Disc Sander Set Up

opaul

Well-Known Member
#1
I received my 9” disc sander a couple of weeks ago and finally got it set up in my shop. My first thoughts were - I should have got this thing sooner.
I haven’t done anything complex with it and in fact haven’t even used it to flatten my flats. But I used it yesterday to grind the initial 45 degree bevel on my knife blade. I couldn’t believe how efficiently it did that.
I took it a step further today and did the second bevel and ended up doing most of the bevel work before I took the blade over to the belt grinder.
I may try to do a complete bevel grind on the next blade
Do any of you guys do you grinding with the disc sander?
 

BossDog

KnifeDogs.com & USAknifemaker.com Owner
#3
I use a disc grinder on every knife - several times. I have ground out a few folder blades start to finish on a disc but not many more than that. I normally do all the grinding on a flat platen belt grinder and then move over to the disc to flatten things up and do the finish. If you haven't already, look into a couple things:
1. don't use PSA discs - stupid expensive and difficult to remove. Use a medium tack adhesive to apply 9"x11" sheets. 3M calls this stuff Feathering Adhesive but there are also other brands under different trade names. It's most commonly used in the automotive sheet metal work. Abrasive applied with medium tack adhesive can be peeled off and re-used when you need to change grits.
2. consider putting a thin piece of rubber between the disc and abrasive. This gives is a very slight cushion and allows you to press in harder to clean up stubborn spots. The rubber cushion won't appreciably hurt your "flatness"
3. flat platens on a belt only get things kinda flat, a disc will give you a much flatter finish.
 

opaul

Well-Known Member
#4
I use a disc grinder on every knife - several times. I have ground out a few folder blades start to finish on a disc but not many more than that. I normally do all the grinding on a flat platen belt grinder and then move over to the disc to flatten things up and do the finish. If you haven't already, look into a couple things:
1. don't use PSA discs - stupid expensive and difficult to remove. Use a medium tack adhesive to apply 9"x11" sheets. 3M calls this stuff Feathering Adhesive but there are also other brands under different trade names. It's most commonly used in the automotive sheet metal work. Abrasive applied with medium tack adhesive can be peeled off and re-used when you need to change grits.
2. consider putting a thin piece of rubber between the disc and abrasive. This gives is a very slight cushion and allows you to press in harder to clean up stubborn spots. The rubber cushion won't appreciably hurt your "flatness"
3. flat platens on a belt only get things kinda flat, a disc will give you a much flatter finish.
Thanks BossDog!
Great advise. One think I noticed is that this will heat up very very quickly!
 

scott.livesey

Dealer - Purveyor
#5
try an 8" with thin rubber from manufacturer, Covington makes them, find them at lapidary shops on line. 8" is a standard size for lapidary and metal lab grinders, find SiC PSA discs for 40 cents or less on eBay, wet/dry also. as far as heat, I usually run my disc grinder at VFD setting of 20-30hz. slower grinding but doesn't heat up as fast.
 

scott.livesey

Dealer - Purveyor
#6
disc speed is definitely an issue. I have a porta-cable combo 4x36 belt and 8" disc fixed speed. if you are not careful, metal turns blue and wood turns black and smells bad.
 

opaul

Well-Known Member
#7
disc speed is definitely an issue. I have a porta-cable combo 4x36 belt and 8" disc fixed speed. if you are not careful, metal turns blue and wood turns black and smells bad.
Thanks Scott. I've dialed the speed back. I'm going to put a backing pad on the disc as well. I'm sure that will help.
 

EdCaffreyMS

Forum Owner - Moderator
#11
I'm with Tracy......I use a disc a number of times, on nearly every blade I grind. I also agree with PSA discs being crazy pricey!

At first I was using fel-pro gasket material from NAPA for disc backing, then a few years ago I stumbled across some very thin/hard rubber, backed with a woven material that is used in screen printing machines for T-shirts. A local outfit was changing their machines out, and they just gave it to me..... it was in pieces approx 2'x2"....... I used 3M 90 spray adhesive to apply it to my disc grinders..... trimmed it, and used it's been there every since. I use a cheap spray glue to attach sheets of the same paper I use for hand finishing.

I also second Scott's input...... SLOW is the way to go. I can't remember that last time either of my disc grinders were above 20% on the controllers.

Likely the best thing I've ever done in the way of the disc grinders is going with the Neilsen changeable disc system. It's a bit pricey, but boy does it ever work well. They offer both flat and 1 degree beveled discs, which are held in place by rare earth magnets.......only issue I've ever had was getting careless when changing out a disc face.....and my reward was a nice blood blister where is pinched the poo outta me. :)
 

KenH

Well-Known Member
#12
I use a disc grinder on every knife - several times. I have ground out a few folder blades start to finish on a disc but not many more than that. I normally do all the grinding on a flat platen belt grinder and then move over to the disc to flatten things up and do the finish. If you haven't already, look into a couple things:
Several months ago I rigged up a disk grinder disk accessory for my 2X72 grinder with a solid aluminum disk. It worked just fine, but never really used it. Perhaps it was the solid aluminum that kept it from being good? Now after rubber backing it's used on most every blade as Boss says.

1. don't use PSA discs - stupid expensive and difficult to remove. Use a medium tack adhesive to apply 9"x11" sheets. 3M calls this stuff Feathering Adhesive but there are also other brands under different trade names. It's most commonly used in the automotive sheet metal work. Abrasive applied with medium tack adhesive can be peeled off and re-used when you need to change grits.
For sure, Boss has it right.

2. consider putting a thin piece of rubber between the disc and abrasive. This gives is a very slight cushion and allows you to press in harder to clean up stubborn spots. The rubber cushion won't appreciably hurt your "flatness"
Here it is - once I put the rubber backing on disk, it changed everything. Just works so much nicer and wouldn't consider anything else. For sure the VFD to control speed is required. Slow is the word for a disk grinder.

]3. flat platens on a belt only get things kinda flat, a disc will give you a much flatter finish.
Until you've tried it, just can't comprehend how much difference it makes. Really makes the grind lines stand out also. Before I'd hand sand to get the bevels fully flat. With disk grinder, I can fully finish sand the blade in the time it used to take for first grit of sanding.
 
#13
I use a disc grinder on every knife - several times. I have ground out a few folder blades start to finish on a disc but not many more than that. I normally do all the grinding on a flat platen belt grinder and then move over to the disc to flatten things up and do the finish. If you haven't already, look into a couple things:
1. don't use PSA discs - stupid expensive and difficult to remove. Use a medium tack adhesive to apply 9"x11" sheets. 3M calls this stuff Feathering Adhesive but there are also other brands under different trade names. It's most commonly used in the automotive sheet metal work. Abrasive applied with medium tack adhesive can be peeled off and re-used when you need to change grits.
2. consider putting a thin piece of rubber between the disc and abrasive. This gives is a very slight cushion and allows you to press in harder to clean up stubborn spots. The rubber cushion won't appreciably hurt your "flatness"
3. flat platens on a belt only get things kinda flat, a disc will give you a much flatter finish.
3M has a repositional adhesive spray that I have been using with great success. I've stopped using the feathering adhesive.
 
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