Square Edge Jig Protrusion

[Dr.Al]

Setting a tool in an Eclipse style honing guide for a given bevel angle is really quick: shove the tool in, offer it up to a pre-made stop, tighten the guide.  Even without a pre-made stop, using one of these edge distance gauge things things makes it very quick.

By contrast, setting up the SE-77 square edge jig requires using the WMB-200 and squinting to see whether the angle is right while you tweak the support bar up and down. That felt to me like a bit of a faff, so I thought I'd figure out the maths that gives the protrusion for a given support bar offset.  It ended up being quite complicated, but I like maths, so that's okay 

Anyway, what that ends up with is the ability to set the support bar to a particular distance from the wheel (which is easy with a setting tool a la Micha Schmid and Keld Petersen) and then set the tool protrusion in much the same way as you can with an Eclipse honing guide.

Unfortunately, it's not quite as simple as that as the wheel diameter and tool thickness have an effect.  For most practical uses, small changes in wheel diameter can be ignored, as can tool thickness changes so I think it's okay.

Anyway, having done all the maths, I thought I'd turn it into a calculator and stick it on my website (so it runs in a browser and doesn't need any spreadsheets or other software installed on your PC).

If anyone is interested, the calculator is here:

https://www.cgtk.co.uk/woodwork/calculators/tormeksquareedge

There's also one for manual honing guides here:

https://www.cgtk.co.uk/woodwork/calculators/honingguide

I'd welcome any comments

Screenshot:

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[cbwx34]

Looks interesting.

My question is on the calculator for the SE-77.  In the second "honing guide" calculator, you make a distinction between the "Protrusion Measurement" and the "Reference Surface", indicating that if they're the same, then blade thickness doesn't matter.  But in the "Tormek square edge" (SE-77) calculator, you indicate that blade thickness does matter, but your diagram there seems to indicate that the Protrusion and Reference Surface is the same.

I ask because in most other calculators in this forum for the SE-77, blade thickness doesn't seem to be a factor.

(I attached your pics for reference.)

Nice work!

[Dr.Al]

Thanks for the interest and the very good question!

The reason for the tool thickness having an effect is different for a honing guide to the SE-77.

As you've read, on the honing guide it's because of the protrusion being measured from a different face to the reference face.

On the SE-77 it's because the grinding stone is circular rather than a flat surface. As the tool gets thicker, the inner end of the bevel moves around an arc, slightly changing the angle. The effect is small, but there is an effect.

Does that make sense? If not, I can draw a couple of diagrams to make it more obvious.

I guess it does depend on what you define as the bevel angle. As I'm usually taking chisels to a bench stone after grinding on the Tormek, for me it's the angle created by a line joining the two ends of the bevel. If you're only using the Tormek, it's arguably the angle at the tip, which won't change with tool thickness I think.

[cbwx34]

Thanks for the interest and the very good question!

The reason for the tool thickness having an effect is different for a honing guide to the SE-77.

As you've read, on the honing guide it's because of the protrusion being measured from a different face to the reference face.

On the SE-77 it's because the grinding stone is circular rather than a flat surface. As the tool gets thicker, the inner end of the bevel moves around an arc, slightly changing the angle. The effect is small, but there is an effect.

Does that make sense? If not, I can draw a couple of diagrams to make it more obvious.

I guess it does depend on what you define as the bevel angle. As I'm usually taking chisels to a bench stone after grinding on the Tormek, for me it's the angle created by a line joining the two ends of the bevel. If you're only using the Tormek, it's arguably the angle at the tip, which won't change with tool thickness I think.

The part you added at the end (that I put in bold) is what I meant.  There is examples showing change beyond the tip, for example:

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^{A drawing by forum member Jan}

Does bring up another question though maybe you can answer.  I know this came up at least once before here and I thought the conclusion was you couldn't really go directly from a wheel to a flat stone using a preset angle (you could match it manually but not using a preset setting, if that makes sense.)  Is this right and/or how do you match them?

Thanks.

[Dr.Al]

A bit more on bevel vs tip angles that will hopefully answer your question along the way...

I'm using tip angle to refer to the angle right at the tip, straight off the Tormek and bevel angle to refer to the line that joins the cutting tip of the bevel with the back edge of the bevel:

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Let's say I want to sharpen a chisel with a 25° cutting edge.  There are different ways I could go about this: I could target a 25° tip angle or I could target a 25° bevel angle.

Let's target a 25° bevel angle.  I put 25° into my calculator and set up the Tormek accordingly.  I then grind away a hollow bevel.  Once I've done this, I plonk it on my waterstone and fidget it around until I can feel the tip and the back of the bevel lying on the stone:

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In theory I could do this in a honing guide as well, but to get exactly the right angle could be a bit difficult.  Having said that, as long as it's roughly the same angle as ground in the Tormek (i.e. I use my Tormek calculator for the Tormek angle and my honing guide calculator for the honing angle), then it should be close enough that I can get to the finished angle without too much bench stone work.

Once I've rubbed it back and forth on the waterstone a few times, the front and back of the bevel have been worn away and now the tip angle is the same as the bevel angle (25°):

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Another way I can approach this (and probably the way I do most often) is to grind it to 24° (or lower) bevel angle on the Tormek and then put the chisel in a honing guide at 25°. That is equivalent to tilting up the blade very slightly and hence I take away a bit of steel at the tip but not at the back of the bevel, and end up with a 25° secondary bevel.

This latter method has the advantage that the next time I sharpen the chisel, I just go to the bench stones and grind at 25°, gradually increasing the size of the secondary bevel until it's time to regrind the primary bevel on the Tormek.  As I'm only taking material off near the tip, the resharpen process is very quick (less than a minute usually, and about the same time with or without a honing guide).

If I'd targeted a 25° tip angle on the Tormek, but still wanted to finish with a 25° secondary bevel off the stone, I'd have a lot more material to take off at the back of the bevel before I'd be able to touch the tip (this was modelled with a 200 mm wheel):

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Of course if I was happy with going straight from the Tormek to using the tool, then the tip angle is what I'd be interested in.  For me however, it's much, much quicker to resharpen an edge using a bench stone than it is to using the Tormek, so I want to be able to maintain the edge without the Tormek: the Tormek comes out again when I need to recut the primary bevel.

The maths associated with the tip angle is quite a lot simpler than the maths for the bevel angle, so I can't see any reason why my calculator can't do both.  I'll need to do some more detailed drawings explaining the difference and why you would want one or the other, so I doubt I'll get it updated today (I spent far too much of Saturday working out the maths for the bevel angle and I'd like to do something else with my Sunday!), but I'll post again on here when it's done.

[Ken S]

(From your Tormek Square Edge Protrusion Calculator article)
"Setting up the Tormek with the angle setter is quite time consuming (compared to using a simple reference with a honing guide). By fixing the offset from the support bar to the wheel, a fixed tool protrusion can be used, which speeds up the setting process, especially if you have on of these edge distance gauges."
This procedure does not have to be "quite time consuming". I agree; if setting very chisel from scratch is a new adventure with the Anglemaster, it can be quite time consuming. In 2010, I did set up a chisel with the Anglemaster. (I could just as easily done this us by using one of the math programs.) By adapting the Tormek TTS-100 slightly, I have not needed to measure any more chisels, and set up is both rapid and consistent. This has the additional benefit of automatically compensating for any wheel wear. The two holes work like the edge instance gauges you describe.  Prefer to use the closer hole to keep chisel protrusion shorter. With the Distance set this way, I set the Protrusion of the initial chisel with the Anglemaster. With the chisel secured in the jig, I transferred this setting to one of the slots of the TTS-100 using a fine point Sharpie, noting the 25°. Subsequent chisels are just lined up with the Projection mark. The Distance does not change, and can be quickly  reset if needed. The TTS-100 works brilliantly with turning tools. I don't know why Tormek never extended its use to chisels and plane blades.

Over the years, I have appreciated the math posted on the Tormek Forum. We all benefit from it, even if many of us (including me) do not fully understand it. I think your statement from your same article keep the theoretical and the practical in good perspective:
"It's worth noting that the protrusion will also vary with tool thickness (as it will with a plane blade fitted into an Eclipse style honing jig) and also with wheel diameter. The effect of tool thickness is probably small enough to be ignored and wheel diameter will change fairly gradually (or not at all if you're using a diamond wheel), so I don't see this as too big an issue."

Ken

[Dr.Al]

Thanks Ken, that's interesting.  The TTS-100 does sound like it might work well for consistent set-up.  How consistent is it across different wheel diameters?  If, for example, you rough ground a tool on a 150 mm bench grinder with the BGM thing and then took it across to the Tormek with a 250 mm wheel, would you get the same bevel angle?

The reason I ask is that only this morning I was regrinding a scrappy old chisel and I used my calculator to set up the jig for rough grinding on the bench grinder with the BGM and then moved across to the Tormek (resetting the projection with the jig) and the angle was pretty much spot on, so the Tormek work was a matter of seconds.  It would be good if the TTS-100 can achieve that as well.  Maybe I'll have to add a calculator for custom angles with the TTS-100!

What I've since done is played around with the calculator a bit and I worked out that if I set the Tormek (250 mm wheel) up with a 33 mm setting tool (so 10.5 mm gap) and the 1450 rpm bench grinder (200 mm wheel) up with a 40 mm setting tool, then the protrusions work out roughly the same (at least for the two angles I'm most interested in: 20° and 25°).  With that set-up, I can go directly from bench grinder + BGM to Tormek.  Of course that would have been a heck of a lot easier if I'd bought the T-4 with the same size wheel as my bench grinder!

Despite saying I wasn't going to do it today, I've added tip angles to the calculator: the maths was really very simple indeed so it didn't take very long at all.

[cbwx34]

A bit more on bevel vs tip angles that will hopefully answer your question along the way...
...

Yup, all good.  Thanks!

Thanks Ken, that's interesting.  The TTS-100 does sound like it might work well for consistent set-up.  How consistent is it across different wheel diameters?  If, for example, you rough ground a tool on a 150 mm bench grinder with the BGM thing and then took it across to the Tormek with a 250 mm wheel, would you get the same bevel angle?
...

I think that's the purpose of the TTS-100 (but could be wrong since I don't use one.)

You might find some of what forum member Rich Colvin has done interesting...

SE-77 & TTS-100

Projection Jig for TTS-100

 

[Ken S]

Like CB, I do not own a BGM-100.I do have the parts; however, for the rare occasions when I want a coarser wheel, I use a Norton 3X 46 grit wheel wet with my Tormek. I am not a fan of the BGM-100 used dry. In my opinion, dry grinding defeats the purpose of the Tormek.

Tormek has a patent on the TTS-100. The two metal wheels automatically with diameter changes, including switching from 250mm to 200mm wheels. I don't worry too much if the bevel of the coarse wheel is identical with the final wheel. The coarse wheel is for rough work.

Ken

[Dr.Al]

Like CB, I do not own a BGM-100.I do have the parts; however, for the rare occasions when I want a coarser wheel, I use a Norton 3X 46 grit wheel wet with my Tormek. I am not a fan of the BGM-100 used dry. In my opinion, dry grinding defeats the purpose of the Tormek.

I completely understand that sentiment if the Tormek + Norton 3X works for you. I haven't found a good UK source for coarser Tormek wheels (like the Norton 3X one you mentioned), otherwise I might have bought one. I got the 1450 rpm grinder as a result of frustration with the Tormek (which I'd bought primarily for regrinding bevels).

I'd been regrinding a few tools (notably 6 mm thick plane blades) to a different angle & in the end had given up: it felt like the Tormek was going to take all day to regrind the bevel, either with the standard wheel or the coarse diamond one.

With the 1450 rpm grinder & an 80 grit CBN wheel, it was done in a few minutes, albeit requiring frequent dips in water. At least it runs a lot cooler than a 3000 rpm bench grinder: dipping in water is every minute or so rather than every few seconds.

Right now if I was ever forced to sell either the Tormek or the 1450 rpm grinder + BGM it would be a no-brainer: the Tormek would go first (but I'd keep the Tormek jigs to use on the 1450 rpm grinder ).

Tormek has a patent on the TTS-100. The two metal wheels automatically with diameter changes, including switching from 250mm to 200mm wheels. I don't worry too much if the bevel of the coarse wheel is identical with the final wheel. The coarse wheel is for rough work.

Ken

I'm really interested in understanding this better. I'll have a play with the maths & see what comes out.

[Ken S]

I don't have a lot of faith in grit numbers, at least as the only determining factor. I have found that my DC-250 360 grit diamond wheel cuts faster than my 220 grit SG-250, even after being freshly trued. Also, I do not consider the DC especially coarse. Have you considered using your 80 grit CBN wheel wet with your Tormek? I used mine this way with Honerite Gold anticorrosion solution before I acquired my diamond wheels. Looking at your website, adapting the bore size and thickness to the Tormek would not seem difficult for you.This is not as fast as dry grinding; however, it is noticeably quicker that regular wet grinding and it is both cool and dust free.

Ken

[Dr.Al]

I don't have a lot of faith in grit numbers, at least as the only determining factor. I have found that my DC-250 360 grit diamond wheel cuts faster than my 220 grit SG-250, even after being freshly trued. Also, I do not consider the DC especially coarse. Have you considered using your 80 grit CBN wheel wet with your Tormek? I used mine this way with Honerite Gold anticorrosion solution before I acquired my diamond wheels. Looking at your website, adapting the bore size and thickness to the Tormek would not seem difficult for you.This is not as fast as dry grinding; however, it is noticeably quicker that regular wet grinding and it is both cool and dust free.

I hadn't considered that, but I will now 

It would certainly be nice to have a grit free grinding method.  The CBN wheel is smaller in diameter, but I imagine that would be okay.  I'll have a look to see what the bore is at some point (and hence whether it can be fitted to the Tormek).

[Ken S]

One of the fascinating things about the Tormek for me is trying to imagine what Torgny Jansson, the inventor, was thinking over the years, what I call "the Tormek philosophy". I believe his original and continuing intentions were to make a high quality simple one grinding wheel machine primarily for resharpening rather than for heavier grinding. I believe the stone grader was added to provide a finer wheel like the original natural stone after switching to the coarser man made aluminum oxide SG. He chose not to offer a true coarse stone. These stones were certainly available; I just do not think he wanted a stone to remove that much metal. The Tormek was invented in the era of high carbon steel.

He certainly could have designed the Tormek with two grinding wheels. I think he liked the simplicity of a single wheel machine, one that his father would use to sharpen his woodworking tools. Multiple wheels including diamonds were added after he died. I do not know if he had any part in developing multiple wheels. The present online classes seem to reflect a continuing preference for the SG, although the diamond wheels are finally starting to get more coverage.

His jigs, especially the DBS-22 drill bit jig and the combination of the SVD-185/6 and TTS-100 reflect a high proficiency of engineering math. At the same time, they are user friendly for users who do not possess higher math skills.

I remember an early forum question. The member asked if the Tormek could be used to sharpen drill bits. Jeff Farris, the moderator, answered, "not yet". Innovation is ongoing, both at the factory and from the forum.'

Ken

[John Hancock Sr]

He certainly could have designed the Tormek with two grinding wheels. I think he liked the simplicity of a single wheel machine, one that his father would use to sharpen his woodworking tools.

Completely agree. It seems to be that his idea was for woodworkers to be able to sharpen chisels and plane blades simply and easily when are always pretty sharp so if used properly never require heavy grinding. The additional wheels, jigs stone graders just makes it so much more versatile.