Hapstone R2

B

burdog

Joined
May 15, 2018
Messages
18
Just getting into guided sharpening and I'm having an issue I can't quite figure out. Picked up the Hapstone R2 and getting pretty comfortable using it. I set my sharpening angle at 17 deg using GemRed digital. When I flip the knife over to check the other side it shows my angle to be 16.2 deg. I have checked all the screws and everything is tight. I moved the knife around in the clamp and rechecked the angles and it is still .8 deg off from one side to the other. I have watched several youtube videos and found nothing helpful. I really hate to reset the angle every time I flip the knife. Any ideas what I'm doing wrong?
 
If you've tried it with the knife re-clamped in different positions (even better to try it with a different knife) and you keep getting the same amount of error, then it is likely a tolerance issue with either the clamp assembly or the rotating mechanism not being perfectly squared up. This would essentially be a manufacturing defect, so nothing you are doing wrong. The Hapstone clamps are a bit thin compared to other brands, so being 0.8° off is not surprising. 0.8° is really not much, but if you want perfection then your frustration is understandable. You could try to take the issue up with Hapstone or whichever vendor you purchased it from and try to get a replacement. But don't be surprised if they tell you that being less than 1° off is not a problem in their eyes.
 
20yard said:
If you've tried it with the knife re-clamped in different positions (even better to try it with a different knife) and you keep getting the same amount of error, then it is likely a tolerance issue with either the clamp assembly or the rotating mechanism not being perfectly squared up. This would essentially be a manufacturing defect, so nothing you are doing wrong. The Hapstone clamps are a bit thin compared to other brands, so being 0.8° off is not surprising. 0.8° is really not much, but if you want perfection then your frustration is understandable. You could try to take the issue up with Hapstone or whichever vendor you purchased it from and try to get a replacement. But don't be surprised if they tell you that being less than 1° off is not a problem in their eyes.
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I think you're right about it being a manufacturing defect. I like perfection or darn close to it! I may reach out to Gritomatic and see what they say about it. Thank you for taking the time to respond.
 
Gritomatic used to have instructions on their website on how to adjust that variation out. But they have changed the website a lot, and don't seem to have it anymore. maybe if you ask they could send them to you.

O.B.
 
A lot has to do with how the blade is ground. To be exact it will need a flat side on each side to clamp onto.
A lot of kitchen knives have what looks like a v grind from spine to edge (not sure of the exact name for this) and this is where the issue comes from.

I have used some foam sheeting between the blade and the end of the clamp (on each side) to mitigate this and it works pretty well.

This is what I got but at the time I got it in a 2 pack.
 
K80Shooter said:
A lot has to do with how the blade is ground. To be exact it will need a flat side on each side to clamp onto.
A lot of kitchen knives have what looks like a v grind from spine to edge (not sure of the exact name for this) and this is where the issue comes from.

I have used some foam sheeting between the blade and the end of the clamp (on each side) to mitigate this and it works pretty well.

This is what I got but at the time I got it in a 2 pack.
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Thank you. I might give that a try!
 
So burdog,
did you checked your clamps as per gritomatic instructions with angle cube, ruler and flat piece in clamps?
 
TheOne45 said:
So burdog,
did you checked your clamps as per gritomatic instructions with angle cube, ruler and flat piece in clamps?
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I used a Mitutoyo digital caliper measuring to the bottom of a thick metal ruler clamped firmly in the two clamps. I took all measurements off my quartz kitchen counter top. I checked each measurement several times so I feel good about my numbers. I used a steel ruler from a combo square that checked flat (no rocking) when layed flat on my counter top. I completely backed off the rear most screws as suggested in the instructions so it looked to me like the clamp was completely flat on the ruler. I pushed the flat ruler up against each screw in the clamp and tightened firmly.

.04mm left to right difference.
.68mm left to right difference when clamp is rotated 180deg.

I checked the clamping bar level before I first started and found it is not perfectly square to the base. .22mm left to right difference one way and .33mm difference when flipped.

It appears to be a manufacturing issue to me. The question would be is it within acceptable tolerances and/or is it enough to worry about?
 
Another Shepherd said:
For a full flat grind, put the first clamp on the ricasso near the handle where the two sides of the knife are parallel. Tighten the clamp very firmly. Then you can put another clamp closer to the tip, but don't tighten it quite as much.
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That method got me a little closer. Same knife set at 17deg is now 16.5 when flipped.
 
burdog said:
thick metal ruler clamped firmly in the two clamps
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i think you are fine with those measurements.
Did you also checked angle difference with ruler in clamps.....stone on the ruler then angle cube to zero and then flip clamps 180 and check angle again.
 
TheOne45 said:
i think you are fine with those measurements.
Did you also checked angle difference with ruler in clamps.....stone on the ruler then angle cube to zero and then flip clamps 180 and check angle again.
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.3 difference with ruler in the clamps. Best i could do with the knife was .5 which tells me the factory bevel on that knife is probably off a little?
 
burdog said:
.3 difference with ruler in the clamps. Best i could do with the knife was .5 which tells me the factory bevel on that knife is probably off a little?
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Factory bevels are often a little lopsided. Sometimes very lopsided. 0.2 degrees off is very good. 1 degree off would still be good.
 
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