first real grinding question

[doublearrow]

I got my 440c steel from the supplier and it had the normal black mill scale i think it's called on it. Before the KMG I did everthing by hand including sanding all this crap off. Tonight I tried holding the blade parallel to the direction of belt travel flat against the platen. This cause severe pits in the blade. This raised a number of questions. For now I'm going to mainly flat grind but grinds won't go all the way to the top. How do I sand the flat parts like the tang and ricasso flat so handle material and bolsters sits properly? Also before grinding bevels do I want to take these parts to final grits on the belt then hand sand the rest of the way? I tried searching grinding flats and against the platen but nothing really answered my question. If there is something else I should search just let me know. THanks in advance for the help.

[SteveS]

>> How do I sand the flat parts like the tang and ricasso flat so handle material and bolsters sits properly?

No magic there. Just put them vertical against the platen and flatten. Work your way up the grit chain. I keep them tilted a bit one direction, then change the direction when I change grit.

>> Also before grinding bevels do I want to take these parts to final grits on the belt then hand sand the rest of the way?

I work the tang/ricasso and the blade bevels up the grit chain at the same time. But you do want the ricasso pretty well finished (about 220 grit) before you bring the grind line up where you want to. After everything is done then start the hand sanding.

Hope that helps,

Steve

[Bernez]

Ryan,

It would be easier to flat grind on a circular sander with a foot switch.
Apply some pressure on your blade (with some holding jig) which is on the sander plate, it's now flat, then switch the power on (not to much pressure on the blade at first). When you are ready, switch the power off, but keep the blade on the surface of the grinder till it's completely stopped. That way it's stay flat.
The blade must be constantly in contact with the grinder, with or without power.
Hope this helps.

Bernez

[doublearrow]

Thanks for the help guys. I tried just putting it vertical on the platen, but that's when the divots formed. It looks like I hit it with a ball peen hammer at different strengths. One guess I have is I started out with too smooth of grit (150) and applied too much pressure. I stuck the blade on a magnet then flat up against the platen. The longer I held it the more divots formed. I know for sure it's not the steel itself. Thanks again

[george tichbour]

Divots can be caused by the metal vibrating against the platen or by lumps of grit on the back side of the belt.

I would check the belts for contamination on the backs then check the platen itself paying special attention to the lead edge where the belt splice could be catching, slightly round that edge if it is not already rounded.

Vibration is your enemy. Do you you nave vibration during grinding? Why? not enough pressure, metal hanging up on guards or top wheel keeping it from contacting the platen completely. Does the grinder stall out when you put enough pressure on the metal to keep it from vibrating........replace motor with higher horsepower.

Having said all this I never use a platen because I had all of those problems, I do the flats after grinding the bevels by going down the face of the contact wheel. Flat grinding is a matter of hollow grinding on a 14" wheel and flattening it out vertically on the contact wheel and touching up with a file.

[doublearrow]

I don't think you guys have any idea how much ya'll have helped me. Now I'm in another dilema. I spent about 5 hours trying to figure out why my belt moves side to side about an eighth of an inch. Is that something that is normal? I don't know enough about grinding and my grinder to know if it is something that is supposed to happen. I set the tension spring at every possible tension and placed the platen in about every possible position. I tried different belts, brands, grits, and weights and all were the same. It didn;t mess with me while I was grinding a blade, but it did considerably when I used scraps to practice plunge cuts. With my limited knowledge it seems impossible to cut plunge cuts with the belt moving side to side that much. Also I wiggled the rollers to look for play and found none. If ya'll have any advice I'd love to hear it. And I could be looking for nothing this maybe normal for all i know.

[navajas]

Where did you get your belts and what brand are they?
Roland

[doublearrow]

I got my belts from texas knifemaker's supply. The brands are norton, hermes, and j-flex yellow belts. Also I got a 9 Micron but I'm not sure of the brand. I just grabbed a mixture to test the waters and see what I felt comfortable with.

[Jason Cutter]

I'd be very wary of a belt that starts to wobble from side to side. My grinder runs very smooth and even, so when the belt starts to go side to side even less than 1/8th inch each way, it usually means the butt splice or lap joint is about to give and a total belt failure is about to happen. Very painful when the belt actually goes - smacks you hard a few times. However, if you have a dud belt to start with - it might just mean you have a dud belt.

I'd mirror what George Tichbourne and Steve S have said. Check your platen often - if the platen isn't flat, well, not much is going to turn out flat. Its a simple matter of placing a metal ruler against the platen and noting where its flat and where its not. There will always be areas of wear but thats OK, And make sure the platen is positioned far out enough that the belt is running flat over it, and not dipping in to create a convex grind. However, you have to judge for yourself how far out so the grinder doesn't stall or create too much heat going over the platen. Worthwhile also running your fingers along the backside of the belt to check for those dreaded welded grit that gets caught behind the belt.

Flat grinding on a platen, especially tapered tangs or along the entire surface of the blade is hard work for the grinder, go slow and let the steel work itself down. Excessive pressure can not only bind up the machine, you could overheat the steel to the point warpage starts to happen to cause you headaches. Fresh belts of course will help too. Change the belt as soon as flat shiny spots start to appear anywhere on the ground surface. Below 400grit, the surface really needs to look like it is being "ground" with a fresh scratch pattern.

Good luck. Have fun. Jason.

[doublearrow]

Thanks Jason for the help. I went out and messed with it for about 3 more hours. I completely redid my set up and even bungie corded my table to the ground. The belt side to side went to less that 1/32 which I thought was exceptable. My platen was brand new so the flatness was right on. When I redid the set up (motor mounted on one inch thick wood with hinges on one side to change speeds on the step pullies) the vibration seemed to lessen to a great extent and things started going my way. Without ya'lls help I would have a clue as to where to start. I appreciate it.