Why do I need VS disc sander?

[LCoop]

Well that's interesting Josh, "you will get a (very small) hollow using a beveled disc"! How's that happen? To be honest I mostly always make smallish hunting knives anyhow with the exception of some larger kitchen knifes.

 

[NC Biker]

Well that's interesting Josh, "you will get a (very small) hollow using a beveled disc"! How's that happen? To be honest I mostly always make smallish hunting knives anyhow with the exception of some larger kitchen knifes.

The bevel disc is designed so that you don't catch a large blade on the opposite side of center where the disc is spinning in the opposite direction. It does create a micro hollow grind which Rob of Beamont Metals calculated to have a .0005" concave depth over a 1.5" surface. It's not at all noticeable. I lot of makers say they have no problem using a flat disc, but I like the 1° bevel just fine.

 

[Josh Rider]

The disc is a cone. Even with a 1 degree taper, it's still noticeable. Not too hard to hand sand out and less evident if you rock the blade, but I wanted to be more efficient at sanding so it only made sense to me to get a flat disc. If you paint the blade with dykem after you grind with the disc, then hand sand, you'll see the dykem in the middle of the blade. I ended up trading mine to a member here. I was working on a chef knife today and once you practice a little, you won't worry about it crossing center. Keep your pressure on the side you're working on.

 

[REK Knives]

I still don't understand why one would use a disc to grind knives on instead of a 2x72... in my experience the disk paper wears out way quicker than a belt will because of the difference in surface area. And you can get grinds pretty flat on a belt grinder, why would you need flatter? I understand that it's great for getting stuff flat (like for guards and tangs/scales and stuff). But I have a vs disc grinder w/ KMG's work rest and I very rarely use it (not that I'm a knifemaker specifically, but I do most things involved in knife making).

Just trying to wrap my small brain around this, thanks guys =)

 

[kuraki]

Flattening the bevels on a disc after the belt just makes hand sanding faster. If your not going to hand sand, there's not much point.

 

[LCoop]

I'm still confused why a 1 degree bevel causes a "hollow" ground on a flat disc. I'm close to ordering but would like some more input of why?

 

[kuraki]

I'm still confused why a 1 degree bevel causes a "hollow" ground on a flat disc. I'm close to ordering but would like some more input of why?

Think about if it had a 30 degree bevel and you'll get it.

 

[LARRYZ10]

I started out with a flat disc but later kept hearing the benefits of a 1 degree taper disc and so I bought one and used it for about six months. I did not like it and felt that I had less area to use for flattening. I sold it and put the flat disc back on. Later I bought the Rod Neilsen interchangeable disc system and have both the original and the newer thinner discs. I use my disc grinder on every knife at some point and I like the flat disc best. Other knife makers like the 1 degree discs so it depends on your own experience but I would suggest the flat disc first. Just my opinion based on my own experience. Larry

 

[Karl B. Andersen]

If you have a tiny bit of distal taper on your longer blades the tapered disc is not necessary.
The point of the knife isn't on the disc past the center point.
I use a flat disc and find no reason for a tapered disc.

 

[kuraki]

The little bit on bevel sanding I do on my disc is usually done across 10 o clock and 2 o clock or a bit higher so flat works best for me as well.

 

[Kevin Powers]

Even grinding on a flat disc can produce a slight hollow if you're grinding on the outside edge of the disc and not holding the blade parallel to the disc. The benefits of a variable speed disc are tremendous in my opinion. I use my disc more than my belt anymore. I use it to dovetail bolsters and handle material, flatten blades, smooth blades after surface grinding, flatten scales, square guards, square spines, just about everything that needs flattening or shaping that isn't a tight radius. The biggest thing that has helped on the disc for me is purchasing a rubber backer from K&G. I haven't taken it off since I glued it on.

 

[Craig Daniel]

What are the benefits of the rubber backing?

 

[kevin (theprofessor)]

For me, the disc is a great shortcut for finishing non-ferrous stuff, and a safe way to shape wood. It doesn't go too fast, and it gets me from rasp and file marks to flat and ready to hand sand. Long sheaths, handles, etc.

Also, when a knife has metal bolsters, the disc keeps the metal and wood in the same plane. You can get them both to 400 grit on the machine, and then take the wood to 600 or 800 and not remove enough to screw up the transition. Going up through each grit by hand on both, it is so easy to screw up the transition and take too much wood.

Pommels, butt caps, spacers, getting them flatter (or getting milling machine marks, or file marks, off). There are tons of things these can do.

I love mine. I use it on knives, and on the tools that I make so I can make knives (like chisels for sheaths).

 

[Josh Rider]

Even grinding on a flat disc can produce a slight hollow if you're grinding on the outside edge of the disc and not holding the blade parallel to the disc. The benefits of a variable speed disc are tremendous in my opinion. I use my disc more than my belt anymore. I use it to dovetail bolsters and handle material, flatten blades, smooth blades after surface grinding, flatten scales, square guards, square spines, just about everything that needs flattening or shaping that isn't a tight radius. The biggest thing that has helped on the disc for me is purchasing a rubber backer from K&G. I haven't taken it off since I glued it on.

Kevin, did you have to remove some of the rubber around your disc? I bought the same one, it's a little oversized, and it throws the balance off. I was debating on cutting around the disc.

OP: Either way you go, the 3m feathering disc adhesive is well worth the money. I was using the spray adhesive with ok results, then switched to the 3m tube and really like it. You can remove the sandpaper and put a new piece on without tearing the piece you removed. Nice if you want to move through the grits quickly.

 

[Drew Riley]

If you have never seen the Tim Hancock video on knife grinding - get it. It changed my life.

Well, it's hard to resist that sales pitch! Just ordered a copy.
I bought Flat Grinding With Harvey Dean and The Fine Art of Hollow Grinding with Johnny Stout when I first started making knives. Both were somewhat helpful at the time. Curious to see how Mr. Hancock does it.

Somehow I think this thread is going to turn into my next shop tool purchase.

 

[Kevin Powers]

What are the benefits of the rubber backing?

Smoother surface finish and cuts faster. It also takes away some flatness if you aren't careful.

Kevin, did you have to remove some of the rubber around your disc? I bought the same one, it's a little oversized, and it throws the balance off. I was debating on cutting around the disc.

OP: Either way you go, the 3m feathering disc adhesive is well worth the money. I was using the spray adhesive with ok results, then switched to the 3m tube and really like it. You can remove the sandpaper and put a new piece on without tearing the piece you removed. Nice if you want to move through the grits quickly.

I did not. I don't use the disc at high enough speed to notice a wobble. I use spray adhesive that is repositionable. I find that using sandpaper that has good paper on the backside or even that non-slip 3m stuff from lowes helps remove the paper cleanly.

Well, it's hard to resist that sales pitch! Just ordered a copy.
I bought Flat Grinding With Harvey Dean and The Fine Art of Hollow Grinding with Johnny Stout when I first started making knives. Both were somewhat helpful at the time. Curious to see how Mr. Hancock does it.

Somehow I think this thread is going to turn into my next shop tool purchase.

If you look up videos from Travis wuertz hammer in you'll see previews of tims methods. He sure can grind a blade quickly. I was lucky enough to show Tim one of my bowies last year and I explained that I ground everything freehand and he told me to quit working so hard. Use a rest and a push stick and things get done fast.

 

[Kevin Powers]

One other positive I haven't seen listed is the ability to do your plunges and plunge shoulders. Also with a disc you can look over the top of the material to the backside and see what you're grinding.

 

[Drew Riley]

Well, all this talking about disc grinder gave me the bug. Found a 1hp 3 phase Baldor on Craigslist about 2 blocks from where I work for $40. It's a 143T frame, so the shaft is a 7/8" vs the standard 5/8", but I plan on making my own hub anyway, so it shouldn't be a problem. Think I'm gonna try something similar to the Nielsen system if I can dial my lathe in a little tighter.

This could be fun.....

 

[LARRYZ10]

Well, it's hard to resist that sales pitch! Just ordered a copy.
I bought Flat Grinding With Harvey Dean and The Fine Art of Hollow Grinding with Johnny Stout when I first started making knives. Both were somewhat helpful at the time. Curious to see how Mr. Hancock does it.

Somehow I think this thread is going to turn into my next shop tool purchase.

Andrew, I have watched the same videos that you bought and I bought a lot more knife grinding videos. I have watched Tim Hancock's video and I found it had some useful information but the audio was terrible and tough to follow. A much better video in my opinion if you want to know more about hollow grinding is Steven R Johnson on making the sub-hilt fighter. It is long but very detailed and packed with good technique. I think it might be the best video on hollow grinding that I have ever seen. I remember thinking at the time that it was kind of expensive but it helped me so much it turned out to be a wise purchase. Larry

 

[Drew Riley]

Andrew, I have watched the same videos that you bought and I bought a lot more knife grinding videos. I have watched Tim Hancock's video and I found it had some useful information but the audio was terrible and tough to follow. A much better video in my opinion if you want to know more about hollow grinding is Steven R Johnson on making the sub-hilt fighter. It is long but very detailed and packed with good technique. I think it might be the best video on hollow grinding that I have ever seen. I remember thinking at the time that it was kind of expensive but it helped me so much it turned out to be a wise purchase. Larry

Ah, I had almost forgot about that one. I do actually have a copy of that one as well, but it's been so long since I've seen it. I'll have to see if I can dig it up and re-watch it again.