My disc cutter units have gotten dull from lots of use and misuse
I recently started using the flat diamond hone I had for kitchen
knives. It is 2" x 6" and has a fine and course side. Start with the
course side as the punches are hardened. Use water to lubricate.
Hold the punch near the bottom and use an oval motion. Ever few
sweeps turn the punch 1/4 turn. Once you feel the edge of the punch
becoming crisp/sharp rinse off the punch to remove the course residue
and work on the fine side.
Hi Pat - same thing happened at my community college - I called local
machine shops for quotes, took it to the cheapest one - they did a
great job. Actually had 2 disc cutters - it was the same price as one
might have been, as the expense is in setting up the job - see if you
can get an extra one for the students to abuse, and paint the
striking edge red, with matching red band around the mallets/dead
blow hammers - the abuse on ours seemed mostly from students
striking the cutting edge.
Sterling Bliss, LLC
I’ve had good luck using a belt sander to resurface those disc
cutters. If you have a new belt, say a medium grit, and hold the
bottom of the cutter against the rotating belt, turning the cutter as
you work, you can get a flat surface back on your disc cutters. Take
care not to get the cutters hot while grinding, and keep the cutter
rotating while you grind to keep the bottom perpendicular to the
punch. Any bur generated on the edge of the cutter by the grinding
will need to be carefully removed with a sanding stick afterwards,
say a 400 grit.
Those cutters are not terribly sophisticated devices. As long as the
edges are sharp and the outside diameter fits within the cutter die,
they seem to cut just fine.
And yes, most issues with these cutters seem to be from people using
them wrong side up, trying to cut an impossibly thick material with
them, or using a steel punch to remove them from the die. ( we use a
small wooden dowel and a mallet to drive the cutters out of the die
And I’d like to take a moment to sing the praises of belt sanders!
I have definitely sharpened disc punches this way. I also have a
diamond lap which I use for…lapping… And also for sharpening or
honing tools. Works great. It is made by Hi-Tech in Simi Valley CA.
I have a lot of disc punches covering a wide variety of diameters.
The larger ones are Pepe. I have had mixed success with their tools
but I really like the punches. One thing with the larger punches
though: They are cut on a bias. The cutting surface is slated. This
is so the punch cuts only a portion of the arc of the circle at a
time. A large disc would be tough to cut through all at once with a
flat punch. One or two whacks usually drive it through. I use a large
brass or bronze mallet. Harbor Freight has them at reasonable prices.
I have gone thru a belt sander just about every two years. They are
worth every penny and the small size that uses a 1" x 30" belt is
perfect for most small shops. I’ve convinced several schools to get
belt sanders ( actually I bought them and they reimbursed me) for it
really does speed up filing and fixing steel tools. I’ve regrounded
more disk cutter punches than I can recall, too many dapping punches
and old hammers. My 2 disk cutter sets have held up very nicely and
half of the punches haven’t had to be reground in 15 years. However,
every school I teach at, disk cutters get abused so much. I’ve seen a
student use a dapping punch to try to punch out a disk - had to
refinish the domed part. The amount of abuse school tools take is
unbelievable, even when you are hovering over students, stepping in
at the slightest miscalculation. It is worth having a belt sander,
and Harbor Freight carrys both the small and larger version. Just
make sure to stock up on the sanding belts!