Grinding blades with power tools/sanders discussion

[Corneel]

Very, very rarely will I resort to the 6" grinding wheel on the other end - way too fast and aggressive, in fact I'm thinking of replacing it with a polishing mop for honing carving tools.

That's probably why I like my grinder so much! I guess there is a learning curve for this too. I've been using these kind of grinders for over 30 years now, but I can still remember how I got my first lesson from some mechanic at the learning place where I was at that time. I was scared shitless for that thing and burned a couple of lathe bits before i got the hang of it. Now I could do it in my sleep. Let the wheel do the grinding, don't press to much, and keep a finger near the edge on the back of the blade at all times to feel for heat.

 

[aesmith]

I find a conventional 6" grinder works for me, with a 100 grit (I think) white wheel. This is for grinding, not sharpening, so I don't grind right to the edge. What the grinding does is to reduce the size of the sharpened bevel so it resharpens quicker. My grinder actually has a slow wet wheel, but it's such a hassle and cysts so slow that I can't remember when I last used it. I sometimes wonder if the best option would be one of those 1/2 speed grinders that you sometimes see.

Tony S

 

[Derek Cohen (Perth Oz)]

I mainly grind on a Tormek. It is only used for plane blades and bench chisels, and I sharpen lathe chisels on a 8" half-speed grinder. The latter is set up with the Tormek BGM-100 tool rest, which allows switching between Tormek and dry grinder ...

I have come to dislike the Norton 3X wheel for the mess it makes. It fills the air with grit and this is a health hazard. It is over a year since it was last used. The white Norton 46 grit wheel is the only one used now, and it is nearly as bad with the dust it creates.

Now I am waiting delivery of a 1 1/2" wide 180 grit CBN wheel for the 8" grinder ..

http://www.d-waytools.com/tools-diamond ... heels.html

Something like this (on the left) ...

Promises to be exceptional ... and should be at the price (ouch)!

- no dust!
- fast and cool grinding
- no wear to the wheel and settings never change
- no dust ... did I mention that?
- better visibility as the guards are no longer required (steel wheels)
- balanced for minimal vibration

The great thing is that they work as well on plane and bench chisel blades.

Anyone here have experience of CBN wheels?

Regards from Perth

Derek

 

[bridger]

I mainly grind on a Tormek. It is only used for plane blades and bench chisels, and I sharpen lathe chisels on a 8" half-speed grinder. The latter is set up with the Tormek BGM-100 tool rest, which allows switching between Tormek and dry grinder ...

I have come to dislike the Norton 3X wheel for the mess it makes. It fills the air with grit and this is a health hazard. It is over a year since it was last used. The white Norton 46 grit wheel is the only one used now, and it is nearly as bad with the dust it creates.

Now I am waiting delivery of a 1 1/2" wide 180 grit CBN wheel for the 8" grinder ..

http://www.d-waytools.com/tools-diamond ... heels.html

Something like this (on the left) ...

Promises to be exceptional ... and should be at the price (ouch)!

- no dust!
- fast and cool grinding
- no wear to the wheel and settings never change
- no dust ... did I mention that?
- better visibility as the guards are no longer required (steel wheels)
- balanced for minimal vibration

The great thing is that they work as well on plane and bench chisel blades.

Anyone here have experience of CBN wheels?

Regards from Perth

Derek

I haven't used that wheel. I'm looking forward to hearing your reports of how it works out for you. I have used plenty of bonded diamond products. what I can say for sure is that there will be metal dust (swarf) produced, and it will be airborne unless it is trapped in a coolant flow. an aggressive airflow dust collection system would probably be able to trap the vast majority of it, but has the danger of hot sparks in an enclosed system with LOTS of supplied combustion air.... what I observe around my grinders is that the dust produced is almost entirely metals anyway

 

[Cheshirechappie]

If I remember rightly, CBN (Cubic Boron Nitride) wheels are used in the engineering industry, usually for toolroom rather than production grinding, for carbide tools and the harder grades of High Speed Steel (M42, for example, which having a high cobalt content is tough stuff to grind).

For woodworking, I think it may be a bit 'overkill' for steel grades like O1 and vintage cast steel, but it may have advantages when grinding some of the more exotic steels like D2. That's 'informed speculation' rather than direct experience, though, so it'll be interesting to see how it performs in a 'real life' woodworking situation.

The Norton 3X (pink?) wheels have quite an open, friable nature, which means that whilst they grind much cooler and are less inclined to glaze than the commoner wheels supplied with bench grinders, they break down more quickly - hence the dust.

(One of the reasons that Sheffield grew up as a cutlery and tool-making centre is that as well as plenty of water power and local coal supplies, it had supplies of millstone grit for grindstones. This was a mixed blessing, since the local stone is silicaceous, and when it broke down, the dust in the air got into the grinders' lungs and gave them silicosis. You were lucky to survive into your late forties as a Sheffield grinder, until the use of Millstone Grit wheels was banned in the very early 20th century, with man-made wheels being substituted.

Occasional hobby exposure to grinding wheel dust probably won't do too much harm, but occupational exposure can do. As Bridger says, good extraction or flood cooling is a wise health precaution.)

 

[Derek Cohen (Perth Oz)]

Hi Bridger and CC

The bonded diamond wheels were going to be the business. However it became apparent that diamond wears rapidly when grinding carbon as it is carbon itself. Very expensive wheels that promised a lot and returned little.

Boron nitride, on the other hand, does not have this weakness. It is nearly as hard as diamond and unaffected by carbon steel. While it is intended for HSS, it works just as well for high carbon steels - indeed any steel as long as it is hardened. I have read reviews and reports of its use over several years (it has been around quite a while but only used in home operations in recent years), and all have been highly complimentary. This is not a speculative material. I would not have laid out $220 if it was unproven.

Will it grind any better than a Norton white or pink wheel? That depends on the perspective one has. The very best grinder, in my opinion, is a Tormek. Its downside is that it is slow. Still, it does the job and creates an even hollow that is easy to freehand on. I have no doubt that.someone else would be equally satisfied with a cheap 6" grinder wheel. The Tormek makes it simpler, and the 6" requires more skill. Do I think I will get my monies worth out of a CBN wheel? Yes, if this means that the result is as clean a grind as the Tormek, that it has completed the task without heat buildup (the CBN runs as cool as the Tormek), and there is also no dust in the air, which is what I have read. We'll see, and I will report back later.

Regards from Perth

Derek

 

[JimB]

It will be interesting to hear your take on CBN Derek. I finally forked out the money and one arrived this morning. I certainly look forward to less dust.
It always surprises me how clean equipment is in photographs but then I'm a naturally untidy person.

 

[JimB]

Just tried it on a chisel (carbon steel) that needed regrinding. I went right to the edge with no change in colour. I've washed my hands in hotter water.
My Scheppach wet-grinder would do the same job but, setting up and cleaning sludge out of the reservoir afterwards and the time taken actually grinding means there is no real comparison.
Longevity? Time will tell but a great start.
ps. ground a couple of HSS skews since the above. A little slower as you might expect but still cool. 8)

 

[RogerP]

Like Jacob I use a belt sander but in my case a small cheap Draper 4'' bench top model I've had for many years. I use the blue Zirconia belts from Abtec - they last for ages and are okay for wood as well as metal. I did originally make a jig but don't bother with it any more. It's fast, easy and accurate enough by hand and eye.