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TOPIC: Using the Variable Thickness Stone Adapters

Re:Using the Variable Thickness Stone Adapters 2 months 3 days ago #18545

  • tcmeyer
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As discussed above, I experimented with my VSTA's using a series of my blocks, all of which have been modified to add bronze bushings to tighten their angular variability.

After my intial testing and comfortable that ten readings would be valid, I then took ten readings of eight blocks, after using the VSTA adapter to set each block to the reference angle.

The readings were as follows:


19.9 19.9 19.9 19.9 19.9 19.9 20.1 19.8
19.95 19.9 19.95 19.95 20 19.9 20.1 19.9
19.95 19.8 20.1 20 20.05 19.85 20.05 19.85
20 19.95 20 19.95 20.05 19.95 20.1 19.8
19.95 19.95 20.05 19.95 20.1 19.9 20.1 19.8
19.95 19.9 20 20 20.05 19.9 20 19.85
19.9 19.9 20 20 20.1 20 20 19.85
19.9 19.9 19.95 19.9 20.1 19.85 20.1 19.75
19.9 19.9 20.05 19.9 20.05 20 20.05 19.85
19.9 20 20 19.95 20 19.95 20.05 19.9

19.93 19.91 20.00 19.95 20.04 19.92 20.07 19.84


Sorry, but the spreadsheet doesn't copy very well, but you get the drift...

The results show that properly used, the VSTA (SWAT for you old-timers) should produce angles within about 0.23 degrees of each other, or plus/minus 0.115 degrees. If I toss out the last two sets of samples, the range is much better at +/- 0.07 degrees. As for you statistics guys, come on. Lighten up.

Note that each stone was reset to the reference angle with the VSTA, so the variability listed included all the possible contributing factors - The variability in the stone, the execution of the VSTA procedure and the actual taking of readings.

Any questions?
Last Edit: 2 months 3 days ago by tcmeyer.
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Re:Using the Variable Thickness Stone Adapters 2 months 3 days ago #18547

  • mark76
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Wow, interesting experiment! It seems that you can get very accurate results using the VTSA. Particularly since the your measurement results include not only the actual angle differences, but also measurement errors ;) . (I know how difficult it is to measure a 0.1 degree angle difference with an angle gauge. And these things are accurate up to x only, too.)

Did you include stones in your test set that are much thicker than the stock stones? Like the Chosera's?
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Re:Using the Variable Thickness Stone Adapters 2 months 2 days ago #18561

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I don't have any stones that are more than 0.020 or 0.030 different, so I can't say for sure.

But I did a little checking of the geometry in a simple CAD program. It occurred to me soon after the VSTA came out that the micro adjusts set the offset at about 10 degrees, but the actual difference in thickness showed up at about 20 degrees for most of my sharpenings. In other words, the VSTA was designed to correct for thicknesses in stones used at about 10 degrees. However: large differences in stone thickness could fall outside of the micro-adjust's range, and require movement in the base at the degree bar, which is not at 10 degrees, but at zero degrees.

Stone thicknesses which were adjusted for within the range of the micro-adjusts - say 1/4", would result in angular errors of only about 0.10 degrees. Changes in the degree bar setting are done horizontally and don't account for the angle of the rod. If my method is right, a 1/2" offset taken in the horizontal axis could produce an error of 0.65 degree for the resultant rod angle. Pretty awful.

A lesson from this? Set-up your VSTA's with the thinnest of your stones and the micro-adjust's set near their inboard limit. This would allow you to make whatever adjustments you needed for thicker stones with the micro-adjusts and reduce any geometric errors. You don't want to use the degree bar as the offset method. So how thick are the Choseras?

So far as I know, this is the first time anybody's pointed to this problem. Has anybody else noticed this? Am I full of sh__?
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Re:Using the Variable Thickness Stone Adapters 2 months 2 days ago #18564

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Tom,

Do you still have the original arms from your sharpener with the u-joints? If so, I'd love to see what you observe using the VSTA with those arms.
--Clay Allison
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Re:Using the Variable Thickness Stone Adapters 2 months 2 days ago #18570

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I've got the original arms, but I don't have any original blocks. The idea is interesting, but the original arms are only adjustable in the horizontal axis. I'll have to at least try it to see how well it works with stones of roughly the same thickness. Maybe later this week.

I don't know if you picked up on it, but the first three columns of data were using the same stone - just repeating the setting procedure.

Clay: Do you know what the thickness of a Chosera block is? Didja get my gift package yet?
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Re:Using the Variable Thickness Stone Adapters 2 months 2 days ago #18571

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tcmeyer wrote:
I've got the original arms, but I don't have any original blocks. The idea is interesting, but the original arms are only adjustable in the horizontal axis. I'll have to at least try it to see how well it works with stones of roughly the same thickness. Maybe later this week.

I don't know if you picked up on it, but the first three columns of data were using the same stone - just repeating the setting procedure.

Clay: Do you know what the thickness of a Chosera block is? Didja get my gift package yet?

I think it would be interesting to study the differences of using the VSTA with the original and upgraded arms.

Just got the package now, thanks!

Choseras are 5mm thick.
--Clay Allison
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Using the Variable Thickness Stone Adapters 1 month 4 weeks ago #18614

  • Gus
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First, thanks for your original post. I think it's very clear and useful.
Would you be able to describe any more precisely how you converted your paddles? What tools you used. etc.? Anything you're willing to share. I see that you say a little more in reply to another response which is already useful.
It's very important for me to find a way to add bearings to all of my paddles, but I'm not sure if I will be able to do it myself or whether I will need to find help doing it. I use my tools for work everyday for a micro precision task and if my knives are not "just right" it's as if they aren't sharp at all. Other posts about technique have helped me to work around this problem to some degree, but not entirely. So I can't thank you enough in advance for any help on this issue.
Last Edit: 1 month 4 weeks ago by Gus. Reason: Read other responses more carefully.
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Using the Variable Thickness Stone Adapters 1 month 2 weeks ago #18696

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Hi TCMEYER,

Thanks again for all the info on this link! I sent you a private message a while ago. I wonder if perhaps you didn't receive it and therefore am cluttering up this thread with a public/private message asking if you did. Sorry if I'm not using the forum correctly by doing this. If I am, anyone reading this: please feel free to tell me to: DESIST :)
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Using the Variable Thickness Stone Adapters 1 month 2 weeks ago #18697

  • EamonMcGowan
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Gus wrote:
Hi TCMEYER,

Thanks again for all the info on this link! I sent you a private message a while ago. I wonder if perhaps you didn't receive it and therefore am cluttering up this thread with a public/private message asking if you did. Sorry if I'm not using the forum correctly by doing this. If I am, anyone reading this: please feel free to tell me to: DESIST :)

Gus,
Welcome to the forum! How are you going to figure this thing out if ya don't ask questions?? I would say your safe to ask away around here. Everyone is always real eager to help the next guy coming along.
It looks like things may have got confused with your PM? TCMEYER is always willing to help. I would wait as he should be along soon and will see this.
Good luck with your WE and remember to always have fun!
The definition of insanity is to do the same thing over and over again and expect a different result?
An old Irish toast, May the wind always be at your back, may you always have work and may you be in heaven a half hour before the devil knows your dead. Cheers!
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Using the Variable Thickness Stone Adapters 1 month 2 weeks ago #18702

  • tcmeyer
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Thanks Guys!

I've PM'd Gus and must apologize for the error of my ways. When I invited Gus to send me his e-mail address, someone else jumped in ahead of him. Since the name was completely different, I thought it was Gus, and having sent him the requested info, I stopped checking my PM's.
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