Hollowing tool question and a nod to Odie

[odie]

After the Tom Wiesring article I started using 600 grit and really got it sharp.

600gt is the finest grit I'm aware of for grinding wheels. We must consider the practicality of grinding wheels with very fine grits. For one, they will be very slow to remove metal, when doing the entire bevel of a gouge. The only practical solution to this, would be two wheels, one of a fine, and one with a coarse grit.....the fine grit table set to a slightly different degree. ......Then, there is the consideration that a 600gt wheel will not be as sharp as would be 600gt honing by hand.....because of the single direction vs multiple directions consideration.

For me, I've been honing for so long, that it's second nature, and very quick. I can be back at the lathe in 30 seconds, or so.....and the edge will be starter fresh. To my way of seeing this, those who rejoice in the advantages of the exotic steels are not seeing this from another very important perspective. The edge will begin dulling immediately, no matter what the steel......and, if the edge dulls slower (which is the entire philosophy of buying the exotic steels in the first place) it becomes more difficult to make the decision of just when to sharpen.....or, keep turning. The whole reason we want a sharp tool, is to get a cleaner cut, a cut without tear-out (therefore eliminating the aggressive sanding requirements).....and, a 100% sharp tool is more capable of achieving that, than an 90% sharp tool. As the wood spins, we can't tell how well the cut is proceeding when we use our senses to "feel" the difference between 100% and 90% sharp.....but, we sure can tell the difference between 100% and 75% sharp. When I turn a bowl with the industry standard M2 steel, I may re-hone a dozen times and re-grind once, and to me, it seems like a great trade-off to maintain sharpness that ultimately produces a cut that requires less sanding. You just don't want to create tear-out, requiring you to re-do the surface, or sand the hell out of it!.....when you could have produced a better surface in the first place!

-----odie-----

 

[Neil S]

@Bill Blasic: HSS is a generic name used for steel that cuts steel. Crucible Particle Metal (CPM) and Powdered Metal (PM) are a process not a type of steel. HSS can be made with the PM or CPM process. Cryo (cryogenic) is a process used to temper HSS it is not another kind of steel.

A good summary there Timothy on those terms.

I have and use all of the commonly used turning steels and in my limited experience (somewhere north of 1,000 pieces, but I stopped counting a long time ago) a well made M2 will perform very well and is good value for the money.

I sharpen my gouges in batches, about a dozen at a time, and use them all until they are no longer cutting to my satisfaction, then resharpen them all again. Used in that way, one after the other, I get to know how they compare and IME there isn't much difference between them. I know that others have found otherwise.

On the steels, I have found that M42 takes the keenest edge (off #360 CBN) and V15 is the most durable but never gets as sharp. V10 is a good all round workhorse and a well made M2 is worth its place in the tool rack.

I will post separately on 'sharpness', which is another and more complex topic.

 

[Neil S]

I will post separately on 'sharpness', which is another and more complex topic.

Sharpening is a complex topic. Learned articles and whole books have been written on the topic and nothing gets experienced turners hopping onto boxes to extol the merits of their particular method than this topic

Of course, it is always useful to glean information from those who are more experienced than yourself. I don’t have a particular ‘axe to grind’ on the topic, so to speak, other than to say to new turners that your own experimentation and observations will get you to a method that will work best for you. Following are some notes that new turners might find useful.

• Sharper is not necessarily better. Sharpening is a tradeoff between the time it takes to get an edge sharp and how well it then cuts. Your sweet spot will not necessarily be the same as it is for other turners.
• The keenest of edges will only last for seconds while turning. The point at which the edge is no longer cutting well enough is a personal preference and will vary between turners.
• The edge for finishing cuts usually requires a finer edge than for roughing down cuts. Roughing cuts are about the volume of wood removed, Finishing cuts are about the surface finish after the cut. Always sharpening to finishing cut sharpness may be unnecessary for most of your turning time.
• The sharpness of an edge may be determined by the method and abrasive medium, but the durability of an edge has as much to do with the steel as the sharpening method.
• One aspect of sharpening that is not talked about very much is burnishing. Abrasives pull steel particles off the edge and leave some particles prone to subsequently breaking away. Burnishing pushes steel about (typically done to form a burr) and back into the steel matrix. The return on effort comes down to personal preferences. I carried out some experiments and microscope observations that showed that ‘honing’ with a diamond plate is a combined form of abrasion and honing.
• Gouge bevels are often a neglected half of sharpening an edge. Bevels that still have milling tracks left in them of a size that is coarser than your grinding wheel will be sub-optimal.
• For those who like a micro edge, polishing with a rag wheel and abrasive paste (viz David Weaver’s unicorn method) may suit some turners on more acute edges, like on skews.
• Besides experience and the stuff between your ears, a $10 jeweller's loupe is the next most valuable item of sharpening equipment.

When you look at an edge under magnification you can learn stuff about what is going on at the very edge. The following sequence shows a scraper burr edge that was raised with a 45 micron diamond plate and what happened to it in use. Images are 200x mag.

Burr raised before use


After 30sec use


After 60 sec use​

 

[Neil S]

When you look at an edge under magnification you can learn stuff about what is going on at the very edge.

A few more mag images...

Thompson 3-8in bowl gouge
sharpened - flute not honed - 200X


Thompson 3-8in bowl gouge
Flute honed - 200X
​

Your thumb can only tell you so much about the edge. Magnification can add to your understanding.

 

[Timothy White]

@odie: I agree with your assertions 100% if we are talking about M2 HSS 60-80 grit friable stones and full bevels.
May I ask what do you use for a hone? There are 1000 grit CBN wheels available for Tormek.
The bevel I use on my gouge is only 1/16th“ or less, that small bevel is difficult for me to hone. I do hone the flute. One very light pass on my 600 grit CBN wheel restores that edge to very sharp. The 600 grit CBN wheel cuts so fast that every second or third pass I need to recut my secondary bevel to narrow the primary bevel back to 1/16th“. Even a 600 grit CBN wheel will remove CPM10V or PM42 HSS quickly and efficiently. (I mention these two steels because they are generally considered the toughest.)
@robo hippy: Yes, another sharpness debate. I believe sharpening is the number 1 reason that new turners loose interest and drop out followed by grind angle flute shape then finally technique. The stock answer that the new turner gets to these questions is “Whatever works for you”. Come on man they barely know how to spell lathe and think chuck is a nickname for Charles.
When I started woodturning in the early 1970’s my mentor and I hadn’t heard of a woodturning chuck SRG spindle or bowl gouge it was a parting tool round nose scraper and a skew. A continental gouge was available but for some reason we never used it.
We used high carbon tool steel because “ you can’t get that new gangled high speed steel sharp” this appears to be a ridiculous statement but using the sharpening media that worked well on high carbon steel on HSS was an exercise in futility.
The statement (quote) stuck and became law. Along comes harder HSS for use in the metal working trades and this creates a need for better sharpening media. Just because CPM10V woodturning tools appeared on the market didn’t negate the need for a new media to sharpening them. When I bought my first Doug Thompson tools CPN10V there were no CBN wheels available to sharpen them so we ground them with what we had. There were diamond hand hones available. CBN wheels showed up at SWAT a year later they were $300.00 a pop. Needless to say not many ,if any, were sold. The next year Johannes Michelson came to swat and had for sale CBN wheels. In his booth he demonstrated these wheels. I bought a 120 grit and a180 grit. some of the professional turners also say the light and switched.
The point I’m trying to make, when technology changes other supporting technologies must change to compensate.
Another proverb. “Carbide is tough but you can’t get it sharp”well Mike Hunter can.
Why do we do the same thing the same way and expect different results?

 

[odie]

@odie: I agree with your assertions 100% if we are talking about M2 HSS 60-80 grit friable stones and full bevels.
May I ask what do you use for a hone? There are 1000 grit CBN wheels available for Tormek.
The bevel I use on my gouge is only 1/16th“ or less, that small bevel is difficult for me to hone. I do hone the flute. One very light pass on my 600 grit CBN wheel restores that edge to very sharp. The 600 grit CBN wheel cuts so fast that every second or third pass I need to recut my secondary bevel to narrow the primary bevel back to 1/16th“. Even a 600 grit CBN wheel will remove CPM10V or PM42 HSS quickly and efficiently. (I mention these two steels because they are generally considered the toughest.)

Tim.....I'm using a diamond cone for the flute, and a flat diamond hone for the bevel side of the edge. Both are 600gt.

As I mentioned in another post, if you're going to use a wheel to create the cutting edge, then a pass with a hone on the flute side of the edge would be a good follow-up to that method. I see you are doing that. The problem, as I see it, is a 600gt wheel will not create an edge as sharp as a 600gt hone. This is because of the differences in creating that edge with a single direction, as opposed to multiple directions.

If you're only grinding 1/16" on the end of the bevel with your 600gt cbn wheel, then you must be grinding the bevel itself with a different method.(*) This is also something I addressed in another post, by suggesting the bevel is done with a coarser grit, and followed by your 600gt cbn wheel to create the cutting edge itself.

(*)Edit: It appears as though you are grinding both the cutting edge and the bevel with the 600gt cbn....is that correct? If this is so, and the 600gt cbn is satisfactory for the bevel, then why not just skip the 1/16" pass on the edge, and just go with the entire bevel up to the cutting edge itself.....(something doesn't make sense here.)

-----odie-----

 

[Brian Gustin]

(*)Edit: It appears as though you are grinding both the cutting edge and the bevel with the 600gt cbn....is that correct? If this is so, and the 600gt cbn is satisfactory for the bevel, then why not just skip the 1/16" pass on the edge, and just go with the entire bevel up to the cutting edge itself.....(something doesn't make sense here.)

-----odie-----

I would suspect that may be because off the grinder (assuming typical 8" wheel), your gouge is gonna have a bit of hollow grind, and if you use a diamond card (1200 grit or so?) to hone the subsequent bevel, you end up with a 1/16" micro-bevel on the very cutting edge (and the heel, but who cares about a heel besides a podiatrist?) Though there'd still be bit of burr on the flute side of that edge unless you have a round or cone honing rod, which I'd bet many turners would not bother to get, figuring the burr would be gone as fast as a keen honed edge would be in any case.

 

[odie]

I would suspect that may be because off the grinder (assuming typical 8" wheel), your gouge is gonna have a bit of hollow grind, and if you use a diamond card (1200 grit or so?) to hone the subsequent bevel, you end up with a 1/16" micro-bevel on the very cutting edge (and the heel, but who cares about a heel besides a podiatrist?) Though there'd still be bit of burr on the flute side of that edge unless you have a round or cone honing rod, which I'd bet many turners would not bother to get, figuring the burr would be gone as fast as a keen honed edge would be in any case.

In Tim's post, he is not using a diamond hone on the bevel side of the cutting edge. he's using his 600gt cbn wheel for both the bevel and the 1/16" micro bevel. My question is, if the 600gt wheel is satisfactory for the bevel, then why not use it exclusively up to the cutting edge.

-----odie-----

 

[Brian Gustin]

Ah I see where that's buried in his post... in that case, I'd agree with the question - Me, I might grind away the heel of the gouge down to a thin primary bevel (but find that honing does nicely the same thing) and then grind a third heel bevel for clearance on inside curves (but that'd just be for bowl gouges) but I can't imagine specifically shooting for a fine primary bevel with a grinder when I can achieve that by honing the hollow ground edge.

 

[robo hippy]

Well, not sure if he makes them any more, but Ken Rizza did used to make a 1000 grit CBN wheel. Tormek has diamond wheels up to 1200 grit. I did find with skews on the 1000 grit wheel, there was still a burr, and the burr has to be gone for smooth cutting. The skew would cut fine in one direction, but not the other. this is where stropping comes in. You can get cheap black 'polishing' compounds at the local big box hardware/tool stores, which is about 800 grit. I use a piece of plywood to put the compound on, and some times I go to my Tormek because the wheel is more convenient.

robo hippy

 

[Neil S]

I did find with skews on the 1000 grit wheel, there was still a burr, and the burr has to be gone for smooth cutting. The skew would cut fine in one direction, but not the other. this is where stropping comes in. You can get cheap black 'polishing' compounds at the local big box hardware/tool stores, which is about 800 grit. I use a piece of plywood to put the compound on, and some times I go to my Tormek because the wheel is more convenient.

A piece of plywood and a stick of cutting compound is cheap and effective for removing the micro burr. If you happen to have a Tormek that will be quicker. Even quicker will be a stitched rag wheel (6 or 8") on a bench grinder... a 2 second pass on the burr side and the burr is gone.

I know of a professional woodturner who kept a rag wheel on a bench grinder running constantly next to his lathe while turning some woods and he refreshed the edge half a dozen times on that before re-grinding on the stone wheel end of the grinder. A loaded rag wheel will not only remove a burr it will also quickly form a new micro edge. When you turn 9 to 5 x 6 days a week, year in year out, you refine your methods to the ones that are most efficient for you.

I use a rag wheel to maintain a high polish on the flutes of my gouges. That not only removes any buildup of burr metal on the flute side of the edge but also cleans out any build up of crud. I do a 4-5sec pass on the rag wheel every 3 or 4 sharpenings of the bevel. I don't rag strop the bevel as I don't find there is a worthwhile advantage for doing that.

A rag wheel strop is good for getting into and maintaining the flute, but many gouges come with milling tracks that have to be ground out first with diamond or CBN. I use a Victorinox oval diamond 'steel' for that on my larger gouges. The ovals steels with a taper on the end provide profiles that are closest to match the parabolic flute.

I've found rag stropping scrapers and skews works well for me. It does 'dub' the edge, that is you get more of a curve towards the edge than a tight micro-bevel, so the primary bevel needs to be more acute to get the required included angle at the edge. I have always used diamond plates (and flat stones before that) at the lathe for those tools and still do so along with the rag strop.

Cloth rag wheels are cheap but you do need a bench grinder with a spare end to mount it on. If you happen to have a second lathe that is another option.

It is just another effective sharpening method among countless others, but it may suit some if for no other purpose than to keep those gouge flutes polished to perfection.

Here are some images of polished and unpolished bevels/flutes and the resulting burrs... showing a polished flute or upper bevel creates a more even burr.

Uneven burr on unpolished
Crown Pro-PM 1in bowl gouge
off #120 diamond wheel - 200X


Scraper - milling tracks -
before polishing - 200x


Scraper - polished upper bevel to
#12000 - before burr - 200X


Scraper - with 45 micron diamond
honed burr on polished upper bevel - 200 X​

 

[robo hippy]

Hmm, now you are making me think again..... I have been pondering now to remove burrs from a set of carving chisels I picked up last summer. I was thinking a bunch of MDF wheels with different profiles. This rag wheel idea might work. Are these like the buffing wheels?

robo hippy

 

[Neil S]

Hmm, now you are making me think again..... I have been pondering now to remove burrs from a set of carving chisels I picked up last summer. I was thinking a bunch of MDF wheels with different profiles. This rag wheel idea might work. Are these like the buffing wheels?

Down here we call them stitched rag wheels, like this...

https://www.toolmart.com.au/josco-jst20050.html

Not sure what they call them over your side of the pond. The multiple rows of stitching keep it a bit rigid. Some of the buffing wheels that have fewer rows of stitching are too floppy for this purpose. I use a 1/2" wide one and undid the outer row of stitches to open it up a bit.

 

[Timothy White]

In Tim's post, he is not using a diamond hone on the bevel side of the cutting edge. he's using his 600gt cbn wheel for both the bevel and the 1/16" micro bevel. My question is, if the 600gt wheel is satisfactory for the bevel, then why not use it exclusively up to the cutting edge.

-----odie-----

@odie: just to clarify I grind a 55 degree bevel on my bowl gouge then I grind a secondary relief bevel at around 40 degrees then I grind a tertiary bevel at about 30 degrees to remove the heel of the gouge the Primary bevel (rubbing bevel) is the one that is 1/16” wide this is the cutting bevel not a micro bevel, this bevel is very difficult to hone proprely. The secondary and tertiary bevels are formed with a 70 grit CBN wheel and are not honed.
when I go back to the grinder I black out the primary bevel before sharpening. 600 grit CBN takes off so little metal that if your setup is not perfect it is very possible that edge of your gouge won’t get sharpened.
I’ve used two terms in my posts, grind and sharpen. I try not to use them interchangeably. To clarify: I grind with 70 grit CBN I sharpen with 600 grit I hone with a 600 grit Alan Lacer tear drop diamond hone.
I sharpen my SRGs with my 600 CBN then I hone them by hand till the bevel is no longer concave before returning to the 600 grit grinder. I have two SRGs, one is a 1” M2 steel the other is a 1 1/4“ CPM10v I like and use both My favorite? The sharpest one.
Odie if you ever get the chance to sharpen on a 600 grit CBN wheel Do it and try the tool straight off the grinder. You will be amazed.

 

[odie]

Odie if you ever get the chance to sharpen on a 600 grit CBN wheel Do it and try the tool straight off the grinder. You will be amazed.

Yes, I would like to have that opportunity. Thanks for the response, Tim.

-----odie-----

 

[Bill Boehme]

I hone with a 600 grit Alan Lacer tear drop diamond hone.

That shape with one small radius edge and one large radius edge is known as a slip stone.

 

[Timothy White]

That shape with one small radius edge and one large radius edge is known as a slip stone.

I stand corrected. My head is both bloodied and bowed.
But it is confusing because it ain’t a stone

 

[Bill Boehme]

I stand corrected. My head is both bloodied and bowed.
But it is confusing because it ain’t a stone

Yeah, I know, but that's what they call it. Since Alan Lacer says that it is a slip stone, that settles that.