Recommendation? My grinding curse

NickHFSS

NickHFSS

Joined
Jun 26, 2020
Messages
155
Hello everyone , so I have this recurring problem for quite some time now , when I don't have to make many blades at same time , I just go and hand sand it out with a hard backing.
But when you have to make a few , its pain in the but...
Whenever I am making scandi grinds , always about 2" from the ricasso I have the sanding dent , before you jump in here's my thoughts and two cents
It could be the backing issue, but whenever I free hand sand I don't have this problem...
It could be the grinding jig issue , but I tinckered with it , the same , got a second one , the same....
it could be the belt issue , but it happens with different belts
It could be of course my skill issue , but I've tried to change the technique , start grinding from different sides , tried different pressures , speed , the same happens.....

After all of that I'm stuck and I don't know how to fix this , maybe someone more experienced can give me any thoughts on how to fix this ?
Heres my steps,
Cubitron II 36 initial grind
Ht
3m trizact A300
3m trizact A 65
3m trizact A45 (here you can already see it , maybe it was there before but the grind was too ruff)
3m trizact A30 I think , whichever corresponds with 600 grit...
cork 400
cork 800 ( at this point that place changes color , not from overheating but turns slightly more metaly color
cork no grit
buffing wheel

I try to do less hand sanding and more grinding as its faster when you have to do more then a few, thats why I prefer not to ditch the jig.

any help is welcome.
 
This is the infamous 2" bump.
What happens is that you focus on the plunge and a) spend more time there, and b) lift the ricasso to feather the plunge and thus dig the edge of the belt into the bevel right at the 2" mark.
The trick is to do some very light passes with awareness and not lift the ricasso. Smooth the plunge by gently bumping into a flexible belt running it about 3/16" over the edge of the platen.
 
Richard338 said:
This is the infamous 2" bump.
What happens is that you focus on the plunge and a) spend more time there, and b) lift the ricasso to feather the plunge and thus dig the edge of the belt into the bevel right at the 2" mark.
The trick is to do some very light passes with awareness and not lift the ricasso. Smooth the plunge by gently bumping into a flexible belt running it about 3/16" over the edge of the platen.
Click to expand...
To be honest that was my first thought obviously , because of that I even quit starting grinding from the ricasso , I grind from the tip now and as I get close to the ricasso I start to lift the tip side and finish sanding ricasso with tip of the belt
 
Are you pulling or angling the blade away a bit to cut the bevel in the curve at the tip? It's possible as you pull away that you inadvertently twist the blade at the same time and cut a bit deeper in that spot. That's the only other thing I can think of if it's not the 2" bump.

Eric
 
What kind of platen are you using? How is your belt tracking?

One of the things that might help with the 2 inch bump is better lighting and getting used to look from above when grinding, and constantly being aware of how you approach the belt (jig or free hand) and how (and where) the blade contacts the belt. You need to be able to see that small gap between the blade and the belt before you feed the knife to the grinder.
 
I'm not sure if this will help at all..... but I must be doing something odd too in the earlier stages of the grind?
I freehand grind my bevels/edges.
Somewhere about midway being done with my primary, I will switch to my disk grinder to clean up, and flatten out the surface.
I would have some dips, dings, scratches, and valleys. It only takes a little bit to clean it up.

After doing that, it seems like I am able to hold a clean line when going back to my 2x72, and the rest of my grinding looks good.
I assumed that cleaning up on the disk gave me a nice flat blade surface to work from instead of trying to micro-chase the needed clean up on the belt grinder. Not sure.

*also adding a glass, then even better yet Carbide platten seemed to help with my looks.

Just a thought, and more info.
 
Poor body position when grinding. Either rocking body or rocking hands. Your feet not spread for even balanced stance and elbows not tucked/locked in tight against body/stomach. Watch the spark trail off grinder. If its not a full platen width you arent square or your hands arent square and applying even pressure to platen. Slow down, gently place blade against belt 2" wide spark trail then ease back towards Riccaso.
 
FredyCro said:
What kind of platen are you using? How is your belt tracking?

One of the things that might help with the 2 inch bump is better lighting and getting used to look from above when grinding, and constantly being aware of how you approach the belt (jig or free hand) and how (and where) the blade contacts the belt. You need to be able to see that small gap between the blade and the belt before you feed the knife to the grinder.
Click to expand...
I have a cast iron backing , its fairly new and has an even surface , I have a graphite attachment I can put on if that would help.
Some belts track perfect some not so well

When I work on knives without a ricasso , I aproach diagonally betwen the grits to see the progress and I've never had such issue.
As I said I try to not even spend much time on that place and start grinding from the tip and then as I get to the end I even lift the tip side and have just part of the belt touching the ricasso
 
not sure cast iron is the best material for a flat platen. Never used one, so I do not know. I would consider getting a tempered glass platen liner...or, if you are so inclined one of RD Knives' carbide platens.
 
When I was a newer user of a grinder, I had this issue. I softened the edges of my platen by ever so slightly rounding the sides. This took away the hard line at the edge of the belt. I soon got better at grinding and when I added a glass platen liner, I had learned grinding without making a 2" line ... and the problem was gone ... most of the time.

One note of advice - I would change your A65 belt step to an A100 belt. I find the drop from A300 to A65 too much.
For a satin finish, I use A300-A100-A45-A16 - hand sanding.
If I am doing a brushed finish, I do A300-A100-A45-Scotch-Brite belt.

I never got into cork belts. I used them for a while, but I don't like trying to get a fine finish on the grinder - YMMV.
 
I found a glue on graphite platen i bought years ago , I put it on just to try and I got magnificent results from the first try so maybe its platen issue , I rounded over the edges but I want to get a glass platen , probably pirocelam , where would you recommend me to buy one ? Thanks
 
Big game changer for me is to not start grinding at the ricasso or tip but in the middle and move to the tip or ricasso.

Today I ground a blade with a file guide again and it was a big help.
Also give free hand a try
 
Stacy E. Apelt - Bladesmith said:
When I was a newer user of a grinder, I had this issue. I softened the edges of my platen by ever so slightly rounding the sides. This took away the hard line at the edge of the belt. I soon got better at grinding and when I added a glass platen liner, I had learned grinding without making a 2" line ... and the problem was gone ... most of the time.

One note of advice - I would change your A65 belt step to an A100 belt. I find the drop from A300 to A65 too much.
For a satin finish, I use A300-A100-A45-A16 - hand sanding.
If I am doing a brushed finish, I do A300-A100-A45-Scotch-Brite belt.

I never got into cork belts. I used them for a while, but I don't like trying to get a fine finish on the grinder - YMMV.
Click to expand...
Thanks for always giving great advice sir!
I wanted to send you a message and can't seem to find how.
What glue would you recommend for the glass platen?
 
NickHFSS said:
Thanks for always giving great advice sir!
I wanted to send you a message and can't seem to find how.
What glue would you recommend for the glass platen?
Click to expand...
Not Stacy, but..... I've used Gorilla Glue's version of sticky tape (double sided) with success.

*some people mill a ledge for the platen to rest against.
some drill/tap and use the screw heads to achieve a similar effect.
 
NickHFSS said:
I found a glue on graphite platen i bought years ago , I put it on just to try and I got magnificent results from the first try so maybe its platen issue , I rounded over the edges but I want to get a glass platen , probably pirocelam , where would you recommend me to buy one ? Thanks
Click to expand...
I just recently purchased one from Little Bear Knives, he has pretty much any size you could want, along with a metal safety shelf. I mounted mine with with double sided gorilla mounting tape. I haven’t used it much yet, but its stayed on so far.
 
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