Wolfie,

The angles are not critical. Clearance angles (front and side) are usually between 5 and 10 deg. Rake angle zero (ie flat topped) for brass and cast iron and about 20 deg for steel.

You will find a straight knife tool wil cope with 90% of your work and you can grind others as and when required.

Yes, you can use an ordinary bench grinder with Harold's grinding rest. If you look at his book "Tool and cutter grinding" he tells you how to improve it. I use my rest with a cheap 15 euro grinder fitted with cup wheels but straight wheels will handle most jobs.

Ady,

Carbide tools are harder than HSS but certainly not tougher. They can easily be chipped if abused. HSS will also be easier to grind.

Russell.

Wolfie,

For most of my routine turning I use inserted tip tooling. I have rather a lot of holders probably far more than I need – but the most useful ones are these:

SCLCR holder, takes CCMT tips; the most used, basic knife tool, will do turning and facing.

SCLCR boring bar – similar shape to above, but on longer shank and geometry optimised for boring

Q-cut parting tool – the best parting tool I have used, by a country mile.

You can find most of these on the Greenwood website, **LINK**

A word about quality and price. The Greenwood prices are high, but the special offers are a good deal less. You can get Glanze tools much cheaper from Chronos; the quality of the holders is OK – not as good as the Greenwood ones, but acceptable. The tips seem to be much more brittle than the more expensive ones, so I don't like them. The Greenwood site is well worth reading for the helpful guidance.

For really fine shaving cuts, a good sharp HS toolbit is slightly better – not as much as some would have you believe, I have done tests on mine and found a 0.5 thou cut with carbide is relatively easy, less than this and they are inclined to rub. I generally have a conventional knife tool and a 45 degree chamfering tool in HS set up for both my lathes.

Other points:

(1) Ady suggests sharpening TC tips on a green grit wheel. Don't waste your time, green grit is a total PITA, get a diamond wheel, they are cheaper, work better and are virtually indestructible:

**LINK**

Use a cup wheel for preference.

(2) You can find toolholders and tips quite cheaply on eBay – but take care, a lot of them are surplus industrial-sized tools and may not fit on your lathe. If you do find some common tips, for example CCMT 0602 or 0604, from a good maker (e.g. Sandvik) at a good price, snap them up even if you have to buy 10.

(3) You can get holders which use the obtuse corners of tips for rough turning, they won't cut to a shoulder but will happily chew massive cuts off in straight turning.

(4) Even carbide tips can be freshened up with a diamond hone.

(5) Your best course may be to buy a cheap set from Chronos and then experiment to see how you get on – for example:

**LINK**

I think you have a Myford 7 – if so, the 10 mm size will be the one for you.

David

Edited By David Littlewood on 16/07/2012 12:49:03

Hi Wolfie,

HSS is an excellent choice for lathe tools. It is cheap, easy to grind to shape, rarely breaks or chips, can run hot and cuts beautifully. I have gone back to good old HSS after a few months using indexable carbide tools. Some swear by them but HSS (and high carbon tool steel such as silver steel) has been used for many years by some of the best. Once you have the basic shape and angles ground they are very easy to touch up with a small oilstone (slipstone) from time to time, even still mounted in the toolpost. A simple grinding rest is adequate but Harold Halls is very good but you will need to fit a cupwheel to one end of your grinder. I managed without any modification, just remove the guards and wheel from one end.

Also as Russell says, carbide tools are harder but not tougher than HSS and as he says are very easily chipped.  Remember toughness is not the same as hardness, carbide is like glass, very hard but brittle, HSS may not keep it's edge as long as carbide but as I said, is very easily touched up by honing with a slipstone in situ.

As for shapes and angles, Sparey in 'The Amateurs Lathe' shows the three basic shapes needed. Here is a copy of part of his sketch:

A) is a right hand knife tool

B) is a 'corner tool'

C) is a round nose tool and

D) is an example of a knife tool used for brass, you should have a round nosed and corner tool as well for brass (and CI)with the same reduced top rake.

The angles are not critical but it doesn't hurt to get as close to the theoretical ones as possible. I would add a LH knife tool as well.

There are others but these shapes will manage for 90% of any work you do. Here is my version of the HH grinding rest before it was damaged in my garage fire:

I have since managed to resurrect the poor thing

Best regards

Terry

Edited By Terryd on 16/07/2012 15:53:46

Forget recommended angles on HSS turning tools they are not the best for amateur work. Increase the angles a lot then most steels will cut a lot better. Always keep your tools SHARP. The " recommended" angles are meant to give the longest life for production runs.You cant easily see 2 thou wear on the tool's cutting edge but obviously you cant take a clean 2 thou cut with it because you are trying to cut with a round bar 4 thou in diameter instead of a blade. If the turning becomes rough it is neary always because the tool is not sharp ENOUGH , even if you cant see or feel it. Stoning is risky as you are likely to radius the cutting edge giving the above result. Avoid it. Stoning the cutting edge of the tool does cannot help as its only producing waste swarf ; only the extreme tip of the tool leaves the required finish and a small, well-relieved radius there will improve the finish. Colin

But if you do take a diamond dresser to your wheel, keep it well away from your lathe (and other tools) when you do it, the dust is very abrasive.

David

Sounds like you're running the lathe too slow. Colin

Just a thought, Wolfie, that the tool is much less likely to give a"thready" finish if the cutting face is parallel to the chuck face or, preferably, the point trailing the face so that the side of the tool tends to push away from the cut rather than being drawn or digging in to it even if it means resetting the tool to finish a face. Colin

No one mentioned tangential tools….

Hi Wolfie ,

(1) If a tool looks something like one of the standard shapes , is sharp and set at or just below centre height it will usually cut reasonably well . More finesse is needed for advanced work but not for general jobbing .

(2) Far more important for getting a good finish on turned work are the angles of presentation of the tool cutting and trailing surfaces to the workpiece .

A complex thing to explain but just for an example next time you turn a length of bar down try a tool with about 80 degrees between cutting and trailing edges and set the tool for the finishing cuts so that the trailing edge is almost glancing the work – just about 5 degrees off . A sharp tool set this way will produce a superb surface . Repeat with a more acute angle tool and trailing edge 20 or more degrees off and you will cut a screw .

Most noddy books describe tool shapes but this is really only a small part of the story . Effective turning also needs consideration of the whole cutting zone geometry plus depth of cut , cutting speed and absolute and relative feed rates .

The cutting zone geometry derives from the tool shape and the angles of presentation – complicated a little by the fact that the geometry gets skewed because tool and work are moving relative to each other .

No need to get into this in any great detail for basic turning but its always worth giving a bit of thought to what is actually going on in a particular cutting set up .

(Anyone that likes things like 3d geometry and relative velocity might like to imagine themselves sitting on the workpiece surface and seeing how the tool cutting edges are coming towards them . )

(3) Cutting surfaces on tools are always shown as dead flat in books . It is much easier when grinding freehand on a simple wheels to leave the tool surfaces with the slight curvature of the wheel rim on them .

(4) The effectiveness of an otherwise perfectly good tool set up will will be spoilt completely if the cutting edge is significantly above centre height .

At centre height best but a little low is usually ok for general work .

(4) There is nothing like trial and error for fast learning about turning and grinding tools – if one set up doesn't work try another .

Regards ,

Michael Williams

re (3) above the well known Boxford book recommends just above centre without giving a reason but probably to provide a small outward thrust when facing to take up the play in the nut.

Hi Guys,

Just for once i am keeping out of this topic and leaving it to the other tangential disciples.

chriStephens