Tool to cut a recess

[John K Jordan]

Another thread discussed using a recess and how to make it.

This is what I use. I ground this shape on an old tool. It's held horizontally and used as a scraper so I angled the cutting edges back on all three sides for a relief angle. The cutting edge is small enough that it won't catch. The working end is angled away from the axis of the shaft to get in close to the center even when the blank is supported by the tailstock.

Dovetail_A.jpg

Dovetail_B.jpg

I ground this tool with a square-edged CBN wheel. This works extremely well, far easier to use than my previous methods.

The dovetail angle in my quick sketch might not look like enough but it is - it's drawn about 7-deg off perpendicular to the surface but I never measured the dovetail angle I cut. You don't want too great an angle or the sides of the jaws can bear against the weak area at the surface of the wood instead gripping of deep inside the dovetail where the wood is strong. (It's actually better to use an un-dovetailed recess such as from a Forstner bit than angle the dovetail even a little bit too much.)

I typically make the dovetail 1/8" to 3/16" deep depending on the size of the piece and the wood, sometimes smaller, 1/16" or so.

JKJ

[Reed Gray]

Okay, so why the angle? I would guess that it is because if you have the tailstock engaged, then if you had a straight dove tail tool with the tail but at a 7 degree angle or so, you wouldn't be able to like up the tool handle and shaft with the ways of the lathe.... I have the more standard straight type. I use the straight face of the CBN wheel to shape it and resharpen it. Saw one that the local Woodcraft Store owner had for 'over 3 years and it still is the same size'. He would hone the top surface only. I prefer the burr, since it is a scraper. I have ground the tip off side ways a couple of times now....

robo hippy

[John K Jordan]

Okay, so why the angle? I would guess that it is because if you have the tailstock engaged, then if you had a straight dove tail tool with the tail but at a 7 degree angle or so, you wouldn't be able to like up the tool handle and shaft with the ways of the lathe.... I have the more standard straight type. I use the straight face of the CBN wheel to shape it and resharpen it. Saw one that the local Woodcraft Store owner had for 'over 3 years and it still is the same size'. He would hone the top surface only. I prefer the burr, since it is a scraper. I have ground the tip off side ways a couple of times now....

robo hippy

Yes, as mentioned with the tailstock supporting I can't easily use a tool straight, especially on a smaller diameter recess for 50mm jaws.

I've been using it for a long time and have never sharpened it after the first time, I just hone the top with a little diamond hone. No need for a burr since it cuts cleanly in any wood I've tried, in fact I was surprised at how cleanly it cuts pushing straight into the wood. With the tool held horizontally as I use it, a significant burr might be catchy, I haven't tried.

I think it doesn't need sharpening much since I only use it to cut the recess, not use it extensively as with a standard scraper and the amount taken off at once is small.

Here's a picture of the tool from the top.
Dovetail_C.jpg

When I show it at a demo people always want dimensions and photos. I don't know how many have made and use one except for a local guy.

JKJ

[Peter Blair]

Funny, at least to me John, how the universe works. I made this tool about a year ago. I didn't want to modify a tool I have but did have some nice cutters purchased at an auction. My shape is very similar to your and was needed because this it the tool I mostly use to reshape a bowl after it had dried and gone out of round so the tail stock must be used. Like yours I sharpened mine once but left the burr. As you may be able to see I added a short piece of square stock in line with the cutter for support. I use mine to turn the recess OR tenon round.
.IMG_5885.jpg

[Reed Gray]

I did try mine for a bit with the honed top. Didn't cut nearly as fast or as cleanly in a lot of woods. The honed one did okay for some of the harder woods, but anything soft it just shreds. I do clean up the recess with hand tools though. The small fluteless gouge from Thompson in a shear scrape (no bounce at all like when rubbing the bevel), and a detail type tool for the wall of the dove tail. The recess is my finished bottom, and this leaves a 220 grit sanding surface.

robo hippy

[John K Jordan]

Peter, Nice, and adjustable too! Clever. I have also used mine on the tenon but I don't use tenons as much now. I sharpened both sides and the front.

Reed, I agree about the softer wood, if needed I use a trick StLeger had to clean up - use a 1/4" round skew pushed straight in at the right angle. It cuts with one side of the very point and cuts quite cleanly in anything (with very light cuts). Mostly I prefer to turn harder woods and almost always dry. That may make a difference.

I've been thinking about how to design a Forstner-type bit that will cut a dovetailed recess. I've sketched a design that will probably work but I'll bet it would cost too much to make! Consists of several angled, spring-loaded radial cutters spread by a tapered disk as a fat flat-bottomed center pin contacts the bottom of a hole drilled with a standard Forstner. A spring-loaded center point in the center of the fat pin would register with the center point left by the Forstner. It would have to remove very little wood since the hole was already the right diameter at the opening. The cutters could be similar to those used in fly cutters on a mill and replaceable. Just can make one and patent it and get rich, just remember me in your will.

JKJ

[Leo Van Der Loo]

recess tool.jpg

I had made and shown this tool several years ago, as the question came up of how to cut the recess with the live center and tailstock in the way, I have shown it a few times after.

For the few times I would need this I used a cheap carbon steel tool and ground it to suit me then.

The angle can be ground to what will work best with your lathe and live center so you can get in there to cut the recess.

The cutting edge is less than 90 degrees so I can get a nice sharp corner in the recess and there will be less change of the tool grabbing if both edges engage the wood.

[Reed Gray]

John,
That is pretty much what I do with a detail type/vortex type tool that I saw Allen Batty use, made from half round stock and sharpened to 30 degree bevel and maybe 50 to 60 degree sweep. Makes a glass smooth cut on the edge of the recess.

I have pondered a dove tail forstner bit. Probably similar to what you said, drill straight first, then spring loaded crank out carbide blades to the 7 or whatever angle is necessary. Probably too complicated to be worth the effort to make. I frequently get asked if I dove tail the recess I drill to turn the outside of the bowl, and no I don't. I do drill deeper than the tooled recess I use for the bottoms of my bowls, but haven't found the taper angle to be necessary. I can't crank on my chucks enough to break the wood, and I am on the Brute Squad..... If I have to remount using the same recess, it never goes back on and runs true, though with my tooled recess, I can get it 'close enough'.

Leo, that is pretty much identical to mine. I think I got it from Packard, many years ago. I have experimented with a burnished burr and that works well too.

robo hippy

[John K Jordan]

I frequently get asked if I dove tail the recess I drill to turn the outside of the bowl, and no I don't. I do drill deeper than the tooled recess I use for the bottoms of my bowls, but haven't found the taper angle to be necessary

I get asked the same thing and am sometimes met with disbelief when I tell them the straight-sided hole works fine, even if not deep. I suspect the slight compresability of the wood plays a part in the security.

One reason I dovetail is for appearance. When I leave the recess in the bottom the slight dovetail hides any small marks made by the chuck jaws.

bottom_IMG_4749.jpg IMG_7426.jpg IMG_7435.jpg penta_maple_ellis_c_IMG_5435.jpg

Making the angle of the dovetail not quite matching the jaws (a bit wider than the jaws at the top) helps too since the jaws can't even touch the wood at the surface. Usually there are no marks since most of what I turn is not from soft wood and I tighten the jaws a little differently than many.

JKJ

[Richard Dooling]

Usually there are no marks since most of what I turn is not from soft wood and I tighten the jaws a little differently than many.

JKJ

Can you explain what's different in your approach?

Richard

[John K Jordan]

Can you explain what's different in your approach?
Richard

I'm not absolutely certain the method is the only reason, but I think it is at least part of it. A lot of times people insert the chuck key and tighten once with a lot of force, sometimes because this has worked in the past and when they didn't use a lot of force the chuck ended up not being as tight and may need to be retightened later during the turning. The method I (and some others I've met) uses less force with the key but gets the chuck very tight right off the bat and hasn't needed to be snugged later. Two people told me recently this method made a difference for them.

Basically, it's tightening repeatedly in alternate key sockets but never really cranking down hard. I wrote the following recently in a thread on another forum in response to a question about an eccentricity problem and the possible need to tighten the chuck often. (There was more but this is the chuck tightening part)

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Tightening the chuck and stuff
John K Jordan 2/19/2019, 11:43 pm

Chuck tightening: I generally don't retighten during turning or need to (using good, dry wood.)

I think the need to retighten may be from backlash in the gears due to normal manufacturing tolerances: when you tighten the first pinion gear, friction at the teeth, axle pin, and race holds its teeth tight against the teeth of the larger gear on the scroll plate in the "tightening" direction. But the second pinion is left with the teeth in contact on the wrong side, in the "loosening" direction (since the large gear is driving the second pinion instead of the second pinion driving the large gear.) This play can cause the large gear on the scroll plate (and the jaws) to quickly loosen a bit.

Instead, I tighten a different way than some:

- Tighten the first socket moderately (not with a lot of force).
- Immediately rotate to the opposing socket and tighten again with the same amount of force. You will almost always find it will tighten a little more.
- Then rotate on around to the first socket and tighten again.
- Repeat.
- After several cycles you will feel that no more tightening is even possible without increasing the force dramatically. This will happen quickly on hard, dense woods such as ebony and may take a few turns on softer wood such as cherry. At this point I usually go around at least once more with a little more force just to check.

I heard a wise man once say "tighten the chuck in all six places." And a surgeon told me she was taught in medical school to tighten exactly like that when chucking drills and cutters. I use the same method now on drill press, mill, metal lathe, etc.

Unless the wood is punky, soft, or wet, it should be as tight from the start as it will be later. Try it.

JKJ

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[Richard Dooling]

Interesting. I must have seen someone somewhere do this because somehow I picked up this method. I also try to tighten just enough out of a concern that I could crack a recess in expansion mode.

[Reed Gray]

I heard years ago about tightening on both key holes, or on my drill press, all 3 holes. I was told this was an old machinist trick. It does give a more secure mount. Even when turning green wood, I pretty much never need to tighten again. If there are metal stains from the chuck jaws, a little concentrated lemon juice will take it off in seconds unless I let it sit for a few days, then it takes an hour or more. I do think my chuck jaws all have very slightly rounded edges. A few gouges from coring accidents...... No clue as to why they seem more rounded than when new. With all the coring I do, I want the dove tail.

robo hippy

[Randy Hogan]

I get asked the same thing and am sometimes met with disbelief when I tell them the straight-sided hole works fine, even if not deep. I suspect the slight compresability of the wood plays a part in the security.

One reason I dovetail is for appearance. When I leave the recess in the bottom the slight dovetail hides any small marks made by the chuck jaws.

bottom_IMG_4749.jpg IMG_7426.jpg IMG_7435.jpg penta_maple_ellis_c_IMG_5435.jpg

Making the angle of the dovetail not quite matching the jaws (a bit wider than the jaws at the top) helps too since the jaws can't even touch the wood at the surface. Usually there are no marks since most of what I turn is not from soft wood and I tighten the jaws a little differently than many.

JKJ

John, do you do the intricate detail work on the bottom of your bowls after you turn out the inside? Or prior to removing the inside of the bowl? If after, what method do you use to hold the bowl to the chuck to do the detail work on the bottom? Thanks!

[John K Jordan]

John, do you do the intricate detail work on the bottom of your bowls after you turn out the inside? Or prior to removing the inside of the bowl? If after, what method do you use to hold the bowl to the chuck to do the detail work on the bottom? Thanks!

Randy, for these "squarish" dished platters and most bowls and platters I hold the blank in a screw chuck and turn the bottom and outside entirely including smoothing and applying finish, at least the first coat of my usual danish oil finish. Then reverse and hold by the recess to turn the top/inside.

BTW, after using negative rake scrapers for initial smoothing, for each side I take the piece off the lathe and mount the chuck on a carving/finishing stand to hand scrape, sand, and apply finish to that side.

carving_stand_B.jpg

I like the look of the detail in the bottom and the recess makes a sort of frame or shadowbox for anything I write on the bottom. Not having to reverse again to turn away the recess is quicker too and easier, especially with larger pieces and those difficult to hold other ways (Cole jaws, vacuum, jammed).

JKJ