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Old sharpening methods...
Forum: All About Edges
Last Post: Bud
9 hours ago
» Replies: 9
» Views: 47
Edge Retention/Rolling Te...
Forum: Edge Sharpness Testing
Last Post: Bud
9 hours ago
» Replies: 72
» Views: 1,186
Knife sharpening to 20-40...
Forum: All About Edges
Last Post: KnifeGrinders
9 hours ago
» Replies: 8
» Views: 74
Rockwell C Linearity Stud...
Forum: Relevant General Discussion
Last Post: EOU
02-17-2018, 01:38 PM
» Replies: 26
» Views: 375
related to Rockewll Hardn...
Forum: Relevant General Discussion
Last Post: Ken S
02-16-2018, 07:27 PM
» Replies: 0
» Views: 20
Hardness vs performance
Forum: Relevant General Discussion
Last Post: KnifeGrinders
02-16-2018, 06:06 PM
» Replies: 9
» Views: 63
Cabon steel vs Stainless ...
Forum: All About Edges
Last Post: Mark Reich
02-15-2018, 09:35 PM
» Replies: 13
» Views: 176
Mini electric kiln projec...
Forum: Knife Making & Bladesmithing
Last Post: Jan
02-15-2018, 03:24 PM
» Replies: 83
» Views: 1,037
Lincoln and the axe
Forum: Relevant General Discussion
Last Post: Mike Brubacher
02-14-2018, 02:47 PM
» Replies: 1
» Views: 79
3 day gun show
Forum: Knife and Blade Reviews
Last Post: Mark Reich
02-14-2018, 10:14 AM
» Replies: 2
» Views: 47

  Old sharpening methods...
Posted by: Edgepal - 02-17-2018, 12:15 PM - Forum: All About Edges - Replies (9)

[Image: ifvo0k.jpg]

This picture shows a Medivial method for sword sharpening. If you study this picture you se that they use special wood tools to hold the edge angle. The tool is triangel where one side can be moved and they also use a  angle suport.

On the table below the sword you can se a cow antler. In this antler is fat mixed with fine quartz sand as abrasaive.

Can we learn anything from this old method? Smile


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  related to Rockewll Hardness study
Posted by: Ken S - 02-16-2018, 07:27 PM - Forum: Relevant General Discussion - No Replies

I would like to share some observations inspired by the Rockwell Hardness topic, but not directly on topic. I have no desire to hijack the original topic.

EOU quite correctly referred to the metrically challenged US. While this is true, our excuses are wearing very thin. Each conversion between systems introduces an error factor. This seems preventable.

Mark referenced using rulers. There are several substantial differences between rulers (also called rules). In my opinion, the pick of the litter are the Starrett satin chrome rules. Unlike less expensive photoetched rules, Starrett rules have marks which are engine cut. The marks are V shaped, which allows for greater accuracy. Satin chrome finish makes them easy to read in bright or dim light. They are available in many graduations, the most common being "4R" (1/8, 1/16, 1/32, and1/64”) Of course, they are also available in metric. There are none better (and they are priced sccordingly, although they will last a lifetime)

Each time a high quality rule is used the chance of error is lessened.


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  Hardness vs performance
Posted by: grepper - 02-15-2018, 10:33 PM - Forum: Relevant General Discussion - Replies (9)

I know very little about different steel types, but I do know that some hard steel is very brittle with others are far less brittle.  I’m sure performance wise some hard steel way outperforms others for knives. 
Mr. Mark, I don’t know what the hardness is of the 52100 steel that you use is, but I’ve seen videos of you bending them.  Scary to watch but amazing!  Those seem virtually unbreakable with any kind of “normal” or even very hard use and the ability of the blades returning to straight after bending was stunning!
I have the feeling that a knife could vary several RHC points over the length of the blade.  Is that correct?

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  Knife sharpening to 20-40 BESS detailed
Posted by: KnifeGrinders - 02-15-2018, 10:06 PM - Forum: All About Edges - Replies (8)

By request of one of our customers we've made a short video documenting sharpness of his Reate Horizon-Ti in M390.
This one:

This reminded me that I shamelessly used part of Mike's video from his YouTube channel in another our video.
Better late than never: Mike, apologies for not asking for your permission, I hope you don't mind, do you?
It's this one: https://youtu.be/4irTV1xZ-EM

But back to that Reate - as long as we were documenting sharpening it anyway, on its example I've detailed how we sharpen knives to sharper than razors, using old and new photos and microscope images.
Added a few contemplative bits as well.
Hopefully you may find something useful for yourself out of it.

Sharpening steps are detailed on our Australian forum:

Unexpectedly, we've encountered a funny situation with the edge oxidation, because of which we cannot deliver a knife to the customer same sharp as it comes out of our workshop. Though we do get sharper than razor edges out of our workshop, I am yet to find a way to deliver them to the customers.
Owing to the oxidation, sharpness drops a little by the time the customer gets his high-end knife, and the edge has just a Gillette DE razor sharpness, not sharper (no showing off meant).

With mainstream steels the oxidation can be removed by stropping on a clean linen/jeans/leather, but this doesn't seem to work with the high-end corrosion-resistant steels.
I can restore initial sharpness by stropping on a leather with #100,000 diamond suspension, stripping off the oxide layer, but the restored sharpness lasts for a few hours, and drops back as soon as new oxide layers form. Actually this is an expected behavior from the Chromium added for corrosion resistance.

This oxidation challenge is a new area for me, came to my attention only when we started getting sharper than razor edges, and I do not have a solution at the moment.
Any advice pointing in the right direction will be much appreciated.

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  3 day gun show
Posted by: MaxtheKnife - 02-13-2018, 05:51 PM - Forum: Knife and Blade Reviews - Replies (2)

It was not our best show by any means especially for 3 days, but happens..

This is one of the many pocket knives we sharpened at the chantilly va event.

A Medford......Praetorian with titanium flames......

A big edc .......I like it

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  Rockwell C Linearity Study
Posted by: EOU - 02-13-2018, 02:11 PM - Forum: Relevant General Discussion - Replies (26)

Edge On Up & Jan Svancara
Foreword: Over the past few months we have worked closely with Jan in preparing this study. These words are ours though and it is not our intention to obligate Jan to each proposed fact and detail contained in this opening statement. We'll be hearing more from Jan in subsequent posts and then it will be, proverbially, "straight from the horse's mouth". We hope that old saying translates well into Jan's native language. We admit, in advance, to being poor discussion leaders on this subject having never been present while a Rockwell test was  conducted but that doesn't curb our curiosity concerning what Rockwell numbers mean in a practical sense. We haven't been able to find a study that correlates one Rockwell number to another in relatable terms. Perhaps one of our members has. If so, we'd sure like to hear about it here.
We confess to being a curious bunch around here and that's not always a good thing. The surface hardness of a sharpened steel edge has little  to do with measuring its sharpness level but still, we find ourselves wondering "how much harder is Rockwell 60 is than Rockwell 30?". We've noticed that we're not alone in this curiosity. We've seen and heard the question, using some set of Rockwell test numbers, asked many times and no one seems to have even a good guess at an answer. We've had our thinking caps on here and now we're ready to, at least, begin a discussion of the question. We don't think that we can answer the question in its entirety but do have some confidence that we can begin to get our arms around the subject. With the help of our good friend Jan, who happens to be the curious sort as well, we're going to try and find out just how long our shirt sleeves are. Please keep in mind that none of us pretend to be some sort of "metallurgical Rockwell whisperers" here. We're only attempting to apply, what we feel, are common sense observations and calculations to an often asked question. We'll begin with a little background:
The Rockwell was, originally, a 0-100 scale utilizing a round ball indenter. We see that engineering types now disagree on the useful upper extent of the Rockwell C.  Some say 65 and others, 70 or 80. A 0-100 scale makes for easy calculations though when pondering the relationship between one Rockwell test number and another. If the scale is linear then the answer to our question (how much harder is 60 than 30) can be quickly arrived at;  its twice as hard. If you've ever hand sharpened a Rockwell 55 knife and then a Rockwell 62 knife though you're likely to suspect that it required far more than 10% or 12%  more elbow grease than a linear relationship would demand, to accomplish the task. Anecdotally then, we might suspect that the scale is not linear. One close look at the shape of a Rockwell C indenter tends to confirm our anecdotal suspicions.

[Image: rockwellfigures.png]
The  indenter shape  has evolved as well. The Rockwell C scale was born along with the 120 sphericonical  indenter. This new test was found to be more suitable for harder steels, the kind of steel that knife makers utilize. Each increment on the scale represents a penetration depth of .002mm (.0000788 inches) or about 1/80,000th of an inch for we metrically challenged Americans. In 1918, a reading of "0" would have meant that the indenter fell on some very hard material, presumably a diamond surface, and a reading of 100 would have meant that the indenter had fallen on very soft material. It is our understanding that a Mr. Wilson of the Wilson Mechanical Instrument Company changed that around in the 1920's. We assume that this reversal was instituted by Mr. Wilson because he thought that a higher level of hardness should be represented by a higher (greater) number. This scale reversal has caused us some consternation when thinking about the linear or non-linear aspects of the Rockwell C because, with today's Rockwell C scale, less is more and vice versa.
The scale is, presumably, a differential one in that it is measuring the difference in penetration depth between, first, an applied minor load (10kg) and then the 150kg major load. This study does not attempt to calculate or compensate for the minor or "pre-load" penetration depth because it is believed to be inconsequential to our results and ambitions here.
The geometric shape, a sphericonical cone, of a Rockwell C indenter suggests that the Rockwell C scale cannot be linear. As the indenter travels deeper into the test sample it presents a larger and larger surface area to the sample. Each tick downward on the Rockwell C scale represents an additional .002mm penetration into the test sample. Since the Rockwell C uses a fixed force (150kg) the hardness of the test sample  determines the depth of penetration. So, now we have the rub; while the indenter is traveling deeper into the sample, indicative of a softer material, the contact surface area is increasing which should make it increasingly more difficult for the indenter to penetrate. This then would then seem to have some mitigating effect in calculating the "softness" of a material.
This increase in surface area of the indenter can be calculated and then presumed that this increase has proportionate effect on the linearity of the measured results. In a subsequent post here we will present those calculations for common Rockwell C measurements.
The foregoing is an attempt to open a conversation. Perhaps this has all been figured out already and we, along with a number of other people, just haven't been exposed to the information. Your input will not only be appreciated but is hereby solicited.

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  Knife Review: Spyderco Bradley Bowie
Posted by: subwoofer - 02-13-2018, 04:53 AM - Forum: Knife and Blade Reviews - Replies (3)

[Image: 00-Spyderco-Bradley-feature-P1290812.jpg]

It's not something I've been able to properly define, but there are some knives that just look 'right' from the moment you first see them, and the Spyderco Bradley Bowie (designed by Gayle Bradley of course) is one of those. Many knives have specific purposes and their design reflects the requirements of those; the Bradley Bowie manages to make itself a truly general purpose knife, just as happy preparing camp food, dressing game, battoning wood, or on manoeuvres carried by service personnel.

[Image: 00-Spyderco-Bradley-feature-P1290817.jpg]

Author's Statement for Transparency and Disclosure
The test sample/s featured in this article have been provided for technical testing and review by the manufacturer. Test samples are retained by the reviewer following publication of the completed review for the purposes of long term testing and product comparisons.

All output figures and test results published in this review are the sole work of the reviewer, and are carried out independently and without bias. Test results are reported as found, with no embellishments or alteration. Though best endeavours are made to maintain the accuracy of test equipment, the accuracy of these results is not guaranteed and is subject to the test equipment functioning correctly.

The Blade and Handle Geometry:

Most knife specifications have a basic description of the blade geometry, but in this section I will be taking a more detailed look at geometry and balance.
[Image: 35-Spyderco-Bradley-grind-P1300258.jpg]

Using a set of gauges and precision measuring equipment including a Vernier protractor, callipers, fixed radius gauges and the unique Arc Master adjustable radius gauge (the one that looks like a crossbow).
[Image: Knife-measuring-P1180483.jpg]

These measurements have been tabulated and are presented along with a few reference blades (8" Chef's Knife, 5.5" Santoku and the popular Fällkniven F1).

Key aspects such as the primary bevel angle, grind type, blade depth, blade thickness, length, weight are detailed, along with balance information.
[Image: 36-Spyderco-Bradley-bevel-P1300261.jpg]

The 'Balance relative to the front of the handle' tells you if the knife will feel front heavy, or if the weight is in your hand (a positive value means the weight is forward of the front of the handle). The 'Balance relative to the centre of the handle' indicates how close to a 'neutral balance' the knife has in the hand.
[Image: 34-Spyderco-Bradley-balance-P1300250.jpg]

In the case of full convex grinds the approximate centre of the grind is used for the primary bevel angle estimate.

[Image: More-Marker-V2-100h.png]
(Wherever you see the 'Read MORE' marker, it indicates that the Extended Version of the review has additional content at that point. Viewing the extended version helps support further reviews, but please ensure you return to this Forum for comments and discussion.)

The blade is made from PSF27 steel.

New for 2018! BESS Certified sharpness testing:

The BESS 'C' scale of sharpness, developed by Mike Brubacher (Brubacher Edge Sharpness Scale) will now become part of Tactical Reviews' knife testing process. Initially this will be used to verify the sharpness of the factory edge and allow the knife to be brought to a minimum standard sharpness before testing a blade's cutting performance.
[Image: More-Marker-V2-50h.png]

The Bradley Bowie's factory edge has an average BESS 'C' sharpness of 374. This original edge will slice thicker paper/card, but although it bites into the edge, it starts to tear thinner paper rather than cut.

[Image: BESS-Certified-Bradley-Bowie-IMG_20180210_104149.jpg]

Explained by the Maker:
[Image: More-Marker-V2-50h.png]

A few more details:

Standard Spyderco packaging is used for the Bradley Bowie.
[Image: 01-Spyderco-Bradley-boxed-P1290746.jpg]

Both Knife and sheath arrive in plastic bags. The sheath has come out of the bag slightly, but the knife is still fully covered.
[Image: 02-Spyderco-Bradley-box-open-P1290753.jpg]

In the box are the knife, sheath and information leaflet.
[Image: 03-Spyderco-Bradley-box-contents-P1290755.jpg]

Mainly due to the choice of steel, there are a few layers of protection for the blade. With the plastic bag removed, the first layer is a cardboard sleeve.
[Image: 04-Spyderco-Bradley-blade-protector-P1290760.jpg]

With the cardboard sleeve removed we find a wrapping of Vapour Corrosion Inhibitor paper, plus a plastic tip guard.
[Image: 05-Spyderco-Bradley-blade-protector2-P1290763.jpg]

And there it is, kept pristine by the wrappings.
[Image: 06-Spyderco-Bradley-with-sheath-P1290766.jpg]

We are going to have a look round the sheath first. Not just any old Kydex sheath, in fact not Kydex at all, but its higher performance alternative - Boltaron.
[Image: 07-Spyderco-Bradley-sheathed-P1290769.jpg]

The back of the sheath...next onto some details.
[Image: 08-Spyderco-Bradley-sheathed-P1290772.jpg]

In contrast to the black Boltaron and rivets, the belt clip fixings are silver coloured.
[Image: 09-Spyderco-Bradley-sheath-fixings-P1290774.jpg]

As expected with this type of sheath, the Boltaron is moulded around the end of the handle and has been cut and sanded to its final size and shape.
[Image: 10-Spyderco-Bradley-sheath-opening-P1290778.jpg]

[Image: More-Marker-V2-50h.png]

The belt clip itself is open at the bottom, but tightly sprung with a hook shaped end. Once positioned on a belt it will not easily come off again.
[Image: 14-Spyderco-Bradley-belt-loop-P1290790.jpg]

Near the tip of the knife is a drainage hole. Ideally this could have been further down at the actual blade tip, as a small amount of water can still stay in the sheath if it becomes soaked.
[Image: 13-Spyderco-Bradley-drainage-P1290786.jpg]

Now onto the knife. Just take in that full flat grind and long sloping swedge.
[Image: 15-Spyderco-Bradley-angle-P1290793.jpg]

The PSF27 steel specification is engraved under Spyderco's name.
[Image: 16-Spyderco-Bradley-steel-plunge-P1290795.jpg]

A finger guard is formed out of the full thickness tang and handle slabs.
[Image: 17-Spyderco-Bradley-guard-P1290800.jpg]

[Image: More-Marker-V2-50h.png]

The full thickness tang is prominent in the slim handle.
[Image: 20-Spyderco-Bradley-handle-back-P1290810.jpg]

There are relatively sharp corners to the plunge line - potential stress concentrators.
[Image: 21-Spyderco-Bradley-plunge-P1290826.jpg]

Gayle Bradley's logo appears on one side of the blade.
[Image: 23-Spyderco-Bradley-GB-logo-P1290829.jpg]

All the corners of the G-10 Handle are well rounded preventing any hot-spots. Only a small section of the handle edge next to the ricasso is not fully rounded.
[Image: More-Marker-V2-50h.png]

What it is like to use?

I've already mentioned that the design of this knife really speaks to me, and just looks right. This is absolutely confirmed by the feel in the hand; it really does work as well as it looks like it will.
Excuse the potential connotations here, but that semi-polished G-10 handle is asking to be touched, stroked and held, much like a worry stone. Every part of it is smooth, the type of smooth that doesn't drag, catch or stick like a full gloss polish can. It has got to be one of the best feeling handles I've come across, and you don't want to put it down.
[Image: 31-Spyderco-Bradley-handle-texture-P1290893.jpg]

Even wet or sweaty, there is plenty of grip despite its smoothness, in fact the least amount of grip I found is with a completely clean and dry hand. The rounded edges remove any hotspots; you are much more likely to get a blister due to wearing gloves (and their seams creating a hotspot) than anything to do with the handle.
[Image: 29-Spyderco-Bradley-in-hand-P1290876.jpg]

Personally I prefer a thicker handle for a bit more of a handful, but in this case I like the lower profile handle with less 'presence' on the belt (or as I often do, slipped in a large pocket). There is enough handle to allow you to really work the blade hard without adding bulk.
[Image: More-Marker-V2-50h.png]

As is often the case with the type of sheath used here, the retention is pretty stiff, and the knife doesn't easily come out. You need to lever the sheath away with your thumb, or end up with severe 'sheath recoil' and an uncontrolled slash of the blade as it flies out. In the sample received here, the edges of the Boltaron had sharp corners from the final shaping and these were catching on the knife, especially on re-sheathing the knife.
[Image: 32-Spyderco-Bradley-kydex-stiff-P1290897.jpg]

[Image: More-Marker-V2-50h.png]

Unfortunately, I've not had as much time using this knife as I would normally fit in before completing a review, so haven't gone through enough sharpening cycles, or seen how sensitive to corrosion the PSF27 really is. It has definitely been wet, cut damp materials and covered in corrosive finger prints and so far hasn't become marked. I'm hoping this steel proves more stain resistant that its composition might suggest.

With the choice of ever better stainless steels, I don't want to worry about corrosion, and personally might have preferred a steel that is not on the wrong side of stainless levels of corrosion resistance. I'm also not subjecting a blade like this to demolition work, so the ultimate performance of PSF27 is not entirely relevant to me in this knife. That said, it is nice to know there is a great deal of strength in reserve, especially if you choose this as a survival knife or for military applications.

Review Summary

The views expressed in this summary table are from the point of view of the reviewer’s personal use. I am not a member of the armed forces and cannot comment on its use beyond a cutting tool or field/hunting knife.

Something that might be a ‘pro’ for one user can be a ‘con’ for another, so the comments are categorised based on my requirements. You should consider all points and if they could be beneficial to you.

Things I like
Excellent general purpose blade.
Superb handle with semi-polished G-10.
High performance PSF27 steel.
Conveniently slim overall package.
Sheath can be configured for right or left handed use.

What doesn't work so well for me
Slightly over-stiff sheath retention.
PSF27 steel is not quite 'stainless'.

[Image: 22-Spyderco-Bradley-angle-rear-P1290827.jpg]

[Image: Click-for-more-V5-800resized-first.png]
(Moderators, there is a reciprocal link at the end of every review on Tactical Reviews.)

[Image: Round-Sticker-V1-0.png]

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  Cabon steel vs Stainless steel
Posted by: SHARPCO - 02-09-2018, 10:01 PM - Forum: All About Edges - Replies (13)

Though sharpened in the same way, carbon steel has a different feel when cut compared to stainless steel. So the Japanese sushi knives are often made of carbon steel.

Where does this difference come from?

Can this difference occur even when the BESS scores are the same?

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  Lincoln and the axe
Posted by: Ken S - 02-09-2018, 02:08 AM - Forum: Relevant General Discussion - Replies (1)

"Give me six hours to chop down a tree, and I will spent four hours sharpening the axe."

This quote, and many versions of it, are often attributed to Abraham Lincoln. (Not all scholars agree.) While it extols the virtues of good preparation and using sharp tools, Lincoln must not have been much of a sharpener. We often praise a job for the amount of work and time which went into it. If that was really the case, the hours I spent freehand sharpening a chisel with my venerable oilstones would be far more praiseworthy than Grepper's quick once over kally treatment with a 150 belt and a leather belt, no matter what the BESS numbers indicated. Sadly, Mr. Oilstones (or Mr. Water-Stones) will often be perceived as a more skillful and dedicated sharpener than Mr. Grepper, who must be taking cheap short cuts instead of taking the time to "do the job right". His cutting a fishline does not seem nearly as impressive as operatically slicing a piece of paper.

I recently needed to have my garage refrigerator repaired. As a friendly old telephone troubleshooter, I enjoy talking with repair people. The repairman diagnosed the trouble before he got out of his truck. Ohio winter+frig in unheated garage = no heater unit installed. He deftly installed the unit in five minutes. Some people would have thought he didn't do much; I was impressed with his skill. Problem solved.

I appreciate the skill Grepper has shown and shared. He correctly analyzed the kind of sharp (toothy) edge needed to do the task properly, and found a direct and efficient way to achieve that edge. And to measure it. While I admire President Lincoln as a great man, I would prefer to have Mr. Grepper do my sharpening.


ps Grepper's new knife sharpening jig ain't too shabby, either.  Smile

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  New Kalamazoo 1SM knife rest system
Posted by: grepper - 02-06-2018, 09:56 PM - Forum: Relevant General Discussion - Replies (9)

Recently an Exchange member contacted EOU with regard to the guided Kally knife rest system that was mentioned in an EOU post, and I have previously mentioned a few times in posts that a new rest was in the works for the Kally.  This is about the new rest.

First, a bit of history:  The first knife rest I made for the Kalamazoo 1SM was many years ago with proof of concept being nothing more than an angle cut on a piece of wood that sat against the belt.  Albeit crude, the thing actually worked well enough to warrant continued development.

It then went through five or six other designs which I made and used.  Here is an image of the design just previous to the current version.

While all of the previous designs worked pretty well, they all had some issues and areas that needed improvement.  So I decided to do a complete redesign to fix any issues and incorporate the needed improvements that were identified over the years. 

Some of the features needed in the new rest were:

Allow edge of belt contact up to the knife handle.
0° - 50° sharpening angle using adjustment screw for accuracy.
Graduated angle adjustment gauge.
Horizontal adjustment for perfect belt alignment. (No two Kally’s are the same.)
Quick and accurate screw in/out adjustment of rest distance from belt.
Use materials that will not scratch the blade.
Replace the weak and flexible original tool rest.
Include a platen with a window for stiffer area of the belt.
Rest can be placed in the window of the platen, over the platen or above the platen.
Use heavy gauge steel to eliminate flexing during sharpening.
Simple and quick plug & play installation.  Loosen two nuts, remove the old and replace with this.

The new design includes all of the needed improvements and fixes the problems indentified in previous versions.  It works very well.

The design started about six months ago with a crude drawing.

It was painfully clear that my child level artistic abilities weren’t up to the task, so I did the design work in CAD.  Here are a couple of CAD images of the completed rest and platen system.

From those designs, our own amazing Mr. Mike got the parts made.  Here is the unit installed on my Kally.  In these images the rest is positioned for sharpening above the platen.  The second image shows the holes drilled in the side of the platen to facilitate different rest positions. 

I would like to thank Mr. Mike for his invaluable assistance in being a sounding board for design concepts, providing feedback and suggestions, helping me to understand designing for manufacturability, and for the actual production.  Without his participation this would have not have happened.  Thank you Mike!

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