Any turners using CBN grinding wheels?

[graduate_owner]

Hi all, this is a follow up to a post I placed in the general woodwork section last week. Wondering what CBN wheels are like for use on turning tools. Any opinions on the Axminster £99 ones, I was thinking of getting the 180 grit version with my Christmas present vouchers?

K

 

[Paul Hannaby]

I use a CBN wheel and it has proved very effective. It doesn't need to be dressed, stays flat and grinds fast and cool. What more can I say! The only down side is that if the bushes aren't spot on (cheap grinders sometimes aren't), you can't true up the wheel in the usual manner by dressing the wheel so you may need to get some precision machined bushes if you run into problems.

 

[SVB]

I use one on a slow speed grinder (an aside) and wouldn’t hesitate to buy another when my coarse wheel needs changing also.

Simon

 

[Robbo3]

Original question - any-users-of-cbn-sharpening-wheels-t109878.html

My reply - IMHO the 180 grit isn't fine enough. It shows up every striation across the bevel.
I had a job fitting mine onto the 1-1/4" bushes that come with the Axminster slow grinder.
Axminster's response was that the bore is 32mm even though it's stated as 1-1/4" on their web page.
Luckily the bushes run true in a woodturning chuck so some fine emery solved my problem.

graduate owner asked - What do you use to grind your tools, apart from the cbn wheel? What I am wondering is how does the 180 cbn compare in coarseness to alum oxide wheels.

Axminster AT8SRG2 8" slow running grinder mounted on a King Hieple's base
- http://detroitareawoodturners.com/uploa ... iltjig.pdf
- http://www.axminster.co.uk/axminster-tr ... der-505195

Ebay jig (but with a vari-grind gouge holder)
- https://www.ebay.co.uk/itm/Gouge-chisel ... SwbtVZPbga

Forgot to compare with a tool ground on an 80 grit white stone but will when I get the chance.

 

[graduate_owner]

Thanks guys

K

 

[Robbo3]

Gouge protrusion jig - 59/63/75mm.
Length gauges for gouge jig
Vari-grind gouge holder lengthened to suit change from 6" to 8" grinder.

Poor photo of striations.
Curved skew = 180 CBN.
Spindle roughing gouge (Brendan Stemp version) = 120 Sorby Pro Edge

 

[graduate_owner]

So do you need to hone after grinding on the cbn or can the tools be used effectively straight from the wheel?

K

 

[Lazurus]

So do you need to hone after grinding on the cbn or can the tools be used effectively straight from the wheel?

K

I always use straight from the grinder all tools except the skew, which I sharpen mostly with a diamond file, only re grinding when absolutely required. never honed anything as it is quicker to pass over the grinder, only a few seconds each time. I cannot see the benefit in fine honing turning tools when they are so easy to resharpen mechanically.

 

[Robbo3]

Now I disagree with Lazurus, not because he's wrong but because he has the skill to 'quickly sharpen a tool' & I don't.

I have to refine my methods & tooling so that I get repeatability with as little hassle as possible so that tools are sharpened as soon as they need it.

I agree that honing is not practical because of the amount of work the cutting edge is asked to do, however it can be beneficial just before that last finishing cut.

I find that a 600 grit diamond hone saves a lot of grinding on the two tools that are ironically, probably the easiest to grind ; the skew & the scraper (negative rake or conventional).

 

[Arnold9801]

For those that have responded on this post, what bench grinders do you use and how do you find them? I’m following another similar post re which sharpening system and am trying to find justification in an alternative to the expensive Robert Sorby belt sharpener!

So the slow speed grinders are a keen option, but don’t seem to be much choice for them in the U.K.

Regards

 

[Phil Pascoe]

Don't buy a ProEdge if you prefer hollow ground tools. As above, I once in a while hone before taking a final cut, but in several years of being a member of a club with some exceptional turners I have to say I have never seen anyone hone anything or say they do it.

 

[CHJ]

For those that have responded on this post, what bench grinders do you use and how do you find them? I’m following another similar post re which sharpening system and am trying to find justification in an alternative to the expensive Robert Sorby belt sharpener!

So the slow speed grinders are a keen option, but don’t seem to be much choice for them in the U.K.

Regards

I've never seen the need for slow speed grinders, like developing the lighter touch in turning itself grinding the tool edges is a technique that needs to be learnt, relying on slower cutting speeds to reduce cutting edge burning is not in my mind the way to go.
A Sharp White wheel or a Blue Crystalline cuts fast and cool, especially the later.

I started with a very cheap and basic grinder in circa 2004 and it's still going strong with the original white wheel and a aftermarket blue wheel. albeit relocated elsewhere.

 

[graduate_owner]

I was asking about honing after grinding because Robbo mentioned the striations on the tools after cbn grinding. Are these important? Do they need removing? Do they affect the sharpness of the tool?
Also, how do tools ground on a cbn wheel compare with tools ground on a white / pink/ blue aluminium oxide wheel in terms of sharpness and striations?

I am trying to get an idea as to whether to go for a cbn wheel or not. I like the idea that they can't shatter so there is the safety aspect to consider, although I have never met anyone who has had a wheel disintegrate while sharpening tools.

K

 

[CHJ]

I think Striations, no matter what the grinding media, are a function of the grit size and how the grit is spaced and presented.

A bit like nicks in a Planner blade, if you offset the nicks the next blade round removes the evidence.

Looking at a tool bevel when ground on 180/240 grit wheel can look rougher finished than one on 120 grit zirconium belt.

Striations can leave witness marks on final finishing, but using the gouge in slicing mode usually shears off irregularities so they are well within light sanding range and outside normal vision perception. I have one Bowl gouge that has grinding striations in the gouge flute as manufactured, resulting in a notch or two in the cutting edge, I can see these on the cut surface and endeavour to hone the gouge flute from time to time to reduce the defect.

Personally very rarely hone an edge, perhaps two or three times a year I feel the need to finesse an edge of a skew, not that I do too much spindle work and as a lot of my pieces use Cascamite, edges last a millisecond or so regardless.

 

[Dalboy]

I have never had any problems using a tool straight off of the grinder as any edge normally does not last that long anyway(depending on wood) I do use a diamond credit card to touch up the skew when needed. The only other time is if the club is away demonstrating at an event then I do use it on other tools as I don't want to lug a grinder around with me but then I am only turning for about an hour maybe two at the most as I tend to turn small quick things otherwise the public get bored and like to see an end result.
I do sharpen freehand and every so often will set up my jigs to reshape if needed

 

[Phil Pascoe]

Irrespective of any finish quality I would seriously consider a CBN wheel for one reason - the diameter doesn't change. If you use a permanently set projection gauge for a sharpening jig you only need one quick pass on the wheel to complete the sharpening - if you are paying many tens of pounds for large gouges and you can double or treble their life expectancy, why not?