Disc or belt?

B

Brian.Evans

Registered Member
Joined
Aug 20, 2011
Messages
3,267
I am sitting here at work thinking about making knives and a thought popped into my head. It comes from bits and pieces of stuff I've heard elsewhere.

Almost everyone focuses on using a belt grinder for knives, but is there a reason why a 9" disc wouldn't work just a well? I guess a person wouldn't have the contact wheel options, but for flat grinding, it seems a 9" disc paired with a file guide to cut in the plunges would work really well.

A used motor is $125, disc attachment $90, and VFD is $200. ~$400 for a very versatile piece of equipment.

What say you all?
 
I think most new makers overlook a 9" disc as an option when buying their 1st grinder. Disc grinders are awesome!
 
I agree that the disc grinder is a huge asset. I rough grind w/ 60 grit on a 2x72 and then switch to disc for all of my clean up up to 600 before hand finish. It is best if you have a reversable motor or have a way of setting up two disc that run in opposite directions. I use both 9" and 12" the nice thing about the 9" is you can cut your own discs out of sheet paper.
 
But how does it work as a person's only grinder? Worth it or save your money and get a 2x72?
 
I got my disc grinders after my 2x72 so it is hard to imagine life with out it. There are also cheap ways to do both with out droping thousands on either or both.
 
Honestly, I'd spend $400 on a good disc grinder before I'd spend the same on a Craftsman 2"x42".

I have a 2"x72" GIB and 2- 9" discs. But, if my 2"x72" died tomorrow(assuming I actually had shop time.:(:() I don't think I'd miss a beat making knives.

One of my mentors only used a 9" disc for 15-20? years before building a 2"x72".

Another maker who's work I greatly admire has 3 of RW Wilson's discs lined up in a row...

I say get one. In fact, a 1,725 RPM reversing 1ph 3/4hp motor for $100 and a 9" disc for $100 shipped would get you grinding tomorrow.

I use the edge of my disc to rough shape handle material, shape blade profiles, etc.

Buy one of Bruce Bump's carbide faced file guides for $95 or so and you can have beautiful plunges too. You can do swept/angled plunges or straight plunges depending on how you grind.

Also, because the disc is the same on the right or left, it cuts your plunges the same on both sides. :D

Buy some 3M feathering adhesive and you can change paper easily.

I suggest a steel disc too.
 
How does a person do straight plunges with a disc?

Also, what paper do you recommend?

Is 3/4 hp "enough?"

Bevel or flat disc?
 
The other thing i just though of that you should take into mind is that you are limited somewhat on blade lenght when it comes to grinding on a disc easily. really a 4 -4.5 inch blade is all you can fit on a 9" unless you grind in multiple stages. Also profiling with a table is doable but a 2x72 has definite advantage over a disc when it comes to overall profiling and profile ceanup.
 
You can do a sword on a disc.... There is no limit on length. Even with a flat disc there is 4.5" of down force to 2" of up force on a 6.5" blade. I was using mine to clean up the flats on my current project, a 10" blade.
I have a RW Wilson 1/2 degree bevel disc with a 3/4hp reversing motor on one of RW Wilson's disc stands.

To do a full straight plunge all you do is pull the knife up and down the edge of the disc using a file guide.
I bought some Blaze 9" discs but also just bought some of the Rhynowet Sandpaper too but haven't used it.

I just bought a 1.5hp 3ph motor with a flat disc for my second disc. I have it wired but work and life's been keeping me from the shop for a few weeks to get it running.
I chose flat as a few makers I know that use discs a lot, all use flat discs.....
 
Good call. Overlooked the bevel. I run flat discs and I use them for all lenghts and know they can be tricky for some. I was attempting to point out pro and con for someone just jumping in. I am not trying to sway you one way or the other just making suggestions.
 
I'm trying to setup a 9" disc as well, I have a beastly 2hp wetsaw (tilesaw) that is belt driven at a constant 3200 rpm.

My only issue is I cannot find the disc I want anywhere, I want a 3m cubitron 987c, 3m will sell a box of 25, and hillas has a minimum purchase of 100.... so If anyone knows where I can get a few of these discs, that would be great. Going to be working some m390
 
Funny this should come up again. I've been giving serious thought to getting the HF 12" Direct Drive Disc Sander (with 1.25HP motor). It keeps occurring to me that the disc grinder would be far more useful than the 4x36 belt sander I have for working on flats. That belt sander has been a pain to use for anything other than sanding the crusty crud off newly stabilized wood. I may just take the plunge on that disc sander soon.
 
I am new to knife making, only about 6 months. I have a craftsmen 2" x 42" belt/disc grinder. I never use the disc grinder. I also have a bench grinder that we use all the time for getting the shape of the blade form before grinding an edge. Between my sons and me, we have made at least 25 knives on the craftsmen belt grinder.
 
That's funny. I use my disc on my craftsman all the time. I love using it for profiling. It seems to work better than the flat platen for that.

I'm going to try a smallish blade on it today if the kiddos will ever decode to take a nap. Lol. It won't work incredibly well with AO PSA discs, but well enough for me to see if I'd like a 9" disc.
 
It is probably just me, the disc spins so fast that it seems I have better control with the belt. The few times I have used the disc, I ended up taking off too much.
 
Denver65 said:
It is probably just me, the disc spins so fast that it seems I have better control with the belt. The few times I have used the disc, I ended up taking off too much.
Click to expand...

That is why a 9" disc with a speed control is the best choice for a disc grinder. Not the cheapest but definately the best.
 
I used a disc exclusively for over 18 years. I started with a shop made disc that I started and a machinist finished for me, a .5hp 1ph 1750 rpm 110v motor I wired to reverse. I made a couple hundred knives on this including 10+ inch blades. Even recurves. I then upgraded to a better disc I made heavier and even more balanced. Then I added a 1hp DC variable speed. Made an even heavier disc and loved it so much I soon picked up a VFD and set up my current set-up. It is now a 1.5hp 3450rpm motor 146t frame with a 7/8" shaft with disc that is 3/4" thick. I know you all are reeling about the rpm. I got used to using that higher rpm pretty quick. It runs smoother and I am used to it. The best thing is I can slow it way down. The only drawbacks to a disc I found were the paper wears out pretty fast. I used AO for my heavy roughing and it does not last nearly as long as the ceramic but at 35 cents a sheet it is much more cost effective. Also grinding heavy recurves is difficult and I had to do a lot of hand work. I use 9x11" paper and trim it to the disc. I use Franklin sanding disc adhesive or 3M feathering adhesive. When I change the disc I use a propane torch to warm the paper and glue. This helps the paper peel off cleanly and I can do 25 or more changes before I have to re-apply the glue.

I finally built a KMG clone 2 years ago. I am just now getting used to it. The reason I decided to build one was the fact that the belts last longer and I can get more done. But for fine work I still go to the disc. I can get things much flatter on the disc and I have more control. The belt really hogs off the material and that is what I mainly use it for. It also comes in handy for handle work and slack belt grinding is also a plus. The belt is very versatile and can do a lot the disc is not suited for with all the attachments that are available. As far as the straight plunge lines, get anuncle Al's carbide fixture and grind to the fixture. Check out Mike Q's plunges sometime, he finishes them on a disc.

I would suggest if you have a limited budget and a smaller shop start with the disc then when possible get a belt. I would definitely get a disc over a 2x42 craftsman. Then save my pennies for the belt.
 
tryppyr said:
Funny this should come up again. I've been giving serious thought to getting the HF 12" Direct Drive Disc Sander (with 1.25HP motor).
I--ffff I were to ever get a 12" disc I'd take a serious look at getting "seconds" belts in large sizes so I could at least
cut my own.
Ken.
Click to expand...
 
If your looking for a disc grinder, I offer one with interchangable 9" discs in flat and 1 degree bevel. It has proven to be a very handy tool. You can check it out @ www.nielsendesigndiscgrinder.com
using this system allows you to run either a flat disc or 1 degree bevel disc on the same motor. the discs interchange in seconds.
Some say a disc grinder is the only way to get a true flat grind on a blade.
take care
Rod Nielsen
 
You must log in or register to reply here.
Back
Top