Bowl From a Board Burning Blues

[Steven Borruso]

Greetings all ,

Getting back into turning after a several decade hiatus. Have progressed lately from twig pots, to segmented, to hollow forms, to hybrid resin, and recently onto Bowl From a Board.

The result of my first attempt (16" diam bowl) turned out OK but getting there was rather frustrating due to massive burning issues when parting off the rings (except the first ring).

I built a tool rest jig to steady the 1/16" Sorby parting tool along with later "sinking" the whole tool into a larger DIY handle. The first ring (at 45 deg. angle) parted off fine. The remaining rings
were a nightmare of burning wood (almost gave up several times). Tried varying lathe speeds, tool rest height, attack angle (45, 50, 55), flipping the tool, all to no avail.
The wood used is cherry, bloodwood, oak and walnut (all dry).

Any advice and/or suggestions (other than scrapping this idea for a bandsaw solution ;-) is most appreciated.

Here's a "project progress" link showing filmstrip of all pics from along the way - Burned Bowl From a Board

Thanks !
Steve

 

[Michael Anderson]

I have yet to do a BFB, but it’s on my list. @Alan Miotke Al gave a really nice demo in Portland on his process. Great visuals—he might be willing to share the presentation file (I also think it’s located on the SWT site, but could be wrong - consider joining if you’re not already a member).

That said, considering your problem, I imagine the burning came about because of two reasons.

1) How often did you sharpen your parting tool? 1:16” doesn’t hold its edge for very long, especially with dry and dense hardwoods (mainly looking at you, Bloodwood).

2) You may be pressing too hard on the wood, especially the smaller rings. Like with gouge, the closer you move to center, the lighter your touch should be.

Aside from these, it may be helpful to use a diamond parting tool for this. The compromise is a wider kerf, but it can be quite helpful for reducing friction (especially when approaching sidegrain).

 

[hockenbery]

Greetings all ,

Getting back into turning after a several decade hiatus. Have progressed lately from twig pots, to segmented, to hollow forms, to hybrid resin, and recently onto Bowl From a Board.

The result of my first attempt (16" diam bowl) turned out OK but getting there was rather frustrating due to massive burning issues when parting off the rings (except the first ring).

I built a tool rest jig to steady the 1/16" Sorby parting tool along with later "sinking" the whole tool into a larger DIY handle. The first ring (at 45 deg. angle) parted off fine. The remaining rings
were a nightmare of burning wood (almost gave up several times). Tried varying lathe speeds, tool rest height, attack angle (45, 50, 55), flipping the tool, all to no avail.
The wood used is cherry, bloodwood, oak and walnut (all dry).

Any advice and/or suggestions (other than scrapping this idea for a bandsaw solution ;-) is most appreciated.

Here's a "project progress" link showing filmstrip of all pics from along the way - Burned Bowl From a Board

Thanks !
Steve

Sharpening between rings will help. Beeswax on the side of the tool will help.
Using a different tool or wider kerf will solve the problem.

That parting tool is going to rub on the smaller diameter rings unless you cut a wider kerf which you don’t want to do because it reduces the overlap. The binding of the tool is causing the burning. You will get the least binding with the tool above center by 1/2 its height.


If you have a diamond parting tool it will produce much less friction. They are generally less tall. And the wide part at the center line is the only part rubbing on most rings. You still can get a little binding on the smaller rings. A 1/16 extra clearance cut may do it there.
I have a tiny ancient sears parting tool that is about a 1/2” tall. I grind it at an angle so that the right side leads. It’s great for cuttin smaller rings.

 

[Richard Findley]

Hi,

That parting tool ought to be ok but it needs to be sharp. The other thing I’d recommend is giving it a little wiggle as you cut, your jig will probably prevent that, but a wiggle will slightly open the kerf and release any binding. I usually use an 1/8” diamond parting tool freehand and have never had burning. Looking at your finished bowl, you do need to work on your sharpening as those marks in the bowl’s end grain are from a blunt tool used with a lot of pressure. Try not to bully the work, it needs more finesse than that.

I hope that helps

Richard

 

[Brian Gustin]

Agree with Richard, looks like your parting tool is dull, for one thing, you're pushing it in too hard - it should be sharp enough that just touching it to wood it'll peel a whisper thin shaving - I find with mine , I need to resharpen or touch them up about every half inch or so of depth (I need better quality tool steel!) Also I made my own 1/16 parting tool out of an old machine shop hacksaw blade - it is just carbon steel, not HSS so I often have to sharpen that too. I also will swage it a bit before sharpening (This involves a little precision hammering to "squish" the tip wider than the blade - Swaging is one of the ways they'd "set" massive sawmill saw blades way back when) It creates the kerf for the blade to run in , then I resharpen , and it doesn't get stuck.

I want to get a diamond parting tool myself, but can't really justify the cost of a quality tool when my current tooling does fine, if I sharpen often (and considering how little I really use them, I don't mind the extra time spent sharpening) But as mentioned, you're binding the tool, pushing too hard, and IMHO it needs sharpening which might help with the first two issues.

 

[Tom Gall]

You can try using a "cutoff" blade available from industrial supply companies. You would have to come up with a way to mount in a handle or buy a holder used with a machine lathe. I checked some companies just now and can't believe the prices.
You might try Ron Brown's new parting tool (P-type blade) with or without a handle. I might even buy one to replace my old homemade version. He also has his own "BfaB" jig in case you might be interested.

Parting Tools

Parting Tools

longworthchuck.com

 

[John K Jordan]

...my first attempt (16" diam bowl) turned out OK but getting there was rather frustrating due to massive burning issues when parting off the rings

Sounds like you need more clearance, some how.

I also prefer "diamond" parting tools, but I sharpen them differently than I've ever seen. And, as said, sharp, sharp sharp! Even parting tools should be ground and honed until they are shaving-sharp.

Another great type of parting tool (I don't remember the name of the one I have) is trapezoidal in cross section, i.e., the width at the top is the widest place in the cross section of the tool. Those I have look a bit like the one you are using but are made with a shallow flute ground all the way down the top edge of the tool. These cut very well and don't put friction on the sides of a straight cut, but those I have are fairly tall and might have trouble making the radius of the ring sections. If not afraid to modify one, most of the steel below the wide top could be ground away for a enough distance from the tip to cut through the board at the angle you use; you would lose a bit of stiffness but not much.

Also, if you have extra diamond parting tools and don't mind grinding one into a special shape, you can slim the tool behind the cutting edge for clearance. I keep a box of old cheap or free tools that I often grind to modify into special shapes as needed.

Also, since you are alternating the woods and don't have to keep the figure as close as possible to match, seems like you could simply cut wider grooves - cut a little depth then move over a bit and cut again, repeat. Might result in a slightly smaller diameter bowl if your board size is limited.

JKJ

 

[Richard Coers]

Hopefully this won't come across like I know what I'm talking about, I don't want to upset anyone.
You need more side clearance on your cutter. Your steel blade is too tall and is rubbing hard on the side of the kerf. Here is how a Ring Master cutter is ground.

View: https://www.youtube.com/watch?v=hCjW77xznXY&t=58s

 

[Bob Sheppard]

You can try using a "cutoff" blade available from industrial supply companies. You would have to come up with a way to mount in a handle or buy a holder used with a machine lathe. I checked some companies just now and can't believe the prices.
You might try Ron Brown's new parting tool (P-type blade) with or without a handle. I might even buy one to replace my old homemade version. He also has his own "BfaB" jig in case you might be interested.

Parting Tools

Parting Tools

longworthchuck.com

Tom- I see that Ron has a buy one, get 2nd one 25% off on his parting tool. I'd be happy to in on that with you.

 

[Doug Rasmussen]

As Richard say's you don't have enough clearance on the blade's sides. You should be able to see where it's rubbing and burning.

If you can't see where it's rubbing mark the blade on the sides with a felt tip marker. Do a cut, where the marker is worn off grind some relief.