Beat CBN Grit size

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Sammy-2016

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Joined
Oct 27, 2016
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53
Location
San Antonio, Texas, USA
Hello Fellow turners :)
I got me a new Rikon 8" grinder but I dont like the finish that stock wheels give me.
would someone give me a little advice on an 8" CBN Wheel Grit size? (180, 240, 350, 6000 ?)
Thank You all
Sammy
 
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I have a 350 grit CBN wheel and it is great for sharpening HSS tools.

I kept an 80 grit white aluminum oxide wheel (Norton) on the the other end of the grinder for my non-HSS tools and if I want to reshape the profile of a tool.
 
I think you will find a large number of varieties here. It is a matter of figuring out what you specifically want to do. Duncan mentioned what he uses and why. CBN should only be used with HSS. Other steel and particularly softer steels will mess up the CBN.

I have two 8 inch grinders and use a CBN 180 and 800 on one grinder and use aluminum oxide on the other for metals other than HSS.

The reason: I went with a 180 for shaping and 800 for finer sharpening, which I use as touch up just before I switch over to scary-sharp for fine tuning of the edge. That is my personal process and most others will have theirs, based on their particular needs.

One thing I learned from experience is that even the 800 will cut HSS to sharpness fairly easy if the tools are already shaped. I had many HSS hand chisels that had never been shaped (a large set given to me by a Japanese friend a few years ago). I also had a water wheel grinder that keeps the tools cool while grinding. BUT each tool took hours to shape at that slow speed with water wheels, then when I heard of CBN, I jumped on a 180 for shaping and 800 for fine tuning. I do believe that with the patience I developed in waiting on a watered wheel grinder to shape a chisel, I could have been excited with how fast an 800 CBN cuts! 😁

One item I would recommend checking out: self aligning washers for CBN wheels.
woodturnerswonders.com

Self-Aligning Spherical Washer, 3-piece set for one CBN Wheel

Some problem grinders will create a little side to side movement in the wheel due to seating problems against the the shaft shoulder near the motor housing, or unequal pressure from the shaft nut. This movement will interfere with the accuracy of sharpening when using the wheels. We have found...
woodturnerswonders.com woodturnerswonders.com
 
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I have an 80 & 180. I have hardly used the 80 at all, I got it for an exceptionally good price at an estate sale after one of our Coastal Bend Woodturners members passed away. I think I will eventually replace the 80 with a 350. just saying……..
Smokey
 
Smokey S said:
I have an 80 & 180. I have hardly used the 80 at all, I got it for an exceptionally good price at an estate sale after one of our Coastal Bend Woodturners members passed away. I think I will eventually replace the 80 with a 350. just saying……..
Smokey
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Gentlemen,
Thank you all for the reply and the great advice.
Hank, thank you for the detailed explanation. Are traditional turning tools HSS?
I heard about the spherical bearing to take up any wobble. Do you recommend i get them?
Thanks to all again
Sammy
 
Yes, traditional turning tools that do not have "carbide inserts" as their cutting edges.

I have the spherical washers and they do well for me. Spherical washers/spherical bearings - If one is skillful and knows how to fix things and take up or make tiny adjustments to their tools, they could probably do without them and not have a problem. But if one does not have the time for such learning curve, the spherical washers/bearings will be beneficial. They were helpful to me.
 
Have a look at D-Way Tools, it's where I got my CBN wheel for grinding the relief on my step drills. They are VERY robust and show no signs of wear after heavy use.

CBN Grinding Wheels| D-Way Tools

We have been using CBN grinding wheels for sharpening our turning tools for years and have found them to be a real asset. The wheels are factory balanced, which makes the grinders run very smooth. The grinding wheels have 1-1/2" face to use, they don't need any dressing therefore you don't have...
d-waytools.com d-waytools.com
 
To join the thread; CBN wheels tend to be more aggressive than the same grit of oxide wheels so you can use a higher grit and get a finer edge on the tool. I have a 350 grit wheel for normal sharpening and I could go higher still.

As far as "traditional" tools. Someone already mentioned that you should not sharpen carbon steel tools on CBN. If you have very old tools, they may be carbon steel.
 
A few months ago a well known turner said he compared the surface after using gouges sharpened at two extremes, perhaps 80 grit and 400 grit, and found no difference in the amount of final sanding needed. A coarser grit faster for shaping, but does remove more metai when touching up the cutting edge thab a finer grit. Perhaps some here will make their own comparison on the surface left on bowls/spindles from coarser and finer grits.

I've not seen discussion of the surface finish left on non-wood materials.
 
donstephan said:
A few months ago a well known turner said he compared the surface after using gouges sharpened at two extremes, perhaps 80 grit and 400 grit, and found no difference in the amount of final sanding needed. A coarser grit faster for shaping, but does remove more metai when touching up the cutting edge thab a finer grit. Perhaps some here will make their own comparison on the surface left on bowls/spindles from coarser and finer grits.

I've not seen discussion of the surface finish left on non-wood materials.
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hmmm. I guess he would say honing is useless. There are some processes (segments and in particular sanding segments with brass or aluminum in it) will not finish well WITH sanding. A sharp tool way beyond 400 grit will eliminate the need for sanding when sanding only spreads contamination.
 
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Here is a link to an article by Tom Wirsing. He is an internationally know Woodturner. He explains the differences in tool steels and ginding/sharpening with CBN wheels. http://www.aawexplo.wwwmi3-ss30.a2hosted.com/aaw_cs1_pdf/AW3303p38-41.pdf

he is considered an expert on the subject by many people in the Turning field. He has demonstrated twice for my local club. The first time he brought all his technology with him and our members could see the differences under high magnification like the pictures in the linked article.

i have a 180 and 600 grit wheels for the reasons he explains in the article.
 
JimB said:
Here is a link to an article by Tom Wirsing. He is an internationally know Woodturner. He explains the differences in tool steels and ginding/sharpening with CBN wheels. http://www.aawexplo.wwwmi3-ss30.a2hosted.com/aaw_cs1_pdf/AW3303p38-41.pdf

he is considered an expert on the subject by many people in the Turning field. He has demonstrated twice for my local club. The first time he brought all his technology with him and our members could see the differences under high magnification like the pictures in the linked article.

i have a 180 and 600 grit wheels for the reasons he explains in the article.
Click to expand...
Jim, thanks for this. This points out the difference in the carbide vs HSS that was evident early on, especially when in carbide inserts came 0n the scene in pen turning. I love the long lasting edge of carbide inserts but they didn't give the cleanness of cut that properly sharpened HSS could.

I was left a little confused on one issue though - it indicated that there are levels of carbide added to the HSS to make it stronger and the edge last longer. I understand that. But in general, the CBN wheels were not designed to sharpen carbide cutters, while the article indicated HSS has small amounts of carbide added. I'm still mulling that.
 
Hank, CBN wheels are not designed for carbide cutters because of the curve of the wheel. You need a flat surface. Some CBN wheels have CBN on the sides but that would be a very difficult area to use with the cutters. Also, even a slow speed grinder is running too fast for a small cutter like that As it would grind it away to fast.

I sharpen carbide cutters (scrapers) using a carbide or diamond credit card style 600 grit hone. Note that I don't believe you can do this with cup shaped carbide cutters.
 
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