How I Sharpen #3: Carving V Tool - Part 1

V Tools are a special case so I've decided to divide this entry into two parts.  In this part I'll review the tool geometry and the goals I have for getting it sharp.  Then in a later entry I'll show the actual sharpening.  I'm doing this because V tools are one of the tools that gives me the most trouble.  It's also one of the tools I use most in relief carving so I take the time and effort to get it right.

The tool I'll be sharpening is a 60 degree tool from Ashley Iles but the ideas behind the basics translate directly to other angles.  At the heart of the tool, you have two chisels that come together at the bottom.  If only it were really that simple....

A forged blank for a V Tool is basically this:

If we look at the end of the tool, we see where it gets it's name.

Like I said, this is basically two chisels that come to an apex.  So we just sharpen the two bevels and we're ready to go, right?  Well, the problem is the apex part.  You can see, the apex is actually rounded and thicker.  This is a result of the forging process but also a necessity for function.  If the two sides met perfectly at the apex, the tip would be so fragile it would break even in light duty wood.

So how do we work with the actual geometry?  Well, we can start by adding those two bevels and see what happens.

I put a 15 degree bevel on each leg and you can see that they do come to a point but you also have that section between the inside radius and the point where the bevels meet.  That material strengthens the apex of the chisels but it's also a blunt section that's not going to cut and will resist efforts to push the tool through the wood.

So next let's reduce that section with a third flat bevel applied to the keel (the flat on the bottom of the tool) that's set at the same angle of 15 degrees that the chisel legs are sharpened at.

Now we have three flat bevels and have reduced the blunt section at the apex significantly.  We also notice that the keel bevel sweeps back further than the chisel bevels.  This is due to the bottom section being thicker than the sides.  But even now, we still have two small portions that will resist cutting on either side of the apex.  We could rotate a bit and keep grinding flat bevels but if we do that enough times, eventually we will end up with a radius.  So let's skip the in-between steps and treat the radii where the chisel bevels and the keel bevel meet as a gouge.

After sharpening one side like we sharpen a gouge, we see we are at a sharp edge on the chisel leg, at the keel, and at the intersection of the two.  So doing the other side:

End-on all we see is a sharp edge, no more blunt spots.

Now, this seems simple but, it's really easy to take one stroke too many on the stone when working on the keel in which case your apex will move back behind the chisel edges.  Unfortunately all you can do in that case is grind the end back to square and go back to the beginning.  Another thing we'll find if we look at the tool with the finished cutting edge from the side is that we essentially have 5 bevels now - two chisels on the sides, a flat on the keel, and two gouges at the transitions.  And due to material thickness and geometry, these all have different lengths:

One could live with it in this case but if we can smooth the transitions in all these bevels, we'll have a smoother profile that will move more easily through the wood with less resistance.  That part is a little more art than science though so I'm not going to try to approximate it here.  I'll show it in the next installment when I actually sharpen one of these boogers.

I'll add here that the quality of the forged tool is critical with a V Tool.  A lower end tool will be a frustration.  Here are some of the things to look for:
  • Symmetry.  The side legs should be a straight line, at even angles meeting at the keel.
  • Quality steel.  You want the legs to be fairly thin and the steel, particularly on the inside should be dead flat and highly polished.
  • Small internal radius at the keel.  If this radius is too large, the tool will cut more like a gouge with wings than a V tool.  We can't practically achieve an actual V with a sharp apex between the sides but the closer you can get, the better.
  • The keel should be a thin flat line that runs the length of the tool.  If it's more like a cone, it will have inconsistent geometry and be too thick to cut easily.

In general, a forged tool from a reputable maker will fit the bill.  A cast tool will almost certainly amount to a pile of turds.

More specifics and the how-to in the next entry.  Until then!
Nice write up. 

Ryan/// ~sigh~ I blew up another bowl. Moke told me "I made the inside bigger than the outside".

V tools vex me.  Ill be re-reading this multiple times.  Thanks for this kenny!
Yeah, they’re tough. I bought slip stones specifically for that…

Ryan/// ~sigh~ I blew up another bowl. Moke told me "I made the inside bigger than the outside".

I had slip stones too, just wish I could find them.... 

Nicely done Kenny. 
Gotta make a drawer George. Only way to not lose stuff is to lose it in the drawer…

Ryan/// ~sigh~ I blew up another bowl. Moke told me "I made the inside bigger than the outside".

A lot of stuff I never even considered!
Got a cheap set of carving tools from the FIL, but aside from the small gouge, I've never tried to sharpen any of them .
Ah the V-Tool. It has a reputation for being the most difficult carving tool to sharpen, but I commissioned my Ashley Iles 3/8" 60 degree v-tool on diamond plates followed by oil stones and I didn't find it that difficult really. Time consuming yes, but not difficult. Since then I have a bought a Tormek T8 with the standard synthetic SG250 wheel, the Japanese waterstone wheel and the course, fine and Extra fine diamond wheels. After I finished my Three Hares carving, I decided that I was going on a mission to buy all the carving tools I would ever need. I now have around 180 tools with about 50 still awaiting commissioning. I try to commission 4 or 5 of tools each week before I start work. Anyhow, the reason I bring this up is that I use the side of the diamond wheels (not the circumference) to shape the tool and lower the cutting angle to where it feels good in my hands. Like you, I don't measure the angle. I have recently innovated a genius solution (if I do say so myself) to sharpening on the side of the diamond wheels which I hope to do a video about shortly, before posting it here. Pointless posting the project yet as nobody would have a clue what it was without the video. LOL.

Andy -- Old Chinese proverb say: If you think something can't be done, don't interrupt man who is doing it.

I would definitely be interested in that video Andy!
Cool, good info, cheers.