Summary and example of the small platform jig

[GKC]

The topic of the "small platform jig" has come up again in a recent post so, for posterity, I have gathered the links to the previous discussions of (homemade) small platform jigs, and set out the details of the one I have made.

None of this discussion is original to me: all of the ideas came from the following threads, which I gather here for those who want to do the background research or just to have the main threads (at least, the ones I could find) gathered in one place:

•   Ionut's "Small knife blade rest – improvisation" thread
https://forum.tormek.com/index.php?topic=1191.msg3308#msg3308
•   Herman's "Homemade knife rest" thread:
https://forum.tormek.com/index.php?topic=1592
•   Herman's "Re: Ionut's small knife jig" thread:
https://forum.tormek.com/index.php?topic=1560.0
•   CB's thread "The one change you should make to the Tormek":
https://forum.tormek.com/index.php?topic=3459.0
•   CB's thread "Finally made a homemade knife rest":
https://forum.tormek.com/index.php?topic=3610.msg23411#msg23411
•   Y-Not's thread: "The learning curve":
https://forum.tormek.com/index.php?topic=3586.0
•      Elden's thread: "Self-contained jig based on Herman-Ionut jig"
https://forum.tormek.com/index.php?topic=1605.msg6897#msg6897

As discussed in these threads, there are many potential uses for a small platform jig.  Also, it can save some calculations and re-positioning when using the Anglemaster for the sharpening of blades that are tapered from the spine to the edge (this is discussed in the threads).

Here are the details of the small platform jig that I made; there are some pictures below.

I made the plate out of ¼" aluminium stock, instead of 1/8", for (1) stiffness; (2) extra height above the scissors jig platform for handle clearance; and (3) countersinking the attaching screws flush with the plate.

I used the scissors platform as the method of attaching the platform to the USB for the reasons discussed in the above-cited threads.  (Note that the adaptation of the scissors platform does not interfere at all with the use of the platform for its intended purpose with the scissors jig: when the small platform is removed, the scissors platform just ends up with two innocuous holes in it.) 

If I had a T2 jig, I might have tried using it as CB did: it looks like it would be at least as effective and maybe less bulky than the scissors jig platform, though perhaps providing less support for the plate.  The challenge of adding support for the plate (with the tools I have) also steered me away from kwakster's otherwise very elegant use of a bare Torlock collar with a plate attached and undergirded (see "The one change..." thread).

I located the small platform at the righthand edge of the scissors platform because that was what Herman and others did; this was pure imitation, it might be that the location of the plate on the scissors platform doesn't make any difference.

2" (matching the width of the wheels) is the maximum width of a small platform like this, so that blades can slide along the platform with their bolsters or handles right up to the edge of the wheel, and thus be sharpened along their whole length. 

The 2" plate for my small platform turned out to be 5 3/8" long.  I ground the angle of the leading edge at 15 degrees so that the thin edge of the plate would be close to the wheel for the most acute angles I was likely to use it for—about 15-20 degrees.  When I raise the USB for a more obtuse angle, the front edge stays tight to the wheel, so it still works in the 20-40 degree range.  (If I had ground the platform edge for a more obtuse angle, the edge of the plate would be rise above the wheel when the platform was lowered for more acute angles.) 

I drilled the holes in the piece of aluminium bar, then used them to locate the holes in the scissors platform.  It would have been cleaner to then thread the holes in the scissors platform, but I wanted a tool-less connection, so I drilled through-holes in the scissors platform and used wingnuts to fasten the machine screws underneath the scissors jig platform.  The tapered stainless steel machine screw heads grab the aluminium plate themselves without needing to be held, so attachment and removal of the plate just involves spinning the wingnuts—no tools needed.

Based on earlier comments, I tried various non-slip surfaces on the platform to minimize blade scratching from the platform surface, but I find (as Rick and others have noted) that the scratching isn't from the platform surface itself, it's from the grit getting on the platform (or on whatever it is surfaced with).  Regular wiping helps.  A good surface covering is felt, because the grit seems to disappear into it, but the softer the platform surface, the less precise the work.  I am now trying a wide piece of Velcro as the platform surface, because the grit can fall below the surface that is contacted by the blade, but there is still some stiffness to support the blade.

It might be that now that we have the small knife jig, one of the main drivers for the platform jig has gone, or at least diminished.  However, I quite agree with Ken's view that there are many other potential uses for a small platform jig, including the ability to sharpen just about anything on the platform, with flexibility that the Tormek tool rest (SVD-110) does not provide.

Gord

[Ken S]

I have been involved with the small platform project since the beginnng. A member post, wanting a better way to sharpen very small knives, sparked an email dialogue between Ionut and me. My interest was hypothetical. Ionut actually made up a prototype, but then moved on. Shortly after that, Herman made his small platform. Herman has stuck with the project and truly deserves to be recognized as the father of the working small platform.

Over the years, I have developed several ideas as to what works well for small platforms:

1) The platform, either full size or small, works best with Tormek's patented Torlock. The Torlock lets the user easily securely hold a platform. It works much better than a straight bore.

2) I like the lower center of gravity scissors platform better than the higher center of gravity Torlock platform. (Herman uses the scissors platform.)

3) My first choice for a small platform is the knife jig of the T2. In my opinion, this is the ideal beginning platform. It has a low center of gravity, and a narrow base with a Torlock. Unfortunately, Tormek only sells this as a complete assembly. This decision was only made after CB and I posted ideas for using this T2 assembly as a small platform. The complete assembly sells for $90 US. To me, the price makes the scissors jig the most practical starting point.

4) The single platform is just the tip of the iceberg. Interchangeable platforms specifically designed for specific applications has the potential for so much more.

At the end of the blitz, Winston Churchill stated that this was not the beginning of the end, but that it was the end of the beginning. I believe we are at that stage with the small platform.

Ken

[Elden]

Not to contradict Ken in saying "the Torlok is the best approach", I can personally state that I had no problem using just a piece of pipe.

https://forum.tormek.com/index.php?topic=1605.msg6897#msg6897

[Ken S]

Elden,

I have no doubt that you have no problems with plain pipe. I also think that the Torlock can do this more easily with less effort.

Ken

[Dutchman]

... snip
Based on earlier comments, I tried various non-slip surfaces on the platform to minimize blade scratching from the platform surface, but I find (as Rick and others have noted) that the scratching isn't from the platform surface itself, it's from the grit getting on the platform (or on whatever it is surfaced with).  Regular wiping helps.  A good surface covering is felt, because the grit seems to disappear into it, but the softer the platform surface, the less precise the work.  I am now trying a wide piece of Velcro as the platform surface, because the grit can fall below the surface that is contacted by the blade, but there is still some stiffness to support the blade.
...
Gord

I use my platform (in stainless steel) with the support bar in horizontal position, so with the stone turning away from the knife.
Then I do not run the risk that the platform "snaps" in the stone.
I have no problem with scratches. Now I understand it 

[GKC]

Good point Ton, having the wheel turning away from the platform would reduce the amount of grit that would get between the platform and the knife. 

It is encouraging to hear that you find that method to work, because one of the challenges of knife sharpening on a platform (discussed at p.18 of the manual) is that the knife blade tends to climb up the wheel (changing the grinding angle), and this effect is more pronounced when sharpening from the horizontal (wheel turning away) position.  This seems to be the reason that Tormek has not introduced a platform jig for knife sharpening, even from the vertical (wheel turning towards) position.

But if it works for you, perhaps the effect is not all that problematic--I will give it a try.

Gord

[RickKrung]

I don't use a platform jig for sharpening knives much.  I did use it for sharpening a machete, which I did on the slow speed grinder and then the Tormek.  But, my sense of the climbing thing is a matter muscle memory and the balance between two types of pressure, against the platform and into the stone.  Too little pressure against the platform and the blade can be grabbed by the stone and pulled off the jig or pushed up, depending on how you are using it.  Too much pressure of the blade into the stone may also have that effect.  It occurs to me that it is also a matter of muscle memory in holding the knife in a way as to brace it so it can't be grabbed by the stone, along with developing that balance of the pressures. 

Rick

[Dutchman]

... snip
Too much pressure of the blade into the stone may also have that effect. ...

Yes, I had to learn that.

[kwakster]

This user Spyderco Resilience was done on my version of the small platform jig.
In the pics there is still a bit of burring at the heel, which is also the tricky part to sharpen on this model with the small platform jig, because of the non-existing ricasso at that point in combination with the slightly protruding handle.
I had to use the edge of the stone (an SB-250 Blackstone) to get there at all, and as you can see it's not visually perfect.
After sharpening it was deburred freehand on the Tormek leather wheel.
The new edge measures an almost exact 30 degrees inclusive and the apex is keen enough to whittle one of my chest hairs from root-to-tip at 3 centimeters from the point of holding.

[cbwx34]

This user Spyderco Resilience was done on my version of the small platform jig.
In the pics there is still a bit of burring at the heel, which is also the tricky part to sharpen on this model with the small platform jig, because of the non-existing ricasso at that point in combination with the slightly protruding handle.
I had to use the edge of the stone (an SB-250 Blackstone) to get there at all, and as you can see it's not visually perfect.
After sharpening it was deburred freehand on the Tormek leather wheel.
The new edge measures an almost exact 30 degrees inclusive and the apex is keen enough to whittle one of my chest hairs from root-to-tip at 3 centimeters from the point of holding.

Looks good (as always)!

Did you have to tape the blade to avoid scratching?

Ever consider cutting in a "sharpening notch"?

Has that blade been thinned?

[kwakster]

With this knife i actually forgot to tape the surface of the jig, normally i use a piece of packing tape on it.
I never tape the blade itself.
BTW: maybe i've found something better than packing tape, still have to try it.

This is a customer's knife, and i don't know if he wants a sharpening notch.

The blade on this knife has not been thinned,

[jeffs55]

Why would you have to tape the blade to avoid scratching? Do you mean with the stone?

[GKC]

Why would you have to tape the blade to avoid scratching? Do you mean with the stone?

When using a small platform jig you are sliding the face of the blade along the surface of the platform.  Grit from the stone gets between the blade and the platform and can scratch the blade.  Putting something softer (like tape or felt) on the platform helps, or you could tape the blade. 

The threads referenced at the beginning of this post suggest some other ways to minimize the risk of scratching the blade, including frequent wiping of the blade and platform.  I am finding that a 2" strip of (one side of) Velcro on the platform works, but I still wipe the blade a lot.

Gord

[Ken S]

"But, I still wipe the blade a lot." (Gord)

What more can we learn from wiping the blade? If we have more than one similar (or identical) knives, and wipe the blade after every few strokes with one and after every stroke with the other, will we see a difference in the amount and depth of scratches?

If we wipe just the blade with one knife; just the platform with one blade; and both with the third knife we wipe both the blade and platform, will we see a difference in the scratches?

If we repeat these tests so that we can see the scratches from both grinding directions, is there a difference?

If we modify the platform from a straight edge to resemble a capital letter E by excavating a bit between the two areas between the end and middle legs, is there a difference in scratches?

Testing like this may seem to take a lot of time. Compared with possibly going forward with fewer or no scratches for many years, the amount of time seems well spent.

Ken