grip the skew handle near the ferrule. I line up the end of the handle under the elbow for leverage, and tuck my elbow or forearm against my side for support and then do the "turner's sway". The other hand holds the tool against the tool rest with an underhand grip for fine control, or overhand grip for heavier cutting. I find that the "ferrule grip" works best with a handle design that has a bulge near the ferrule. Give it a try.
As for toolrest heigth, I believe the 1/4" above center thing is just a starting point. I adjust the toolrest height/distance from work combination to wherever it needs to be so that the handle ends up in the position that's right for me.
Happy turning,
Rick
Maybe that's the key, Steve ... keeping the handle parallel with and under the forearm with the grip at the ferrule. My last practice session that's how I was holding it and yes, it was a much more pleasant experience!
Dennis in Bellevue WA
[email protected]
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