Author Topic: Difficulty of milling the knife jig  (Read 1202 times)

Offline SHARPCO

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Difficulty of milling the knife jig
« on: July 09, 2018, 05:44:47 am »
For a thick knife sharpening, I thought I had to mill the jig like Wootz did. But all of the machinists said, "For this work, I have to make a another jig that holds your jig, which is expensive."

I suggested them to fix it with vise, but they said it would not be enough.

Is there another good way to fix the SVM-45 to a milling machine?

Offline RickKrung

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Re: Difficulty of milling the knife jig
« Reply #1 on: July 09, 2018, 09:20:14 pm »
For a thick knife sharpening, I thought I had to mill the jig like Wootz did. But all of the machinists said, "For this work, I have to make a another jig that holds your jig, which is expensive."

I suggested them to fix it with vise, but they said it would not be enough.

Is there another good way to fix the SVM-45 to a milling machine?

I can appreciate those machinists' perspective.  The knife jig has very little area for grabbing it in the vise and has raised lettering on the back side, complicating setup in a vise.  I think they see it as way more trouble than it is worth, especially considering it is a one-off job with an unwelcome risk of screwing up the knife jig. 

Raised lettering on the back, which would best/easiest dealt with by milling it away.


Here is a setup that I might use for removing the raised lettering.


Here is a setup that I might use for milling the recess on the clamping side. 


All in all, considering the time I spent figuring out the setups, then doing the work, I figure between 1-2 hrs of shop time, meaning around $100 minimum.  If a shop is busy, they are not going to want to mess with such a puny job.  I don't want to do it for others as I don't want to be doing machining for others for pay.  Ruins the "play" that machining is for me doing my own projects. 

Anyone who wants to can take these photos to a shop and ask what it would take/cost for them to do it this way.  Let us know how it works out. 

Rick



« Last Edit: July 09, 2018, 09:21:51 pm by RickKrung »
Quality is like buying oats.  If you want nice clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes at a lower price.

Offline SHARPCO

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Re: Difficulty of milling the knife jig
« Reply #2 on: July 10, 2018, 02:12:44 am »
I can appreciate those machinists' perspective.  The knife jig has very little area for grabbing it in the vise and has raised lettering on the back side, complicating setup in a vise.  I think they see it as way more trouble than it is worth, especially considering it is a one-off job with an unwelcome risk of screwing up the knife jig. 


All in all, considering the time I spent figuring out the setups, then doing the work, I figure between 1-2 hrs of shop time, meaning around $100 minimum.  If a shop is busy, they are not going to want to mess with such a puny job.  I don't want to do it for others as I don't want to be doing machining for others for pay.  Ruins the "play" that machining is for me doing my own projects. 

Anyone who wants to can take these photos to a shop and ask what it would take/cost for them to do it this way.  Let us know how it works out. 

Rick

Thank you very much Rick.

You explained the perspective of the machinist well and I could understand it.

Your photos will be helpful.

Offline RickKrung

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Re: Difficulty of milling the knife jig
« Reply #3 on: July 10, 2018, 09:26:29 am »
I figured out a better way to mill recesses in the clamping surface of the fixed jaw of the knife jig.  It uses precision parallels under the back side, located where there are no raised letters.  One simple setup, photos show that it is within 0.0005" of being parallel, assuming that surface is parallel with the jig centerline (an assumption that has to be made). 




Last photo shows how the front edge of the jig was squared up, using two precision parallels in the mill table slot.  Not indicated and so maybe not perfect, but well within the working parameters of how I insert and clamp blades in the jig. 


A while back, I bought a second SVM-45 with the idea that I would mill the recess to allow better centering of wider blades.  I sorta forgot about that as I found the second jig quite useful when sharpening multiple knives.  Having figured out this simple setup, I think I'll go ahead and mill a recess in one of them and start working on centering the blades for better symmetry of bevels. 

Rick
« Last Edit: July 10, 2018, 09:29:18 am by RickKrung »
Quality is like buying oats.  If you want nice clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes at a lower price.

Offline Ken S

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Re: Difficulty of milling the knife jig
« Reply #4 on: July 10, 2018, 01:48:18 pm »
Sharpco,

Rick's advice is quite good. Much of the time cost in machining is in the set up. If you wanted sixty jigs modified, the set up time could be allocated to each unit. An hour set up time for one knife jig would become costwise one minute for each of the sixty knife jigs. The cost of the hour is still the same; it is just divided up.

When Robin Bailey first introduced his extended support bar, he hoped around twenty forum members would order one. That would have made the individual cost per unit very reasonable, far less than having each of the twenty work individually with a local machinist.

Milling different depths into the knife jigs is certainly a big step forward for precision knife sharpening. I think the long term solution will be self centering jigs. I have no insider knowledge with Tormek, however, when Tormek makes significant changes to a product, they change the model number. The T3 was redesigned and became the T4. The T7, after several design upgrades which did not change the designation, was redesigned and became the T8. The truing tool became the TT-50. The SE-76 became the SE-77; the SVD-185 became the SVD-186. Both of these new jigs are quite remarkable.

The knife jig was somewhat redesigned with zinc and a new locking mechanism. These improvements were not significant enough to warrant a new model designation. With the long knife jig, only the locking mechanism was changed.

Tormek has been making significant product investments in the knife sharpening market. The T2 is designed only for knife sharpening. The DWF-200 and DWC-200 diamond wheels are designed primarily for the knife specific market. I think the rubber honing wheel may be the beginning of a revolution in deburring for knives. I believe we will continue to see significant advances in knife sharpening from Tormek. I cannot imagine these advances not including new knife jigs.

Ken

PS to Rick: Do you think it would be practical to deepen the slot using a belt grinder with a good platen? I would want to work slowly and frequently measure with calipers both the depth and the parallelness (such a word?). Worst case scenario, a spare part might be needed.

Offline SHARPCO

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Re: Difficulty of milling the knife jig
« Reply #5 on: July 10, 2018, 01:52:18 pm »
I figured out a better way to mill recesses in the clamping surface of the fixed jaw of the knife jig.  It uses precision parallels under the back side, located where there are no raised letters.  One simple setup, photos show that it is within 0.0005" of being parallel, assuming that surface is parallel with the jig centerline (an assumption that has to be made). 

Last photo shows how the front edge of the jig was squared up, using two precision parallels in the mill table slot.  Not indicated and so maybe not perfect, but well within the working parameters of how I insert and clamp blades in the jig. 

A while back, I bought a second SVM-45 with the idea that I would mill the recess to allow better centering of wider blades.  I sorta forgot about that as I found the second jig quite useful when sharpening multiple knives.  Having figured out this simple setup, I think I'll go ahead and mill a recess in one of them and start working on centering the blades for better symmetry of bevels. 

Rick

Awesome!

Offline SHARPCO

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Re: Difficulty of milling the knife jig
« Reply #6 on: July 10, 2018, 01:59:24 pm »
Sharpco,

Rick's advice is quite good. Much of the time cost in machining is in the set up. If you wanted sixty jigs modified, the set up time could be allocated to each unit. An hour set up time for one knife jig would become costwise one minute for each of the sixty knife jigs. The cost of the hour is still the same; it is just divided up.

When Robin Bailey first introduced his extended support bar, he hoped around twenty forum members would order one. That would have made the individual cost per unit very reasonable, far less than having each of the twenty work individually with a local machinist.

Milling different depths into the knife jigs is certainly a big step forward for precision knife sharpening. I think the long term solution will be self centering jigs. I have no insider knowledge with Tormek, however, when Tormek makes significant changes to a product, they change the model number. The T3 was redesigned and became the T4. The T7, after several design upgrades which did not change the designation, was redesigned and became the T8. The truing tool became the TT-50. The SE-76 became the SE-77; the SVD-185 became the SVD-186. Both of these new jigs are quite remarkable.

The knife jig was somewhat redesigned with zinc and a new locking mechanism. These improvements were not significant enough to warrant a new model designation. With the long knife jig, only the locking mechanism was changed.

Tormek has been making significant product investments in the knife sharpening market. The T2 is designed only for knife sharpening. The DWF-200 and DWC-200 diamond wheels are designed primarily for the knife specific market. I think the rubber honing wheel may be the beginning of a revolution in deburring for knives. I believe we will continue to see significant advances in knife sharpening from Tormek. I cannot imagine these advances not including new knife jigs.

Ken

PS to Rick: Do you think it would be practical to deepen the slot using a belt grinder with a good platen? I would want to work slowly and frequently measure with calipers both the depth and the parallelness (such a word?). Worst case scenario, a spare part might be needed.

You're right Ken.

I think Tormek should make a new self-centering jig like you.

Offline Ken S

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Re: Difficulty of milling the knife jig
« Reply #7 on: July 10, 2018, 02:20:28 pm »
We live in hope.

Ken

Offline RickKrung

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Re: Difficulty of milling the knife jig
« Reply #8 on: July 10, 2018, 05:44:57 pm »
...snip...
Ken

PS to Rick: Do you think it would be practical to deepen the slot using a belt grinder with a good platen? I would want to work slowly and frequently measure with calipers both the depth and the parallelness (such a word?). Worst case scenario, a spare part might be needed.

Ken,

First, there is no "slot" on the fixed jaw of the jig.  It is all one flat surface except for very minute relief in the center with very narrow strips on the edges at the same level as the rest of the jaw flat.  The only reference on the bottom/fixed jaw for squaring a knife are two cast "pins".  It is the top/movable jaw that has the relief with a shoulder on the back. 


I have only casual experience with belt grinders.  I have two belt sanders, a 1" and a 4".  I've used the 1" mainly for deburring metal parts, usually bandsaw cutoffs.  The 4" was bought for bamboo fly rod making and has been used mainly for wood working, but in the past 6 mos. I bought metal cutting belts for the 4" and discs for my 12 disc sander.  Even so, they are used only occasionally.

My initial reaction to your question is No, I do not believe a belt sander is a suitable tool for making the reliefs in knife jigs.  My thinking is that it would be too difficult to keep the relief flat all the way across.  I think there would be rounding at the sides, leaving relief "crowned". 

I think it would take substantial work to modify/create a rigid platen for the belt and a rigid method of holding the jig.  I have not yet conjured in my mind what that might look like.  I think, if you were to want to try it, start with some practice pieces, beginning with wood and move on to aluminum, before trying it with a real jig. 

Also, I think that filing would have a better chance of resulting in a flat relief.  You could do most of the metal removal with a belt sander but finish with a file.  I have heard the classic tales of the old German masters requiring new apprentices to start by making perfectly square and flat steel blocks only using files, but I am sure even my father did not start out that way.  I certainly do not have the skill with files to even come close. 

If I were to try it with a file, I'd set up some sort of jig arrangement that would keep the file parallel and flat so that it only remove the high spots in the middle left by the belt sander.  I would not be as concerned about the shoulder on the rear of the recess as far as keeping it flat, as I think the way we mount knives, while a squared shoulder is nice, aligning the knife by eye, using Jan's template, I usually adjust the knife to be square to the top line, without detailed reliance on the back shoulder. 

But, those are just my thoughts.  Maybe someone with more experience with belt sanders can enlighten us.

Rick

P.S. I would hyphenate it: parallel-ness, but spell checker still thinks it is misspelled  :)
« Last Edit: July 10, 2018, 05:47:04 pm by RickKrung »
Quality is like buying oats.  If you want nice clean, fresh oats, you must pay a fair price. However, if you can be satisfied with oats that have already been through the horse, that comes at a lower price.