flat grind on my 8in blade

kungfumo

kungfumo

Joined
Aug 21, 2006
Messages
533
So I just started getting back into blade smithing. I have a bar of S7 thats
.250 thick, that I cut out a nice 8in blade camp knife. I'm now trying to get the flat grind on the blade with a crapy a$$ craftsman 36in belt sander and files. I have put about 2 hours into is and have not made very good progress. Yes the steel was annealed(SP?).

What would you suggest besides buying a new belt sander, to cut the edge? I have a 80 grit belt on it now and its taking a Loooooong time due to the power of the sander. Any good files for this kind of stock removal?
Thanks.
 
Your quickest, easiest and cheapest bet is probably going to be to get some low-grit (like 36), high-quality (Norton and 3M are the brands to trust) belts.

It'll make all the difference in the world.

Now, if you've got room in the budget for a proper variable speed 2x72 grinder, by all means, go for it, and that will help too, but even there, cheap abrasives vs. top-shelf abrasives is going to come up as an issue.

:thumbup:

Mike
mscantrell at gmail.com
 
The most precious tool in all of knifemaking is one of the toughest to acquire and yet is totally free for the taking: patience. :)
 
Try giving trugrit.com a call, ask them for their most aggressive 36 grit belt -I think Norton makes it. An 80 grit is not aggressive enough to grind the bevels on a thick bowie. 80 grit belts are more suited for grinding 1/8" stock (ie. small knives).
 
I've tried grinding with a 4x36.....and if you've put 2 hours on an 80 grit belt, you should have changed belts an hour and a half ago :D

Aluminum oxide belts are the most common type for a 4x36 and they just don't last that long on steel. And 80 is way too high to start out with.
Try to find a couple 36 grit belts, get ceramic or zironia if you can (you might have to buy online). It will make a world of difference. The 4x36 is going to grind slowly for the most part anyway, so you can stick with the 36 grit alot longer. I wouldn't step up grits until you've got it 80% ready for heat treat.
 
If funds are limited and a lot of steel removal is in order, try an angle grinder.
 
Tanks for the replys. I the belt I have on there now is a norton. I will try a 36 to see how well it cuts.

ok so little off topic but why only finish 80% then send to heat treat? YES I'm a noob:)
 
Good thinking, Fitzo! The angle grinder is something I use frequently, but it didn't occur to me to mention it.

Kung, usually there's two reasons you don't finish all the way before HT.
First is that the HT process will create some scaling, which will make your surface rough, so you'll have to go back through the grits again to end up smooth. No need to get it all shiny twice, when only the second time counts.
Second reason is that you'll want to leave some thickness, or you'll get warping. The guideline that seems to be commonly accepted is to have the edge remain about the thickness of a dime. Then grind it thin after HT.

Hope that helps!

Mike
mscantrell at gmail.com
 
I used a Craftsman 4x36 for a long time. It is slow but you can grind an 8" blade with it. Most hardware stores only carry 50, 80, 120 grit so you should start with 50 and probably use one new belt per side. If you've put 2 hours into it then you should probably be done with at lest one side. It takes time on that grinder but it can be done and the results can be nice if you're patient.
 
kungfumo said:
Tanks for the replys. I the belt I have on there now is a norton. I will try a 36 to see how well it cuts.

ok so little off topic but why only finish 80% then send to heat treat? YES I'm a noob:)
Click to expand...

Mike explained it pretty well. You need to leave a little meat there to help prevent warping or cracking when you heat treat it.
What I was saying is that you can use that 36 grit belt until its almost ready for heat treat, and then switch to another belt to take the deep scratches out and clean it up. Its easy to get in a hurry and try to switch belts and start polishing things, but get it pretty close to where you want it with the coarse belt.
 
Awesome thread, I think I'm getting a sander like kungfumo's for Xmas. About angle grinders... I was looking a while ago, and holy crap, you can pick one up for $20. Think it's worth it to a beginner to buy one for hogging out profiles, do the rest on the 4"x36", and just wear it out till I move up to bigger grinder?
I mean, they're almost disposable, they're so cheap.
 
I started using my 4.5in harbor frieght grinder on this originaly, first with a cut off wheel to cut out the ruff shape then a grinding bit to carve it out. This works very well. I also have a 9in grinder for some of the bigger stuff:D

I do alot of tube work for 4X4 tube chassis and things like that so I like tools.

I do ALOT of work with my grinders, my suggestion is that if you do at least 3 or 4 hours a week with your grinder buy a dewalt or something better, not harbor frieght. I have been through 7 in the last 2 years. They are getting wise to me and wont take them back now.:grumpy:
 
kungfumo said:
I do ALOT of work with my grinders, my suggestion is that if you do at least 3 or 4 hours a week with your grinder buy a dewalt or something better, not harbor frieght. I have been through 7 in the last 2 years. They are getting wise to me and wont take them back now.:grumpy:
Click to expand...

OK, that makes sense. Sounds like I can get by with a cheap one then... cool!
 
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