Disc sander/grinder questions

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lanternnate

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Nov 5, 2016
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First is it a disc sander or a disc grinder? Darn hard to search for info because different folks like to use a different name, anyways real questions:

I’m just a hobbyist maker. So far I just give away anything I make, making this hobby a one way money equation. My shop space consists of the back patio (currently 25 degrees outside) where I forge and a corner of the basement for tools. So space and $ are limited for this hobby. After forging, if I want a clean finish rather than brute de forge, flattening things on my little 1x42 with not so awesome tracking and a less than truly flat platen isn’t amazing. I know a real 2x72 with a legit platen would do a better job than my 1x42 and be a versatile tool, but that whole money space thing. I have been reading up on disc grinders, and it seems one could be the ticket for getting nice clean flats with less $ and space committed than a 2x72. I’ve also watched Nick Wheeler’s videos where he finish grinds his bevels on a disc. In searching I’ve found plenty of folks discussing doing the same. I haven’t really found discussions on if you could do more than just the finish grinding. Given that I forge every blade to shape and forge in bevels typically, would it be realistic to do all of my grinding on the disc instead of just finish work? That would let me delegate my 1x42 to handle work where it seems to do better than blade work and at least hold off a while longer on worrying about a 2x72.

If I do take the plunge with a disc grinder, reversing sounds to be a requirement. A 9” disc to use sheets also sounds to be the ticket. Is variable speed essentially a requirement as well or only in the nice to have column? When it comes to power what should the minimum be? It appears many have used 1hp motors, but trugrit sells down to a 1/3hp. The common thing I’ve seen for 2x72 is no less than 1hp, but I can’t figure out if the same holds true for a disc. And the final question, flat or beveled disc? Flat seems like it would be better for, you know, getting things flat. On USA knife maker they claim the bevel is so small it’s flatter than a human can manage anyways. Truth to that? If going with a truly flat, just how big of an issue is it for the end of the blade to be catching the up spinning side of the disc?

Sorry for all of the questions. Did my best to read through the old threads and managed mostly to confuse myself, so I figured I’d try putting it all together in one place.
 
a 9" disc sander is an invaluable tool at an excellent price, I don't think I could make knives at a good level without one.
1 HP is plenty for the 9" you can get more if you want, 1.5hp or go less, I don't think to matters too much
add a disc for $100 and a more $ for a VFD, you really do want the variable speed
I prefer a flat disc, I don't see really any practical benefit to the beveled which I have used in the past.

I'm currently finish grinding a 8.5 kitchen blade on the 9" disc sander with flat disc and no issues with the end of the blade catching up etc.
 
I honestly think new makers would be better off using a 9” flat disc as their first “budget” grinder before moving to a better 2x72.
A.C. Richards taught me to forge and he also sold me on using a disc.
You can rough in the bevels just as easily as on a 2”x72”. I barely use my flat platen for flattening anything.
I run 2-2”x72” grinders and my 9” disc off of one KBAC-27D VFD. I have a plug wired into the side of the VFD and switch my second grinder and disc out depending on my needs. I “need” to get a second VFD for the disc eventually.

Also, DO NOT GET A BEVELED DISC. That’s my opinion. I had one to start because people here said I needed on for longer blade. Rubbish. Think about it. A beveled disc is a cone. So essentially you have a minute hollow grind. Trust me. It’s impossoble to get anything flat on a beveled disc and the great advantage of a disc is how easy it is to get stuff flat.

I also have the Nielsen System for mine with a work rest that indexes from 90 to 45.

Disc grinders rule and belt grinders drool.
 
Disc sanders are very handy. I agree that a flat disc is probably the way to go. I have two 9" disc sanders. One has a flat disc, one has a 1˚ bevel. I don't dislike the 1˚ but the vast majority of my work on disc sanders is on the flat disc. My machines are not VS so I built them using 1750 rpm motors instead of 3400 rpm motors to try slowing things down a bit. Even so it's still pretty fast. Get variable speed. 1 HP is fine.

If I only had so much money to spend on either a 2x72 or a disc I would get the 2x72. But once you have the 2x72 the disc would make a great addition to the shop. They do have a learning curve though. Working close to the plunge line can be tricky. Also, changing paper is a little tedious, at least with my set up. Plan on changing paper often as it wears quickly.
 
Changing the paper is what keeps me wondering.
How long does the paper last? Use only one grit size?
 
This is great info guys, thanks. Brian, that was exactly the info I was looking for.

I’m not overly worried about the paper changes. I watched a bunch of videos on changing with feathering adhesive. It looks rather painless. It looks like if you use the stickers on PSA discs it’s a major pain though. I don’t expect the sheets last anywhere near as long as a 72” belt, but my current 1x42 belts aren’t exactly endurance champions. I figure at least the 9x11 sheets are more affordable.

One more set of questions, rubber or cork backing? I’ve read they’re useful for thin high grit sheets to minimize scratching from bumps behind the sheet. Do folks run one or the other? Do you have them permanently affixed or go straight steel for low grits and only put on the backing when hitting a certain grit? Is there a preference between cork and rubber?
 
Hengelo_77 said:
Changing the paper is what keeps me wondering.
How long does the paper last? Use only one grit size?
Click to expand...

I try everything and found that double tape work best for me . How long the paper last depend from paper /AO , zirconia , ceramic / and how much and on what kind of steel you use disk sander .I finally found big sheet of zirconia 40 grit /from which they made belt / for my disc sanders ....and I am waiting to get some ceramic sheet in 40 grit ;)

YdrAO6F.jpg
 
Brian Ayres said:
I honestly think new makers would be better off using a 9” flat disc as their first “budget” grinder before moving to a better 2x72.
A.C. Richards taught me to forge and he also sold me on using a disc.
You can rough in the bevels just as easily as on a 2”x72”. I barely use my flat platen for flattening anything.
I run 2-2”x72” grinders and my 9” disc off of one KBAC-27D VFD. I have a plug wired into the side of the VFD and switch my second grinder and disc out depending on my needs. I “need” to get a second VFD for the disc eventually.

Also, DO NOT GET A BEVELED DISC. That’s my opinion. I had one to start because people here said I needed on for longer blade. Rubbish. Think about it. A beveled disc is a cone. So essentially you have a minute hollow grind. Trust me. It’s impossoble to get anything flat on a beveled disc and the great advantage of a disc is how easy it is to get stuff flat.

I also have the Nielsen System for mine with a work rest that indexes from 90 to 45.

Disc grinders rule and belt grinders drool.
Click to expand...
I prefer angled discs. Having the far side of the disc pulling on the blade is annoying and its hard to keep steady. With the angle you have more control.
 
I use a beveled disc and its so slight the dish it makes that a couple minutes hand sanding flattens it out its a must on longer blades I feel also what plays a huge difference is the backing you use right now I have 1/8 in cork glued on and makes feathering areas a lot easier. VFD is a must its too damn dangerous WOT. Look up
Nick Wheeler on YT he has some valuable info on disc's
 
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