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Change in tooling aids shop
New York custom shop finds diamond-coated carbide solves tough machining challenges [From CabinetMaker^®, January 2006.]

Problems with resharpening
Tim and Steve Prendergast, the brothers who founded Paragon in 1999, were frustrated by the frequent resharpening cycle these materials demanded when using traditional solid-carbide tooling.

'We were averaging 600 lineal feet before the tool needed to be sharpened," says Steve Prendergast. .'Part of the problem we came across was that every time we got the carbide sharpened, we not only had to change the tool. we also had to recalibrate the CNC to accommodate the smaller size created by the sharpening. This all takes time and money."

On one project in particular, this problem became really apparent. That on-going project involves fabricating and assembling display holders and listening stations for a line of music CDs. The display boxes are cut from pre-finished red oak plywood. Prendergast says the finish used was very hard on the tooling in their VyTek CNC router. For this project, since the customer paid per box and there were orders of 1,000 boxes at a time, Paragon could make more money if it could make the boxes in less time with fewer tool changes and machine recalibrations.

Diamond solution Prendergast had seen advertisements for diamond tool coating in trade journals, but he had not seriously considered using the coating because he was afraid of the cost. Then he was contacted by a local company, Diamond Tool Coating Inc., that offered multilayer nanocrystalline CVD diamond coating for carbide tools. DTC's vice president Paul Otto gave Prendergast a sample tool to experiment with. Otto didn't hear from Prendergast for six months, when the tool finally gave out, and Prendergast was ready to order more. "We found that, although the initial cost of diamond tooling is two to three times that of carbide tools, the increase in lineal footage as well as the lack of downtime from changing the carbide tooling makes the investment well worthwhile in our application," says Prendergast. "And we don't have to worry about the logistics of sending the tools out to be sharpened, which includes the cost of purchasing several extra tools and keeping track of when they would be back in service."

Not all commercial - While Paragon's work emphasizes commercial store fixtures such as grocery displays, bank teller lines and solid surface countertops, it also does residential millwork projects like this library built-in.

Comparing costs
To make his decision on diamond-coated tooling, Prendergast made a cost comparison for a 1/2inch down-shear bit. Initial cost of the diamond-coated tool was $130, compared to $60 for the carbide tool. But the diamond-coated tool produced 4,000 lineal feet of cutting. The carbide tool needed sharpening after 600 lineal feet.

Prendergast estimated that sharpening the solid-carbide tool five times cost $75 for the actual sharpenings, plus an additional $5O in lost time from changing and recalibrating the machine (10 minutes lost per change). With these costs figured in, the total cost of the solid carbide tool was $185, and the total lineal footage produced by the carbide tool was still only 3,000 feet. The solid-carbide tool therefore cost $0.061 per foot, while the diamond coated tool cost only $0.033.

Why it works
According to Roger Bollier, president of Diamond Tool Coating, "The advantage of crystalline-diamond coatings for carbide cutting tools is that they combine the hardness of natural diamond with the strength and relative fracture toughness of carbide. Diamond is a super-hard material that resists abrasive wear and is virtually impervious to corrosion when machining abrasive nonferrous metals, graphite, plastics, wood and composite materials."

The crystalline diamond is grown onto the surface of an indexable insert or round tool using a chemical vapor deposition process. The hard diamond coating protects the carbide tool from chipping when the tool contacts hard particles.

For many materials
Prendergast quickly discovered the advantage of using diamond-coated tooling wasn't limited to plywood. "We now use the diamond tooling for cutting other materials, such as flake board, melamine board, as well as solid surface," he says. "The diamond tool leaves a nice, smooth, clean finish. The guys in my shop love it."

He says prefinished plywoods are where he's gotten the best results, adding that a single tool used to dado plywood is believed to have produced 12,000 lineal feet of cutting. He says the advantages are not so great on melamine, but it's still a big improvement over a conventional carbide bit.

On solid surface material, Prendergast doesn't do the same kind of long runs that he does in plywood, so he hasn't made a direct comparison of the longevity of the diamond bits there. But he says the real advantage in solid surface is cut quality. "It's a really nice cut." he says. "It goes through solid surface like it's butter. It's worth it because of cut quality."

Thousands at a time - When Paragon gets orders for these CD racks, the jobs involve 1,000 boxes at a time.

Matching tooling to the shop Paragon is a production-oriented shop with 16 employees working in 35,000 square feet. Most machining is done on a VyTek CNC router. They also use an SCM beam saw, an SCM sliding table saw and an SCM edgebander. There is also Norwood thermoforming equipment. Prendergast says the diamond coated tooling makes sense for their operation, but he says it may not be so cost effective for every shop. "If you're cutting a lot, doing high production, then you should try it," he says. "It also saves time in calibration. When the bit is done, it's done, but it holds calibration until then. For hand routers, it's not worth it."