What are the disadvantages of diamond tools?

Diamond v. Carbide : Weighing the Costs and Benefits

Under the right conditions and with proper maintenance and handling, significant cost savings can be achieved by running polycrystalline diamond (PCD) tooling.   Understanding the basics of diamond tooling is important when contemplating its use in your own production line.  First and foremost, think of it as the marathon runner, as it will yield the best results in continuous and steady cutting of homogeneous materials. Diamond tooling is not advisable as an all-round tool that will be required to meet demands of a wide range of cutting applications on a day to day basis.  So, if you are machining different materials and want one tool to do it all, the diamond tool will not be able to excel as well as it will if you are machining, for instance, 3/4″ MDF all day long.

Polycrystalline diamond is manufactured in a high-pressure, high-temperature laboratory process that fuses diamond particles onto a carbide substrate, which, in turn, allows the diamond to be brazed onto a tool body.  PCD has an exceptionally high wear resistance factor, in particular with abrasive composite materials that are often difficult to machine with carbide.  Examples are:  particleboard, MDF, OSB, high pressure laminate, phenolic, fibre glass etc.  Depending on what material is being machined, it is not unheard of for a diamond tool to outrun carbide by a ratio of 300 : 1!  Nevertheless, when deciding whether to switch, be conservative in your cost analysis and base your decision on the diamond bit lasting 25x longer than carbide.  You won’t be disappointed!

The original developers of synthetic diamond were GE (Specialty Materials Division) and DeBeers  (Element 6) who pioneered this process and mastered the know-how of synthesizing diamond for industrial cutting applications.  Meanwhile, there are a number of synthetic diamond tool blank manufacturers, and the quality, durability and wear resistance is not always equal.

When shopping for a PCD tool, it is important to discuss your proposed use and expectations in detail with the tool manufacturer as this allows for selection of the proper PCD grade (grain size), and optimum tool design.  In particular,  you want to be certain that there is no more PCD on the tool than actually needed (i.e. don’t order a tool with 1.1/4″ cut length when you only cut 3/4″ material because that needlessly increases the tool cost.

To understand the complete picture and compare “apples to apples” when shopping, it is important to ask the following questions:
How many times will I be able to sharpen this tool under normal wear conditions?
What will it cost to sharpen this tool?
How long will it take to turnaround a tool when sharpening?

If you neglect to get answers to these questions,  you might be in for a surprise to find you were sold a “disposable” tool that cannot be sharpened at all, or can only be sharpened once.  Or, you might think you are getting a bargain when you buy the tool, only to find you are going to be expected to pay 50% of the new tool cost to get it sharpened.

These factors significantly affect the cost per linear foot machined so are important to know when doing a cost comparison or justification for PCD tooling.  Below is an example of a cost comparison using a diamond saw blade versus a carbide tipped blade:

$.0028/$.0143 = PCD costs 19.6% of carbide when comparing $/Linear Foot (80.4% cost reduction) 

Another advantage of PCD tooling, apart from the longer tool life,  includes the quality of finish which is often significantly improved and therefore requires less sanding.  With carbide tools, the finish starts to deteriorate from the very first cut onward, whereas the diamond tool maintains a nice clean finish right up until it becomes dull…..at which time it plummets and should be pulled for sharpening.  Pushing a diamond tool to run a little longer once it shows signs of becoming dull  (a good indicator is when the machine amps increase), can result in a substantially larger sharpening cost as the diamond face can shatter and require re-tipping/replacing of the cutting edge.

At first glance PCD tooling seems expensive when compared to carbide however when we compute the cost per linear foot machined, in the right application, PCD will be revealed as the only choice for discerning shops that are cost conscious.  As you can see from the cost calculation above, the investment in PCD tools pays off rather quickly. Some of the top PCD applications are machining abrasive materials, composites and workflows that do high volume of the same cut and material type.

With PCD router bits, maintaining correct chip load is very important as heat buildup during the cut will damage the diamond and can lead to tool failure.  Accurate tool clamping systems with close tolerances are also essential as is firm material hold down to avoid any vibration during the cut.   For specific questions about PCD tooling, please contact us or give us a call at 1-800-544-8436