Sorby Hollowing Tool Cutter - should it be ground with undercut?

[Mark Greenbaum]

I have been acquiring different hollowing tools for urns and HF's. I recently bought a slightly used Sorby Swan Neck Tool, and the cutter appears to have been ground to a very shallow undercut, almost like a scraper with the bur on the top surface. I tried it yesterday, and even at dead center the cutting is not happening. I will post photos of it later when I get home. I am not sure if the previous owner custom made this cutter, because I don't find anything like it online. All of my previous cutters and ones used at JCC Folk School had a pretty good undercut, similar to a bowl gouge.

[Reed Gray]

The hollowing tips are pretty much all scrapers, so common bevel angles are between 60 and 70 degrees. They do work better with a burr. Generally fresh burr off of the grinder, or hone and burnish.

robo hippy

[Mark Greenbaum]

Thanks, Reed. That's about what I thought, but this has maybe 1 degree undercut, and it's like a flat wall going into the inside bore. I'll post pics if I can ever get my new phone to sync with this laptop.

[Mark Greenbaum]

I just re-ground the cutter to have about a 50 degree bevel, and with a bur on top. The tool now works, but man it gets scary because the center is not in line with the shaft, and has a tendency to grab and rock over.
381204Whole Tool
381199Cutter viewed from top

381201Cutter end viewed from bottom
381202Close-up of cutter from bottom (notice no draft angle on edge).

This is 3/4" diameter shaft into the handle - are Sorby tools glued into the handle? If I heat the shaft with a heat gun, can I melt the glue enough to free the tool from the handle? Then I could make an adapter for my DIY Articulated Hollowing Rig, and feel less stress. Thanks ahead of time.

[Jeffrey J Smith]

Mark - I’ve got that Sorby hollowing tool - and use it very rarely, usually to clean up the surface after hollowing. It needsto be used with the straight part of the shaft on the tool rest, if you’re on the curved end of the swan neck, it’ll want to catch and turn out of the cut. It is a scraper, so I sharpen with about a 70degree bevel, and take only very light cuts. It does work well to clean up tool marks, but since going to a Hunter cutter on my captured hollowing system, tool marks are pretty much a thing of the past.

[Mark Greenbaum]

Thanks, Jeffrey for the advise. I looked at the Hunter Osprey #1 for my rig at the TAW Symposium, but even $65 was too much at the time. I will probably go to that tool soon.

[John K Jordan]

I just re-ground the cutter to have about a 50 degree bevel, and with a bur on top. The tool now works, but man it gets scary because the center is not in line with the shaft, and has a tendency to grab and rock over.
...
This is 3/4" diameter shaft into the handle - are Sorby tools glued into the handle? If I heat the shaft with a heat gun, can I melt the glue enough to free the tool from the handle? Then I could make an adapter for my DIY Articulated Hollowing Rig, and feel less stress. Thanks ahead of time.


I have three similar tools, the large straight, large swan-necked, and one small version. The hollowing cutters that came with mine are small rods (about 1/4" diameter, flattened on one side), one with a rounded tip and the other with a more pointed tip. I actually use the tool more as a smoothing scraper on the inside with the teardrop shape.

Is this the cutter you showed? http://www.rockler.com/bullet-cutter-with-1-2-blade-for-rapid-stock-removal-rs232c
If so, it looks like it's supposed to be used in the straight shaft version of the tool (RS200KT) which would avoid the off-center instability. It's hard to tell from Sorby's photos, but it looks like the similar cutter that comes with the swan neck tool (851C) is a different shape than the one you show. Could you drill another hole in the cutter and move it back a little? Or it would be pretty easy to make a straight shaft version of the tool. As Jeffrey mentioned, when using the swan neck tool you do have to make sure the tool rest is far enough back to be on the straight part of the shaft but I suspect you are already doing that.

You can remove nearly any tool that has been epoxied into a handle by heating it to soften the glue then twisting. I use a propane torch and heat close to the handle. (Mike Hunter said he does the same.) I suspect a heat gun would not get hot enough. I've done this with several tools that came handled so I can use them in my own adapters. I don't know if the Sorby is glued - you might try twisting without heat first.

JKJ

[Mark Greenbaum]

John:

The cutter is similar to the Rockler, but has a slot to the side from the hole. It appears to be a modified cutter either from HSS stock or made from one such as you linked to. The cutter has very little relief (or no relief) from the top side. I re-sharpened it to about a 50 degree bevel, and it works, sort of, but I am trying to make an urn (more like a shallow spitoon) that has about 8" diameter at the belly, and a total 7" tall, through a 1.25" diameter Forstner bit bored hole. I purchased this tool at a club meeting last week, with hopes it would help me to get to the undersides of hollowform. I am probably pushing the limits of both the tool and my skillset, with a piece of at best, questionable spalted silver maple firewood. I will try to post pics tonight when I get home.

[Mike Nathal]

The tool should be quite stable given the small amount that the cutter sticks out past the line of the shaft. It should not cause the tool to "torque over" I have used this tool for smoothing and it works well. You should have no trouble with a hollow form of the dimensions you mentioned. I too wonder if you have the straight part of the tool on the tool rest. Also it is possible that when you are deep into the piece, you might fall below center if you are tilting the shaft rather than having it horizontal.

[Mark Greenbaum]

I made sure I was on the straight part of the shaft, toolrest (bottom of the flat of the half-round shaft) level with center of the piece, and handle flat. Maybe I am trying to be too aggressive with waste removal? I was scared enough to turn off the lathe and go get dinner. I packed the bore with fresh shavings to keep the moisture content stable until next session, tonight.

[Bruce Schoenleber]

381234381235

This tool? The straight cutter is 70 deg.

[Mark Greenbaum]

381234381235

This tool? The straight cutter is 70 deg.

I've made cutters like that for my other hollowing tools, from old metal lathe too bits. I was trying to use what I had bout, but perhaps that's not a good path.

[Reed Gray]

I would consider that type of cutter to be for fine finish cuts rather than for any kind of roughing.The smaller bits on the bottom would be more for roughing. For beginning hollow forms do a 'closed' form rather than a vase. Closed form would have opening smaller than the vessel itself, more in the shape of a wine glass. Much easier to see inside of and see what you are doing. A vase form with a smaller neck is much more difficult, at least till you practice a number of times.

robo hippy

[Mark Greenbaum]

I have done several deep urns, I took a class at JC Campbell Folkschool 3 years ago for deep hollowing, and I've completed a few since then.
381259 381258 both of these are ambrosia maple about 12" tall x 7" diameter.

But I am trying to get this one together as a challenge to stretch my skills (without breaking them, or myself, or my tools & lathe). I may have to make some tooling adjustments for my DIY Articulated Hollowing System to make this particular form less stressful, though.

[Kyle Iwamoto]

Personally, I use the small cutter that Bruce showed for roughing and your style cutter for finishing also. IF I hand hollow. That being said, if you're doing those deeper vessels, I'd invest in a captured or articulated rig. And that is another whole can of discussion.......

[Mark Greenbaum]

Personally, I use the small cutter that Bruce showed for roughing and your style cutter for finishing also. IF I hand hollow. That being said, if you're doing those deeper vessels, I'd invest in a captured or articulated rig. And that is another whole can of discussion.......

I have a thread over in the Green Monster Group: https://sawmillcreek.org/showthread.php?256651-DIY-Hollowing-System-Articulated-Arms-on-a-mast; that shows my homemade articulated arm hollowing rig. It works, just needs some refinements.

[Mark Greenbaum]

Here's the vessel in the rough. I managed to get it semi-finished and lacquered tonight.
381308

[Brice Rogers]

Mark, I have a homemade clone of a Hercules. I find that if I accidentally try to cut at the 9 o'clock position (the side), that I get some twisting torque. But, if I position the tool so that I am cutting more at the tip (maybe 10:30 to 12 o'clock), there is not any twisting.

The tip that you were using looks fairly large. If you narrow the cutting surface, it will have less torque. Just a thought....