NeilS
1st February 2012, 02:09 PM
The purpose of this thread is to capture the collective understanding we have about the differences between Diamond and CBN Grinding Wheels to help anyone making a decisions between these two abrasive.
Diamond and CBN grinding wheels are expensive and a significant step up in $s from ALOX, which most of us used quite happily for many years. They are not a necessity and have only come into consideration because they have become more affordable as an abrasive over the last year or so. But, anyone thinking of getting one will still want to consider the options carefully before taking the plunge.
What we know already:
There is an extensive thread here (http://www.woodworkforums.com/Diamond%20and/or%20CBN%20Grinding%20Wheels) on diamond wheels started by Brendan Stemp, which also has some info on CBN .
There is a CBN wheel thread here (http://www.woodworkforums.com/f8/cbn-wheel-first-impressions-141625/) started by Bruce (Bellyup).
And a thread with a link to Cindy Drozda's video on cleaning/lubing a diamond wheel, here (http://www.woodworkforums.com/f8/diamond-grinding-wheel-lubrication-138129/) provided by Trevor (gtwilkins).
Jim Carroll has just announced (http://www.woodworkforums.com/f8/cbn-wheels-147482/) that he will be stocking CBN wheels very soon, currently in customs
DIAMOND
I have been using the #120 Woodriver diamond wheel most days since April last year.
197002197003
There were two major concerns raised about these wheels back when we bought them. One was that the diamonds would be gobbled up by the iron in the tools (not worn away but a reactive process at the molecular level). The other was that they chronically load up and stop cutting and/or burn the steel.
On the first concern, I put the micrometer across the diamond matrix a few days ago to measure the loss over the last 10 months. As you can see from the above pic I measured the matrix depth and wrote it on the wheel when I installed it, 6.95mm. When I remeasured it again a few days ago it is still 6.95mm! For my practical purposes and the way I'm using the wheel, I'm not concerned now about diamond loss.
On the second concern, yes these wheels load up (but no quicker than ALOX) and this reduces the cutting speed of the wheel when this happens. I haven't noticed any tendency to burn the steel when this happens. I clean mime out from time to time using a rubber abrasive cleaning stick. I turn the grinder off and apply the stick as the wheel is running down, this way if a big chunk of rubber comes off and goes between the wheel and guard (I have left the outer rim of my guard on the grinder) it is less likely to bend something important like my grinder shaft. If the wheel was burning my tools when it becomes loaded I would clean it more often, but it's not and therefore I'm cleaning it less often. Yes, it cuts a little bit slower when loaded, but also gives a finer edge which is a trade-off I'm comfortable with.
The Cindy Drozda video link above on her method of cleaning/lubing a diamond wheel is very worth looking at if you want that wheel to cut at optimum speed.
So far I haven't detected any developing run-out or uneven wear. Recently I put a straight edge across the face of the wheel and couldn't detect any light.
The Woodriver diamond wheel produces a fine almost polished bevel and edge which I'm finding a pleasure to use. At this stage it has been some of the best $s I've spent on turning gear.
Other than the diamond wheel from D-way, I'm not aware of any other economical options.
CBN
Recently I purchased a #180 CBN wheel from D-way.
197004197005
Unlike the above diamond resin matrix wheel, this one appears to be a thin layer of CBN sintered directly to the aluminium wheel. Correct me anyone if I'm wrong about that. It also has a face that is half as wide again as the above diamond wheel, which is a nicer working area.
Installed on the grinder with the supplied bush the face of the wheel ran true, which is essential as nothing is going true it up that we have in our workshops.
First thing to note was the amount of spark coming off the wheel and the amount of metal melting away off the end of my tools. There is much less spark than off an ALOX wheel, but a lot more than the above diamond wheel which generates hardly any at all. If the level of spark is a factor for anyone this might be important. This may change when the wheel has runs in.
As this wheel has a higher grit rating, I was expecting it to cut finer yet again than the Diamond #120. Not so, well not so far. It feels to me more like #100 at this stage, so no wonder my expensive tool steel disappears when I use it. This had its advantages when I recently wanted to grind 10mm off the end of a gouge, but not for regular edge maintenance. Wade (Robo Hippy) made the following contribution in another thread which adds the perspective of how they perform after being used for a while:
On the CBN wheels, I asked my myrtle wood turning buddy how he liked his shortly after he first got them. He told me the cutting edge did not last as long as the one he got from his standard wheels. Probably to being too coarse. I told him to wait a while. These wheels do 'break in'. When new, the 180 cuts like 100 to maybe 120 grit. I talked to him at our last meeting, and he says they are fine now. Now, that mine are broken in, they cut more like 180 grit (only comparison I have is with the matrix style CBN wheels I used for years, 150 grit, and mirror polish). I did talk to Cindy Drozda about her Woodcraft diamond matrix wheels, and she said they were always loading up and burning until she started her oil on a brush for the wheels, and they stopped doing that. So far, I haven't noticed any tendency for the CBN to load up.
Early days for me on the CBN, so it will be interesting to hear from anyone else who has ground down more mm/inches of tool steel on theirs or is having a different experience.
---
PS - Diamond is the preferred option for tungsten carbide, but I understand CBN will still do the job but less effectively. Correct me anyone if I'm wrong about that.
Diamond and CBN grinding wheels are expensive and a significant step up in $s from ALOX, which most of us used quite happily for many years. They are not a necessity and have only come into consideration because they have become more affordable as an abrasive over the last year or so. But, anyone thinking of getting one will still want to consider the options carefully before taking the plunge.
What we know already:
There is an extensive thread here (http://www.woodworkforums.com/Diamond%20and/or%20CBN%20Grinding%20Wheels) on diamond wheels started by Brendan Stemp, which also has some info on CBN .
There is a CBN wheel thread here (http://www.woodworkforums.com/f8/cbn-wheel-first-impressions-141625/) started by Bruce (Bellyup).
And a thread with a link to Cindy Drozda's video on cleaning/lubing a diamond wheel, here (http://www.woodworkforums.com/f8/diamond-grinding-wheel-lubrication-138129/) provided by Trevor (gtwilkins).
Jim Carroll has just announced (http://www.woodworkforums.com/f8/cbn-wheels-147482/) that he will be stocking CBN wheels very soon, currently in customs
DIAMOND
I have been using the #120 Woodriver diamond wheel most days since April last year.
197002197003
There were two major concerns raised about these wheels back when we bought them. One was that the diamonds would be gobbled up by the iron in the tools (not worn away but a reactive process at the molecular level). The other was that they chronically load up and stop cutting and/or burn the steel.
On the first concern, I put the micrometer across the diamond matrix a few days ago to measure the loss over the last 10 months. As you can see from the above pic I measured the matrix depth and wrote it on the wheel when I installed it, 6.95mm. When I remeasured it again a few days ago it is still 6.95mm! For my practical purposes and the way I'm using the wheel, I'm not concerned now about diamond loss.
On the second concern, yes these wheels load up (but no quicker than ALOX) and this reduces the cutting speed of the wheel when this happens. I haven't noticed any tendency to burn the steel when this happens. I clean mime out from time to time using a rubber abrasive cleaning stick. I turn the grinder off and apply the stick as the wheel is running down, this way if a big chunk of rubber comes off and goes between the wheel and guard (I have left the outer rim of my guard on the grinder) it is less likely to bend something important like my grinder shaft. If the wheel was burning my tools when it becomes loaded I would clean it more often, but it's not and therefore I'm cleaning it less often. Yes, it cuts a little bit slower when loaded, but also gives a finer edge which is a trade-off I'm comfortable with.
The Cindy Drozda video link above on her method of cleaning/lubing a diamond wheel is very worth looking at if you want that wheel to cut at optimum speed.
So far I haven't detected any developing run-out or uneven wear. Recently I put a straight edge across the face of the wheel and couldn't detect any light.
The Woodriver diamond wheel produces a fine almost polished bevel and edge which I'm finding a pleasure to use. At this stage it has been some of the best $s I've spent on turning gear.
Other than the diamond wheel from D-way, I'm not aware of any other economical options.
CBN
Recently I purchased a #180 CBN wheel from D-way.
197004197005
Unlike the above diamond resin matrix wheel, this one appears to be a thin layer of CBN sintered directly to the aluminium wheel. Correct me anyone if I'm wrong about that. It also has a face that is half as wide again as the above diamond wheel, which is a nicer working area.
Installed on the grinder with the supplied bush the face of the wheel ran true, which is essential as nothing is going true it up that we have in our workshops.
First thing to note was the amount of spark coming off the wheel and the amount of metal melting away off the end of my tools. There is much less spark than off an ALOX wheel, but a lot more than the above diamond wheel which generates hardly any at all. If the level of spark is a factor for anyone this might be important. This may change when the wheel has runs in.
As this wheel has a higher grit rating, I was expecting it to cut finer yet again than the Diamond #120. Not so, well not so far. It feels to me more like #100 at this stage, so no wonder my expensive tool steel disappears when I use it. This had its advantages when I recently wanted to grind 10mm off the end of a gouge, but not for regular edge maintenance. Wade (Robo Hippy) made the following contribution in another thread which adds the perspective of how they perform after being used for a while:
On the CBN wheels, I asked my myrtle wood turning buddy how he liked his shortly after he first got them. He told me the cutting edge did not last as long as the one he got from his standard wheels. Probably to being too coarse. I told him to wait a while. These wheels do 'break in'. When new, the 180 cuts like 100 to maybe 120 grit. I talked to him at our last meeting, and he says they are fine now. Now, that mine are broken in, they cut more like 180 grit (only comparison I have is with the matrix style CBN wheels I used for years, 150 grit, and mirror polish). I did talk to Cindy Drozda about her Woodcraft diamond matrix wheels, and she said they were always loading up and burning until she started her oil on a brush for the wheels, and they stopped doing that. So far, I haven't noticed any tendency for the CBN to load up.
Early days for me on the CBN, so it will be interesting to hear from anyone else who has ground down more mm/inches of tool steel on theirs or is having a different experience.
---
PS - Diamond is the preferred option for tungsten carbide, but I understand CBN will still do the job but less effectively. Correct me anyone if I'm wrong about that.