Jump to content
Sign in to follow this  
Gerhard Gerber

Disc Grinders?

Recommended Posts

My big contact wheel is setup to be a disc grinder as well, but I've never used it.

A friend pointed out yesterday that it might be the answer to getting some troublesome blades done, but I've never used it.

I believe disc grinders can be tricky and dangerous, any basic pointers?

Believe it or not I've been unable to find spay contact adhesive in this part of the 3rd world, I have an old can from my dad to try.

Any problem with normal contact adhesive if I manage to spread it evenly?

Any specific type of sanding paper I should go for?  There's not a massive variety available locally, maybe a general characteristic to look out for?

 

Thanks 

Share this post


Link to post
Share on other sites

the trick to the tricky part is not to grind past the center once you cross that line it will try to spin the item out of your hand but a good disk grinder is essential to getting a good fit up with bolsters and guards ie i wouldn't make a knife without one you think you can get flat on a belt grinder but i can make two pieces of wood stick together using a disk sander

Share this post


Link to post
Share on other sites

I read an article some time ago, gist of which was another knife maker showed the author how to use a disc sander correctly, it was game-changing, but not much else IIRC.

What abrasives do you use? 

Share this post


Link to post
Share on other sites
Posted (edited)

It has been game-changing for me. All my knives go to the disc after the belt grinder. Makes it real easy to get my flats dang near perfect and reduces the hand sanding time tremendously.

You always want to be grinding on the side of the disc that is moving down. Many disc grinders for knifemaking are reversible (with a VFD or otherwise) so that you can reverse the motor and move to the other side of the disc to work on the opposite side bevel instead of turning the knife updside down. Like dragoncutlery mentioned, if you cross the center line and apply pressure on that side, it can pull the work up toward you. A lot of discs for knifemakers have a 1 degree bevel from the center of the disc to the outside. In this way, you can do really large blades across it and once you cross that center line, the far side of the disc is no longing contacting the knife so there's no risk of it throwing the blade up at you. I know of a few guys that do it without the beveled disc but you just have to be careful with it.

And obviously it is fantastic for flattening your handle material.

I like to use the 3M Feathering Adhesive in a tube (don't know if this is available in your part of the world). It stays on the disc and remains lightly tacky. You put it on once and get quite a few disc paper changes before you need to re-apply. It never gets too sticky so you can swap out grits and go back to the old ones lots of times.

I'm not sure what size your disc is. I've opted for the 9" disc grinder because the common size of sandpaper over here is 9"x11". I just apply my feathering adhesive, stick the whole sheet on then trim around the wheel. It's a lot cheaper than buying pre-made discs. I use Rhynowet Redline as it seems to be the best performing sandpaper for the price. Discs tend to wear out the paper pretty quickly and the cheap hardware store sandpaper just doesn't work.

Edited by Cody Killgore
  • Thanks 1

Share this post


Link to post
Share on other sites
17 minutes ago, Cody Killgore said:

3M Feathering Adhesive

1+ for this stuff, works great and allows you to switch grits often. I have an old 12 inch disc grinder so I have to buy premade discs, Someday I will "upgrade" to a 9 inch especially since mine have a slight vibration as you get to the outer edge. 

I have also seen several guys put their disc flat on the table (looks kinda like a potters wheel) and wondered if that wouldn't make some jobs alittle easier... Or maybe have one that switched between the two positions. 

  • Thanks 1

Share this post


Link to post
Share on other sites

Thanks Cody.

I know about the 3M stuff from a video, but as mentioned I haven't even been able to find a spray-on contact adhesive.

3M is a sad story, I believe the local agency was closed, we still get 3M products here but just the occasional items that chain stores happen to stock.....like sticky tape :angry:

I'll try the sanding paper I've got, it's the best I've been able to find in sheets, and I'm mostly using the shop rolls for hand sanding.

Two more questions:

- What grits are generally used? I was considering 180

- how do you measure the wheel? Diameter?

 

I feel a bit stupid for not thinking of this earlier, I suspect the only way to fix the cleavers would be to remove the handles. That's 2 pieces of unique micarta and lots of hours wasted......

Share this post


Link to post
Share on other sites
49 minutes ago, Gerhard Gerber said:

I know about the 3M stuff from a video, but as mentioned I haven't even been able to find a spray-on contact adhesive.

I know this isn’t going to help you find it where you live, but it isn’t actually a spray adhesive, it’s in a tube.A9790483-EAEA-4336-9F6B-0E1690282F65.jpeg

 

Share this post


Link to post
Share on other sites

:D Gotcha.......just had zero hope of finding the stuff but I also seem to recall contact adhesive being used.

Share this post


Link to post
Share on other sites
Posted (edited)

I'm sure you could use contact adhesive. But, I imagine that being a little on the sticky side.

The thing about the feathering adhesive is that it stays tacky like a post-it note. 

Part of it depends on how much you intend to use it. I go from 120 up to 600 or so with the disc. So swapping out all those grits quickly is a lot easier if you can find some lighter tack adhesive. 

You just don't want to have to fight it and use adhesive remover on it every time you swap some sandpaper. 

Edited by Cody Killgore

Share this post


Link to post
Share on other sites

I've got two cleavers I need to get presentable..........then EVERYTHING becomes a problem for another day......

Share this post


Link to post
Share on other sites

Sorry  missed this earlier Gerhard. I use the disc for everything, blades, handles, pieces-parts like guards and bolsters, almost every part of the knife touches the disc at some point. The blades get finished from 120/150 all the way up to 400 and sometimes 600 grit on the disc. Handles go from 60 to 600 grit. Rough grind (before HT) on the blade, I only go to about 150 or 220. Variable speed and reversible is almost a necessity.

I use any kind of spray adhesive I can find and just lightly dust the wheel. The sand paper is used very rapidly so I just want it to stick to the plate for a little while. If you cannot get spray adhesive, they do make pre-cut sanding discs with a peel & stick backing. Maybe you can find those.

As for technique on how to use it for blade grinding/finishing, look here at about 15:15

https://youtu.be/il88qhfoJnQ

 

  • Thanks 1

Share this post


Link to post
Share on other sites

Thanks for the tips Joshua.  My grinder is reversible and I have speed control, the disc is 9" in diameter. I'll need to add weight to the stand because the setup is not stable with side pressure. 

I can get flap discs, but the normal sandpaper type.

I've seen the Scotchbrite wheels used so many times in videos that I have a few packs of Scotchbrite kitchen scourers that I want to try and turn into a wheel. 

I've messed up the one side of one cleaver badly with that modified belt, I'll need to go back to 40 grit that side anyway.

Share this post


Link to post
Share on other sites
On 3/11/2019 at 7:47 PM, Joshua States said:

As for technique on how to use it for blade grinding/finishing, look here at about 15:15

https://youtu.be/il88qhfoJnQ

 

Thanks Joshua, that WHOLE video helped!

If there's anything wrong with Youtube, this is it.......I get Alec Steele shoved down my throat. which only makes me jealous, and never in a million years would I have found your video if you hadn't linked it.....

  • Thanks 1

Share this post


Link to post
Share on other sites
On 3/12/2019 at 12:11 AM, Gerhard Gerber said:

I've seen the Scotchbrite wheels used so many times in videos that I have a few packs of Scotchbrite kitchen scourers that I want to try and turn into a wheel.

I just remembered that they actually make 2x72 belts out of this stuff. You might want to see if your belt supplier can get some.

https://www.knifemaking.com/category-s/1369.htm

Share this post


Link to post
Share on other sites
4 hours ago, Joshua States said:

I just remembered that they actually make 2x72 belts out of this stuff. You might want to see if your belt supplier can get some.

https://www.knifemaking.com/category-s/1369.htm

My (local) belt supplier couldn't find a certain part of their anatomy with a hand full of t-paper :wacko:

What I find really frustrating is it seems even the South African (where I have to source most things) distributor for a company like Pferd doesn't stock the full range of their belts.....none of the good stuff.

Share this post


Link to post
Share on other sites

Anyway, onto more pleasant subjects........I think.

After one experiment I now need a proper disc grinder :lol:

If I hadn't tried the experiment with the belt I'd be done with the one cleaver, but the experiment left very deep furrows, and the deepest dip is left.

True enough the sanding paper didn't last long and I have a mess to clean up before attaching a new piece, but at least I have a way to get it done.

Not all moonshine and roses, I did manage to put marks in with the edge of the wheel, and for the cleavers a bigger disc would help......dangerous toy.

Share this post


Link to post
Share on other sites

The 1 degree bevel discs are great for longer than tiny knife sizes. Allows you to pass across the front. Beaumont used to make them. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×