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Stromberg Knives

Stromberg Knives

strombergknives.com
Joined
Jan 3, 2015
Messages
856
Hey guys!

I've been grinding lengthwise for some time now, it has been great for nice plunge lines and prep for a quick hand sanding session. I built a contraption based on @Nathan the Machinist 's ideas. Unfortunately I had problem with heat building up and I wanted to be able to do both left and right sides in horizontal mode.

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I've been pondering a better design and stumbled upon a drawing from @kuraki which gave me the idea to test this.

So, let me introduce to you... The Plunge Line Expediter 10000TM

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It works great! I've done some stress testing by running it up to 20% of 5600 SFPM for about 15 minutes. No excessive heat anywhere to be found.

I tried some quick plunge work, works great (don't mind the strange grinds on the blank, it's a scrap piece).

WUEAsKN.jpg

 
That's an impressive setup - With the 8 mm rollers it helps keep pressure off the belt/platen to reduce heat buildup. I LIKE it. I might try to make one of those myself. I might try your idea of a smaller roller - say 5mm? 5mm might be a tad small, perhaps a 6mm would work?
 
Ken H> said:
That's an impressive setup - With the 8 mm rollers it helps keep pressure off the belt/platen to reduce heat buildup. I LIKE it. I might try to make one of those myself. I might try your idea of a smaller roller - say 5mm? 5mm might be a tad small, perhaps a 6mm would work?
Click to expand...

Thanks!

You'll have to find suitable bearings that'll survive the rpms though. I think 4mm radius worked out as a nice compromise. And I like the look of the plunge lines with it. And not to forget, I will also be using this a lot for lengthwise pre-finishing chefs knives. And for that kind of work, the roller radius doesn't really matter.
 
Very nice work there. Well done.
So do you hold your blank by hand with this? I've wondered about something similar, but with some contraption that allows the blade to tilt left/right but would hold the plunge altitude exactly.
Something like a hinged blank holder that grinds as you swing it into the platen if that makes sense. Maybe it's not necessary?
 
Mark, I'll allow Stefan to comment on how he holds his blades for lengthwise grinding, but I hold by the tang. Remember, when lengthwise grinding the tang extends above the right (or left) roller while grinding the bevel. It takes a bit of practice to get it all working good. What few few blades I've done have been with grinder in vertical position and running in reverse. I grind one side with edge toward me, then flip blade other way so spline is toward me.

I can see how having a roller on both ends so the edge would be up for both bevels giving better visibility would be good. I do enjoy making new tools and might have to try that.

Ken H>
 
Brock Cutlery said:
Very nice work there. Well done.
So do you hold your blank by hand with this? I've wondered about something similar, but with some contraption that allows the blade to tilt left/right but would hold the plunge altitude exactly.
Something like a hinged blank holder that grinds as you swing it into the platen if that makes sense. Maybe it's not necessary?
Click to expand...

I hold the blank the same way I grind bevels, with the edge up to see what's happening. And that's why I wanted to have two rollers, to be able to do the same procedure on the other side of the blank, and still be in an edge up position.

And when I do the other side I switch rotation on the VFD/grinder, so that the belt moves the same (relative) way on both sides. Otherwise you may mess up by the sudden realization that one side of the belt pushes the blade in one direction, and the other side pushes it in the other direction.

And as always, it's a matter of practice. And I try to stay away from jigs so that my grinding skills keeps improving. And what's a better way to learn to control the grind than alternating by grinding in a completely different style (lengthwise).

I made the housing somewhat wider than 2 inches (it's 70mm, 2 3/4") so that I can grind plunge lines on large blades with a forward tilted plunge line, it will give me more room to angle the blank when necessary.

I also tried to minimise the housing for the bearings on the rollers, so that they wouldn't interfere too much with the grinding. That's why the bearings are so petite. But of course they are specced for the kind of rpms I will put them through with this kind of grinding (hint, there's no hogging involved!).
 
Stromberg Knives said:
Thanks!

You'll have to find suitable bearings that'll survive the rpms though. I think 4mm radius worked out as a nice compromise. And I like the look of the plunge lines with it. And not to forget, I will also be using this a lot for lengthwise pre-finishing chefs knives. And for that kind of work, the roller radius doesn't really matter.
Click to expand...
He can use bigger bearing on 5mm shaft .Question is will it be strong enough ?
I think that flanged bearing are good for this setup ............
https://openbuildspartstore.com/flanged-bearing-688zz-8x16x5/
 
Natlek said:
He can use bigger bearing on 5mm shaft .Question is will it be strong enough ?
I think that flanged bearing are good for this setup ............
https://openbuildspartstore.com/flanged-bearing-688zz-8x16x5/
Click to expand...

Absolutely. But as I mentioned, the reason I wanted a small outer radius of the bearing was that I wanted the bearing pocket to be as small as possible. So that it wouldn't protrude too much and get in the way of the grinding space.
 
I have been contemplating a setup like your original, but with a single wheel between the two platens and using the front edge for the plunge "setters". I was thinking that the wheel could be adjustable in and out so the belt rides at a good angle across the corners. I was also considering milling a 1/4" deep pocket with an 1/8" stepped down front edge and glueing some 1/4" thick carbide strips in.
Do you think this would work out?
 
mike-E said:
I have been contemplating a setup like your original, but with a single wheel between the two platens and using the front edge for the plunge "setters". I was thinking that the wheel could be adjustable in and out so the belt rides at a good angle across the corners. I was also considering milling a 1/4" deep pocket with an 1/8" stepped down front edge and glueing some 1/4" thick carbide strips in.
Do you think this would work out?
Click to expand...

Well, if I understood your description correctly, I think a setup like that would have quite the same characteristics as my initial iteration, which I believe has several drawbacks (at least from my point of view, and how I'm using the contraption).

Some of these drawbacks would be; 1) friction and heat build up (which to an extent can be mitigated by increasing the angle you run the belt across, but at the cost of decreasing functionality), 2) more cumbersome to change from left to right grinding action, and 3) running belt over a corner without rollers/bearings will increase the risk of breaking belts.

After further testing I find that the new design addresses all these drawbacks and I'm still happy with it. Next step is to tidy it up and get rid of the all thread rod, which I only used for prototyping. The protruding nuts will need to be flush so they don't interfere with the use of a work rest, for example.
 
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