Tool grinders question

[RobertMP]

I know this topic has been posted before and I think I've read them all.

I've just come back from Ally Pally and the woodwork show. I saw a couple of wet grinding systems on display and for sale at 'show' prices.

What I didn't see was any of the woodturners using anything other than a basic grinder for sharpening as they worked. I even spent a while watching a guy give instruction on sharpening turning chisels - using a small dry stone on the end of his lathe.

I can see the benefits of a wet system but just wonder if it is worth it from a woodturning perspective?

That question aside I was quite impressed with the show. Plenty of demonstrations going on including a number of woodturners working away covering the carpet with their own carpet of shavings. I think I learnt quite a lot just watching and got off lightly only buying an Airshield and filters.
Didn't fancy carrying anything heavier down an icy hill back to the car

 

[beejay]

Hi Robert,
I don't think you should go for one of the wet systems for turning tools.
You will find that the stone will groove very quickly when you start to sharpen your gouges and it will seem an unnecessary expense for turning tools. You also need to buy the special jigs which are not cheap.Also, reshaping some turning tools on a Tormek for example will take quite a while.
These systems are great for regular chisels and plane blades, I use the Tormek and think its the DB's.
For my turning tools I use a bench grinder with 60 and 100 grit white wheels and I now have a TruGrind system which lets me quickly repeat the grind on all my turning tools.
The normal bench grinder spins at 2800rpm approx which if your careful will not blue the blade or you can splash out and go for the Creusen slow speed grinder with 40mm wide wheels but its costly at around £160.
For cheaper grinders, you will find plenty from £20 upwards.
regards,
beejay

 

[PowerTool]

All excellent advice from Beejay - the reason given why it is not worth going for a whetstone grinder for turning tools is that you are sharpening to a different standard than plane blades and chisels - a chisel in contact with a piece of timber on a lathe doing 2,000 rpm will cover the sort of distance a plane does between sharpenings in a large number of seconds :lol:
So sharpening to the same high standard as a chisel or plane is pretty pointless for turning tools.
I use an ordinary bench grinder,and hone with a diamond stone inbetween uses.

Andrew

 

[Anonymous]

I even spent a while watching a guy give instruction on sharpening turning chisels - using a small dry stone on the end of his lathe.

Just curious, was that Reg Slack on the Ashley Iles stand?

I can see the benefits of a wet system but just wonder if it is worth it from a woodturning perspective?

No, I don't think it is... a cheap grinder with a decent wheel added is perfectly adequate.

Was the person demonstrating the sharpening using any kind of jig?

 

[RobertMP]

Interesting replies. You read about these expensive grinders with jigs for gouges etc. and it is easy to get the idea they are the ideal solution for everything.

The guy I bought my lathe from was a keen turner and active club member. I saw only turning related tools there. When I was collecting it he pointed to his Tormek and said 'you must get one of these - expensive but worth it'. Think that was the main reason I was surprised that no one was actually using a wet grinder.

Think it was the Sorby stand where I saw a system based on a belt linisher with a small polishing mop and stick of compound for making the bevel shiny and 'factory fresh' to use the demonstrators words. A belt & disc sander is on my shopping list and I can put a mop on my bench grinder so now I'm wondering if I need to buy anything for sharpening at all!

 

[RobertMP]

I even spent a while watching a guy give instruction on sharpening turning chisels - using a small dry stone on the end of his lathe.

Just curious, was that Reg Slack on the Ashley Iles stand?

Don't think so but they were all starting to look the same by then. There were maybe 3 lathes on the stand. Might have been a turning club. He had a semi circular piece of wood attached at the side of the stone with pen marks showing the height up the stone for the correct angle on different tools and was then sharpening free hand at the level of the mark.

 

[Anonymous]

He had a semi circular piece of wood attached at the side of the stone with pen marks showing the height up the stone for the correct angle on different tools and was then sharpening free hand at the level of the mark.

That sounds like Reg... just goes to show that you don't need to spend money on expensive jigs :wink:

 

[duncanh]

In Woodturning magazine from November last year (issue 168) David Regester did a comparative test of the 2 methods that seemed to be quite in-depth.

Previously he had based his use of a water cooled grinder on an article in the magazine in 1998 (which I haven't read).

In his new test he was surprised to find that the high speed grinder (non-water cooled) produced an edge that lasted longer but didn't give quite as good a cut. The water cooled system didn't last quite as long but gave a better finish.

He now uses the dry grinder to sharpen for roughing out and the wet for finish cutting, though says that if you only have a dry grinder then hand honing the flute is very effective for final cutting.

I originally thought that the wet grinder would take quite a bit longer but he claims that it only takes 4 seconds longer to touch up (but I doubt this includes using the honing wheel). I suspect that most professionals don't use the water system as they think it's more time consuming.

Of course, all this will be probably be dependant on which type of stone you have on your grinder, what type of tool steel you have, the angle you grind at, the type of wood you're cutting, how often you dress the cutting wheel...

Issue 170 of the magazine review the new Sorby system with the sanding belts. It gets a very good review but my first thought was that at £239 I don't care how good it is!

Personally I use this Axminster grinder (which just happens to be on sale at the moment!) and don't have any problems with it. I also use the Trugrind jig on everything except roughing gouges.

Duncan

 

[Anonymous]

If you are able to replicate the settings, be it on a tormek, tru-grind or similar jig, the sharpening time comes down to a minimum.

Fail to replicate the settings accurately and you're into regrinding rather than sharpening... that takes time, particularly so on the Tormek as Beejay mentioned earlier...

Time's only important if you're trying to earn a living from turning, if it's a hobby pastime then it's time spent enjoying yourself ...priceless :wink:

 

[Russell]

My first choice would be a standard grinder with a white stone or similar stone for HSS. I have a lot of customers who use Tormek for woodturning tools and the main benefit is repeatability and the finish of the tools. Honing tools does make a difference when you are working with skew chisels or spindle gouges and some scrapers that are honed give excellent results for shear scarping. How ever I found wet grinding slow and when I am turning I want to get back to work cutting wood quickly. A tormek or wet grinding system is an ideal solution for those who cant get the hang of high speed grinding. There are some who just put too much pressure on and destroy their chisels every time they use a bench grinder. I find most people though can learn I encourage free hand grinding and the use of jigs there is a need for both IMO

 

[ike]

Am I right in thinking you can't 'lose the temper' on HSS steel like you do with carbon steel ? If it discolours it doesn't 'damage' the steel. Makes sharpening the turning tools on a high speed dry grinder a bit more silly person-proof?

Ike

 

[RobertMP]

You definitely do not want to colour hss with heat from grinding. I've ground punch tools made from M2 hss for many years and if you dry grind enough to colour the edge they don't last nearly as long. I'd always take the tool to some water if it was getting too hot to touch near to the place being ground.

 

[duncanh]

I seem to remember reading something somewhere that recommended not quenching tools in water once they were discoloured and too hot from sharpening as it cooled the steel too quickly and caused micro-fractures (I think that was the phrase).
I think it also said that slight blueing of HSS wasn't a huge problem.

I've no idea where I saw this, whether it's true or if it applies to all types of steel.

If you're finding it a problem then it's probably best to do as Robert suggests and put in water regularly. It could be caused by pressing too hard with the tool - I find it needs surprisingly little pressure to sharpen.
It could also be that the grinding wheel needs dressing with a devil stone.

I know that I occasionally do slightly blue tools but if a tool's getting anywhere near too hot to hold I stop and allow it to cool down on it's own.
The wait for it to cool is a good chance to dress the wheel or do a bit of tidying.

Duncan
(only been grinding tools for about 3 years so I may not really know what I'm talking about!)

 

[beejay]

I seem to remember reading something somewhere that recommended not quenching tools in water.

I read that also quite recently. It applies to HSS tools only however and other steels should be quenched in water between passes over the stone.
No idea what the reason is but no doubt to do with the chemistry of the steel.
beejay

 

[Russell]

I have always quench in water with a 1 drop of oil in. Was told that by a engineering and surface grinding company I use for some manufacturing not sure whether what difference it makes.

 

[CHJ]

I came across this thread some time ago, This is about the best technical description of HSS grinding I have seen outside the in depth text books.

The guy is referring to milling cutters but the facts are relevant.

********
From: "Ed Huntress" <huntres2>
Newsgroups: rec.crafts.metalworking
Subject: Re: Flycutter from hell?
Date: Fri, 18 May 2001 02:51:53 GMT

OK, Jack, let's take a closer look at this. You're grinding a material that's designed to *cut* at temperatures as high as 1,000 - 1,100 deg. F (higher for cobalt HSS). It won't be damaged, annealed, or otherwise affected by temperatures below that. But it will develop surface cracks like crazy if it's cooled too quickly, even from temperatures well below its annealing temperature.

The material contains 10 - 15% carbides: chromium carbide, iron carbide, and tungsten carbide. If you grind it slowly, those carbide particles stand proud of the matrix and grind your grinding wheel. It's a tug-of-war. Your absolute rate of wheel wear will be low if you grind gently, but your relative rate of wear will be higher. In other words, you waste grinding wheel by grinding HSS slowly.

To grind HSS effectively you have to use enough pressure to work on the matrix that holds the carbide particles. That's what it takes to grind HSS quickly and efficiently. Because you're applying a lot of local pressure when you do that, it's hard to avoid gouging the wheel locally. Its relative wear rate will be better, but it will lose shape, and the net effect is a toss-up, in terms of how much HSS you can grind with a given amount of wheel.

If someone has told you to grind HSS this way, he or she never learned about the properties of the material or of the results of 100 years of shop experience. I see absurd recommendations on this and many other subjects on the web and sometimes in print, by people who have done things some odd way for 20 years and who claim to be "experts". They were never taught right, either.

So, grind HSS slowly if you want to. As you say, one of the pleasures of doing this for a hobby is that we don't have to worry about production rates. But be careful about the implications of what you're saying. To water-dip HSS between grinding passes is not a wise thing to do. If you're grinding so slowly that you're not heating the steel beyond the temperature at which you can hold it, you probably won't have any problem. But that's not the way HSS is usually ground. If someone heats it up by grinding with firm pressure, and then dips it in water a few times between passes, he'll wind up with a lot of chipped and broken tools. And he'll never know why, because someone told him that the books say to dip it in water between passes.

Ed Huntress
***********

 

[RobertMP]

We used to buy all our punch tooling from Wilson Tool who are one of the largest makers in the world. The reps advice on regrinding was to never get any colour on the grind surface and make sure the heat did not build up. Little and often was the best way too.

I had a look on the american Wilson Tool site and they have a PDF tool maintenance manual with grinding 'rules' on page 11. Not seen the document before but it says much the same thing.

http://www.wilsontool.com/pdf/prodLit/Tooling_Maintenance_Manual.pdf

 

[NickWelford]

I'm just a hobby turner who doesn't turn as much as I would like.
I have a Tormek with a shedload of jigs, a bench grinder with a white stone and an Ashley Isles sharpening system mainly for carving chisels.

I like to have the sharpest tools I can manage, so I mostly use the white stone for roughing gouges, which are not so important and need sharpening more frequently. I use the Tormek for all the others. I use the AI system for honing and touching up and getting a mirror finish on my gouges and skews.
I know it sounds anal, but it feels as if I'm getting a better cut and and a cleaner finish if the tools are sharp enough to shave with. It's probably just me.

 

[Anonymous]

Nowt wrong with that Nick... just goes to show that there's joy and satisfaction to had from every aspect of working with wood :wink:

 

[joekid]

i know its a cheapskate job but i dont care, i got a cheap b&q bench grinder for the princely sum of £10.79, its a real cheapo ,BUT i had very good reason to, my pal had one for a year constantly hammering it with axes any thing he needed sharpening, and got a new one when the wheels worn down,so i can say not all things cheap work out expensive/i cant think oof the name off hand but its very pale grey colour,