Topic: Homemade Knife Rest (HK-50)

[Herman Trivilino]

Good to know, Elden.  I would have thought that someone would have thought of this before and he'd have seen it.

[Jeff Farris]

While Tormek applauds the innovation shown in developing this idea, this forum cannot be used to sell products, and giving the invention a Tormek-like part number is a bit misleading. I've deleted a few posts in some other threads that mentioned sales of this device. At this point, no harm, no foul, but let's keep this thread moving in the direction of a suggestion for a shop project rather than an offer to buy or sell something.

Let's also be careful in comparing what this idea can do versus any old or new Tormek product. There's always more than one way to approach a problem, and generally no one or the other can be declared perfect.

[Rob]

Hi Jeff, hope you're well.

I understand your point about no commercial messages being permissible, that's normal forum policy and given its your BBQ entirely reasonable.

I'm less sure about the suggestion of censoring discussion about the pros and cons of different jig approaches to sharpening problems.  Isn't that just open dialogue about problem solving?

One of the things I really value about this forum is its open honest culture.  You really don't micro manage the message and I like that.

[Herman Trivilino]

Note Jeff said to be "careful" about the comparisons, he didn't say to stop them and he didn't delete posts where these comparisons were made.

There are advantages to the homemade knife rest, or perhaps it would be better to refer to it as a zero-clearance jig, or perhaps a mini-clearance jig.  There are also disadvantages.  It's been discussed before and it's not a new idea.

I've described every step in the process of making them so that anyone else can make them, too.

The disadvantages to this jig are several.  It's not stand-alone, but requires another jig such as the SVX-150.  It scratches the sides of knives.  It's easily damaged because the edge is so thin and so close to the grindstone.

The advantages are that it can be used for knives of all sizes, it can account for tapers on the sides of knife blades when setting the edge angle, and the offset of the blade in the knife handle is a non-issue.

I'm not here to sell them, I'm here to let people know that they can be built and used and are just one more way to modify a jig so that the Tormek machine is a more useful tool.

[Elden]

The disadvantages to this jig are several.  It's not stand-alone, but requires another jig such as the SVX-150.  It scratches the sides of knives.  It's easily damaged because the edge is so thin and so close to the grindstone.

Thanks for pointing these out Herman. I found out about that last one the first time I used it.

For someone who may not have seen it, the jig can be built as a stand alone jig. See:

http://www.tormek.com/forum/index.php?topic=1605.0

[Herman Trivilino]

Used the HK-50 to sharpen some old hatchets today.  I don't own the axe jig so I can't make any comparisons, but the HK-50 did a mighty fine job.

[Herman Trivilino]

I was expecting to use the HK-50 to sharpen my lawnmower blade today, but its shape won't allow it to rest flat on the platform.  I had to break out the SVM-45.  It'd been so long since I'd used it I had to get used to it again. 

[courierdog]

Herman:
I have now discovered this portion of your thread which has the dimensions for the plate. Many thanks.
Some where I think I read that the platform was deforming at the thin edge.
I will most likely fabricate several plates before settling on one, Aluminum, Mild Steel & Stainless Steel
A very thin layer of Teflon on the plate will minimize any scuffing on a blade.
My immediate project is to sharpen my Japanese Kitchen Knives (Santoku & Usuba) which require a 10-15 degree angle for sharpening.
I have tried the Tormek Knife Jigs both SVM 45 and the SVM 14, 0 and I cannot make them work as intended.
I have jury rigged a version similar to the HK-50 and it seems to work better for me.
I would prefer a solution where the rest is horizontal to the top of the machine as I prefer not to work over a rotating wheel.
I would like to know how to post pictures directly & without using photo bucket.
I have another project on the go to sharpen my Metal Lathe Tool Bits.

[Herman Trivilino]

I will most likely fabricate several plates before settling on one, Aluminum, Mild Steel & Stainless Steel

I've made several out of wood, a couple out of some high density plastic that I found, and one out of aluminum.  They all work equally well, although the aluminum one is the most rigid out there on the thin edge.

A very thin layer of Teflon on the plate will minimize any scuffing on a blade.

How do you do that?  I'd like to give it a try.  I used some cheap adhesive-backed felt from a craft store and it works well.

My immediate project is to sharpen my Japanese Kitchen Knives (Santoku & Usuba) which require a 10-15 degree angle for sharpening.

Do you have the Japanese Waterstone (SJ-250)?  If not you'll need to use the fine side of the stone grader on the SG-250 for several minutes to make sure the surface is smooth as glass.

I would like to know how to post pictures directly & without using photo bucket.

You have to host the pictures somewhere on the web, there's no way to host them here on this site.

[courierdog]

Herman:
Thanks for the valuable info.
I have the Tormek SJ-250 Waterstone as well as the SB-250 for my Metal Lathe Tool bits plus the original SG-250
I have been trying to think of a way to use a flycutter to match the curvature on a metal plate match the Tormek Wheel.
The large advantage with the Tormek is the knife edge will have a slight hollow grind edge to it as opposed the flat edge of the traditional Japanese waterstone. My normal 400 grit followed by 1000 grit followed by 5000 grit approach can be shortened to just the 4000 grit SJ-250 once the edge has been shaped using this new approach.
The point about the external picture hosting I do not like as many of the picture disappear when the user looses interest in the subject.

[Bernard Calip]

Herman,

This is my first post.

The white plastic material looks like Teflon to me.

I will be ordering my Tormek T7 on Monday.

[Herman Trivilino]

Page 18 of the Tormek Handbook (which can be downloaded for free once you register at http://tormek.com/international/en/account/register/) explains perhaps why Tormek hasn't developed a tool rest like our homemade version.

Tool Rests and Grinding Jigs
To achieve an even and sharp edge, the tool must be held steadily and with a consistent
grinding angle to the wheel. This is obtained by resting the tool on a tool rest or clamping
it in a grinding jig.

A common tool rest on fast running bench grinders is a bent plate which is usually too short
to support the tool properly. This simple tool rest can be replaced by a larger and more sturdy
support to enable you to hold the tool steadily towards the grinding wheel. The tool rest can
also have a fence which is guided in a slot, so you can keep the tool at 90° or at a specific
skew angle to the grinding wheel.

These type of tool rests have been developed for high speed grinders, where you work with a
low grinding pressure due to the high rpm. However when mounted on a water-cooled grinder
which requires a higher grinding pressure, they do not work satisfactorily. This is because
the pressure which you apply to the tool does not reach the grinding spot but instead goes
to the tool rest. (Picture no 1).

To obtain the required grinding pressure, you also need to push the tool from the handle direction
towards the wheel. Then the tool tends to climb up on the grindstone and the precision
is lost. (Picture no 2). You need to push the tool both towards the wheel and downwards so
that it does not lose its contact with the tool rest. In practice this is not possible.
This effect appears when grinding narrow edge angles and when grinding both towards and
away from the edge. The disadvantage is more severe when grinding turning tools, as they
are often made of HSS-steel which is hard and requires a high grinding pressure.
For turning scrapers which are ground at larger edge angles, this type of tool rest works
satisfactorily on dry or water-cooled grinders. The reason that these types of tool rest work
fairly well on high speed dry-grinders, is that they require a lower grinding pressure and
therefore the disadvantages can be overcome.

[Herman Trivilino]

I've been thinking a lot about the design of the HK-50 and this passage in the Tormek Handbook:

These type of tool rests have been developed for high speed grinders, where you work with a
low grinding pressure due to the high rpm. However when mounted on a water-cooled grinder
which requires a higher grinding pressure, they do not work satisfactorily. This is because
the pressure which you apply to the tool does not reach the grinding spot but instead goes
to the tool rest.

If you look at the ways in which the Tormek Tool Rest (SVD-110) is used,

http://tormek.com/international/en/grinding-jigs/svd-110-tool-rest/

there appears to be a conflict.  But the point is well taken.  Note that in every case where the SVD-110 is being used the edge angle, and thus the grinding angle, is very steep.  Close to 90^o.  At this steep of an angle you really can apply most of the pressure to the tool rather than the tool rest.  But for shallow angles, like you'd use for a knife, most of the pressure must be applied to the tool rest rather than the tool.  If not, the tool lifts itself off the tool rest and the edge angle is no longer maintained.  This is a huge problem when grinding away from the edge, but manageable when grinding towards the edge. 

Thinking about all these things, and having received an Amazon gift certificate,  I decided I'd combine it with some bonus points and a bit of my own money and treat myself to a SVD-110.  It arrived yesterday and after fiddling with it and thinking about ways to attach a HK-50, I quickly realized that the base of the scissors jig that I've been using for this purpose is far better suited to the task.

Here's why.  Consider the distance from the surface of the tool rest to the center of the Universal Support, labeled d in this drawing.



It's about 34 mm.

Now consider the same distance in the case of the base of the scissors jig:



It's about 10 mm.

In other words, you can get the surface of the tool rest much closer to the Universal Support, and thus closer to the grindstone, in the case of the base of the scissors jig.  Therefore when attaching to the SVD-110 the HK-50 would have to be much longer, placing the grinding edge much further from the operator.  So my conclusion is that Tool Rest alone is ideal when grinding tools at blunt angles, but when grinding knives at shallow angles attaching the HK-50 to the base of the scissors jig is a better option than attaching it to the SVD-110.

[tooljunkie]

Herman
Do you have any pictures of your jig in use with some knives.?
Does your jig work better for small knifes?

Thanks
Tooljunkie Dan
(You can never have too many tools)

[Herman Trivilino]

Here's a video ...

https://www.youtube.com/watch?v=AcWAkQmoU8c&feature=youtu.be

The jig shown in that video was the first prototype, which is described this thread ...

http://www.tormek.com/forum/index.php?topic=1560.0

Since that time Tormek has come out with their Small Knife Holder, the SVM-00. I've not had the opportunity to try it yet.

The HK-50 works well for small knives.