Proper tool grinding?

[choochoo_balooParticipant @choochoo_baloo]

A new fundamental workshop skill that I wish to acquire is tool grinding.

I have an off hand grinding machine (Axminster bench grinder) and have experimented with free hand sharpening, but would now like to progress to precise angular grinding work to get the very best from HSS tool steel blanks.

Having read around on Harold Hall's website, I was going to buy his book "Tool and Cutter Sharpening" to be able to make his *simple* grinding rest. Could anyone comment on whether this is a good course of action for an ambitious beginner to precision tool grinding?

I did read and admire the Hemingway Worden Mk3 grinder, but the cost and building challenge is too much for me!

Thanks for any help in advance.

[choochoo_balooParticipant @choochoo_baloo]

[Anonymous]

I don't see how 'precise angular grinding' allows one to get the best from HSS tooling? None of the rake angles are all that critical. About 99% of my HSS tool grinding is done freehand and the tools work just fine. The only time I resort to other than hand methods is when I need accurate radii. In those rare cases I either mill the HSS blank first and then hand grind reliefs, or use the Clarkson.

Andrew

[Chris SheltonParticipant @chrisshelton11794]

It might be worth looking at the Veritas tool grinding rest, cheapest at the moment from Axminster Tools.

HTH

[AjohnwParticipant @ajohnw51620]

This is the grinding jig that I mentioned. It looks a little different to the version I saw in the thread. Kit's and or drawing available from Eccentric Engineering,

**LINK**

Might give you some ideas. Must admit compared with what I remember it looks a bit manic to me however I may not be recalling it correctly.

John

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[VicParticipant @vic]

There is this as well:

**LINK**

[BazyleParticipant @bazyle]

It isn't that difficult to make a rest for 'precision' tool sharpening. This is not for drills and endmills though.

Draw a circle the dia of your wheel. Draw a toolbit with the top against the wheel at the half way up level. The end will be ground at the tangent angle right? Here 90 degrees.
Draw a radius at 10 dergees above the horizontal, its corresponding tangent is at 10 degrees to the horizontal so the end of a tool at this point will get ground to 10 degrees. Now draw in your tool blank, with appropriate thickness at this point and you can measure the height above the half way point that gets you the grinding angle you want.

So all you need is a stout block of wood as a main post then a couple of thin sheets that give you the angles you want – probably 10, 15, 20 only. Allow for a flat steel sheet of say 1/16 on top to prevent the tool digging n and allow you to slide it around. Maybe do your primary grind with an extra bit of shim then remove it for the in service touch up at a slightly lesser angle.

[John HaineParticipant @johnhaine32865]

I built the Acute system and have posted a build thread

**LINK**

But the Harold Hall rest has a good reputation too.

[John ReeseParticipant @johnreese12848]

Freehand grinding will get you any shape tool you are likely ever need. The typical bench grinder has two faults: the work rest is inadequate and the wheels supplied are ill suited to grinding high speed steel. Those limitations acn be corrected quite easily. A work rest similar to the Veritas will make it much easier to use. Friable aluminum oxide wheels do a much better job on high sped steel than those supplied with the grinder. In the US the friable aluminum oxide wheels for bench grinders is listed tn the catalogs catering to woodworkers.

[IanTParticipant @iant]

I agree with some of the posters above that for simple lathe tool sharpening – any system that lets you get some level of repeatability to the angles ground will do the job. I simply replaced the very small support on my grinder with a larger table using the existing mounting holes. A simple sliding plate with swivelling finger does the rest.

However, what I am not seeing mentioned above, is the fact that I use this generally just to shape the tool (not to sharpen it). You certainly can use tools straight off the grinder and they will work OK (I used to do this and still do so sometimes) – but for really sharp tools you need to hone them. At one time I used to (mistakenly) think this meant just making the whole ground face "smoother" but in fact it's about achieving a separate facet on the tool. You can do this by grinding and honing at slightly different angles – or use the curve of the wheel to give the required under-clearance to the honed face. Not only will you have sharper tools but they are much easier and quicker to keep that way.

So my advice would be to use a simple rest to get a consistent ground face and a honing jig to give you sharp tools that are quick and easy to keep sharp. Some can do this freehand but I'm not that gifted I'm afraid.

Usual caveats – my work is usually small in nature and I'm a great believer in small tool sizes (I typically use 3/16" HSS) as (again) it's quicker & easier to grind to initial shape – and my old machinery (not the most rigid) really appreciates sharp tooling. As for other cutting tools, one day I might actually finish the Stent T&C but in the meantime I use single point tooling whenever possible and save my expensive milling cutters for when I really need them.

Just a personal point of view which will certainly not suit everyone but works for me. It took me a good while to get to this understanding though – so I thought I'd share it.

Regards,

IanT

[Martin KyteParticipant @martinkyte99762]

I have made Harold's grinding rest more from a need for a completely adjustable tool rest than for accurate angular setting. As Andy Johnson rightly says the actual angles are not that critical, certainly the 'looks about right' method is perfectly good enough for lathe tools. Threading tools and parting tools do benifit for having the degree of control you get from Harold's rest. The main issue for me was generating flat facets which make tools MUCH easier to hone to really sharp edges on slip stones or diamond laps. It's a fun thing to make and it doesn't take too long to do. I've never seen a decent tool rest on any of the bench grinders on offer (excepting commercial pedestal units) so you need something you can set anyhow. Go for it.

regards Martin

[HopperParticipant @hopper]

Every 16 year old first year apprentice can grind a lathe tool bit and has done so since James Watt's day or before. It's not particularly hard. All you need to do is grind an approximate 10 degree angle on the front, side and top of the end of a square block. Bit of practice and some trial and error and you should be there.

As well as Harlold's excellent book, I could recommend "The Amateur's Lathe" by LH Sparey. Written in the 1940s or so, it is still available in print very reasonably priced today. In it, he goes through very simple and clear instructions for tool bit grinding. All you need to get started is one of those tools, the knife tool. Very very simple. Just take a square block of HSS and grind an angle on the front, then the side, then the top. Done. If you want to get fancy you can put a small radius on the front corner with an oil stone.

Nothing special to it at all. No need for special equipment. Just a bit of confidence and willingness to have a go and keep having a go.

[BWParticipant @bw]

Any links to pictures or threads regarding honing a tool after grinding it ? I too have simply been making the face smoother.

What sort of bits does one use to cut radii in tool steel as discussed above ?

I have almost finished making the HH grinding jig discussed in his milling book and it has been very interesting, can thoroughly recommend just for the fun and interest and learning how to make dovetail slides.

I made it to get better control over angles on thread cutting HSS bits, drill bits and mill bits

Bill

[MWParticipant @mw27036]

Posted by Hopper on 05/08/2016 09:32:47:

Every 16 year old first year apprentice can grind a lathe tool bit and has done so since James Watt's day or before.

I dont want to be the bee in the bonnet but i was in a good college a couple of years ago and i was the only one allowed to grind because only i held a wheels certificate and had experience with them, my tutor wouldn't let anyone else do it because they didn't have them, he said that was the law so he wasn't all too keen on letting them loose on them, it was bad news though because every 5 minutes i'd have someone asking for a ground tool,

i had people 3 times my age at my company asking me to sharpen blades for them because they never had either the gumption or opportunity to learn it. So age is no object there. 

I do agree with what you say about special equipment though, nowt necessary, the only way to learn grind is to free hand! Gotta take it your own way.

Michael W

Edited By Michael Walters on 05/08/2016 20:32:18

[HopperParticipant @hopper]

Wheels certificate? Never heard of it. Has the world gone mad?

[duncan webster 1Participant @duncanwebster1]

The only wheels cert I've heard of is to do with fitting them. Yes I know that a we all fit our own wheels, but if you've seen the mess made by a big wheel breaking at speed, you wouldn't object to having people who know what they are doing fitting them

[JAParticipant @ja]

To start, learn how to grind a knife tool and a parting off tool. That is learn by trying. They will cover 95% of all your turning. By the time you have ground these many times you will be able to work out how to grind more fancy tools such as rounded tools, form tools and thread cutting tools. As stated all the angles are approximate, the tool will cut well if they are about right.

I don't understand the rush to use fancy inserts costing a lot of money but I suppose I was taught to grind a simple tool when I was a lad. This lesson has served me well ever since.

JA

[Anonymous]

Posted by Bill Wood 2 on 05/08/2016 20:09:21:

What sort of bits does one use to cut radii in tool steel as discussed above ?

If I just want to take the sharp corner off a tool I use a medium diamond hone. If I need a more accurate radius there are three options:

1. Use the cylindrical grinder; works best when both ends of a tool can be ground, making the measurement easier

2. Use the radius attachment on the Clarkson T&C grinder

3. Mill it using the rotary table – plain carbide cutters will mill HSS, and leave a good finish. The trick is high rpm, lowish DOC and high feedrates. You want the shear zone to be orange hot. If you need to remove a lot of metal to produce a given tool shape it's easier to rough mill it first rather than spend ages grinding it away.

Andrew

[IanTParticipant @iant]

Hi Bill,

I don't have any photos (at least to hand) to show you but if you look on YouTube for "Toolbit Development" by Oxtoolco – he demonstrates one of the honing techniques I mentioned – namely grinding on the (curved) front of the wheel and then honing the leading edge, which he can do freehand in this case (because he can lay it flat on the stone). You can see quite clearly that a second facet is honed on the cutting edge. He also goes on to 'round' the tooltip, which frankly many (who do not hone) would do anyway.

Honing jigs generally come more into play when cutting a facet on a flat ground edge and broadly come in two forms, either the kind that guides the stone over the tool or the kind where the tool is guided over the stone. All honing can be done freehand of course but particularly for smaller tooling, some guidance is helpful (in my case essential). The 'hones' used can either be the traditional oilstone type or the more modern diamond ones. It's also possible to hone small tools on a steel plate using something like diamantine (mixed with oil) – which is very much like a lapping process in that you get a really polished surface to the cutting edge.

I'd suggest that you try the Oxtoolco approach to begin with – as you can grind on the front of the wheel (the recommended way to use a standard grinder) and don't need any special jigs for honing. I cannot recommend holding the toolbit the way he does it (if you value your fingertips) and I use a very simple sliding table to guide the tool past the wheel – with a movable finger/arm that sets one of the tool grinding angles (the table support sets the other). I don't use chip-breakers either but that's another story.

In summary – try the simple things first and see what suits you best – if you need "more" then you will have some idea of what you are trying to achieve (need) in this area, instead of just jumping in. Small steps are best in this case!

Regards,

IanT

[AjohnwParticipant @ajohnw51620]

Posted by Bill Wood 2 on 05/08/2016 20:09:21:

Any links to pictures or threads regarding honing a tool after grinding it ? I too have simply been making the face smoother.

Bill

I just use a slip stone. Not that easy to find now but the ones on ebay that are used for unclogging diamond wheels wont be too bad. Mine if finer. Places like MscDirect should stock the finer ones. Mine dates from my apprenticeship and is still going strong. It was a bit clogged with HSS but still worked ok, I've recently declogged it by cleaning it up a bit with the diamond honing sticks ArcEuro sell. Some people use these and similar for honing.

The main danger is rounding over the cutting edge with the stone or hone. Might be best to put that on a flat surface and place the top of the tool on it and move the tool around being careful to keep it flat on it. Then do the edges and any rad around the edges, not up and down. I do that periodically around the sides of the tool while it's in the lathe but I often use a V shaped tool. For a bar turning tool that for some reason is being called a knife tool a better trick is to hold it vertically flat on the tool and simply pull it up and do it more often. For the first hone put the stone or hone on a flat surface as per the top etc.

I have another stone that came from a turner. He had worn a groove in it that matched the rad he put on the end of his tools as he held it against it and pulled up every time he took a finishing cut.

A bit if light oil would probably stop stones and hones from clogging, Actually it could be done on emery cloth as well.

John

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[MWParticipant @mw27036]

Posted by Ajohnw on 05/08/2016 23:50:50:

The main danger is rounding over the cutting edge with the stone or hone. Might be best to put that on a flat surface and place the top of the tool on it and move the tool around being careful to keep it flat on it.

I actually do this because it's how my oilstone is intended to be used, as a bench stone where the tool is brought to it.

I wouldn't use emery cloth simply because if anything that is going to slightly round the edge over without some kind of hard backing.

Another way to finish tools is to use a block/piece of copper or brass and use grinding paste.

Michael W

[julian atkinsParticipant @julianatkins58923]

I would agree that with practise free hand grinding of HSS lathe tools is easy and quick. If you havent got the knack then other more sophistcated set ups mght need resorting to.

I have some rather particular injector cone making lathe tools to very accurate sizes. They are all honed as per Hopper's methods.

I was taught how to get a good edge on woodworking tools when in my teens namely chisels and plane blades. That was a good grounding for metalwork lathe tools later on.

I also use clockmakers type gravers a lot in the lathe and this teaches optimum cutting angles on different materials.

Cheers,

Julian

[thaiguzziParticipant @thaiguzzi]

I'm back in the UK for a few weeks end of September.

Among various stuff in the famous Thaiguzzi Suitcase will be a late double swivel, 2 bolt Myford vertical slide, c/w;

large aluminium slotted flat plate bracket to be bolted to the front of a typical bench grinder and long enough to cover both wheels, a heavy duty alloy "L" bracket which the Myford slide bolts to, an assortment of accessories in steel inc. a sq shank holder up to 5/8", and round collets and holder from 1/4" to 5/8".

Basically by reading Harold Hall's T&CG book, and adapting bits here and there, someone will be able to do accurate, repeatable lathe tool angles, and the sharpening of the front teeth of end mills and slot drills.

So, someone who is limited for space, can mill on the lathe, and sharpen tools on the grinder, with no more than 15 minutes to change the vertical slide from milling capability to bolted onto the grinder fixture. Having a second bench grinder would be handy, and leave one for off hand free grinding, and one with white wheels and said fixture attached.

I never used the VS for milling as i've had a mill for a long time, and now have had a Stent for a couple of years, it's all surplus to reqcuirements. Probably take a hundred quid for the lot, plus postage, pm me if interested.

[AjohnwParticipant @ajohnw51620]

I visited some one to buy some tooling once and it turned out he knew one of the people who I did my apprenticeship with who had died. When his small workshop was sold off it included a very simple arrangement for sharpening rather than grinding lathe tools.

He'd taken a 2800 rpm motor and mounted one of those thick wheels on it. They are usually about 50mm thick and solid rather than recessed. Dia varies and they can be used end or side on to the tool. The lot was mounted on a board along with a sort of ramp also made of ply to set the rake angle. There was a groove in the ramp to take an angled guide. He'd used a pump motor so there was a left hand thread on the end of the spindle. Also a shoulder.

I suppose the same thing could be done with a wide recessed wheel but I'd guess he wanted a grade that would break down a little more easily than those normally used on HSS. It might well have been something like a gp 60 grit wheel mainly intended for general grinding – mild steel etc.

Just add one thing. If some one grinds up an around 10 degrees all round bar turning tool do another one on the other end at around 15 degrees or so and try that as well.

John

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Edited By Ajohnw on 06/08/2016 11:00:38

[MWParticipant @mw27036]

For most small machines i wouldnt be very confident about milling HSS as described, i've never heard of anyone trying this without grinding equipment, i would imagine that without a very strong heavy turret mill you couldn't get the rigidity to cut it without the tool going bang. What kind of DOC are we talking about here? they must be very small increments to handle it.

Is the HSS being "cut" in a conventional sense or simply being rubbed down with high friction and temperature of the carbide? One would have to be careful to note the actual grade of the HSS because a cobalt alloy could be even harder. 

If complex geometry is needed to be milled, i would imagine surely a silver steel or carbon steel tool is a better bet for the average model engineer?

By attempting to tackle such a hard material to machine, we can learn alot about why heavy duty mills are classed as such in the first place. A fixed rigid head and a moving table is a sounder arrangement for machine construction. 

I would note before anyone mentions it that it is next to near impossible to anneal HSS without a purpose built furnace to control the cooling process, your typical HSS is prone to "air quenching", it simply can't be done without industry grade equipment. 

It just goes to show quite often that the resources and equipment between users in this "hobby" of ours varies enormously, it can't be said though that the specialist machinery is representative of the majority in real terms of practicality.

For example, the lines "blurred" between a shed user with a few budget machines, cannot expect or aspire to the same standards as an industrial professional with thousands of pounds at their immediate disposal and a vacuous warehouse to fill (and possibly two or three helpful assistants). Nor can the latter find what a hobbyist finds useful. Yet both are described as "model engineers" or hobbyists?

Their work is shown off, as though it came out of a basic machine, it borders on fraudulent and possibly voyeuristic, not a trait to be encouraged or an example to look up to. 

The same advice can't be given for both extremes of the spectrum, people need to be clear about where it is they stand and where they are coming from and who it is they expect to read it, it's simple courtesy of language.

Disgracefully yours,  

Michael W

Edited By Michael Walters on 06/08/2016 13:58:46

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