This Definitive Guide will tell you about PCD, and gives all the tips, feeds and speeds, applications, and techniques needed to succeed with PCD tooling.
What is PCD / Polycrystalline Diamond?
PCD is the abbreviation for Polycrystalline Diamond. Depending on how you want to look at it, PCD is either a material cutting tools are made of or a coating. In the right applications, PCD can significantly reduce your tooling costs as well as your cycle times.
PCD is much harder and more resistant to abrasion the conventional carbide tooling. It consists of diamond particles (diamond grit) that is sintered with a metallic binder, and is one of the hardest and most abrasion resistant tooling materials available.
Like tungsten carbide, PCD is available in multiple quality grades. Better grades include coarser (larger) diamond grain and polished tips that reduce material buildup.
Diamond reacts chemically with some metals including Iron, Cobalt, Nickel, Chromium, and Vandium. As such, machining steel and other alloys with these materials is out. The preferred harder alternative in these materials is CBN.
Materials suited to PCD Tooling include:
- Composites, especially abrasive composites like Carbon Fiber.
- Carbide alloys (e.g. cutting tools) and Tungsten
- Stone, concrete, asphalt, glass, ceramics, gem stones, and semiconductor materials.
- Machining of clean, graded hardwoods (avoid particle board and other wood products containing embedded grit).
- Non-ferrous metals such as aluminum, copper, and their alloys.
- Some soft but tough materials like rubber and resin.
An important consideration is that PCD is particularly brittle. Applications involving lots of vibration should be avoided.
PCD Tools & Cutters
A wide variety of PCD cutters are available.
PCD Diamond Drill Bits
PCD Drill Bits come in a variety of flavors:
- “Vein” style has PCD infused in the grain structure of the bit.
- Brazed has cutting edges brazed onto the bit much like the end mill pictured below
- PCD Tipped has a solid PCD tip such as this photo shows:
Note the dark-colored PCD tip…
PCD End Mills
The photo shows a typical end mill with PCD cutting edges brazed on. PCD is formed in large High Temperature-High Pressure presses as either a diamond wafer on carbide backing or forming a “vein” of PCD within carbide.
Given that PCD bonded to carbide for brazed tools is available, it should follow that PCD inserts are available for indexable cutting tools.
G-Wizard Speeds and Feeds for PCD Tooling on Composites
G-Wizard can calculate speeds and feeds for PCD End Mills and PCD drills.
PCD is a choice on the Tool Material menu of the pictorial popup:
PCD is a Tool Material choice on the pictorial popup…
The actual material removal rates may sometimes be less than conventional tooling, depending on the scenario, but the tool life is 10x – 50x longer. This makes PCD tooling a welcome addition. When you can find a combination where the MRR’s are better than conventional tooling and you’re also getting the tool life benefits, that’s where PCD tooling can really shine the brightest.
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Bob is responsible for the development and implementation of the popular G-Wizard CNC Software. Bob is also the founder of CNCCookbook, the largest CNC-related blog on the Internet.
Hi there I am trying to find the right tool to cut 20mm Trespa
please will you send me the right tooling and specs
Alistair, sorry, can’t do it. Not enough hours in the day for me to optimize everyone’s tooling. You should get in touch with the Trespa people and see what they recommend.
Hi Alastair, we machine a lot of 16mm & 20mm trespa (both athlon and toplab). Approx 18 months ago we changed from 1/2″ tct 2 flute straight cutters to diamond of same size and spec and tool loss decreased dramatically (from roughly 200/yr to 8/yr). whilst diamond costs us around 10x price of tct we feel its still cost effective. Maybe speak to your tool supplier.
Why would you have to worry about machining particle board “with imbedded grit”, if PCD is abrasion resistant?
Jim, it’s not so much a question of abrasion as the shock of hitting a hard (relative to the PCD tool’s hardness) object with brittle PCD.
The grit in wood products is typically sand. Sand contains quartz which is quite hard. Not as hard as diamond, but hard relative to many other things a PCD bit might cut. Now imagine our hapless PCD cutter. It’s happily plowing along pretty fast (because the feeds and speeds for software materials are fast) and suddenly it hits a pretty good-sized grain of quartz. Nothing remotely the size of a pebble, but a largish grain of sand.
Bang. You just shattered a little nick into the PCD’s edge. Now it’s hardly cutting at all around that nick. The tool will fail not too long afterward once that weakness is there.