PSA Sanding Disks

[PoolQs]

I have been learning to use my disc sanders to better my workmanship and flats. I have a 6" (4x36) and a 5" (1x30) combo units.
I am planning on buying a 10" or 12" in a couple of months but don't want to until I have at least learned the basics and uses.
My issue has been trying to switch out the PSA discs. I remember a while back reading about a company that uses/sells "reusable" discs
but I searched the forums and couldn't find them or the video I watched of it.
The original adhesive on the PSA's are very good, almost too good. After using a specific grit and I want to change, I notice that the
heat from using them actually adheres them even better to the disk itself. When trying to pull them off ... rip ... arrggg.
I also leaves a lot of residue that I try to scrap off. Never get it all it seems. Then I try to clean it off with acetone and still stays on.
I would love some wisdom on "reusing" your discs and how to apply them to reuse them.
I have tried 3M Super 77 but seems when the discs get hotter, the adhesive gets slick and the disc starts to slide.

Thanks for all your answers and wisdom !!!
Troy

 

[Frank Niro]

Try Rod Neilson magnet grinder. He only sells an 8" size but includes 4 or 5 discs with his unit. Yes, I ended up with a variable speed one about 6 months ago. I think it's a super machine especially after trying 4 separate single disc machines with no speed control. Frank

 

[NickWheeler]

First off, as a knife maker, you will want a 9" disc. Any fabricator, welder, machinist, millwright, etc will tell you that's a waste of a machine and that you should get a 16 or 20" disc, but those guys use a disc at a totally different level than we do.


A 9" disc (or 8-7/8") will allow you to use 9"X11" sheets of sandpaper on your disc. IMHO, there is NOT a better adhesive for this purpose than 3M Feathering Disc Adhesive---- Yep, it's made just for this purpose!


You can put a sheet of paper on, cut around the disc with it, and BAM- you have a 9" disc. The beauty of the 3M adhesive, is you can peel the disc right off when you're done, and then stick another sheet on the disc.

After a while, you'll want to freshen up the adhesive, and all you'll need to do to clean off the old adhesive first, is wipe it down with either 3M disc adhesive remover, or you can give it a spritz of Goof-Off, and then wipe it down with paint thinner and a paper towel.

I have come to HATE most PSA discs. Most of them will simply be destroyed when you try to remove them, and they cost WAY MORE than using 9X11 sheets!!!

I exclusively use Rhynowet Redline aluminum oxide sheets on my 9" disc. Mastersmith Burt Foster turned me on to this paper many years ago, and I now use it for everything. It costs about $0.45 a sheet when you buy a 50 pack from SuperGrit dot com.

And it is WELL WORTH doing what you have to, in order to set-up a 9" disc with variable speed and reversing capability.


I had a student in the shop the last couple week-ends. We took a forged, rough ground, and heat-treated blade to a 60 grit, 2X72 belt and ground it down close to finish. Then went to the 9" disc and used ONE $0.45 sheet of 120X paper, and ONE $0.45 sheet of 320X paper... and then hand sanded the blade to a nice 320X finish in about 8-10 minutes per side.

No need for a whole pile of $8-10 belts!!!! One belt, two sheets of sand paper and we were ready to hand sand. :thumbup:




With all that said, if you do have PSA discs that you need to save--- you can get some cheap place mats at a dollar store. They'll allow you to stick the disc to them and save it for late. I got that tip from my friend Mike Fitzgerald that used to post here. It works VERY well.

 

[ron_m80]

First off, as a knife maker, you will want a 9" disc. Any fabricator, welder, machinist, millwright, etc will tell you that's a waste of a machine and that you should get a 16 or 20" disc, but those guys use a disc at a totally different level than we do..............

This is quite right. I am finding that while my 16" grinder is awesome, I am stuck with PSA disks that do not swap out. I might try a different backing with 3m adhesive to it like you say.

 

[james terrio]

A 9" disc (or 8-7/8") will allow you to use 9"X11" sheets of sandpaper on your disc. IMHO, there is NOT a better adhesive for this purpose than 3M Feathering Disc Adhesive---- Yep, it's made just for this purpose!

...With all that said, if you do have PSA discs that you need to save--- you can get some cheap place mats at a dollar store. They'll allow you to stick the disc to them and save it for late. I got that tip from my friend Mike Fitzgerald that used to post here. It works VERY well.

What Nick said. Personally, I'm almost always working on more than one knife at a time, so I just wear the disks out before changing them. It doesn't take long. Just as with using sheets on sanding blocks, there's no sense trying to "stretch" a sanding disk or drum. Use 'em like they're free.

 

[PoolQs]

A 9" disc (or 8-7/8") will allow you to use 9"X11" sheets of sandpaper on your disc. IMHO, there is NOT a better adhesive for this purpose than 3M Feathering Disc Adhesive---- Yep, it's made just for this purpose!

thanks for all the info and help from everyone. I did some research on 9" Sanders and can not find stand alones and the combos are with 6" belts (which I don't need) are $350+.
None of the ones that I looked at said anything about reversible. Could some of you tell me the makers brand that you are using or even a supplier for a stand alone.
Thanks again for your help !!
Troy

 

[Bob Ohlemann]

Ok, get ready for some sticker shock! I don't have one of these, I have a 12" but, for knifemaking this is the ticket.

Beaumont VDG-1VSR

Alternately, you could buy the disc for $83 and build your own.

Bob

 

[Stacy E. Apelt - Bladesmith]

And a final note...the HF 12" disc grinders are junk for knife making purposes. The motor shaft is too small and soft for the side load, and will bend.

Use a quality motor of 3/4HP minimum and if at all possible use a 1HP VS motor and controller. Reversible is good, too.
The quality of the disc is what is really going to effect how well the unit runs. While the good ones seem expensive for what appears to be a $20 circle of steel, the machining and tolerances on run out for a good disc are where the expense is. Expect to pay in the range of $90 and up for a good disc.