HF Hollowing Tool Question

[Greg Bender]

I just started a vase using my homemade hollowing tools that use various shaped cutters.My question is about the cutter tips.Is there a different way to sharpen the cutting edge so as to take some of the aggressiveness out of them.I have a few sorby type cutters and they are sharpened like a typical scraper and when very sharp are a bear to use blindly.Is there maybe a double bevel that will work.Pictures of the recommended options willl be really appreciated.
Greg

[Dave Mueller]

Greg,
If you are talking about a "teardrop" shaped scraper, make sure to remove the burr on top. Also, try turning the scraper down to about a 7 o'clock angle rather than horizontal at 9 o'clock. You could also grind a short bevel on the top cutting edge of the scraper which would make it less aggressive. I assume that you are not using the scraper to hollow, only to finish?
Dave

[Mark Levitski]

I suspect that Greg is talking about the 3/16" cutters w/ a scraper grind, not the larger finishing teardrop scrapers. Inform us, Greg.

This type of tiny scraper cutter is widely used for hollowing and is not that hard to learn to control, but it takes some practice. Patience, Greg--if I could learn it, anyone can :). A light touch will help a lot, as well as some techniques for knowing where you are within the form (leave a more protruding step to feel as a reference point to mark your current work area within the form). Presenting the cutter at a slightly downward angle, i.e., less aggressive, as you first contact the wood will help too. With time you will be able to hog out a lot of wood without a catch, and then finesse a more finished cut. A double bevel will not help because you do not ride bevels w/ scrapers.

I guess you could try honing the top face of the scraper as it meets the bevel to remove the burr and make it less aggressive, at least until you get a better feel for it. Similar to Dave's suggestion.

[Richard Madison]

Another little tip for 3/16" tool bits is to grind about 1/4" of the end down to 1/8" wide, and then shape/grind the end like a round nose scraper. Takes a narrower bite so is easier to control.

[Ryan Baker]

Yeah, if you are talking about teardrop type scrapers, make sure they aren't too big. The more surface you have in contact with the piece, the more it will grab. A 3/16" cutter will be much less grabby, but won't leave as smooth a surface.

Honing the burr off the top of the scraper will make it less aggressive too. Grinding a slight top bevel too makes it what is known as a negative-rake scraper -- which is generally considered less aggressive, but will dull very quickly. Search on negative rake scrapers to find more.

Make sure that you have the handle slightly higher than the cutting end of the tool (with all scrapers). The cutter should be at or slightly above center. Angling slightly downward (say 8:30-8:45 instead of 9:00 position -- 7:00 is way too low) may help slightly.

You didn't mention the tool you are using. If it is a swan-neck type tool, be sure your tool support is behind the bend (on the straight part of the shaft). Otherwise, you will get a lot of counterclockwise torque.

The most important thing is to be gentle. Don't try to cut too fast. Hollow forms take time and patience. Practice, practice, practice.

[Greg Bender]

Guys,
to be honest with you,I had not even tryed the tear drop cutter because it seemed like it would take too big of a cut to control.As far as position I've got that right.I've been turning everything else for quite a while but decided to try a HF/ vase and made my own tools,mostly straight shaft types,3/8 , 1/2 , and 5/8" shafts to get my feet wet.They are all round,no flats at any position so I could position the cutter at any position that worked best.I've made tips of all sizes from 1/8" up to approximately 1/2".Even made some easy rougher types with carbide inserts.I just seemed to remember that I had heard at a seminar the demo person,a woman turner ,recommend cutting a secondary bevel on the upper third of the cutting face of a scraper type tool and it would be more forgiving.Realistically,I am trying to reach over the tool rest about 6+ inches so I might be pushing my luck anyway.Thanx and keep the great info coming.
Greg

[Mark Hubl]

Greg,

What type of cutters have you made? 3/16 round stock, 3/16 or 1/4 square stock or tear drops? Would help to know. I grind my cutters (all) at 10 degrees. You can go a little more which will give a sharper bevel, but they will dull quicker. I think less than 10 is to steep to get enough bevel. For the narrower cutters at or slightly above center works for me. If they are being too aggressive you can tip them down a bit. Practice, each piece will tell you what it wants.

If you have made and are trying to work with larger tear drops, like Sorby stuff, then you are a better man than I. I only use the large cutters for finish shear scraping. The small Sorby tear drop shape has bad voodoo for me.

And as many turners will say the answer to the question is "sharpen the tool". I am always amazed at my laziness when it comes to spending 15 - 30 seconds at the grinder or with the diamond hone. I wish there was some one in the shop to hit me in the back of the head.

Some pics of what you got would help, the the fella's can hone in on helping out.

[Ryan Baker]

Was the demonstrator Cindy Drozda by any chance?

The negative rake shape shouldn't really be necessary, but it should be less grabby if you want to experiment with it. Don't hang the cutter any farther out (to the side of the shaft) than necessary, since that creates more lever arm.

Are you cutting side grain or end grain? If you adjust the direction of your cuts to cut side grain instead of end grain, that will help too.

If you grind the bevel more than 10-15 degrees from square it will get aggressive too. I grind mine pretty close to 10 degrees (80 degree included angle).

[Mark Hubl]

Greg,

I must have been typing when you posted. For me, with that size shaft and a standard handle, I would be near the end of my comfort zone. I use a DP with a forearm rest for stability at that distance. Need to keep the bevel horizontal, a couple of tricks for me. I mark the top of the tool to help me keep the tool in the proper position. On taller or more difficult pieces I will also put some blue painters tape and mark it with lines to let me know where I am at. Small, gentle, cuts in small sections. Not really like cutting a long flowing cut in a bowl. Depending on the size work in quarters or thirds.

On this type of tooling I haven't seen too many fancy multi bevel angles. DP, Ellsworth, Jordon all pretty much make a nice consistent bevel. Need enough, but not too much.

[Greg Bender]

Mark and Ryan,
Yes it was Cindy Drozda matter of fact.The cutters that I have made are alot like keystocks with various tip profiles.Small radii to square ends to small tips with gentle radii.I recently got some cheap adhesive tape measures and apllied them to my longer tool shafts so as to reference where I'm at in depth.I'm cutting end grain and tilting the tool face and cutting side grain also.I even tryed reversing my 16/42 and cutting on the back side.I finished making a tool rest from 6 inches of 1.5" wide flat stock to reach in to the vase.I'm in the process of mounting some LED's on the bottom side for illumination.Now all I need is a minature camera and I will be able to hollow from the recliner.As far as sharpening,I hone my cutters on a worksharp with some homemade jigs so no burr and very sharp.Appreciate the help.
Thanx,Greg

[Ryan Baker]

Let us know when you perfect that hollowing-from-the-recliner thing. You'll have lots of customers here for it. :)