Shaping an oval skew chisel

[John55410]

As a new person here (and a novice turner) I don't know if a question constitutes a "topic" but I'll ask it as see what happens.

I want to reshape an oval skew chisel so that it has a curved edge as suggested in "Sharpening Woodturning Tools the Tormek way," page23 and described starting on page 27.  As a point of information, I discovered that this manual has an error on page 28.  The right hand diagram at the top of the page indicates placing the universal support in hole A on the SVS-50 jig while the text says use hole B.  Apparently the text is correct.

My question is: from where will the material be removed on the chisel during this procedure, the heel, the point or both?  Knowing this would help me know what to expect before putting an expensive tool on the grinder.

A second question is whether or not there is a consistent definition of the angle in this manual that is referred to as alpha.  My guess is that for a skew chisel it is the angle between the two planes that form the edge.  If this is correct it would appear to be different from the angle labeled alpha in the top diagram on page 8.  In this case the angle appears to be the angle between the plane of the grinding surface and the center line of the tool shaft.  I find this confusing.

[Herman Trivilino]

A second question is whether or not there is a consistent definition of the angle in this manual that is referred to as alpha.  My guess is that for a skew chisel it is the angle between the two planes that form the edge.  If this is correct it would appear to be different from the angle labeled alpha in the top diagram on page 8.  In this case the angle appears to be the angle between the plane of the grinding surface and the center line of the tool shaft.  I find this confusing.

Hi John,

I'm not sure which edition of the handbook you're using, but the latest is 9.9 and it can be downloaded for free once you register.

http://tormek.com/international/en/account/register/

On page 10 alpha is defined as the edge angle, and beta is defined as the bevel angle.  On a wood chisel these angle are equal, but on a typical kitchen knife the bevel angle would the half the edge angle.

An edge is the intersection of two planes, the angle between the planes is the edge angle.  In other words, the edge angle is the angle at the edge.  The bevel angle is always equal to, or smaller than, the edge angle.  The bevel angle is the angle between one of the edges and a plane that passes through the edge and is parallel to a plane passing through the center of the tool.

Sorry I can't help with your other questions, I'm not a turner.

[John55410]

Thanks Herman.  That's helpful.  If I follow you, on a turning gouge the bevel angle and the edge angle would be the same.  On a chisel, the bevel angle would be half the edge angle.

[Herman Trivilino]

On a typical wood chisel the edge angle and the bevel angle are the same.  In general, this is true because there's only one bevel.

[John55410]

I'm having more problems.  I'm trying to reshape my oval skew chisel, ultimately to give it a curve, but it is taking forever!  I've spent about 45 minutes on just one bevel so far and I have a ways to go.  I'm getting filings as noted when I change the water.  I use the grading stone frequently but progress is painstakingly slow.  I have the universal support in the vertical position with the wheel turning toward the edge and I press down quite hard.  The grinding wheel itself looks a little strange. One side of the wheel is peppered with brown flecks that remain (or reappear) even after using the grading stone.  Any thoughts?

[Herman Trivilino]

Use the truing tool to true the surface of the grindstone.  That'll give you a much more aggressive surface.

If those brown flecks persist I would recommend contacting your supplier.  We've heard reports here of some grindstones that had to be replaced because of manufacturing issues.

[John55410]

Many thanks, will do.

[Rob]

But I'm afraid you've arrived at the dreaded skew shaping. What the Tormek marketing machine accidentally neglects to mention is that the Tormek is rubbish at removing a lot of HSS from a tool with a large surface area.  Or skew chisels and planar knives in normal language.

Persevere by frequently regrading the stone with the truing tool which as Herman says will make the cutting action the most aggressive it is possible to get with a Tormek.  Remain in the towards the blade configuration as that is also more aggressive than the away from mode.  Just keep going is all you can do.  Eventually, (after a couple of weekends), it will be done and then the Tormek gets really useful because from now on you only need to maintain that exact same bevel.  What you just did was technically shaping, now you only have to sharpen. Shaping...long, slow, hurts, boring, lots of metal.  Sharpening...fast, easy, little metal, joy.

The Tormek is great at sharpening period.  It is also capable of shaping but neither efficient nor pleasant to use for that process.  Skews, planar/jointer knives and wide bench plane knives are all laborious to shape.  Do that on a different tool would be my advice.  Given Tormek sell a jig called the BGM-100 I suspect it is also their advice :-)

[John55410]

Thanks Rob--

I think your post saved my sanity.  I was beginning to imagine that there was some inherent flaw in my character that was preventing me from shaping this skew in a timely manner.  I'm putting myself on some kind of regimen--100 passes over the stone and then rest for a while.  You aren't kidding about this taking a couple of weekends.  I will certainly think long and hard before I embark on any reshaping of turning tools again.  I will heed your advice about frequently using the truing tool.  Other than don't ever do this again, I have learned that it is vital to have the stone at the right height so I don't have to use my shoulder joints too much for the downward pressure.  I have also learned that a little oil on the universal support helps the jig move smoothly while moving the tool across the stone.

[John55410]

Has anyone used the BMG-100 that enables the use of the universal support on a regular bench grinder that Rob mentions?  How difficult is it not to burn the edge of the tool, in this case a skew chisel?

[Rob]

Yes....I was rather feeling your pain.  I only started turning just over a year ago but had used the T7 for bench planes and chisels prior to that.  I found it to be extremely useful for sharpening......but then came an old skew dug out from my long deceased Father's turning toolkit.  Wow I'm thinking, what a find, Dad would love the idea of me rejuvenating his old tools. Not been used for over 30 years, heirloom etc etc.  Now I'm really excited and remember I have this fabulous piece of Swedish technology, it'll make short work of creating a shiny new bevel.  I think Dad probably sharpened them on the tablesaw he built from an old washing machine motor given the chewed up appearance of this skew.  I can fix that I thought.

So with ill deserved confidence and positively bursting with Swedish gumption I skidded to a halt in front of the trusty T7.  Boom, out came the jig.  Whammo angle set.  I won't bother to true the wheel, its close enough and anyway, how long can this take?  The rest as they say is history and a procedure you are now thoroughly acquainted with.  The Doctors estimate my knuckle joints will re-attach to my fingers before the end of the year so every cloud has a silver lining :-)

[Wybrook]

Why is it that one of the first things people want to do with a new Tormek is re-shape a skew chisel ? - exactly what I was doing last weekend, for what seemed like most of the weekend ! 

And like everyone else, having finally got there I vowed to never do it again 

[Herman Trivilino]

Did you have two attempts at improving your fate, Rob?  I don't remember if you tried the SB-250 grindstone before finally solving the problem with the BGM-100.

http://forum.tormek.com/index.php?topic=1672.msg7733#msg7733

When are we going to get to see those pictures?

[Rob]

Yes I got the blackstone wheel Herman. Originally for the planer blades after that 8 hour marathon trying to sharpen them on the original wheel.  Truth is I've not been back to them since because I've had almost no need to use my planer.  The problem is woodturning.  Its just so addictive that its temporarily taken over the wood side of my life.  I've even joined a club!!

I always get frustrated with the T when trying to shape a tool, the wider its surface area, the more frustrated I become with the T.  In the end I rolled over and coughed for the BGM which in fact turned out (no pun intended) to be rather good.  I bought a good quality 2nd hand 6" grinder from another wood turner and carefully mounted the BGM against the white wheel.  (is that 40 grit, 60 grit I cant remember...you or Ken would know).  Its the fast metal removal one anyway.

Now most of the time I have the Torlok mounted against that for the flatter end of turning tools.  I do the gouges on the T7 because the articulated jig is superb for fingernail grinds.  I'm still using the blackstone and its probably a little more suitable for HSS but to be honest I didn't really feel the original stone was that bad for sharpening anyway.  You take so little metal off when you sharpen a gouge...just kiss the stone for about 4 or 5 passes and its done.

I did shape my bowl gouge before I got the BGM and that was a nightmare much akin to John's skew experience.  With the BGM now shaping is easier.  But overheating the steel is a constant risk.  I'm considering alternative methods of shaping but haven't made any decisions yet.  Given the cost of the BGM is relatively modest, I think its not a bad solution.

Pictures...did I not post any??  Not like me :-)

[Ken S]

Fortunately Rob lives in a more advanced society than most of us, where repairing one's hands is covered by the National Health Plan.

An old saying comes to mind:  "The longest journey begins with a single step."  What is left out is the wisdom of beginning with several shorter journeys before attempting the longest one.

For new users, I have probably beaten the single chisel advice to death(see the first post in this category). 

For those determined to reshape skew chisels (hopefully not too many), I would offer the following advice:  Rob is on the right track with the BGM=100 and a higher speed grinder.  My dry grinder performs much better with a Norton 3X 40 grit wheel.  "40 grit" is essential.  This is not a high polish operation.  The coarse grit removes metal quickly and at a lower temperature.  Set the skew angle; blunt the edge by approaching the stone at a ninety degree angle; then grind most of the bevel. 

Stop short of grinding to a sharp bevel.  At that point, switch to the Tormek or a finer wheel.  My first choice would be the Tormek with its large diameter (cool running) wet wheel.

A belt grinder with a 40 grit belt would be a good alternative.  Carefully blunt the edge and create the new skew angle.  Do much of the later work on the Tormek.

I would probably at least attempt to do the whole job on the Tormek.  First, I would blunt the skew chisel and establish ant new (blunted) skew angle.  I would do this over several sharpening sessions. Do some other sharpening first; chisels, plane blades, knives, scissors, etc.  Then begin to blunt the skew chisel with the chisel set to the new (skew) angle.  Work on this only until it starts to become tiring. 

Leave the skew chisel in the jig.  Clean the Tormek and close the shop door.

For the next session, repeat the procedure.  Eventually your skew chisel will be reshaped and sharp.  Treat it with the respect it deserves, and think several times before deciding to change the shape of other tools.  Make sure the work involved is worth the effort.

Plan B would be to seek out a good small local machine shop.  Knowing such a place is a valuable resource for many things. A machine shop should have a large Baldor (or similar) grinder, perhaps with a mister.  If the shop owner knows you are not in a rush for the work to be completed, and he can work it in on a slow day, the cost should be minimal, probably less than the BGM-100, dry grinder, and a good wheel.  (Plan to spend around fifty USD just for a Norton 3X wheel.)  For a major reshaping with a large tool, I would contact my local machine shop. The machine shop could either repair a non starting Tormek motor or know where to take it.

Ken