Retrofit for the KJ-45 to make it Adjustable!

[VijayDoshi]

Hi everyone,

I've developed a retrofit for the KJ-45 to bring back the adjustable attribute of the SVM-45 - there's a link to a video at the end of this post.

Update (5/7/2024): the kit  is now available on our website:
https://magnoliaknife.com/products/tormek-kj-45-adjustable-retrofit



Problems with the KJ-45
1.      It's not adjustable, you can't make micro adjustments easily, rendering the wood block technique less useful.
2.   Tool rest handle is too small, long blades pull the knife towards you.
3.   Occasionally you inadvertently use the "short stop" without realizing.
4.   The self-centering aspect is generally solving a low priority problem – we've never-ever had a customer complain about it.
5.   Plastic shaft is not as sturdy as it needs to be.
6.   Smaller torque screw is hard to get tight.

Problems with the SVM-45
1.   Shaft is slightly too short to accommodate very short blades without adjusting tool rest height.
2.   Plastic tool-rest wears out, we wrap electrical tape around the treads to establish tension... after three years it is now stripped.
3.   Not "centered" – though we have not found this to be a real problem.
4.   It's no longer being produced (boo!)

Introducing our retrofit for the KJ-45
1.   Fits precisely into the jig KJ-45 jig.
2.   Fillet cut maintains alignment and allows for variable height
3.   Longer shaft – 20mm longer than SVM-45 handles smaller and larger knives without having to reset tool rest height.
4.   Aluminum guide and tighter threads provide a longer life and more friction to prevent changing adjustment during sharpening – variable friction using lock-tite.
5.   Patent pending since this is an improvement to an existing invention/patent

These will be available for pre-order on our website magnoliaknife.com soon – email me at vijay@magnoliaknife.com if you are interested. 


https://youtu.be/WiammYI1PIs

[tgbto]

Hi,

I'm not sure I got it right but from what I can see in the video, One jaw (the one with the threaded cylinder) is fixed relative to the shaft of the jig, while the other (the "shorter" one) moves. so it would seem that it negates the advantage of the KJ over the KVM, namely to have symmetrical clamping. But maybe I'm wrong.

I believe that an efficient way of solving this is one where the plastic part of the clamp is similar to the KJ, but threaded at the end (as the KVM one) and an adjustable handle is attached. Probably with an additional nut on the far side to solve the problem where the handle rotates while sharpening. As it is a fairly obvious combination of both the old and new design, I'm not sure this would be patentable though.

<edit> And for reference sake, a design for 3D-printing that was uploaded a few weeks ago : See on printables.com . It seems more or less to follow the same idea.</edit>

[cbwx34]

Hi,

I'm not sure I got it right but from what I can see in the video, One jaw (the one with the threaded cylinder) is fixed relative to the shaft of the jig, while the other (the "shorter" one) moves. so it would seem that it negates the advantage of the KJ over the KVM, namely to have symmetrical clamping. But maybe I'm wrong.
...

Pretty sure you're right, which is why (paraphrasing) "centering doesn't matter" is repeated.  Basically, just remaking an SVM jig from KJ parts.

...
Problems with the SVM-45  KJ-45
1.      It's not adjustable, you can't make micro adjustments easily, rendering the wood block technique less useful.
2.   Tool rest handle is too small, long blades pull the knife towards you.
3.   Occasionally you inadvertently use the "short stop" without realizing.
4.   The self-centering aspect is generally solving a low priority problem – we've never-ever had a customer complain about it.
5.   Plastic shaft is not as sturdy as it needs to be.
6.   Smaller torque screw is hard to get tight.

Problems with the KJ-45  SVM-45
1.   Shaft is slightly too short to accommodate very short blades without adjusting tool rest height.
2.   Plastic tool-rest wears out, we wrap electrical tape around the treads to establish tension... after three years it is now stripped.
3.   Not "centered" – though we have not found this to be a real problem.
4.   It's no longer being produced (boo!)
...

I think you had this mislabeled?

[tgbto]

Pretty sure you're right, which is why (paraphrasing) "centering doesn't matter" is repeated.  Basically, just remaking an SVM jig from KJ parts.

Ooh damn, you're right. I don't know the price point for this but postage included it might well make it an expensive SVM-45.

Wouldn't that kind of adapter with the right fit do the trick for le$$ if one doesn't care about centering ? Saw off the end of the KJ before the middle stop, glue it inside the hole, use an embedded M8 nut as an adjustable stop ?

[VijayDoshi]

SVM-45's are nowhere to be found (if you can find a good source LMK!) - so this lets anyone that wants the adjustable-ness of the SVM-45 and has bought a KJ-45 fix that.

Yes - thanks, they were mislabeled - fixed in original post.

This primarily brings back the adjustable aspect that we lost with the KJ-45 that we used to have with the SVM-45, in addition to making the shaft longer than the original SVM-45. On the KJ45 there is only a plastic post that is split so retrofitting it without something like this is likely to be very tenuous.

[tgbto]

Right again, I forgot about the split.

Out of curiosity, have you checked with Tormek that they won't consider it a patent infringement on their SVM-45 and/.or KJ-45 ?

And if not, would it be less expensive overall to just go all the way and may an entire jig from scratch, free from compatibility constraints with the KJ ?

[VijayDoshi]

This qualifies as an "improvement" to an existing patent according to my attorney which; in the U.S., is permitted.
Novelty
The improvement must be new and not known or used by others in the country.
Non-obviousness
The improvement must not be obvious to a person having ordinary skill in the area of technology related to the invention.
Usefulness
The improvement must add a new function or extends the existing function of the invention.

Many people already have KJ-45's since that is what is coming with all the "kits" that Tormek makes and generally is what people seem to start out with. Will see if people buy it or ask for the whole thing as a single unit - that might qualify as an infringement though since I'm not extending the use of an existing product (the retrofit) so I doubt I'l go there. Also, since people would be buying a KJ-45 anyway, what would the damages be to Tormek - basically none.

[Ken S]

I hate to discourage innovation; however, all Tormek SVM jigs made prior to 1992 had longer shafts. Tormek switched to the shorter shafts in present use because some users were leaning on the longer shafts.

Ken

[VijayDoshi]

Interesting, what was the impact of users leaning on the shaft?

[Ken S]

I suspect it placed uneven pressure and uneven bevels.

Ken

[VijayDoshi]

We'll be using these in our business over the foreseeable future I will keep an eye out for any issues.

[VijayDoshi]

Update: We've been using the retrofit for a couple of weeks now. We no longer need to adjust the height of the  USB because we have the additional span of the shaft. We haven't found any issue yet with having a longer shaft other than it makes our work easier. The standard threads are tighter than the acme threads on the original and the fit is a bit looser. This makes for fast adjustment against the wood block we use to align. My employees are very happy since this speeds up their work and they are commission based per-inch. We did a farmer's market and never had to change our USB height the whole day! We sharpened over 100 knives.
In any case, we are pleased. One improvement in the next production run will be to add 5-10 mm of threads at the lower limit to account for even wider knives and perhaps chamfer the end of the adjustment knob more for comfort. The all aluminum construction also seems to be self-lubricating against the USB, only concern there is wear...

[Ken S]

Vijay,

I have some questions about the design of your shaft. I am being curious, not critical.

I have used the kenjig to set up my knives. In a nutshell, the theory behind this is to establish a common setting for the Distance between the USB and the grinding wheel. This would be set before a sharpening session with no need for readjustment.

The Projection of the knives would be set to 139mm. Others have used 140mm which works just as well. This requires at least three jigs to cover the width ranges of typical kitchen knives. the 139mm Projection was determined by the adjustability range of the SVM-45 allowing some wiggle room for wheel diameter wear.

My questions for you:
Is the adjustability range of your jig shaft such that you can establish a common setting for all knives from sal paring knives to large chef's knives? What is that millimeter setting?
Does that range allow for changes in wheel diameter and changes in bevel angles?

Ken

[VijayDoshi]

Hi Ken, thanks for the questions.

We set to 140mm projection (sometimes we need to adjust to match specific bevels) but our default is 140mm to get a 20 degree bevel. The height of the USB changes occasionally as the wheel get's smaller - perhaps once a month. We now only need to change the USB for really, really wide knives like cleavers. The retrofit I've made seems to work for even the smallest blades @140mm. As the wheel gets smaller, we may need to go back to a two USB system for now we can leave it set at about 175mm for a 250mm wheel - it obviously changes as the wheel gets smaller. The smallest wheel we have currently is 225mm and it's still working.
I measure the wheels and use the Grinding Angle Setter for Tormek app to calculate the USB height every few weeks and post a 140 & 130 projection height for my staff to reference.