How sharp, how often & how?

[Jelly]

So I've started getting somewhere with turning things, slowly.

Sharpening has become a major issue through, I do all my hand tools by hand on a fine India stone, followed by slate, with a convex bevel... They're very sharp but neither the technique or the stones are appropriate for HSS turning tools.

Sharpening with a flat bevel is no issue, but I'm at my wits end trying to get really sharp skews. I have access to a bench Grinder with a carbonudrum wheel & assortment of polishing mops, and a linisher with a fine garnet belt.

My temptation is to sharpen with a brief touch on the linisher and then use a firm wheel and compound on the Grinder to polish. I've had more success using the linisher, finishing with the slate stone and stropping on an old welding glove to remove the wire edge, but it's still not as sharp as I'd like (subjectively judged on finish left by a planing cut, my arm hair is too fine for the shave test to work, and I'm not pointing a freshly sharpened skew at my face to test it).


Once I get a chisel sharp, how frequently should I be honing it to keep the edge in good nic, and what techniques are advised.

 

[SVB]

Jelly,

For an turning tools I'd really question the need to hone for general turning. I use all my tools straight off the grinder (normally white Al oxide but have just treated myself to CBN wheel as toy rather than necessity). There is a school of thought that for some of the very hard exotics a quick hone is beneficial but I remain to be convinced.

Not sure if the linisher will do it for you as I am not an expert on grinding medium (the tool will - see Sorby proedge, just not sure on belt type. I think all tool manuf use linishers rather than wheels to shape in factory)..

S

 

[CHJ]

I'm as SVB, use all gouges including skew straight off white oxide or blue ceramic wheel, any attempts at getting the ultimate edge I find a complete waste of time.

Hand tool blades travel at inches per minute, most turning tasks are at something like 26 FT per second, so with the average abrasiveness of turning blanks the finite edge lasts just a few seconds.

I do tickle the edge of skews and the occasional bowl gouge with a diamond card for that last fine cut.

One of the problems you may be experiencing without realising it and are being led to assume they are blunt is if you are honing or burnishing with a soft substrate that there is a subtle rounding of the edge taking place and this is in effect holding the bevel supported cutting edge fractionally clear of the surface, thus presenting as a blunt tool.

 

[Sheptonphil]

"Hand tool blades travel at inches per minute, most turning tasks are at something like 26 FT per minute so with the average abrasiveness of turning blanks the finite edge lasts just a few seconds."

Hi Chas, unless I'm wrong, the turning rate is way more. Even a 4" dia spindle (12" circumference) at 1000 revs gives 1000 feet per minute, 20 feet per second ish. So a honed edge in a couple of seconds has cut 40 feet and taken the edge off.

Phil

 

[Jacob]

I wouldn't dream of sharpening turning tools other than on a wheel, disc or linisher, with just one grit size. No progression through the grits. Just a quick dab at very frequent intervals. Nil by hand except removing the burr from inside a gouge with a slip, but you can do this better with a ply disc on a spindle.

 

[CHJ]

"Hand tool blades travel at inches per minute, most turning tasks are at something like 26 FT per minute so with the average abrasiveness of turning blanks the finite edge lasts just a few seconds."

Hi Chas, unless I'm wrong, the turning rate is way more. Even a 4" dia spindle (12" circumference) at 1000 revs gives 1000 feet per minute, 20 feet per second ish. So a honed edge in a couple of seconds has cut 40 feet and taken the edge off.

Phil

Correct Phil I should have said 26ft per sec.

 

[pennardesign]

I returned to woodturning a few years ago. I realised that I was having terrible problems with end grain tear out, posted a few helps on here, all came back with the same reply - sharpen your tools! I purchased a Tormek, I keep all my tools as sharp as razor blades now (I wondered why Tormek gave you plasters)! I sharpen scrapers after a few finishing cuts, just lightly to turn the burr, before I would leather strop the burr off - big mistake. Gouges I sharpen as soon as I notice they have stopped cutting how I like them, I do have a number of gouges so I will use a few on a bowl before I sharpen them all.

I hope this helps, I know a Tormek is expensive but it really has transformed my turning.

 

[Jelly]

One of the problems you may be experiencing without realising it and are being led to assume they are blunt is if you are honing or burnishing with a soft substrate that there is a subtle rounding of the edge taking place and this is in effect holding the bevel supported cutting edge fractionally clear of the surface, thus presenting as a blunt tool.

This logic is why I've resisted the urge to use the polishing wheel, (which should theoretically give me the highest sharpness but it's no good if it's not where I need it.

The take away I'm getting from this is that gentle, frequent sharpening on the linisher or wheel (probably the former for chisels and the latter for gouges), and no additional steps afterwards apart from possibly taking an excessive wire edge off with my palm would be best.

As an aside, the wheel on the grinder is a 40 grit SiC jobbie (mainly used for grinding carbide lathe and milling tools), which I feel is perhaps too coarse, there are ceramic wheel equipped grinders and a wet-wheel Grinder (with a millstone grit wheel!) buried elsewhere in the workshop, are these worth digging out to use in preference to the coarse, hard wheel.

 

[CHJ]

As an aside, the wheel on the grinder is a 40 grit SiC jobbie (mainly used for grinding carbide lathe and milling tools), which I feel is perhaps too coarse, there are ceramic wheel equipped grinders and a wet-wheel Grinder (with a millstone grit wheel!) buried elsewhere in the workshop, are these worth digging out to use in preference to the coarse, hard wheel.

Yes I suspect your (grey/green?) wheel is too course.

Crystalline Ceramic are fine, rapid cool cutting, little dressing needed, not ultra a fine finish but I use blue ceramic for skew and scrapers.
80-100 grit White Oxide is fine for everyday HSS grinding.

Wet wheels tend to be too fine for shaping HSS and often wear excessively when sharpening narrow turning gouges.

 

[Phil Pascoe]

I can't think of an experienced turner I know that hones anything.

 

[Dalboy]

Like SVB and CHJ I use a white wheel on the grinder and the occasional touch up of the skew and maybe a scraper with a diamond credit card

 

[Mark Hancock]

I can't think of an experienced turner I know that hones anything.

I've a little experience and only hone my skew chisels. They never see a grinder unless they've been damaged/dropped by a student.

 

[CHJ]

..I've a little experience and only hone my skew chisels. .

What with ? I've seen you using a diamond card in the past.


(I dress gouge flutes on MDF discs loaded with green abrasive just to keep them polished & clean)

 

[Random Orbital Bob]

I also hone my skews with a diamond credit card file but still give them a tickle on the pro edge at the start of each turning session

 

[Mark Hancock]

..I've a little experience and only hone my skew chisels. .

What with ? I've seen you using a diamond card in the past.


(I dress gouge flutes on MDF discs loaded with green abrasive just to keep them polished & clean)

Right first time Chas - hone on a diamond card and then sharp enough if I can shave the hairs on my hand

 

[John. B]

Like Bob, a 3 second touch on my Pro edge with either the ceramic or zirconium belt is enough.
The length of time I spend at sharpening is minimal, far less time than with the Tormek and no less sharp.
Once the tool is profiled it is very quick to put an edge on it.
John. B

 

[Paul Hannaby]

I use a flat diamond stone to sharpen my skews and scrapers - not because I want to hone them, that's just how I sharpen them. They rarely see the bench grinder. I sharpen all my gouges on the bench grinder. Honing them just makes them lose their edge quicker.

 

[bugbear]

Fred Pain (a great and famous turner) spoke of using oilstones in his The Practical Wood Turner.

He speaks highly of Welsh Slate, a "Dutch Hone" given him by a barber [I suspect this was actually Belgian Cotecule], Arkansas and Washita.

He then says "most of you will use a manufactured stone" (my italics).

His technique is to bring the stone to the tool, standing at the lathe, which is what he did "in the trade".

He also say that "The chief trouble in sharpening turning tools is to remove the burr caused by the grinding wheel, and that is why I don't grind quite to the edge if I can help it". (for Pain grinding is not for sharpening, but for bringing the bevel, an important part of a turning tool, to the correct shape).

Fred Pain had been a full on production turner in High Wycombe, amongst other things; his book is (c) 1957, and his working career earlier, so he is inevitably talking of carbon steel tools.

BugBear

 

[CHJ]

Carbon steel tools are a different animal, watch any East European turner with his classic home made tools and you will see constant stroking of the edge with a variety of his favourite slip stones.

And a favourite pastime whilst sipping his 'break' drink and chatting with cohorts.

 

[Spindle]

Hi

As you get more experienced you will know when a tool is not performing at its best and needs sharpening - that's the time to visit the wheel / belt. I don't subscribe to removing the 'wire' as this is accomplished within seconds of turning.

Polishing a bevel can however improve the finish straight off the tool - Sorby Spindlemaster being an example when used on softer woods.

Regards Mick