"How To Get The Most from Your Solid Carbide Square Die Drills"
Square Die Drills
Use a diamond Grinding Wheel with a grit size no
larger than 180 mesh. A Green Silicon Carbide Grinding Wheel should not
be used. It will produce a rough cutting edge on the drill-points and will
Use a Flood Coolant to prevent tiny heat check (small slits, cracks, or chunks) which weakens the cutting edge.
In a Rigid Setup, grind the large face first which has a 42 deg. Included angle. Note: The drill must be rotated slightly to match the original grinding.
The 120 deg. Included angle is then ground with a 8 deg. To 12 deg. Heal relief angle, also
the finished reground drill should have a web thickness between 7% and 10% of the drill diameter. The cutting edge, the leading edge of the outside diameter and the front face edge should all meet at a point.
Your Solid Carbide Square Die Drill can only
cut into hard steel when the cutting edges are sharp. To check the sharpness
of the cutting edges, scrape the edges over your finger nail and if you
do not make a very thin nail shaving, the cutting edges are dull. Check
the cutting edges frequently for dullness.
Use a drill lubricant, not just a coolant when
drilling hard steels. A lubricant prevents annealed hard steel chips from
"freezing" to the carbide cutting edges and to the wall of the hole. Failure
to use a lubricant when drilling in hard steels with carbide drills is
the main cause of drill breaks. We recommend a lubricant that contains
silicone oils and powdered graphite for our Square Die Drills.
For best results, use a lubricating coolant
as recommended. Square Die Drills smaller than 1/4" diameter should use
speeds of 600-800 RPM. Drills larger than 1/4" diameter should use speeds
of 200-600 RPM. Use a "Woodpecker Action" to get the lubricant to the drill
point and for chip removal. Do not allow the drill to "dwell" in the workpiece,
the resulting work-hardened surface will be much harder to cut.
For holes smaller than 1/4" diameter, use speeds
of 800-1000 RPM and for holes larger than 1/4" diameter, use speeds of
400-600 RPM. To start, allow the drill to "dwell" for a short time,then
slowly increase pressure until a chip flow begins. Maintain a steady feed
pressure for the entire hole depth. Do not use a coolant - the thermal
shock will crack the carbide.
Sparks and hots chips may be generated sobe sure proper safety precautions are taken before drilling. This procedure is not recommended as the resulting holes will not be exact to size as the annealing process tends to decarbonize the metal around the drilled hole.
Use hand feed only. Ease up at break through or back up the work piece with other hard material. Always keep the drill sharp. It is difficult to drill hard steels up to 70 Rc, do not make the job any harder by letting the drill "dwell". When a drill "dwells" under pressure in the work piece, no penetration takes place. The drill must continuously produce chips to be working properly, if not, the cutting edges are dull.
Caution: Do not use Solid Carbide
Square Die Drills in mild steels below 40-35Rc or for copper, aluminum
and other soft, gumming metals.
International Carbide Corporation