Diamond Tooling Versus Carbide

Diamond bits are not best for every situation. Among other factors, they usually require slower feed rates. January 2, 2012

Diamond tooling has come down in price to the point I've decided to try 1/2" compression for cutting laminated P Bd and melamine bd. The only diamond tooling we've used has been our slatwall bits. Just looking at the geometry the diamond bits don't seem like they would work as well as the carbide.

What experience have you had with them? I've been leery of using them due to the trash in P Bd. We currently get about 50 sheets of melamine on a 3/8 compression before it shows signs of getting dull. On HPL laminated board we are only getting about 15 sheets. That means 3-4 bits a day on HPL. At that rate we can throw away a diamond bit every other day and still be ahead. Can the same feed rate be maintained with the 1/2" diamond as we've been using with 3/8" carbide? On two flute bits we've been running a relatively slow pace of 600" and on 3 flute 900"/min.

Forum Responses
(CNC Forum)
From contributor C:
Not sure on your RPM, but if you are running 18,000 RPM you will be about half of the 600 IPM. Diamond tooling will not run as fast as a spiral. The diamond is on a shear and not a spiral. The big question you would have to ask is what is more important, time or money?

From the original questioner:
We are running 18,000rpm and we are short of enough time available on the router now. Going 300" seems painfully slow and would only worsen our bottle neck.

From contributor G:
Sorry you can only run about 200-250 IPM at 18k. I am sure you are using the 3 flute on the laminate material so you should be getting more sheets. Not all tools are created equal.

From the original questioner:
So, what good are diamond tools for woodworking? We have been using them to cut fiberglass faced aluminum honey comb aircraft panels. Even there they don't produce a really fine cut but it doesn't much matter. 200-250ipm is like watching grass grow.

From contributor C:
Diamond tooling is very application specific. Letís say you have a job and you can afford to let the machine run slower on the feed rate. Also, the material must be suitable for it, mostly man-made items. We sell both but most choose the solid carbide spirals.

From contributor S:
Based upon my experience with diamond router bits, there seems to be a misunderstanding about feed rate. All other things being equal, a diamond bit runs at basically the same chip load as a carbide bit. The difference is in the number of flutes. Because a diamond bit is made differently than a carbide bit (the teeth are staggered), it usually only has one flute, even though it may appear to have more. Therefore, at the same RPM, a diamond bit must run much slower than a two, three, or four flute carbide bit. We once tried a true two flute diamond bit, but the lower teeth broke off.

From contributor C:
From what I have seen a diamond bit has never ran the same feed rate as a S/C Spiral. The diamond is on a shear and not a spiral.

From contributor G:
Diamond has a spot in the wood industry. Courmatt has designed thousands of diamond tools from v-grooving, door (cabinets, interior, exterior) saw blades, edge band, etc. As mentioned it's not for every application. The 1/2 can and is used on small parts and in countries that do not have firms to sharpen spiral tools.

From contributor M:
750 IPM all the time on two sided melamine with an MDF core. We get anywhere from 175 to 250 sheets average per bit and have achieved over 500 on two occasions. We have tried just about every PCD bit out there and 99% said we could not do what we are doing. I don't like to argue when people have already made up their mind. We think outside the box so not sure how PCD will work on PB core. We don't use PBC since we saw sparks one time on our sliding table.

I will say that it is possible with an MDF Melamine but not sure if it is possible with a PB core and because of the loose core you may or may not be able to maintain a clean edge. Only you can decide what is an acceptable edge quality and if you will achieve it cost effectively. It will also depend on what type of CNC you have, your toolholders, collets, and believe it or not if you use a torch wrench at the correct foot lbs.

From contributor C:
Contributor M - if you are running at 600 to 700 IPM with diamond tooling and achieving good results, you are in the top 2% of CNC users. I can say that I have been all over the world and never saw that kind of feeds with good results on diamond tooling, unless you are talking about diamond coated spirals.

From contributor F:
To support Contributor Mís comments about achieving 600+ inches/min with a 1/2" diameter PCD compression bit, it is very possible with the right bit. We arenít the only company to make them, you just need to look at amongst the top PCD tooling manufactures and consider your productionís net cost, not only the initial tooling purchase price. There are cheap PCD bits and there are more expensive ones. The quality of PCD and time spent on the erosion process equates to a higher cost but also a better cutting edge that will last longer, much longer. The standard 1+1 or 2+2 PCD bits that most companies offer simply canít perform at your desired feed-rates.

PCD bits in a diameter of 1/2" or smaller also have to contend with rigidity issues as the router bitís body is softer than your solid carbide spiralís. Again, with a good design, quality materials and attention spent to the erosion process, this isnít an issue but keep in mind that larger than 1/2Ē diameterís are preferred.

To the original questioner: For your particleboard application, you will need to get a diamond tooling company to look over your board with you as most standard particleboard contains many glue pockets, foreign material which makes the density very inconsistent - this can cause fractures in the PCD, leading to failure of the cutting edge and tool breakage if it isnít caught. Then again, some people use good board and experience great results. You simply need to get an experienced tooling company involved and theyíll help you out.

In regards to the HPL, you may find it to be more consistent and friendlier to PCD bits. However, before you make any assumptions, get some material/cut samples and information about your routing programs to a good diamond company. As for your carbide bits, try getting a specialized highspeed two flute solid carbide bit and run it hard. You should be able to get some improvements there given what your original post describes. Generally speaking, 50 sheets shouldnít be your top end.

The PCD bit below may look strange to most of you. This is because its shank is an HSK20C connection designed for the Aerotech System. Itís all I have in my office, so please keep in mind that the design of the cutting edge is what this image is attempting to illustrate - nothing else.

Click here for higher quality, full size image