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Jack Devereux

Sharpening Bridge Knives

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3 hours ago, Jeffrey Holmes said:

Not grinding knives at the moment, but I'll illustrate the parts. It's pretty low tech, but easy to set up.The adjustable aluminum rest attaches to the Tormek's slide arm. The plexiglass rest is placed on top of the aluminum rest with the cut-out portion at the wheel (it's beveled there, so it can be set very close to the grinding surface).  This allows support for the tool at, and on both sides, of the wheel. I use some small clamps to secure the platform once the angle is set and the rest is where I want it. If I wasn't so cheap, I'd buy a second aluminum platform and attach the plexiglass to it permanently.IMG_0675.JPG  

thanks Jeffrey!

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23 hours ago, Jerry Pasewicz said:

Yes, mine are quite similar.  The trick in retaining the curve is how you position your hand when sharpening.  Once you get the flow of your hand movement, the curve evolves;  the curve follows the hand not the other way around....the cool follows shortly thereafter.

That makes sense. Do you establish the shape of the cutting edge and then add the relief in the back of the blade? Are you shaping that on a toolrest similar to the one Jeffrey pictured? Angle wise do you have something specific in mind? When I have managed to get that shape right I find it more versatile than the long straight blade (though some of those pictures are making me want to revisit that style). Thanks for the input! 

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48 minutes ago, Jack Devereux said:

That makes sense. Do you establish the shape of the cutting edge and then add the relief in the back of the blade? Are you shaping that on a toolrest similar to the one Jeffrey pictured? Angle wise do you have something specific in mind? When I have managed to get that shape right I find it more versatile than the long straight blade (though some of those pictures are making me want to revisit that style). Thanks for the input! 

The cutting edge is done before the back is relieved.

I do not shape the knives on a tool rest, it is all done freehand against the wheel.

I have two bridge knives, one with a rather acute angle to the edge, and one more obtuse.  The obtuse angle is used for larger radius cuts.

The curved knives are indeed more versatile.  When cutting a bridge,  a nice flat cut cannot be done consistently with a straight knife; If you look closely, the cuts are always a little bulged in the center from front to back.  With the curved knife the blade can be angled more or less, depending on the radius of the curve, to allow a very slight hollow to the cut.  This cut looks very sharp to the eye because all you see is the leading edge, similar to cutting "f's".  

Larger curved knives are also much better for carving necks, as the angle of the cut increases the higher you get on the blade making it easier to move accurately through the maple.

Btw, these ideas all originate from my training and not any personal epiphany or brilliance.

I told my colleague Mr. Hayes this morning that his knife was being discussed, he informed me that the knife in the picture was one of mine.....that is why it looked familiar.  On a good note, I do still recognize my dog "what his name"..

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Brad gave some very good advice on sharpening these knives--it is so much easier if the blade can be removed from the handle.  With the handle in place, the knives wobble on the holding platform.  If you try to do it free-hand, you lose accuracy in controlling the shape. 

You really want a slight convex blade shape but that can easily come from the final sharpening on the wet-stone since stones are usually cupped.

Mike D

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These are my bridge knives, blade widths are 5 and 6 mm for the smaller ones, 10 mm for the wider one that I use only for the feet.

I have also a narrower blade of 3 mm width, but it seems to me that it has too little mass and that it vibrates too much loosing fluidity during cutting.

I also like the slightly curved blade, removable from the handle, grinded on the platform but mostly shaped and sharpened with waterstones because I don't have a Tormek....:rolleyes:

I find safer to make little change in the blade curve and cutting angle with stones only, not to burn the tips, going freehand on the grinding wheel for me is too difficult and precarious, I admire who can do it.-_-

5985f9315a319_DSC_8435ritrid.jpg.efa3a820faf93ff0a44761aca74c9531.jpg5985f9412aae3_DSC_8443rid.jpg.f3116985393fdf5fa74956f03b994876.jpg

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16 hours ago, Jerry Pasewicz said:

 AI do not shape the knives on a tool rest, it is all done freehand against the wheel.

Is that on a Tormek or a standard bench grinder? I feel like the diameter of the stone has to have some effect? 

 

Davide- those are lovely! 

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5 minutes ago, Jack Devereux said:

Is that on a Tormek or a standard bench grinder? I feel like the diameter of the stone has to have some effect? 

 

Davide- those are lovely! 

These days a Tormek.  It really is not that difficult, the cutting edge is ground parrellel to the sides of the wheel, not perpendicular.  Grinding this way it is easier to hold the blade steady and follow the existing bevel.

 

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5 minutes ago, Jerry Pasewicz said:

These days a Tormek.  It really is not that difficult, the cutting edge is ground parrellel to the sides of the wheel, not perpendicular.  Grinding this way it is easier to hold the blade steady and follow the existing bevel.

 

That makes sense. One more question and I promise I'll stop bugging you! How big is the blank you're starting with? I was trying to put that shape into the standard issue 1/4" Hock blade. Is that size workable? Thanks!

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32 minutes ago, Jack Devereux said:

That makes sense. One more question and I promise I'll stop bugging you! How big is the blank you're starting with? I was trying to put that shape into the standard issue 1/4" Hock blade. Is that size workable? Thanks!

I use the Swiss 6mm blades.  They are not the hardest, but sharpening before cutting a bridge is part of the ritual and does not take very long with these blades.

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1 hour ago, Jerry Pasewicz said:

These days a Tormek.  It really is not that difficult, the cutting edge is ground parrellel to the sides of the wheel, not perpendicular.  Grinding this way it is easier to hold the blade steady and follow the existing bevel.

 

The Tormek is the grinding tool we decided on purchasing for Oberlin. Jerry may use it freehand, and Jeffery may use it with guides, but one way or another, it works quite well for the people who attend from all over the world, who may not want to put a heavy grinder in their overhead bin luggage. :lol:

I don't own a Tormek, and I bring along a couple of grinders that I normally use, but hardly any of the attendees are hankerin' to use these any more.

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Tormek is definitely the best choice, I thought I would buy it a lot of times but in the end, given the little use I make of the grinding wheel, for now I have not bought it yet and I still stay with my old and battered cheap grinder.

If you have experience and a lot of patience you can live with high speed grinder, but for novice damaging tools by overheating is almost a certainty.
 

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Seriously? I shouldn't say anything, I know what professional cameras I had cost, but really, $1200 for a grinder to sharpen tools? I guess if time is money, it will pay for itself eventually.

https://www.amazon.com/Tormek-Sharpening-Complete-Sharpener-Accessories/dp/B01FV4TAKK/ref=sr_1_7?ie=UTF8&qid=1501967295&sr=8-7&keywords=tormek

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42 minutes ago, Frank Nichols said:

Seriously? I shouldn't say anything, I know what professional cameras I had cost, but really, $1200 for a grinder to sharpen tools? I guess if time is money, it will pay for itself eventually.

https://www.amazon.com/Tormek-Sharpening-Complete-Sharpener-Accessories/dp/B01FV4TAKK/ref=sr_1_7?ie=UTF8&qid=1501967295&sr=8-7&keywords=tormek

Amazon  is not always the cheapest place to buy, everyone believes so and they take advantage of it....:rolleyes:

https://www.cremonatools.it/tormek-mola-t-4.html

https://www.cremonatools.it/tormek-mola-t-8.html

The T4 little one costs "only" about 372 euros, the big T8 about 650 euros.

Anyway not cheap at all (in fact this is one of the reasons why I have not bought it yet:)), you can buy an economic slow speed water grinder for less but probably you will have to waste a lot of time in set it up for our purpose.

I hope that "Mr. Tormek" or "Mr. Cremonatools" will send me as a sponsorship at least one T-shirt after this advertisement.......:D

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34 minutes ago, Frank Nichols said:

Seriously? I shouldn't say anything, I know what professional cameras I had cost, but really, $1200 for a grinder to sharpen tools? I guess if time is money, it will pay for itself eventually.

https://www.amazon.com/Tormek-Sharpening-Complete-Sharpener-Accessories/dp/B01FV4TAKK/ref=sr_1_7?ie=UTF8&qid=1501967295&sr=8-7&keywords=tormek

You don't need all the accessories. If your patient you can find one on Craigslist from a guy who thought he was going to get into woodworking or turning bowls but never really got into it. That's how I found mine when the previous owner needed more storage space. T-2000 with a bunch of accessories I don't use for $200. 

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I tend to be a pretty conservative guy and I do not take change lightly, but the Tormek was one of the best tools I have ever purchased.  In a shop with 6 full time violinmakers, it would have been exponentially more expensive to to live without.

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2 minutes ago, Jeffrey Holmes said:

I purchased my first one when they first released a 110V version....  still have it.  Excellent tool.

That was nineteenforty.............

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32 minutes ago, Jerry Pasewicz said:

That was nineteenforty.............

You bought yours is in '55, right? 

Seriously though, the Tormek pays for itself.  I've seen the knockoffs, but I think if you are relying on your edge tools to make a living it's worth the price. 

 

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2 hours ago, Jerry Pasewicz said:

I tend to be a pretty conservative guy and I do not take change lightly, but the Tormek was one of the best tools I have ever purchased.  In a shop with 6 full time violinmakers, it would have been exponentially more expensive to to live without.

That makes complete sense, the time spent sharpening to do good work times 6 every day would make it well worth while.

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3 hours ago, Davide Sora said:

Amazon  is not always the cheapest place to buy, everyone believes so and they take advantage of it....:rolleyes:

https://www.cremonatools.it/tormek-mola-t-4.html

https://www.cremonatools.it/tormek-mola-t-8.html

The T4 little one costs "only" about 372 euros, the big T8 about 650 euros.

Anyway not cheap at all (in fact this is one of the reasons why I have not bought it yet:)), you can buy an economic slow speed water grinder for less but probably you will have to waste a lot of time in set it up for our purpose.

I hope that "Mr. Tormek" or "Mr. Cremonatools" will send me as a sponsorship at least one T-shirt after this advertisement.......:D

I cheated a little (like any good troll) and picked the one with all the toys included - so it was the most expensive. 

I hope they do let you have one to evaluate for an endorsement, I think that would be a very good business decision on their part.

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$1200  for a Tormek grinding system--have you lost your minds?  Have you forgotten what Michael Darnton was talking about a few years ago using a hand grinder?   Here is a link:  https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwj-6LGJzsHVAhXEy4MKHfznCqsQFggoMAA&url=http%3A%2F%2Fwww.darntonviolins.com%2Fviolinmagazine%2Fbook%2Ftools%20and%20sharpening.pdf&usg=AFQjCNE6SnaR5Cqh2IoMqPE3ZSfv6rlS1A

The beauty of a hand grinder is that it is inexpensive and grinds slow enough that you do not overheat the steel. 

A few years ago, Delta made a system somewhat similar to the Tormek.  You should be able to pick up for little money.  Throw out the big grinding wheel and replace with a new one from McMaster-Carr.

Mike D

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3 hours ago, Mike_Danielson said:

$1200  for a Tormek grinding system--have you lost your minds?  Have you forgotten what Michael Darnton was talking about a few years ago using a hand grinder?   Here is a link:  https://www.google.com/url?

Lot's of people get by fine without one, you don't need to get one, and it doesn't need to make sense to you, but it is a great machine.  If time is money, mine has proven profitable many times over. 

The machine (the T-8) itself is now around $800 (I think the top model was it was well under $300 when I bought it in the '90s).  It's a slow turning wheel in a water bath, so burning tools is pretty damn difficult.  You don't need all the toys. I mainly use 3 and I believe the basic machine comes with two of them.

The Delta vertical wet wheel was not nearly as useful.  Jet tried to market a Tormek clone that I found disappointing as well.  

I have a hand grinder, and it's great for some things, but I find it's not for others. 

No, I do not believe I've lost my mind, but if I had, would I really know?   :) 

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7 hours ago, Jerry Pasewicz said:

That was nineteenforty.............

Hahaha...  The 90s.  The first one produced that even resembles what's made now was marketed in the mid 80s, but it was pretty rough.  It's bad enough I remember that.  When I was in school 1984 was a book about the future, not a memory of my son at age 5.

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7 hours ago, Mike_Danielson said:

$1200  for a Tormek grinding system--have you lost your minds?  Have you forgotten what Michael Darnton was talking about a few years ago using a hand grinder?   Here is a link:  https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwj-6LGJzsHVAhXEy4MKHfznCqsQFggoMAA&url=http%3A%2F%2Fwww.darntonviolins.com%2Fviolinmagazine%2Fbook%2Ftools%20and%20sharpening.pdf&usg=AFQjCNE6SnaR5Cqh2IoMqPE3ZSfv6rlS1A

The beauty of a hand grinder is that it is inexpensive and grinds slow enough that you do not overheat the steel. 

Mike D

Hard to believe that so many top professionals from around the planet disagree with Darnton.

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