news from the developers front

[Hannsi1957]

it took a little more time than i thought but it will be worth it. here you can see the prototype of my double-sided closing clamp. finally the knife will be clamped in the center no matter how, it is centered. always the same cutting angle on both sides. this prototype will be reworked but it already works great.

https://youtu.be/ov-ex_1bYz0

cheers Hanns

[cbwx34]

it took a little more time than i thought but it will be worth it. here you can see the prototype of my double-sided closing clamp. finally the knife will be clamped in the center no matter how, it is centered. always the same cutting angle on both sides. this prototype will be reworked but it already works great.

https://youtu.be/ov-ex_1bYz0

cheers Hanns

Hope that's an early prototype! 😳 😉

[Hannsi1957]

WHY?

[cbwx34]

WHY?

For starters:

What angles (low) can you get to?

Clamping blades tapered from spine to edge?

[Hannsi1957]

As I said it's the first prototype and it was all about the function itself. The bracket will be tapered to the largest possible minimum strength. You are welcome to write all your suggestions here and we can see what is feasible and affordable. I have been looking for 2 years for such an implementation and have not found anything like this yet. The people are milling material out of the original clamp to center the knife. This can't be the solution I thought. So give me your ideas and I will read them all carefully and hopefully build a useful tool. I know you can discuss about length and width. But the most important thing for me is to finally have a tool with which I can make sure that the angles match perfectly on both sides. cheers Hanns

[Even]

Hi Hanns.
This looks promising, I have hoped for years that Tormek will come up with a self-centering clamp.
I will definitely buy one from you if you get a good working model.
Keep up the good work!
Even

[jvh]

Hello,

the idea with a right-left thread bolt that tightens paralel clamps is good, but from technical view the construction itself is the cause of secondary problems.

The main was mentioned by cbwx34 - clamping blades tapered from spine to edge (full flat grind "V") is impossible (or at least very problematic) and does not guarantee centering of such knife. The same is valid for other knives with non-paralel blade sides.

Second problem also mentioned cbwx34 and you answered that the bracket will be tapered to the largest possible minimum strength. OK, but it doesn't solve problem with the bolt/knob height, which can interfere with the stone when grinding smaller angles. It will probably also collide with horizontal USB legs when grinding or honing. You can make clamps longer but it brings problems with bending and high load of bolt/thread, or you can make bolt shorter but in that case the thread will be heavily loaded and it will reduce possible clamping force and thickness range.

The third problem is associated with this and it's minimal possible clamping depth, for e.g. narrow blades. It brings clamps bending and bolt/thread load back again.

I wish you good luck to find the best solution and maintaining a reasonable production cost, it can be great jig for knives with paralel blade sides... 


jvh

[cbwx34]

As I said it's the first prototype and it was all about the function itself. The bracket will be tapered to the largest possible minimum strength. You are welcome to write all your suggestions here and we can see what is feasible and affordable. I have been looking for 2 years for such an implementation and have not found anything like this yet. The people are milling material out of the original clamp to center the knife. This can't be the solution I thought. So give me your ideas and I will read them all carefully and hopefully build a useful tool. I know you can discuss about length and width. But the most important thing for me is to finally have a tool with which I can make sure that the angles match perfectly on both sides. cheers Hanns

That's why I said, "hope it's an early one".

I'm hopeful, but not optimistic about this design... mainly because I've seen it before.  Not adapting to blade shape can become a bigger issue than "self centering".  You can add padding, etc. to compensate, but it becomes tedious. 

I'm starting to understand why the solution is so difficult....   

[RickKrung]

Good idea. 

I immediately noticed how high the knob stands, which will severely collide with the wheels, particularly given how close the knob is to the front of the jaws.  My first thought about how to solve this would be with a socket head screw, like a set screw.  So, rather than having a knob on it at all, one would need a hex key to insert into the socket to tighten and loosen, then remove and both sides of the jaws are totally clear.  Slight bother having to handle a separate tool to operate, but I think something that users would tolerate to have the self-centering function. 

The steep angle on the topsides of the jaws look like they will limit how small an angle that may be achievable.  This may have been considered in the design, so may not be a problem, but they just look too steep to me. 

I'm sure there needs to be adequate thickness to support the threads, particularly if the material is aluminum or zinc.  Use of threaded inserts made of stainless could help.  If I were doing this, I would first try the [urlhttps://www.stanleyengineeredfastening.com/brands/optia/heli-coil]"helicoil" style threaded inserts[/url].  I have them as small as 1/4" long.  These are meant for repairing stripped threads in metal, particularly engine parts, but I use them extensively in woodworking.  I have found them in 6mm at a local large hardware chain store, but online supply houses, like McMaster-Carr offer a vast array, plus the tools for inserting them. 

The photo posted here shows removing a helicoil threaded insert from some wood, but the remover could just as well be the insert driver tool. 

Making such a right/left, turnbuckle style screw with a socket head driver would be challenging, for sure.  I am noodling that in my brain as I type.  Turning down one end of a typical set screw and then turning left hand threads on that end, maintaining the thread pitch (M6) on a smaller diameter could be done, but then matching those with threaded inserts could be a problem, as they would be non-standard, left hand, which I doubt is available in threaded inserts.  That might be resolved by making an insert, but that has its own challenges.  M6 left-handed threaded inserts are available, but only at this site, only in 9mm length (0.354") but that could be a very suitable length. 

I just noticed the turnbuckle screw in your jig is a fair bit larger than M6, so maybe threaded inserts are available in more varieties that I've discussed above. 

I am curious about how the jig shaft mounts into the jaw set.  The first frames in your video appear to show it canted a bit, which suggests there may be some movement in that joint, which I think would not be good. Hard to tell, however, as the jig is not shown clamping a blade or in use. 

I'm sure you will keep us posted.

Rick

[RickKrung]

That's why I said, "hope it's an early one".

I'm hopeful, but not optimistic about this design... mainly because I've seen it before.  Not adapting to blade shape can become a bigger issue than "self centering".  You can add padding, etc. to compensate, but it becomes tedious. 

I'm starting to understand why the solution is so difficult....   

I wonder if jaws that would cant from side to side might satisfy the need to clamp tapered blades.  If you notice, there are two small "pins" on either side of the jaws, toward the rear.  I believe these are to keep the jaws aligned, with the pins fixed in one jaw and floating in a slip fitting round hole in the other.  If, instead of a round hole on the floating side, "slots" were used so the pins, while keeping the jaws aligned along the front clamping edge, the floating jaw could tilt or cant to match the blade taper. 

Rick

[Hannsi1957]

Many thanks for the inspiring ideas. We know about the problem of jamming. Of course this must be taken into account. The shape itself should not be the problem, but the force with which the clamp holds the knife. It may be that we have to get away from this idea completely and think of something else. A big problem is quite simply that of price. In my opinion, such a clamp should not cost more than €100. This would probably be in a still reasonable relation to the use. With the hourly wages which are demanded here in Germany this is an absolute challenge. You can be however safe that I do not give up yet so fast on a reasonable in addition, payable solution to work. I have another meeting with my developer today and we will deal with the mentioned problems. I will report further. Keep coming back with your suggestions and objections. The goal should be to develop a reasonable working tool.
Greeting Hanns

[Ken S]

Hanns,

I applaud you for taking on your knife jig project. For many years, the desire for a self centering knife jig has been a popular theme on the forum. The constraints have been many, especially for Tormek. I would guess the SVM-45 knife jig is probably Tormek's best selling jig. Apart from the popularityof knife sharpening, the knife jig is fairly easy to master and costs around $40 US (approximately 35€ ). I have long thought that Tormek could offer a better knifejig. As with any product being marketed, price is a factor. Would the knife jig be as popular if it cost $100 to $150? As a business with financial obligations, Tormek must think this way.

In my opinion, the DBS-22 drill bit jig is Tormek's most advanced jig. The versatility of this jig is amazing. However, to get these amazing results, one needs a higher level of both knowledge and manual skill. It is also Tormek's highest priced jig. I suspect much fewer of these jigs are sold than are knife jigs.

Another set of constraints for a self centering knife jigs is legal. Tormek holds many patents on its products. Look at the accessories available with the clones. The square edge jigs are typical. Most are copies of the jig Tormek made before the SE-76. There are several self centering jigs already on the market. I doubt making a jig for personal use would generate legal problems. Selling jigs might be a different story.

I wish you only the best with this project, and will probably purchase one.

Ken