hollow form tool question

[Terry Achey]

I'm attempting to turn my first hollow form piece (turning a piece of walnut) with a Sorby Hollow Master. The tip seems to dull rather quickly which means allot of downtime removing the tip and grinding a new edge and then reinstalling the tip. Seems cumbersome as compared to sharpening gouges, etc.

Questions:

Is it normal to dull with only a few moments of turning?
For those with Sorby HM experience, is there a better hollowing tool that does the job better and is more user-friendly in terms of keeping it sharpened?
Any other general advice for hollowing tool tips?
I enjoyed my first hollow form rough out and look forward to finishing it. But I must say that I quickly gained an even higher level of appreciation for the stunning hollow form work that many of you post on the site. ;)

Regards,
Terry

[Steve Schlumpf]

Terry - it really all depends on the wood! I also use HSS cutting tips and if you look at the tip carefully just after grinding - you will see that there is a real fine burr on the top leading edge of the bit. That is what does all the cutting for you. Not much there - so the dryer and harder the wood - the faster that little burr wears off.

I usually only go to the grinder once per hollow form to create the edge. After that, whenever it gets dull, I touch it up with a diamond sharpener and form a new burr - usually a better burr than I get from the grinder!

Better hollowing tools? Lots & lots of them out there! Newest thing to use is carbide tips. Work great but no way to create a burr once the carbide is worn - so you have to buy a new cutter.

Hollowing is an exercise in patience! You have to take small cuts, stop the lathe and remove all the shavings, sharpen the cutter, etc. But when you finish you have created something that no one else has! Pretty cool and extremely addicting! Have fun with it! Looking forward to seeing some of your work!

[Scott Conners]

I agree with Steve - get a medium or coarse diamond card and use it by stroking it upward against the bevel to raise a fresh burr. With a bit of practice you should be able to touch up an edge in just a few seconds, and only have to grind every once in a while.

[Jeff Nicol]

Terry, Hollowing is a test of patience and stamina! The only thing I can add that is sometimes just a small difference in where the tool is cutting compared to center can help, I set the rest a little above center so the cutter is tipped down a bit use just the burr. Also which direction you cut can have a great difference in the performance of the tool. You will notice that different sections cut better bringing the tool from the inside bottom out towards the neck and some from the opening in and around the to the change towards the bottom. Doing this lets the cutter shear/scrape more efficiently with less pressure thus saving the burr a little longer.

It is a skill that will grow with practice! Keep at it an you will become better!

Hope we came up with some good answers!

Jeff

[Steve Schlumpf]

Terry - I forgot that I had already posted some photos on how to use a diamond sharpener to put a burr on the cutting tip.

Check this out: http://www.sawmillcreek.org/showthread.php?p=997926#post997926

Hope that helps!

[Bill Mitchel]

Sure helps me, Thanks Steve. So when a burr is created on the grinder even though the wheel is spinning downward an "up ward" burr is made? Is that correct? Sorry I don't mean to hijack this but thought it might help others. I'm not the only one am I :eek:

Thanks
Bill

[Steve Schlumpf]

Bill - you are correct! Difference between the burr from the grinder and the one from the diamond hone - the hone can provide a slightly larger burr which will last a little longer. Plus, it is a heck of a lot easier and takes less time to just hit the cutter with the sharpener than to remove, grind and replace. Hope that makes sense!?

Another thing about the burr - the grinder gives a burr on everything you sharpen. That's why a lot of folks like to hit their gouge with a hone - just to remove the burr and provide a sharper edge. Personally - I just go straight from the grinder to the lathe.

[Burt Alcantara]

Steve,
I had no idea about honing the tip! I've got to try that on my current project. I'm turning a piece of very dense and very dry elm heartwood. I began hollowing with the Monster but gave up and switched to a Trent Bosch straight boring bar. Was able to get aggressive and get a lot of wood out. Once I get a decent amount out I'll go back to the Monster.

The Monster sure makes a big difference. Hollowing with a straight bar wears out my arms quickly. Guess that's what comes with being an old skinny guy.

Thanks for that great tip!!!
Burt

[Reed Gray]

Steve,
I think I may have to disagree with you about the burr from the grinder. It seems to me to be much more heavy duty than the one I get from my diamond hones. Part of which would be that my grinder is 80 grit, and the rough diamone hone is 220 grit, and yes, even though the wheel is moving down, you get a burr on the top surface. On my bowl scrapers, this is especially true. The diamond hone makes a great finish cut burr, and the grinder makes the roughing cut burr. The AAW just did an article about this in their last issue about what type of sharpening gives the cleanest cuts, and the one where you honed the top of the scraper first, then honed the face of it gave the finest finish. For my 'utility' burr, I hone the top of the scraper first to remove the old burr, then grind the face to create the new burr. I do push the scraper into my grinding wheel rather than just kiss the surface. I also do not use the standard grinding wheels, I use CBN (cubic boric nitride, an extremly hard material made for grinding steel) which gives a slightly smoother grind than a comparable grit grinding wheel.
robo hippy

[Steve Schlumpf]

Reed - never thought about other folks using different grit wheels! I use a 120 and a 150 grit wheel and just barely kiss the wheel when sharpening. The diamond sharpener I use is 'course' grit and I am not real sure what that actually measures out to be - but it does give me a better burr than my grinder. Course, I do apply some pressure when using the diamond and that makes a huge difference. Thanks for giving another point of view on burrs!

[Bernie Weishapl]

Steve said it and I agree. If you are doing dry wood you will need to sharpen more often. Green wood I only go to the sharpener twice. Once in the middle of turning and then once for the finial cuts. I and most of the others turn green wood start to finish on HF's.

[Mark Burge]

Terry, thanks for starting this thread. I have just gotten a Sorby hollowing tool (from E-bay) and have been trying to figure out how to use and sharpen it too. Mine is not the hollow master, but one of the ones that has the tip set on top of a flat of the steel bar. The directions that came from Sorby say that sharpening should be done by honing across the top of the cutter. I tried that and it seemed to work-sort of. But I kept thinking that this is removing any burr that might have been there. I thought about using the carbide burr roller(burnisher! that's it - thanks Reed) from my cabinet scrapers. What do you all do?

- Mark

[Reed Gray]

Steve, on reading your reply, my first thought was some thing along the line of "if he gets a bigger stronger burr with his diamond hone than he does with his grinder wheels, maybe he is some one that I shouldn't arm wrestle with, and Bill Grumbine isn't much bigger then I am". The grinding wheel grit on the AAW tests was 60 which is very coarse for my taste. Sounds like I have to experiment some more. 99% of my testing of edges is on bowls and bowl scrapers, not on the hollow form scrapers, even though they are pretty much the same steel. I do have a couple of Doug Thompson's scrapers, and they do hold the edge better than the HSS. Have you ever tried the burnished burr on your scrapers? I don't know if you could get much of one on a smaller hollowing bit.
robo hippy

[Steve Schlumpf]

Reed - on the scrapers I just go straight from the grinder to the turning. Never tried honing it as the burr from the grinder seems to work quite well. I usually only use the scraper for a few quick passes on the bottom of a bowl and I am done with it. Hollowing bits you have use with for quite awhile and - for me - it saves a lot of time to just hit them with the diamond sharpener.

[Terry Achey]

Thanks to all for the advice. Steve, your link was helpful, and as usual nicely done. The walnut I was cutting was closer to dry than green. I soaked in DNA after roughing out and now have it on the drying rack. Just so happens that I recently bought some small diamond hones. I'll try your suggestions next round!

BTW - do you follow the same rule of thumb for rough wall thickness with your hollow forms as you do bowls?

Thanks again to everyone for being so helpful.

Terry

[Steve Schlumpf]

BTW - do you follow the same rule of thumb for rough wall thickness with your hollow forms as you do bowls?

Terry, I try to keep everything real close to 10%. If anything, it pays to leave things a little thick. May take slightly longer to dry but it sure is better than running out of wood when you are trying to finish up a turning! DAMHIKT

Don't be afraid to experiment a little with your sharpening. You'll find a method that will work great for you! When you do - make sure you share it as there are a lot of folks with the same questions. Have fun!

[Randy Hoch]

I appreciate this thread too. Sometimes amazes me what gets overlooked, even with my turning library growing as it is. Thanks Steve and Reed, and Terry for the original post!
BTW Steve, I can actually see the burr in your photos! You rock!

Randy

[Jeff Nicol]

Well here is something else to try and think about. Just like the cabinet scrapers used on flat work the angle of the bur will produce the fine cuts. Here is a link to a burnisher that Packard tools selld by "VERITAS" . This is they way to get the finest consistent bur. You can do the same thing with a round hardended tool shank of a chisel etc. to do the same thing. So just more to think about and try!

http://www.packardwoodworks.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=141403&Category_Code

Jeff