Sharpening question

[Michael James]

I bought the "benjamin's best Ultimate hollowing tool system" prior to finding this rabbit hole. I tried to use it on some end grain and I probably would have done better with a slot head screwdriver. Dull does not describe the lack of edge this tool shipped with.
Sharpening instructions state 'just run a diamond sharpening plate or sharpening stone across the larger diameter of the blade."
So before I ruin a poteintially useful tool, Im guessing more that a couple of people here have used this or similar tools.
Do I remove the tip from the blade / handle and hone that way, or leave it on the handle and hope Im flat? I hollowgrind and hone, and sometimes deburr my scrapers so I "think" I know what they are trying to tell me. Anyone have any jig remedy they'd care to share? Supposedly they are HSS tips, so they should take an edge....
All help appreciated. Thank you!
mj
ps - Jeff N. has shipped out a beautiful walnut handled hollowing tool today, so Im not totally dependant on the above metioned rig.

[Tim Rinehart]

The bits on that tool are flat scrapers, so they should be sharpened, in my opinion, just like a scraper.

If the edge is extremely dull, I'd put it 'cutting edge down' on a grinding platform adjacent to my grinder, and put about a 15 degree grind on it, likely what is already there.

Rule of thumb is that soft woods like to have that burr on the cutting edge, facing up as you cut. The edge can also be burnished on...sometimes I use a small stone to just agravate the edge to create a burr if I don't feel like taking it off the tool and to the grinder. I've also used a hard drill bit shank to push against it, creating a burr/burnishing.

Harder woods get by with just a sharp edge.

Using a credit card hone or other diamond sharpener you can dress it up as well, and that will take away less material than the grinder.

Hope that helps....started rambling a bit there.:rolleyes:

[John Keeton]

I will add, too, that I have Jeff's hollowing tool, and I sharpen those cutters the same way as described by Tim - regardless of the type of wood. I think you will get a better surface with the burr on the top cutting edge.

[David E Keller]

I do what they do with HSS hollowing tips. I turn the bit upside down on the platform to ensure that the wheel drags a burr onto the top surface of the tool. I use about a 15 degree angle, but I don't think that's critical. I've not used a hone for those cutting tips, but if it keeps you from heading to the grinder, it's probably a good idea.

[John Hart]

Oh...I see. I just had to go look up that set of tools.
This is the basic same philosophy as my Sorby Hollowmaster....and the sharpening instructions are essentially the same as what you stated.

The idea is, you don't touch the cutter's bevel with a grinding stone, you simply hone the large surface on a flat sharpening stone...effectively reducing the thickness of the cutter...which take you to a sharp edge.

So...you unscrew the cutter and put it on the end of your finger and do figure-eights on a flat stone.....or use a piece of 3000+ emery paper on a piece of flat marble or tile...but it has to be perfectly flat.

Now..when it comes to endgrain.....forget about it. They work great on the facegrain though. Same story for the sorby that I have

[Tim Rinehart]

Oh...I see. I just had to go look up that set of tools.
This is the basic same philosophy as my Sorby Hollowmaster....and the sharpening instructions are essentially the same as what you stated.

The idea is, you don't touch the cutter's bevel with a grinding stone, you simply hone the large surface on a flat sharpening stone...effectively reducing the thickness of the cutter...which take you to a sharp edge.

So...you unscrew the cutter and put it on the end of your finger and do figure-eights on a flat stone.....or use a piece of 3000+ emery paper on a piece of flat marble or tile...but it has to be perfectly flat.

Now..when it comes to endgrain.....forget about it. They work great on the facegrain though. Same story for the sorby that I have

John,
I completely follow where you're going with that, vs putting the edge to the grindstone, but I've never done my Sorby Hollowmaster tools that way, of course...I still consider myself a newbie, so I may be doing it wrong.
My only question on that method is that it doesn't produce the burr, that is so helpful in peeling away softer hardwoods, vs sharp scraping.
If you use the diamond stone to hone the top surface, would you follow with burnishing the edge? That would make some sense.

I see the Hollowmaster instructions say exactly what you posed. http://www.robert-sorby.co.uk/pdf/hollowmaster-instructions.pdf

Interesting alternative I hadn't considered. I usually thought top honing was reserved for specifically profiled tools, ring tools, thread chasers, spiralers and so on.
Hmmm...thoughts to ponder.

[John Hart]

Oh...don't pull that "I'm just a newbie" stuff on me Tim!!! I know that you're good....and your opinion is valuable!!

I mean look at John Keeton...he's a newbie....He doesn't know anything....he's drunk most of the time...but when it comes to lawn mowing....you'd better listen to him!!!;)

Same sort of thing.:)

Anyway...where I got my instructions was from the Sorby thingie. Here's a url http://www.robert-sorby.co.uk/pdf/hollowmaster-instructions.pdf
and there's a picture at the bottom of the page.

Then..I couple that with some experience that I had honing the faces of spur gears on positive displacement fuel pumps for jets.

I know...that sounds unrelated....but maybe its the same. Maybe Keeton knows.:confused:

[John Hart]

Sorry...I meant to answer your burr question Tim...

I agree...I like to have a burr as well, but I remember when the cutter was new...it cut through everything like butter. And I would loosen it and rotate it....it would cut like butter.

It wasn't until I tried to sharpen it, that it didn't cut as nice.

I did sharpen the bevel once and got fairly good results....but the best results, was when I surrendered, and went and bought a new cutter!!:o

[John Keeton]

I mean look at John Keeton...he's a newbie....He doesn't know anything....he's drunk most of the time...but when it comes to lawn mowing....you'd better listen to him!!!;)Hey Hart, I represent that remark!!http://www.freefever.com/animatedgifs/animated/drunk8.gif

[Tim Rinehart]

John,
Ok, I didn't just start last week. Claiming newbie status just gives me a little latitude in being wrong at times. But relative to so many in SMC and the vortex...I'm pretty new with only a little over a year under my belt. I'll quit saying newbie after 2 yrs...how's that. But will never claim I know it all!

Now, that aside...I'm curious why after you sharpened that the tool didn't work as well. I fear for the repercussions from all to even suggest that your tool wasn't set face down on the grinder, to create the burr.

Did you simply do it the "Sorby way" that is shown in their instructions? And...I wonder if they left the factory in UK having a burr...but it was just really small. Just a thought.

[John Hart]

I remember it being super sharp(like a razor)...but I don't remember a burr. But that could just be my memory and lack of experience. I think my failure lay in the fact that I did not use a nice stone and the stone material rose up (like being plowed) and I ultimately dulled the edge.

Assuming that...I bet I could take a newer white stone that I have and improve the edge.

Another thing...may have been my technique....and perhaps the wood. At that time, I was turning a lot of walnut...and since walnut has a tendency to pull silicone into its fibers, the wood may have instantly dulled the edge....plus endgrain. Endgrain turning as well as endgrain sawing can get you as well.

[Wayne Spence]

I purchased a Sorby hollowmaster about 2 months ago and have yet to have it do anything but burn wood. Grinding the bevel or honing the flat surface makes no difference, still burnt wood. I have been turning about 3 years and woodworking for over 40. Is there any chance they make some of these cutters out of pressed paper?

[John Hart]

I purchased a Sorby hollowmaster about 2 months ago and have yet to have it do anything but burn wood. Grinding the bevel or honing the flat surface makes no difference, still burnt wood. I have been turning about 3 years and woodworking for over 40. Is there any chance they make some of these cutters out of pressed paper?

Yes Wayne...most of their cutters are made from cardboard....It's a little trick they play on their customers! :)

What I found is that type of cutter is only good for one kind of hollowing...and that is an endgrain bowl or hollowform. You have to complete the center bore straight through the endgrain to your desired depth, and then use the hollowmaster to attack the sides of that bore.

If you attempt a facegrain bowl or HF...then attacking the sides will have the cutter addressing endgrain 50% of the time...and it'll just burn.

[Tim Rinehart]

I purchased a Sorby hollowmaster about 2 months ago and have yet to have it do anything but burn wood. Grinding the bevel or honing the flat surface makes no difference, still burnt wood. I have been turning about 3 years and woodworking for over 40. Is there any chance they make some of these cutters out of pressed paper?

Wayne, the only problem I've ever had with these cutters, or any scraper cutter is when I don't bring it in to be at the centerline or a little higher. This provides ample room for the relief bevel to clear the wood going by it. Burning sounds like this bevel is riding...which it should not do.

I experimented once ...repeat ONCE...by making that grind much greater than the 15 degree approximate...and got an UGLY catch. I would think making sure the tool cutting edge is at the 9:00 position, perhaps 9:15...is sufficient to keep the bevel off the wood.

[John Hart]

Well, I did a little google searching and ended up at the Creek. Found this old thread http://www.sawmillcreek.org/showthread.php?t=29553

Not much has changed I fear.

Sorby and others are most likely tooled up to do ultra-precise grinding...something that we mere mortals can never replicate. So to get best performance, we rely on a burr for assistance.

Just a theory

[Jeff Nicol]

MJ, With any of the flat type cutters like the ones I sent you that are made of HSS or Carbon steel, the burr is a key to the cutting. If the cutter is a carbide cutter there will be no burr to speak of just a very sharp edge. It is easy to use a diamond card or hone of some sort to touch up the cutters. What Tim said about raising a burr with something that is harder than the cutter will work. But with these type cutters they work better if the cutter is turned down a bit to get the use of the burr or even just the sharp edge to do the cutting. The ground angle on the cutters is for relief and not to rub, which has already been mentioned. I sent one along that is round, one that is square with one edge that has a slight radius and one that is teardrop shaped. The small end of he teardrop will cut very fast and easy as the cutting portion is smaller, thus less resistance. You will have to play with each of the cutters from the HSS square and the adapters for the flat cutters to find the sweet spot for you. The drill cutter is by far my most used and using it a little bit above center or center and tip the cutting edge down and left to start. Once you get it cutting it can be rolled or moved left to right to use more or less of the swept back edge.

Maybe I will work on the grinding and using video of the drill cutter this weekend and get it posted, but with my Grandson coming on Saturday, I may not get much done in the shop!

Holler if you get stuck!

Jeff

[Thom Sturgill]

Maybe some other flatworkers with neander leaning would chip in. I have not sharpened my Sorby Hollowmaster tip yet, but the round cutter worked great for cleaning up the bottoms of flat-ish side grain bowls when I first started. I will admit that I haven't felt the need for it in a while.

I think flattening the top is sort of like polishing the back of a plane blade. A *sharp* edge the the meeting of two flat planes or a flat plane intersecting a spherical surface. If you dub the edge with a soft stone, you do not have a flat plane, thus no true edge = dull cutter. Use a fine diamond card. A grinder burr is more like cutting with a serrated knife in comparison, and taking a normal grinder wheel to the bevel would be the same even if you did get the top polished.

From my experience with PSI, I would not expect their tool to be quite as well sharpened, but would expect it to take an edge if sharpened with care.

[Allen Neighbors]

A scraper is a scraper, is a scraper... that's true.
But, a scraper can cut hard and soft wood like butter, if it's held on the bevel and then rotated to the correct angle against the passing wood surface.
I've made several cutters from some jointer blades a friend gave me. They will scrape, and they will cut. Like I said, it depends on the angle of the dangle. I sharpen all of mine with the cutting edge up... just because that's the way I learned to do it... about a 15-18 degree cutting edge. It's the same angle of edge that I use on my Oland Tool HSS cutters. (Because I'm too lazy to change the angle of the grinder platform.) :)
Do you think the edge would last longer if I turned the cutting edge down when I sharpen? I may have to give that a try.

[David E Keller]

A scraper is a scraper, is a scraper... that's true.
But, a scraper can cut hard and soft wood like butter, if it's held on the bevel and then rotated to the correct angle against the passing wood surface.
I've made several cutters from some jointer blades a friend gave me. They will scrape, and they will cut. Like I said, it depends on the angle of the dangle. I sharpen all of mine with the cutting edge up... just because that's the way I learned to do it... about a 15-18 degree cutting edge. It's the same angle of edge that I use on my Oland Tool HSS cutters. (Because I'm too lazy to change the angle of the grinder platform.) :)
Do you think the edge would last longer if I turned the cutting edge down when I sharpen? I may have to give that a try.

I don't know if it last longer, but the burr I get upside down seems to cut better for me than when I used to do it the other way... YMMV. I think Jimmy Clewes is the one I heard this from first, but I could be wrong.

[Richard Madison]

Interesting thread. Will try sharpening a couple of my 3/16" HSS tool bits "upside down" and try to judge if the edge lasts longer.

[David DeCristoforo]

I'd like to offer a slightly different perspective. If you were to post on any of the other forums (Neander, General,etc.) the idea that you could go directly to wood from a 120 grit stone... well, I can only imagine the scoffing one would hear. The idea that you should not hone the bevel of a cutter or bit strikes me as being a bit ridiculous. I find tools and cutters that come off my 120 grit stone to be vastly improved by honing. A sharper tool cuts better regardless of what the tool is used for. A lathe chisel will benefit from a "proper" sharpening just as much as a bench chisel. Furthermore, I consider the cutting bits and tips typical of hollowing tools to be "expendable" and I reshape them as needed without much thought. For this reason, I prefer HSS over carbide. Carbide is much more difficult to shape and even though it will hold it's edge longer than HSS, it will not take nearly as keen an edge.