PDA

View Full Version : Diamond and/or CBN Grinding Wheels



NeilS
1st Feb 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.

Jim Carroll
2nd Feb 2012, 09:08 AM
Neil thank you for the comparison.

I think you may be the only person I know that has both the diamond and CBN wheels, so may not get much feedback from others on the comparison.

At the moment due to lack of supply and price these wheels are in very small numbers here in Aus, they are more popular in USA and Europe so it would be interesting to hear from our cousins over the pond for their opinions.

robo hippy
2nd Feb 2012, 01:06 PM
Jim,
I am curious if the CBN Wheels you will be carrying will be the same as the D Way ones. I did show one to the guys who made my matrix CBN wheels (like the Woodcraft Diamond ones but with CBN instead of diamonds) and they said that the wheels were most likely electroplated in a process similar to galvanizing.

There is a Canadian, Andre Martel (I think that is his name) who has been carrying diamond wheels for a few years, and I did chat with him a bit at the last AAW Symposium about them. He did say that the loading of them was a small problem, and not as much with the harder V 10 and V 15 gouges like Thompson and Glaser. I have also heard that much slower speeds help that a lot. I know Fred Holder of More Woodturning magazine has some of them, and likes them. Don't know anything else about them.

I can't remember if Bill Needow's article that was published in the AAW magazine was posted here or not. I did have Bill check out the thread about diamond wheels first. He forgot more about abrasives than I will ever learn, but his conclusion was that diamond is for carbide, and CBN is for steel.

I did touch up some carbide tips for another tool on the CBN wheels. It takes a while.

robo hippy

robo hippy

NeilS
2nd Feb 2012, 05:05 PM
I can't remember if Bill Needow's article that was published in the AAW magazine was posted here or not.



I had put a link to Bill's very good article on Grinder Wheels somewhere here before. But a v. good idea to link it in again here, (http://www.woodturner.org/community/fundamentals/sharpening/grinding%20wheels.pdf) thanks RH. Note, the document is about 2MB in size. In summary, Bill had poor experiences with the various styles of diamond wheel and is now using and prefers CBN wheels.

NeilS
26th Jul 2016, 02:44 PM
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.



That posting was back in Feb 2012.

In Jan this year (2016) I put the micrometer on the diamond wheel again. Here is the result:


389078

So down 0.05mm, but I had created a very shallow 0.006mm dip in the middle of the wheel:



389080 389079

I also took another measurement back in Jan, that time reading just the matrix depth itself and not including the small shoulder behind the matrix (as in the top photo). That measured 5.5mm.

I had an extended period out of the workshop from mid-2012 to the end of 2013, but was consistently in the workshop from Jan 2014 to Sept 2015, so really more like 24 months of solid use from Feb 2012 to Jan 2016.

Then in mid-June I took another measurement across just the matrix and got exactly the same reading as i did in Jan; ie 5.5mm. As far as I can work out, I have only used 0.05mm of the diamond matrix since I've had this wheel, plus that 0.006mm dip in the middle.


389081


To give you a more useful indication of how much sharpening this wheel has done since it was installed in April 2011; I estimate I have turned 50 bowls a year ready to go to the gallery or as gifts over the last five years (5x50=250) + about another 250 rough pre-turned bowls that are yet to be final turned, so all up about 500 pieces. The green woods have been mostly blackwood and native cherry (exopcarpus) and the seasoned wood has been mostly very seasoned (as in old fence posts) red gum. I never turn with less than a very sharp tool; the instant a gouge feels slightly blunt I pick up the next gouge, and so on, until all half a dozen gouges are ready for a touch up, then I sharpen them all in batch mode. This wheel has not been spared.

At this stag all of my turning tools are HSS of one type or another. It may be a different story with tungsten carbide or tantalum carbide.

At the rate I'm using it, this diamond wheel is not about to wear out any time soon!

BobL
26th Jul 2016, 03:43 PM
I've used a CBN wheel from JC for about 2 years and also have a cheap chinese ($10) 6" diamond lapping wheel on the side of the CBN wheel as shown below.

These wheels are mounted on a 1HP 3P grinder running via a VFD (http://www.woodworkforums.com/f65/gmf-3p-1p-vfd-grinder-conversion-188429/2).
The diamond wheel looks flimsy but it does have a substantial (20 mm thick) steel baseplate behind it.
SWMBO has a bout a dozen of these cheap diamond wheels of various grits for her lapidary work - sometimes I use a finer one on her lapidary wheel which is variable speed but does not have that much grunt.

388566

I'm not a regular wood turner so I probably only sharpen and shape wood turning chisels about once a month with the CBN wheel.
I use the CBN wheel mainly to sharpen and shape MW lathe tooling probably about once a week.
I have about a dozen tips that I sharpen, mainly HSS and small Crobalt (no Not cobalt) diamond shaped tips that are my stock MW turning tool.

The diamond lap is used mainly for touching up of TC MW lathe tooling, also about once a week but at most 1 or 2 tips at a time.
I have also used it to occasionally touch up router bits.

The CBN wheel is not quite grinding as aggressively as when I first got it but I have not been able to detect any difference in the diameter of the wheel with any of my cheap micrometers.
The diamond wheel is not used much so is pretty much in its original state.

NeilS
30th Jul 2016, 02:00 PM
I have now rectified the missing photos problem in my post above.

BobL - Thank you for sharing your setup. I like the look of that diamond disc. I have often wondered what a flat grind would do for cutting control with bowl gouges. Where do you buy those discs with an arbor size that would fit a standard bench grinder?

derekcohen
30th Jul 2016, 03:18 PM
Just for interest, here is my experience with CBN wheels - currently standing at about 18 months. Note I do turn, but their use is 95% for flat work (planes and bench chisels).

http://www.inthewoodshop.com/WoodworkTechniques/UltimateGrindingSharpeningSetUp.html

Regards from Perth

Derek

NeilS
30th Jul 2016, 08:36 PM
Excellent coverage of the CBN wheels, Derek.

I appreciate your suggestion that the CBN wheels with the radius might be more suited to woodturners. I occasionally let a bowl gouge slip off the edge on my flat wheel and that leaves some nasty deep abrasions along the heel of the bevel that take repeated resharpening to eliminate. If I bought another CBN wheel I would go with a radiused wheel.

NeilS
14th Jan 2017, 08:47 PM
At the rate I'm using it, this diamond wheel is not about to wear out any time soon!


And, here is a further update on this diamond wheel.

Six months on and many hundreds of gouge sharpenings later I can find no change in the depth of the diamond matrix at the reference point on the rim.

404308

However, as previously reported, the furrow in one part of the wheel is still there (see next photo). I'm having to avoid that area of the wheel because it doesn't run evenly around the full circumference of two wheel and as a result tends to bounce the tool if held against that spot.

It looks like the matrix in that area of this wheel was softer and has worn away (ie let the diamond go) sooner than the remainder of the wheel. Definitely a flaw and not a usage issue as I had previously thought. This would not be an issue with sintered diamond or CBN wheels.

404309

It appears that the Woodriver diamond wheel has been withdrawn from sale by Woodcraft in US, where I purchased it. Maybe this problem was more widespread than just my wheel.

Has anyone else had this problem of just one small area of this wheel wearing away like this?



Stay sharp!

Neil

NeilS
14th Jan 2017, 08:58 PM
404308



Sorry, Taptalk didn't upload that 1st photo. And it didn't let me edit my post.

So, trying again.

404310

Stay sharp!

Neil

NeilS
24th Apr 2018, 03:17 PM
Most turners that have now gone with one of the new low-wearing abrasive wheels went with CBN, so this update is only relevant to those who went with one of the diamond wheels earlier on.

I've been measuring the remaining thickness of my WoodRiver #120 diamond wheel at intervals since I purchased it back in 2011. Here is my latest reading.


434247



So, after seven years of constant use the remaining diamond matrix has only reduced by 0.02mm in thickness. This is the first time that I have been able to measure any loss of matrix at the outer edges of the rim, although as reported previously, the grinding surface hasn't remained perfectly flat/even. That could be rectified by grinding the matrix back flat across with a silicon carbide block, but I haven't felt the need to do that yet.

Repeating, "at the rate I'm using it, this diamond wheel is not about to wear out any time soon!" This may change if I start to sharpen carbide gouge tips on it (diamond being the preferred abrasive for carbide), which may be more severe on the matrix.

If you also have one of these diamond wheels and give it a similar level of use to myself (ie. at least some on most days) I expect it is going to be good for some time yet.

How are the CBN wheels holding up?

smiife
24th Apr 2018, 08:34 PM
Hi neil , I don, t use mine that much , do you know if they
ever need cleaning , if so how ?

dai sensei
24th Apr 2018, 10:21 PM
Good review, I can't recall seeing it earlier, but that could be just my memory :rolleyes:

I have a white wheel on one end and a CBN on the other on my slow speed (1/2 normal) Carbatec grinder. I also have a similar diamond set-up to BobL's on my Tormek, although my side plate is the same size as my wheel, but only use it for my tungsten carbide tools and no obvious wear at all.

NeilS
25th Apr 2018, 11:13 AM
.... do you know if they
ever need cleaning , if so how ?



Smirfe

I used to occasionally run my raw rubber abrasive cleaner across mine, but be v. careful not to allow it to jam between the wheel and rest. Best done while the wheel is running down after being turned off. However, I don't bother doing that anymore. I didn't find any advantage from doing so.

Cindy Drozda (back when she was using diamond wheels) developed a system for continuously brushing something like diesel or kerosene onto the wheel while it was running. It looked a bit too messy to me and I never tried it. Rubbing something like that on by hand and wire brushing it off may help, but I'm not sure what the implications might be of applying a solvents like that to the matrix bond. CBN wheels that have their abrasive sintered directly on to the metal hub are unlikely to ever fragment, however, diamond held in a matrix like a resin bond still has the potential to break away in chunks and.... !!!!

BobL
25th Apr 2018, 11:57 AM
If something sharpened or ground on a CBN or diamond wheel sticks to the wheel then it's the wrong material as they should be self cleaning
There are special cleaning sticks for CBN/diamond but they are not designed for routine cleaning but more to remove stuff that has (accidentally) galled onto the wheel because they will shorten the life of the wheel.
https://www.sharpeningsupplies.com/Cleaning-Stick-for-Diamond-or-CBN-Wheels-P802.aspx

I usually just give the diamond and CBN wheels a blow down with the compressor.

I've ground glass a few times with the diamond wheel and usually spray water onto the wheel while I'm doing and that cleans it well enough but a couple of weeks ago I did a small piece without water and it left a fair bit glass dust embedded on the wheel. It also showed that my wheel needs truing up.


434334

I tried blasting it off with the compressor nut it removed less than half of it.
I tried a few things to clean it up the most successful being a light brief application of fine steel wool
434336

There's info floating around about how steel/iron should not be used with diamond but given that there are long life diamond impregnated thin kerf cutting blades sold for angle grinders then maybe thats no longer correct. I did a brief test of these wheels last year on the MW forum see Metal Cutting Disks (http://metalworkforums.com/f65/t201070-metal-cutting-disks#post1927317)