Cleaning up flat grind

etp777

etp777

Joined
Aug 12, 2002
Messages
2,259
I'm still practicng my grinds, and I have yet to add glass(or even hardened O1) to my platen, so my flat grinds aren't completely flat. Is there any reason I can't go up to slack belt area(or even remove platen) to help clean up transitions from the various little deviations in my grind? Havne't finished bringing up grind to the spine, but I tried it here, as I had changed angle a bit with how I was holding it, and it seemed to blend well, it looks like one continuous bevel now.

Anyways, any input would be greatly appreciated.

Doubt it matters, but if it does, annealed O1 and 2x72 grizzly.
 
One way is to take a real fine file, or a piece of micarta, metal etc. Wrap wet or dri paper around this, and hand sand using a lube. Water with some baking soda in it(helps retard flash rust), WD40, windex, etc. Sand lengthwise, and you can alter pressure to move your grind. When the lube gets muddy(frequently), wipe it off and reapply. Make your strokes long,one way, not short, and back and forth.
Here is a site that gives pointers on hand sanding, as well as numerous other things.

http://www.engnath.com/public/manframe.htm
 
The slack belt area will end up giving you a convex grind profile, the edges get nore pressure than the center.

The trick with flat grinding is not to lift off the platen to look at the blade because each time you put the blade back you get another flat spot. With practice you will reach a stage when you can do the finishing grind without lifting then the final cleanup with a file or sandpaper will be minimal.
 
etp777,

Sounds like we're in the same boat. My flats, as they come off the grinder, aren't so flat. For now I need to flaten them out by hand.

I epoxied a piece of 1x10" glass (from a cheap picture frame) to a block of wood. Clamped some 220 grit across it and go to work.

I take HOURS to do this. But you do get a perfectly flat bevel and straight lines.

Once I get better with the grinder, I hope to be able to skip this step.

Steve

BTW, I'm currently chewing up alot of lattice wood right now practicing.
 
Recently my whole paradigm of knifemaking changed. I am a hobby maker, with a SEARS 2x42 grinder, a very small drill press, and other tools. I only grind outside, and I have to drag my tools out of the shed and set them up all of the time. In short, I don't make knvies often. If I did, I'd just grind and grind and grind, getting better with my grinder. But now, I look at my grinder as a "fast file", one that requires less elbow grease too! THis change took place when I was mad at a grind and neded to clean it up.

To clean up a knife I ground, I used a file and draw filed the knife. This made my flat grinds VERY flat and clean. A trick for cleanign up the plunge cut is to make a safe file. If you like curved plunge cuts, use a round file. For a straight plunge cut, use a square/rectangular file. All you need to do is grind off the teeth on one side of the file. You put the ground side down on the side of the knife and that way you can file into the plunge and make it nice and clean, while not filing the sides of the knife! Slick trick. Until I get a better grinder and a shop and all, I'll be drawfiling. My last 2 knives have been my best, thanks a lot to me going back to using files more.
 
Just draw file the blade to remove any grinding divots.

You can also put the blade on a disk grinder to take that divot out.
 
Flat is flat. If you want a convex grind then slack belt it. Like Mike Hull and Phillip Jones stated, you can draw file it or wrap abrasive paper or cloth on something flat THAT DOES NOT FLEX.

One problem that many folks first starting out is to not keep the piece FLAT against the platen at all times. Never, ever, never pick it up off the platen before making one complete stroke (at least when first starting out). The more you grind, the more experience you gain and can get by with it but for now, just one complete stroke.

I have found that the best way for me is to start from the plunge and move the blade completely to the tip, never going back and forth. To steady myself my elbows are against my hips and I never move my hands or arms and just sway one way or the other. If you do go back and forth, expect to have the dreaded two inch grind line.

If you have a tool rest on your grinder take it off your grinder and use that organic one that God gave ya. My "tool rest" keeps getting bigger and better as the years go by.

C Wilkins
 
Flat is flat thats for sure. What I do to finish up a flat grind. I grind until almost done then put a pad on the platen.Usually a piece of denim just enough to take the bounce out of the belt. This gives you a very faint convex and very easy to control grind. It doesn,t have to go all the way to the spine.
I usually get 4-5 blades ground before having to change.
put some graphite on the pad it last longer.
My $.02
TJ
 
One other thing, many have been helped in the flat grind department, by installing a Pyroceram platen liner, on the existing platen. Your grinder wil run cooler, including the belts, and your grinds will improve. Look for Steve Pryor at CKD, he sells it.
 
In addition to the other comments, I would like to reemphasize using glass or pyroceram on the platen.
Overcoming the faceting problem, as I call it, is mostly one of practice. However, there are a few other things worth mentioning. Worn out belts are hell on the flats and keep the blade cooler if you think this may be a contributor. If you are able, slow down the belt speed. Lastly, ease up on the pressure and let the grinder do the work.
 
I clean all of my flat grinds up on my homemade disk sander. I attached a rubber disk onto the aluminum one. I use spray adhesive with wet/dry sandpaper and stick it to the rubber disk. Trim it with a junk knife (made my own) and sand away. I get no bounce but a very smooth finish. You can sand as high (grit) as you like.

Make sure you use a slow speed motor to drive the disk. You can burn your steel if you aren't careful.

You can get more info here:
http://www.bladeforums.com/forums/showthread.php?s=&threadid=108354&highlight=disk+sander
 
All,

Have a related question...got craftsman 2x42 for xmas and started profiling first blade this week. I am going very slow and taking little bits off at a time (80 grit). I am grinding from edge to spine. I noticed that the blade (1.25 x 1/8) is coming out convexed. Draw filed abit to help flatten, back to the grider for a couple of passes, and it is convexed again! Noticed after inspecting platten that it is about 1/8" away from belt (it is parallell and square tho), causing me to actually have to put pressure on the blade to get the belt againt the platten. Is this enough "gap" that with pressure it would eat edges first causing convex grind? If so how close to belt is platten supposed to be? The platten is as close to the belt as it can go now, so I will have to make the slots a litte longer or add glass etc to platten to get it closer.

michael
 
Michael, yes, modify the platen to push the belt out a little. Or add another piece of metal, or pyroceram to the surface, to accomplish the same thing.
If you need to, bevel, or round the top, and bottom of the platen to facilitate the belt passage.:)
 
thanks Mike - I'll get on it tonight (as I'm already addicted). One other question - was gonna finish to 220 (ats34) before heat treat. How much edge should I leave in 1000's on the edge?

michael
 
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