SVM-45 and SVM-140 jig centering bushing

[jvh]

Hello everyone,

as many others I had a problem with knife centering in jig SVM-45 and SVM-140, because jig does not center the knife correctly and bevel on one side is different from other side.

Therefore I made a centering bushing which is mounted on the jig. Bushing is eccentric and by turning left or right is a knife easily centered. Outside diameter is 15,3 mm, inside 12+0,1, eccentricity ca 1,6 mm, length 25 mm, lock screw M3x3, 5 mm from the end.

Outside diameter is still small to use adjustable stop without any limitation, moreove there can be a gap between the bushing and  adjustable stop (theoreticaly up to 6 mm), which allows to make angle corrections by turning adjustable stop. For angle checking I'm using Anglemaster WM-200 on opposite sides of blade.

jvh

[cbwx34]

Clever!  👍🏼 👍🏼

[Ken S]

JVH,

Your idea is intriguing. It will take me a while to wrap my head around it, however, I do think you are on to something significant.

Good work!

Ken

[Sharpco]

Good idea!

[RichColvin]

Jan,

I've wanted to use the SVM-00 Small Knife Holder with pocket knives which have small blades, but the ones I sharpen always have multiple blades on each side.  This made the angles drastically different for each side.

And I've found that most small blades are too small for the SVM-45 to hold.

I think that a greatly exaggerated version your cam could make this work!   I'm thinking maybe this would need 7-10 mm difference side to side (I.e., 12 mm hole with 20-25 mm outside diameter).

I'm going to make one in the next few weeks.   I'll let you know what I find. 

Brilliant idea !   I'm excited.

Kind regards,
Rich

[Jan]

Congrats jvh! Really brilliant idea!  Thanks for sharing it here.

I could imagine some ticks on the eccentric bushing surface which will help to mount a knife with specific blade thickness.

Jan

[jvh]

Thanks all! 

I forgot to mention one disadvantage - when grinding and raising the handle at the end, the jig axis and therefore grinding angle changes a little bit, due eccentricity of the bushing. It's not a problem for me in the most cases because eccentricity isn't too big and method with jig 's rotation left/right is usable without any influence to grinding angle.

I've wanted to use the SVM-00 Small Knife Holder with pocket knives which have small blades, but the ones I sharpen always have multiple blades on each side.  This made the angles drastically different for each side.

See above - with high eccentricity there is a risk of high angle changes when raising the handle of the knife.

For such knives I'm using correction by turning adjustable stop. Set one side with Anglemaster WM-200, mark start position of adjustable stop, turn the jig and set the same angle on the other side by rotation of the adjustable stop. Count the number of turns, write this number to blade (e.g +2,5) and mark finish position of of adjustable stop. Now, when I'm turning the jig I make angle correction by turning adjustable stop to start or finish position. It's not comfortable at all but it works.

Thanks for sharing it here.
I could imagine some ticks on the eccentric bushing surface which will help to mount a knife with specific blade thickness.

Not here only, see knife.cz 
It's not that easy, the clamps would always have to be in the same position (e.g. paralel), otherwise angle will differ.

[Ken S]

JVH,

I would like to share some thoughts based on your clever new collar idea.

First, let's imagine one of Jan's drawings of a knife jig with an axis line drawn through it. This represents a jig with a knife attached which is perfectly centered and aligned.

Next we add the wooden block used by Wootz in his knifegrinders.com.au you tubes to hold the knife and jig to measure Projection. The jig and knife must lay on the block with Jan's center axis line parallel to the block.

If everything is aligned properly, the edge lines for both sides would fall into the same kerf line on the sliding block.

If the two kerf lines do not match, and can be made to match by revolving the eccentric cam, this would be a major advance!!!

Ken

ps I started this earlier today and just read John's last post after I was going to post this. It sounds like there are some tweaks needed, however, I believe the effort eill be most eorthehile.

[tgbto]

Looking at this thread yet again, I find it very interesting but I don't see how i'll easily procure an eccentric bushing, I'm wondering whether a plain bushing wouldn't do the trick: Say one with a 15mm inner radius, 19 outer, and a M3 thread for a screw say somewhat shy of 5mm long. If the jig is centered, tighten with the screw on the side (no offset), then rotate at will up to 90° where you will have the maximum offset (3 mm).

That I think I could build myself. Any thoughts ?

[LarK]

Wow this looks like a really beautiful and simple solution to the problem. Just add the correct bushing depending on the knife 👍
Now I just have to wait for someone to mass produce them 😂
//Kristian

[Greybeard]

Here is an alternate idea that is blade thickness specific.  - Happy to share .STL files, if other want to 3D print and try.
https://forum.tormek.com/index.php?topic=4868.0

[Ken S]

I can see the benefits of these jigs for the SVM-45 standard knife jig. However, I do not understand trying to use them with the SVM-140 long knife jig. Tormek has always stated that the long jigs are for knives which are both long and thin. A long knife (or machete) which was thicker than the thickness range of the standard issue SVM-45 would certainly not need a modified jig.

Ken

[Scotty]

As an aside, I noticed that you seem to have replaced the tightening knob with a hex screw( correct name?). Any particular reason?

[Ken S]

Good observation, Scotty.

Switching the plastic topped tightening screw came from my investigations trying to see if it was really necessary to use the leather honing wheel freehand with my T4 instead of with the knife jig as stated in the handbook. With the plastic knob facing downward (toward the support bar), sidewise movement of the jig is stopped by the plastic knob. I found that if I substituted button cap screws for the plastic locking screw on the knife jig and the two horizontal sleeves, the jig slid freely. (Actually, almost freely. I needed to grind off a tiny bit of the back of the jig. This amount is so small that it has no effect on the integrity of the jig. If you decide to go this route, you will easily see the spot.)

The Tormek locking screws have a common 6-1 metric thread, 6mm diameter by 1 mm pitch. The button cap screws used a 4 mm Allen (hex) wrench. All Tormek users should have a set of metric Allen wrenches. The button cap screws I found had 12 mm length, slightly too long. I ground off the excess length with my belt grinder, although I could have used my Tormek. They worked very well, with good clearance. If you can find 6-1-10 button cap screws, they will work perfectly with no modification.

In order to provide a no grinding needed option, I switched to 6-1-10 socket set ("grub" screws). These set entirely in the threaded hole and do the job. I suggest a leisurely visit to your local hardware store. There are many useful parts.
I suspect Torgny did the same visit in the early days of the Tormek.

The other discovery with this was that combining the US-430 support bar with the low clearance screws makes both sharpening and honing my ten inch chef's knife a joy. Using an FVB makes this modification unnecessary and really is more efficient. However, for the low budget and/or low volume sharpener, the screws can all be had for $5 US, compared with around $100 for the FVKen

[Scotty]

Thanks.
Still struggling with blade centering in the SVM 45.
Any suggestions other than milling the static bottom of the jig.
I often do more than one group of knives, using the length adjustment so they all have the same projection.
I have 6 SVM 45s.
Should I mill them all and use tape or shims as necessary to center as required?
Had a real problem with  very thick Japanese blade (Deba) with a concave back.
Thanks