What you have heard is true. The more consistent a stationary dressing tool is, the more consistent the grinding. By design, dressing tools with synthetic diamonds can provide a level of wheel consistency few other types of stationary dressing tools offer. While synthetic-diamond dressing tools are not “end-all” products designed to replace natural-diamond tools, they do offer an alternative that takes consistency and productivity in wheel conditioning to a whole new level. Whether you are thinking about trying synthetic-diamond tools or hearing about them for the first time, there are a few things you’ll need to know to use them effectively.

Comparing Synthetics To Natural Tool Stones

Just how do synthetic tool stones differ from natural diamonds?

• Synthetic diamonds are available in a variety of close-tolerance sizes and lengths, whereas natural diamonds tend to mimic one of five basic shapes.
• Synthetics are produced under tightly controlled conditions for consistency to avoid internal imperfections normally associated with natural diamonds.
• Rectangular synthetic stones, often called logs or rods, are longer than most natural elongated stones, giving them a significant life advantage.
• Rectangular synthetic diamonds are consistently shaped their entire length. This ensures consistent wheel conditioning for the entire length of the stone. As noted below, when natural stones wear down, so does their ability to condition the grinding wheel.

What Is It About Synthetics?

It may be difficult to see at first, but over time, dressing-tool diamonds develop wear flats. With natural diamonds, problems begin as wear flats increase in size and eventually become too big. The exact point at which this excessive wear occurs is known as the transition point. Once a wear flat passes the transition point in size, the tool becomes dull and, in turn, it dulls the wheel (that is, closes its porosity) rather than sharpens the wheel (that is, opens its porosity). Synthetic diamonds are consistently shaped so that their wear flats never get larger. This feature gives them a significant advantage because they will never transform sharp wheels into dull ones, as natural stones do. 

Improving Productivity

Unlike natural-diamond tools, synthetic-diamond tools never require indexing (rotating) to keep their wear flats from growing too large too fast. So, an operator using a synthetic-diamond tool no longer has to interrupt production to index the tool in order to keep the wear flats from growing too large. Of course, operating without indexing reduces downtime and thereby increases productivity. Additional productivity gains occur because longer synthetic diamonds simply outlast short natural diamonds, thus reducing tool changes and subsequent CNC machine touch-offs.

Synthetic diamond grows shorter with use and not larger in contact area (wear flat diameter) to the wheel. Consequently, synthetic diamonds can be used effectively until they are quite short—shorter than a natural diamond could ever be. Most manual and CNC grinding machines can readily adjust for diamond tools wearing shorter, whereas few have automatic diamond-tool indexers to maintain wear flat sizes.

Synthetic tools can also be marked at the factory with diamond depth lines. This feature allows operators to forecast diamond life and change worn tools at the beginning of large production runs, thereby avoiding unnecessary production interruptions for tool changeovers.

Specifics On synthetics

Synthetic diamonds are rectangular in shape. However, when they are mounted in tools with only the ends visible, they appear square. The square shapes are used to size the stone for use in a tool. Application specifics such as wheel size, wheel shape, machine type and so on are important factors in specifying a diamond size. The diamond selected is typically the largest (square shape) that does not exceed the size of the transition point. See Figure 1.

The Availability Of Synthetic Tools

With some minor physical modifications, most tool types can be made with synthetic diamonds. Synthetic tools are configured a bit differently in certain situations to favor the rectangular shape of the tool stones. The most popular synthetic tools are blade tools with multiple stones. However, as interest in synthetic-diamond tools grows, so does interest in single points, chisels and diaform configurations. Interestingly, synthetic tools can be configured to dress opposing corner radii in a single pass with CNC. That procedure is something natural-diamond tools have trouble performing.

Six Steps To Getting Started

Once you’ve made the decision to try synthetic-diamond dressing tools, these six steps will help you make the transition successfully:

Selecting a synthetic diamond type
There are two popular synthetic diamond types used in dressing tools; monocrystalline and CVD (chemical vapor disposition). Both work well for truing and dressing conventional grinding wheels.

Monocrystalline diamond, as the name implies, is grown from a single (mono) crystal into a large form, and is then cut into specific shapes for use in dressing tools. Monocrystalline diamonds are easily recognized by their uniform appearance and greenish-yellow color. Testing has revealed that in dressing applications, monocrystalline diamonds are the more durable and more expensive of the two synthetics.

CVD diamonds are produced using a special manufacturing process that creates diamond crystals from a chemical vapor. Once formed, this material is cut into smaller sizes for use in dressing tools. CVD diamonds are uniformly shaped and easily recognized by their black color.

Specifying diamond size and shape
The process of selecting natural-diamond tool-stone sizes and shapes for use in dressing tools is based upon important application specifics such as grinding tolerances, grinding wheel size and abrasive type. This same application information is just as important when selecting synthetic diamonds. However, the process used in selecting the diamonds is very different. Both the size (cross-sectional area) and the length of a diamond are important.

Most diamond tool manufacturers offer a range of synthetic diamonds in 0.4 mm-, 0.6 mm-, 0.8 mm- and 1.0 mm-square sizes. The lengths of the square shaped stones range from 3 mm to 5 mm. The most common length is 3 mm.

Deciding how many stones to use
Unlike operations using natural-diamond tools, in which a single stone is often used, an equivalent synthetic tool may use up to five synthetic stones mounted in a blade. The recommended number of stones will vary by application and is derived directly from the application specifics, which include wheel specifications and finish requirements. As a general rule, the larger the wheel size, the larger the number of synthetic stones that are required and the larger those stones will have to be. Either follow the guidelines shown in Table 1 or contact a Saint-Gobain diamond-tool application engineer for assistance.

Table 1--Synthetic Stone Selection Guidelines
 
Grinding wheel
diameter*
 Recommended number
of stones
 
‹ 11 inches (‹ 279mm)
 1
 
12 – 17 inches (304 – 431mm)
 2
 
18 – 29 inches (457 – 736mm)
 3-4
 
30 – 36 inches (737 -914mm)
 5
 
*For wheel widths › 6 inches, add a stone
 
 

Specifying diamond orientation
When using synthetic diamonds, the orientation of the square-shaped stone plays a very important role in tool performance. Misaligned or poorly oriented stones can negatively impact your ability to achieve optimum wheel conditioning. In general, set the diamond(s) angled or diagonal (as shown ). For heavy-duty applications, rotate the diamond(s) 45 degrees () as needed.

Getting the tool configured correctly
Don’t be locked into existing tool designs. Many conversions to synthetic tools require a slightly different tool configuration, which often ends up being a blade tool. These modifications are often necessary because of the differences between natural and synthetic diamonds. For example, multiple stones should be mounted vertically on blade configurations so only one diamond width makes contact as the tool moves across the wheel. It is also important that the shank orient the diamonds so that the stones are aligned perpendicular to the wheel face as shown in the box, “Tech Tips.”

Using synthetic tools correctly
Operate synthetic dressing tools using the same dressing parameters you use for natural-diamond tools. One word of caution: when overheated, synthetic diamonds tend to weaken faster than natural diamonds. Operators using synthetic tools should be disciplined and not exceed the recommended diamond dressing tool speeds and feeds.

Synthetics Are Worth Considering

Whether you’re considering the use of synthetic diamonds to improve wheel-conditioning consistency or to avoid interrupting production to index the diamonds, synthetic dressing tools have much to offer. As mentioned earlier, synthetic dressing tools will not bring an end to the use of natural-diamond tools. However, synthetics are desirable in certain applications and suitable for use in many different tools types.

Getting started is not all that difficult if you follow the steps outlined above.

Tech Tips For Using Synthetic-Diamond Dressing Tools

Mounting Blade Tools

• Blade tools should be mounted in alignment with the centerline of the wheel. The tool is mounted so that all the diamonds are perpendicular to the wheel face. This illustrates the proper dressing position and angle for common centerless and cylindrical applications.
• Mounted with a 15-degree post holder, the shank of the tool is at a 15-degree angle with the wheel centerline.
• On straight applications, the tool is mounted perpendicular to the wheel face with no drag angle.
   
  How To Use Blade Tools
• Mount the tool on a flat so that the tool is square to the holder. Offset tools will cause the form to cut wide.
• Mount the tool so that all the diamonds are vertical to the wheel face.
• Be aware that a layer tool may become dull between layers. Four or five heavy infeed passes at 0.002 to 0.004 inch will correct this situation.
• Blade tools are not resettable and should not be rotated.
• Use a 3/8-inch stream of coolant at the point of contact to ensure that both sides of the diamond section are protected.
• Use appropriate truing lead.

Whenever mounting a new grinding wheel, make sure the truing system is fully retracted.

CAUTION! It is the user’s responsibility to refer to and comply with ANSI B7.1, Safety Requirements for the Use, Care and Protection of Abrasive Wheels.

 

Diamond Tooling Versus Carbide

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

Question
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. Let’s 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.

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.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.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.Diamond tooling is very application specific. Let’s 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.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 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.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.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 M’s comments about achieving 600+ inches/min with a 1/2" diameter PCD compression bit, it is very possible with the right bit. We aren’t the only company to make them, you just need to look at amongst the top PCD tooling manufactures and consider your production’s 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 can’t perform at your desired feed-rates.

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.To support Contributor M’s comments about achieving 600+ inches/min with a 1/2" diameter PCD compression bit, it is very possible with the right bit. We aren’t the only company to make them, you just need to look at amongst the top PCD tooling manufactures and consider your production’s 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 can’t 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 bit’s body is softer than your solid carbide spiral’s. Again, with a good design, quality materials and attention spent to the erosion process, this isn’t an issue but keep in mind that larger than 1/2” diameter’s 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 isn’t caught. Then again, some people use good board and experience great results. You simply need to get an experienced tooling company involved and they’ll 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 shouldn’t 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. It’s 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.