Surface grinding attachment question

H

Hubert S.

Joined
Dec 14, 2019
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I have started building a surface grinding attachment and I am wondering whether to incorporate a second tilt axis to allow tapering as well as grinding bevels. From what I have seen, the SGA by Travis Wuertz allows this by inserting a small sine plate where the arm with the magnetic chuck attaches to the tool arm, and the Reeder SGA has a hinge. I don't really have a concrete plan on how I want to build the thing yet, but I think I want to use a single tool arm and the hinge seems easy enough to incorporate. That being said, I am not entirely sure how useful this feature really is. Is anybody out there using an SGA regularly to grind in bevels and if yes, on what kind of knives? Or are there other applications that I don't know about? I make mostly kitchen knives and plan to make a few slipjoints. I can imagine some uses, e.g., a honesuki with a straight cutting edge or maybe a nakiri or usuba, but I'm not sure if it's worth the trouble.

I started on the chuck today and it was slow going on the minimill, but I did get the stock cut to size.

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Richard338 said:
I'd say go for it. If and when I get one, two key operations would be tapered tang and distal taper.
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I am going to do the distal tapering feature for sure. The questions is whether I really want to be able to tilt it so I can do bevels. Travis Wuertz has a video series from a hammer-in in 2015 where he demonstrates how to do it. It's a rather lengthy video series and he explains the setup with the sine bar in detail in the first four videos. Here is a link to the fifth video where the grinding starts:
 
Ah, now I understand. I still want to grind my bevels even if seeking perfection is an endless battle.
 
Adding an adjustable angle feature will make you very happy. Imagine perfect bevels on FFG blades, wakizashi with even shinogi, etc..
 
Thank you, Richard and Stacy. I will try to incorporate it. If it saves some time getting 80-90% of the material removal done quickly, I think I would probably end up using it.

The thing I cannot quite figure out is how you can get a distal taper and a bevel ground at the same time (other than the distal taper you get automatically from the blade getting narrower towards the tip). I seem to recall Don Reeder mentioning grinding both distal taper and bevel in one of his videos, but does not show it. In my understanding, which might well be wrong, the blade has to point forward for one side and backward for the other when grinding bevels, since the bevel angle can only be set in one direction. But the distal taper angle can only be set in one direction also, which would make a symmetric grind impossible. The only way I see to do it is to make one tilt axis swing in both directions, but that seems tricky for repeatability and rigidity. I guess I'll just have to build it and then see what the thing can do.
 
Set the taper first, and then tilt the plate. It takes a bit of finagling to get the taper right (and you need a stop clamp), but it isn't hard.
 
Stacy E. Apelt - Bladesmith said:
Set the taper first, and then tilt the plate. It takes a bit of finagling to get the taper right (and you need a stop clamp), but it isn't hard.
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I can see this working well for the right side of the knife, probably good for some Japanese blades. But I cannot wrap my head around how to do the second side if there is a distal taper involved, because both axes can only tilt in one direction. I might make one of the axes tilt in both directions.
 
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