Using New Diamond Disks

Using New Diamond Disks

(Do I spell it disc or disk? Whatever...)

New diamond lap disks are amazing to behold--all sparkly in the sun (you do check them out in the sun, right?) and super-rough on your hand.  But using them for the first few hours can be pretty challenging since new disks have a break-in period where they're so aggressive they are difficult to use.  The one's I import are super-high quality and very dense with diamonds but tricky during break in, so here are some use notes:

  1. These disks have strong backing magnets which is great since they stay safely on the machine.  However, when putting them on your lap grinder, they will pull very hard and 'snap on' once they are close to the platter.  Unless you lower them very slowly and have your fingers clear when they snap on, they can painfully pinch your fingers.  So be super-careful as you lower the disk--especially the last 2"--that's when it wants to snap on. I keep my entire four fingers underneath the disk, and as I lower it I use the fingers on my other hand to check the edges to ensure it's centered.  When I can feel the edges are aligned on all sides (except where my hand is), I remove my hand quickly and let it snap on.
  2. Also because of the strong magnets, these disks require some muscle to get off the machine.  What's worked for me is cutting a small V-shaped notch in the backing magnet on the edge of the disk (see photo below) so you can wedge a butter knife or flat-head screwdriver under the disk to pop it off. I mark where this "V" opening is with Sharpie on the face of the disk so I know where I should insert my tool.  (The disks are really rigid, so won't feel the notch when you're grinding).
  3. The first time you use a disk be sure to use scrap glass, hold securely and pay close attention.  New disks are sharp and 'grabby' until the fresh diamond surface evens out a bit through wear.  So instead of glass gliding smoothly on the diamonds, the disk will tend to grab the glass.  When breaking in a new disk I try to find a solid scupture or casting that needs a lot of glass removed.  If I don't have something I'll ask friends.  Until the wheel grinds through something like a foot of glass, it's going to be grabby.  Once its past this period, it's much easier to use.  Be patient (and careful).  
  4. Until 60 disks are broken in they have a tendency to chip the edges of your glass, so be sure to bevel edges (on a belt sander) before and as you grind to reduce this chipping. Once broken in, this is less of an issue.
  5. For finer-grit disks like 220 and up, I've found a bit less water helps reduce hydroplaning and helps you maintain grinding action and control.  During break-in of new fine-grit disks, I've also used some dish soap on the wheel to help reduce the grabbines.  Applied in the center, the water will distribute it and it's usually effective for 5-10 seconds of grinding before being washed away.  Experiment to find what works best for you--more/less water, soap, etc. but be careful.
  6. To avoid high spots, be sure to keep both sides of the wheels clean.  Most people neglect to clean the magnet side but that's where metal or glass bits can get stuck and embedded into the magnet and create a speed bump.  If you have a high spot, identify where on the wheel it is and check the backing magnet for stuck dirt or glass, then your wheel surface.
  7. To extend the life of the disk and make it work consistently, I only turn the disks in one direction. 
  8. I've never had to re-dress my disks, but if yours doesn't seem to be cutting as well as it used to, I'm told this may help.
  9. Don't drop them on the edges on a hard surface or your toes.  They're heavy and can injure themselves or you.

Hope this helps use these disks.  Be patient and use them--once they're broken in they are amazing and consistent for years of use. (Of course depending on your volume and what you grind, your mileage may vary :).