Dremel has recently come out with new CBN (cubic boron nitride) metal-cutting rotary tool cut-off wheels, which they say lasts at least 20x longer than the brand’s standard fiberglass-reinforced wheels.
RotoZip, also a Bosch-owned brand, previously released 4-inch CBN metal-cutting discs, but we’re both surprised and excited to see this material introduced into the rotary tool accessories market.
So what’s so special about CBN? For starters, CBN, also written as c-BN, is the second hardest (stable and mass producible) substance known to mankind. The only harder material is diamond. This makes CBN a superb abrasive material.
Dremel came out with a diamond-impregnated cut-off wheel years back, but diamond-abrasive cutting tools are mainly used for cutting hard materials like tile, brick, and ceramic materials. Diamond abrasives are not often used to cut metal materials for a number of reasons.
I have used diamond wheels – and even a diamond band saw once – and they all required slow speeds and lots of cooling. Softer or tougher metals can be a nightmare to cut with diamond, as the particles end up trapped in the workpiece, reducing the effectiveness and lifetime of the diamond abrasive wheels.
Diamond just isn’t suitable for use in handheld tools to cut dry metal materials.
Additionally, have you ever looked into the major alloying materials that turn iron into steel? Carbon. And diamond is a crystalline form of which element? Carbon. Can you see what I’m getting at? There is the potential for diamond abrasives to carburize iron, steel and other carbon-friendly metals, even if proper attention is paid to lubrication and cooling.
CBN, however, holds up very well at high temperatures, does not require lubrication or slow speeds, and is not soluble in ferrous metals, making it a better abrasive material for metal-cutting applications.
CBN is a sort of ultra-hard abrasive super-material.
So… when Dremel says these new metal-cutting cut-off wheels can last at least 20 times longer than their next-best reinforced cut-off wheels, I believe them.
In addition to greater longevity, these cubic boron nitride cut-off wheels should maintain their diameters throughout their usable life spans. They’re not going to shrink down in size, and will maintain relatively constant diameters. There are two benefits to this – maintained full-depth cuts and faster cuts.
When you have a larger diameter wheel spinning at a set speed, say 20,000 RPM, and a smaller diameter wheel spinning at that same speed, the larger wheel will move more abrasive material through the cut. It’s the equivalent of using a jigsaw or reciprocating saw with a longer linear cutting stroke. More abrasive/cutting action at the same speed should mean faster application speeds. This is a presumption not mentioned in any listings for the new Dremel accessories, but I don’t see any reason why this would not apply.
The new discs will be available in two styles:
- 506CU: fits standard #402 mandrel, 7/8″ diameter, $20
- EZ506CU: fits Dremel EZ Lock-style mandrel (#EZ402), 1-1/2″ diameter, $22
Dremel’s 1-1/4″ fiber-reinforced cut-off wheels are priced at about $15-$22 for a 20-piece bulk pack, and the EZ Lock ones are a bit more expensive. The non-reinforced abrasive cut-off wheels are even more economical, but tend to break more frequently and wear quite quickly.
So why buy (1) of these cubic boron nitride cut-off wheels instead of (20) or more of the standard reinforced wheels for the same money? While you might see comparable numbers of cuts for (1) CBN wheel as with (20) or more reinforced wheels, I think that the speed of cuts is going to be the secret advantage.
With reinforced wheels, you see maximum cutting performance when they’re fresh and new. Once they start wearing down, performance immediately starts to drop. These new wheels shouldn’t shrink, which could mean constant cutting performance. Plus, the abrasive CBN grit could potentially cut quicker compared to what Dremel uses in their fiber-reinforced wheels, further adding to the new wheels’ other benefits.
In addition to relatively constant blade diameter – and presumed cutting speed performance – Dremel has said that these wheels don’t break. Their exact words are that these wheels don’t break. They don’t say reduced breakage, they say no breakage. Maybe this is why they say the new wheels last at least 20X longer, because these discs will keep cutting under conditions that would shatter or otherwise damage the reinforced wheels. Although fiber reinforced-discs don’t break anywhere as easily as lesser discs, they do break.
If you couldn’t already tell, I am very excited about these new cubic boron nitride cut-off wheels. They’re a bit pricey, but I think this will be more than balanced by the accessories’ performance benefits and greater longevity.
If all of Dremel’s claims are true, and I think they are, these cut-off wheels should last far longer than any metal-cutting rotary tool cut-off wheel currently on the market.