Tip to remove horizontal grind lines

J

jawilder

Joined
Jun 27, 2006
Messages
2,331
I know that I can't be the only one who occationally gets those annoying horizontal grind lines on a long blade. They often come when you lay the blade flat against the platen and always start at the plunge. That might be a good way of starting a plunge, but unless you tilt the tip away from the belt you end up cutting a gash with the opposite edge of the belt as well.

I was recently working on a 8" Chef knife and noticed a few of these grinding imperfections. I admit it, I get them from time to time... well, most of the time on long blades. Suddenly I remembered a trick that Dan Graves showed us at the last hammerin. If you haven't gone to one of his, you SHOULD!

His trick is to stack up a scotchbrite belt UNDER a 360 J-flex blelt on your grinder. It takes a few tries to get the tracking and lining right so they don't slip off, but my goodness, this method works great! Use it on a slack belt as you would to get a convex grind. The extra stiffness behind the J-flex helps to keep your flats straight while blending in the grinding imperfections.

I forgot to take pics, but here is a crude diagram to show what I'm talking about

ScotchbriteJflextrick.jpg


As you can see the scotchbrite belt is usually a bit longer than the J-Flex, so it will buckle/bow up. Try to make it so that happens between the contact wheel and drive wheel. I'm not sure if I tried this using a flat platen but it will certaily work as a slack belt.

Give it a try sometime. I image this method would be a good alternative to the multiplaten as it is basically the same thing - a slack belt with stiff lining underneath
 
I've tried that before, and it works great.

The only problem is that it usually takes me several trys to get both belts aligned properly.
 
I'm so going to have to try this. All 3 Wilton grinders at the school workshop have severely dished platens that give me bad headaches trying to get good grinds with. A stiff 36 belt is fine, but the thinner and more flexible belts get wonky.
 
Don Nguyen said:
I'm so going to have to try this. All 3 Wilton grinders at the school workshop have severely dished platens that give me bad headaches trying to get good grinds with. A stiff 36 belt is fine, but the thinner and more flexible belts get wonky.
Click to expand...

What school? I did quite a few classes at Pima; if Pima take them to the machine shop and have them flat ground.
 
Ive used this trick multiple times ever since he showed us it at that hammer in. Man it works great too!
 
David66 said:
What school? I did quite a few classes at Pima; if Pima take them to the machine shop and have them flat ground.
Click to expand...

It's the Blacksmithing/Knifemaking/Metal Workshop class at the West Campus Pima. I'm also taking the manual machining classes, but for me to do any of my own work I have to take an independent study course.

Also, it's mostly bevels and tapered tangs that's throwing me off. I'm not sure how I would do those with the surface grinder...
 
Don Nguyen said:
It's the Blacksmithing/Knifemaking/Metal Workshop class at the West Campus Pima. I'm also taking the manual machining classes, but for me to do any of my own work I have to take an independent study course.

Also, it's mostly bevels and tapered tangs that's throwing me off. I'm not sure how I would do those with the surface grinder...
Click to expand...

I'm sure David meant taking the platens off the grinders to have them surface ground to be flat again...
 
Tait said:
How would that compare to using a rotary platen?
Click to expand...

I must admit that I've never used a rotary platen but my understanding is that there are two main "magical" benefits to it. One is the ability to choose the amount of slack behind the belt. This is done by using wheels that are closer/further apart. The other area of benefit the RP has is the cushioned belt that rides behind the grinding belt. This gives you somewhat of a firm backing that still countours around the work piece.

The later is the reason I suggest this method might be a good alternative to the Rotary Platen. I don't mean to suggest this replaces the RP, only that there is a way to get a firm slack belt without having to spend $500 on extra equipment.
 
Brian Ayres said:
I'm sure David meant taking the platens off the grinders to have them surface ground to be flat again...
Click to expand...

Oh! That makes much more sense :P

That would have to go through the staff, and 99.9% probability they won't do a thing about it. No modifications allowed, etc; can't even jb weld a piece on there. Also, the whole platen is a cast piece, and the the platen is already 'lower' than the wheels, which are not adjustable. Grinding it flat would just make the wheels stick out more.

I'm just going to build mine some time and not have to worry about that.
 
You could apply a ceramic, or piro ceran overlay on the platen with GB weld. Would this raise you above the wheel height? I ended up building a whole new platen set up to give me room on the left hand side on a similar type machine, and then cut holes in the ears to hold the upper and lower wheels so the wheels became adjustable,. Frank
 
You must log in or register to reply here.
Back
Top