Which Grit for Slack Belt?

C

cliff355

Joined
Apr 19, 2003
Messages
1,232
Gents, after pouring over considerable counsel regarding slack belt grinding and convex edges, I have decided to give this a try. However, the finest grit belt I can find locally for my 1" x 42" machine is #120. That seems to work well enough for lawnmower blades but I am a little reluctant to put a khuk on it.

So, I sent off for some #400 and #600 belts and am wondering: Are those too fine or not fine enough?
 
I start with a 220 usually for general edge grinding.

I only start with a 120 if I have to completely redo the entire geometry of a very beat-up knife - as this is sure to alter the profile of the edge, and I will have to grind forever at 220 to get rid of all the scratches. :confused:

If also depends on what you're putting the convex edge on.

If you're adding it to a large 18"+ khuk - you may run out of patience and want to go ahead and use the 120 - you'll go crazy just sitting there waiting for the 400 to wear it down.



Here's what I'd recommend for first time "convexing" a good sized khuk: (for any skill level)
  • 1 - Tape up the blade lengthwise (except the part you want to reprofile = around 3/4" wide - or an extra 1/4" above the secondary bevel) with blue masking tape - or drafting tape, etc - it's the not-so-sticky stuff that leaves no residue.
  • 2 - Start with a new 180 grit belt and figure on spending 2/3 of your total time on this belt - be patient! Hold the khuk so that the spine is within 1/4" of the belt - adjust according to your machine. Push the knife back and forth, straight-arming it like a saw. This is important! You don't want to ruin the heat treat or alter the blade edge by spending too much time in one spot. Also, I've found that to preserve the exisitng edge on the tip you have to lift the handle and turn slightly as you finish. One long solid smooth motion. Can't emphasize this enough.
  • 3 - After you have completely altered the profile and edge to how you want it, move to a 220 grit belt. Then, 320, 400 and 600. Each time bring the entire edge back up to the same level of polish.


    (You'll hate me for suggesting this next part - but after you've done it once - you'll be hooked... :p )
  • 4 - Take all the tape off the blade - no doubt there will be a few scratches. Grab some sandpaper, put the knife in a vice, get a drink and turn up the radio - you'll need it. :rolleyes:

    Go back to 220 and start handrubbing to get the scratches out. It will mar your existing magic finish, but that's ok for now. Rub the blade lengthwise and plan on again spending 2/3 of your total time at the 220 grit level. Once you can no longer see the lattitudinal scratches and only longitudinal scratches, move onto 320, 400 and then 600.
  • 5 - From there, if there are no deep scratches left, load up a scrap piece of leather with green rouge and continue hand-polishing. I don't even bother with higher grits anymore. You could, but to me, it's a waste of time on a khukuri. You'll eventually acheive a slightly foggy but still mirror finish - just not glassy. It will look "oily" which is similar to the magic polish put on by the kamis.

    One note about hand rubbing: As long as you are moving in a straight line, you can run your paper all the way to the cutting edge without harming it - you'll be sharpening it, actually. You'll be able to tell if you still have a wire edge because it will catch on the sandpaper. As a general rule - you should sand until you no longer feel any "resistance" to the paper (this applies to 400+ grit papers)

  • 6 - Lastly, provided you profiled the edge correctly, all you will need is a stropping to get a hair-poppin edge.

Good luck and post pics!

Dan
 
On the subject of slack belt sanders, can anyone recommend a good "starter" model to me? I basically want something to sharpen blades with, possibly using it to make a few knives as well, since I'm working on building a small forge, for the heck of it.

TC
 
Get a 1" x 42" model belt sander. Believe it or not - it is 10 times better than a 1" x 30" and costs just a fraction more.

If you have to go cheap - get one from Harbor Freight

Otherwise, try Delta. Watch the Home Depot and Lowes ads for deals at $99.

Dan
 
Pendentive:

Thanks so much for those instructions. I'm going to print them out and hang them over my bench. However, it looks like another order of belts will be necessary (180, 220, 320) before taking on this task. Home Depot and Fleet Farm don't carry any 1x42 belts, and Sears seems to be phasing them out.

Thnderchyld:

That grinder I have was the cheapest one Sears made about seven or so years ago (4 amp). Now their cheapest one seems to be a 2" x 42". Mine cost about $89 and it seems like the current "low end" grinder goes on sale for about +/- $100 every couple months.
 
www.supergrit.com seems to stock them in various grits. I haven't dealt with these people personally, but they were mentioned here some time ago.

(it's supergrit, not supergrits).
 
cliff355

I have ordered from Supergrit and Lee Valley. Both have excellent belts at good prices with great customer service. Orders only took 2-3 days to arrive.

Oh, and by the way, splurge if you can and get at least 3-5+ of each of those grits. You'll need 'em and they're cheaper in packs.

Best of luck.

Dan
 
Starting out with Aluminum Oxide belts is a good idea. Once you've got a firm grip on your particular grinding style/needs you'll want to move up to a Blue Zirconia belt which lasts much longer.

Thought I'd just add that you can get A/O belts on eBay in a whole variety of grits for $.50 to $1.00 per belt. Check out barbkat as a seller. She's a nice lady with good prices and she'll mix and match for you if you want.

Dan
 
Dan, you are a very expensive person to know. Now I'm looking on Google for 1 x 42 belt grinders. Thanks a lot!
 
Cliff where in MN are you located? My guro in eskrima is a knife maker, and he mentioned a place locally that had a good deal on belts. I forgot the name, but if you are located near the metro area, I can email him about it again. May be worth looking into.
 
Originally posted by Aardvark
Dan, you are a very expensive person to know. Now I'm looking on Google for 1 x 42 belt grinders. Thanks a lot!
Click to expand...
:D :p

Call my wife - she's starting a support group...:eek:


Guys, I'm going crazy here - I leave for Blade tomorrow!!

Dan
 
Pen:

Thanks for the tip on sources for belts. The belts I ordered were from Supergrit and they seem like a fairly professional outfit (email shipping notices, etc.). Lee Valley never occurred to me, but I have bought alot of stuff from them and will probably order the next load of belts from them also.

Fredrico:

Though I am not located in the metro area, I swing through there several times per week. If your guro knows a good source of belts I would definately make a point of stopping by there. Also, I'm completely stumped as to where to find that green polishing compound -red rouge is even hard to find at times.
 
Lee Valley has the green stuff. "Veritas Honing compound" It resembles a big square green crayon and is packaged in a very plain white box.

A speciality wood-working store will likely have it also--(Here there is an OK one called Rockler's, a chain which often has it in stock.) Seems like wood-workers honing chisels and planes are the only folks that have an interest in using strops and really fine stones. Even then, the demand seems so low that stock is one or two. Or zero. Of course, one stick of the compound is pretty much a lifetime supply for many.
 
Cliff I emailed my instructor, but he's been having computer problems lately, so I dont know when he'll be able to get back to me. However, Menards carries red rouge, never checked for the green stuff. Have you tried Fleet-farm? There is a specialty wood store on Lyndale (near uptown) that may have it, fancy place, with all sorts of exotic woods, but again I cant remember the name.
 
Fredrico:

Naturally Menards is the only place I haven't tried, but I got a stick of red rouge from Sears last week which should hold me. If you find out where to get belts around the cities, please post. Fleet Farm doesn't have much rouge, but they are well stocked with genuine Hooflex so I can't complain.

Firkin:

Thanks for the info on veritas compound. I'll be sending off for some belts from Lee Valley in the next day or so and add on some of that green stuff.
 
Cliff, I just got a reply from my instructor. Seems like my memory was all off, and he isnt getting his belts locally. Though the place he's getting them at, doesnt sound bad. Here's what he said about them:

"The place is called Rhino Abrasives and they sell by
the dozen. The deal is, you can break up an order
into whatever grits you want, but the price will be
about $28...and then they'll double your belt order
for the same price. So...remember that when you order
that you're going to be getting 24 belts for $28."

I tried googling them, but couldnt find any websites. Maybe someone else can come up with a site?
 
Fredrico:

Well, thanks for checking. I just sent off to Lee Valley for some belts and green buffing compound. By the time all this stuff arrives I should have enough spare time on my hands to start grinding. You'd think an outfit like 3M would be selling stuff like this all over the place around here, but they probably ship it to Canada so Lee Valley can send it back.
 
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