Ferrous, facing, HSS tool geometry

Hello all. I'm new to home metalwork, and have at long last had the time to start experimenting with grinding my own HSS tools for my ML7 lathe.

I'm now experimenting with obtaining the best surface finish when facing steel(s), and am hoping this thread can be a convenient reference for me and others to learn other approaches. I gather HSS tooling is rarely 'only one way will work'.

My current approach is:

use parallel (to lathe axis) QCTP station, ~ 1mm radius round nose, LH so as to cut into the centre. (I will upload a photo later when I get chance!)

Please do contribute, all advice gratefully received.

Edited By choochoo_baloo on 22/10/2021 16:51:59

Sparey's "The Amateur's Lathe" is my bible when it comes to HSS.

One of my older books, can't find the stupid thing, tabulates a full page of different tool shapes for roughing, finishing and other purposes. I suspect the variety of shapes date from the Carbon Steel era: in comparison HSS is very forgiving.

Writing in 1950, Sparey said "many tools of old-fashioned shape have become redundant. " Of knives vs round for steel, he says "They are much to be preferred to the round-nosed tool usually recommended for amateur use on steel, as these invariably produce chatter. A good knife tool will do 80% of amateur turning."

With a knife, Sparey suggests finish is achieved by setting the tool almost parallel to the work to produce a rubbing action in conjunction with slow turning speed, fine-feed, and plenty of lubricant. Works for me.

Be interested to read what others think, but I mostly use the same HSS tool for roughing and finishing steel. Admittedly I don't do exhibition work but it doesn't seem necessary to fuss with different tool profiles. Sharp is better than rounded and it is necessary to experiment with feed-rate and depth of cut

Dave

There is not too much need for ‘experimenting’ - it has all been done time after time and more times. Stick to the accepted norms is my advice.

I've been advocating using HSS on a Myford (as opposed to insert tooling) for many years now but I confess that when it comes to grinding 'correct' profiles I'm hopeless cause.

Hopeless, that is, not in achieving the shapes but very reluctant to grind new ones and usually prevaricate until they really become necessary. I've long come to the conclusion that it's only the tip (to the depth of cut) that does the work so any previously ground tool to the correct parameters gradually becomes misshapen to almost being unrecognisable from its first form - but it still works! Fundamentally I have three basic shapes on the go all the time one left hand knife for turning, one right hand for facing and a tapered round nose tool for finishing either. This latter is probably the most used 'stock' tool. There are other variations of course but for the most part I use tooling ground from 1/4" or 6mm diameter FC3 (throw away) cutter shanks held in mild steel holders - an ideal material and usually a free source if you know a friendly machine shop.

The main thing is to observe what's happening at the tool and 'tweak' the cutting geometry at the very tip to suit material and work piece

Tug

Thanks Dave I have read that chapter of Sparey. When I tried to follow his advice (ie RH knife for facing) I suffer chatter each time.

...Does Sparey mean swapping in a LH knfe, exploiting this rubbing, and moving perpendicualr to the end face? I admit I found his bit unclear.

That's precisly my point; I've struggled to find much (Sparey aside) on HSS geometry for facing.

Turning/boring/parting all have plently of references. Just struggled to find many for facing.

If possible could you upload some photos please? As said above, I am keen to learn more about effective HSS grinding!

A mirror image of the "turning" style would be a good place to start as most left hand tools are a mirror of the right hand.

Useful page on HSS lathe tool grinding on *** Steve's Workshop ***

I have always thought it odd that a tool that cuts towards the headstock is 'Right Hand' - it cuts from the right and a 'Left Hand' tool cuts from the left towards the tailstock. Seems contrary to me but...

John

Edited By Journeyman on 23/10/2021 10:18:15

Ian Bradley's "The Amateur's Workshop" gives angles for grinding tools, as will many other books on the basics of lathework..

For most materials, 5 to 10 degree clearance angles seem to suffice.

Possibly with a small radius stoned all the way down the front edge, to improve the finish. The rad must go all the way down the edge, or the tool might rub.

Brass seems to be quite happy with minimal Top rake.

It could be argued that the radius should be a little larger than the feed rate per rev, so that the radii cut overlap.

For most of what we do, because of the materials that we use, it probably will not matter if the clearance is a degree or two away from the "ideal"

Maybe, for facing a knife tool ground as a left hand tool and mounted parallel to the axis would do the job.

For light cuts, an ordinary right hand knife tool presented to the work to provide a clearance angle of five degrees to the face would probably perform satisfactorily for light cuts. Deep cuts risk chatter because of the width of the chip being produced.

The Diamond tangential tool has a variety of clearance angles, because of the way in which the tool is oriented, and quite atop rake, but it functions very well, and only needs one face grinding, the other angles being produced by the holder.

Probably more important is keeping things as rigid as possible, so that the angles ground on the tool are those at which the tool is consistently presented to the work.

Some may disagree with some or all of the above. What matters is what works best for you and your machine.

Howard

I often use a grey or brown garyflex block to finish my parts.

… It cuts the right-hand end of the workpiece [as viewed by the conventionally situated operator].

So there is some logic there.

MichaelG.

.

P.S. __ I have always thought it odd that an Easterly Wind blows from the East rather than heading Eastward

… but so be it.

Edited By Michael Gilligan on 24/10/2021 08:59:03

Misconception - simple word eh.

Since I began machining I have always thought and referred to as such that a lathe tool that cuts towards the headstock is a left hand tool but no, a tool moving in action toward the left is a right hander - logical really - really???.

Ah well, it just goes to show that sometimes ignorance is pure bliss and that you really can learn something new each day - right hand it is.

Tug

I always remember by thinking which hand I'd be using if swinging an axe into the material. Works for me

Rob

Left or right handed spade/shovel users? I’m right handed, but use both with left hand at the bottom of the shaft. I use my left foot on the spade. So which am I? Left or right handed?

I pull a bow or catapult with my left hand holding the article and my right holding the projectile. Not that good at it as my left eye is master. The only thing I definitely do left handed is shooting a gun - left shoulder, left master eye. I can manage most bolt action rifles from my left shoulder (it seems cack-handed trying to operate the bolt with my left hand on a left-handed air rifle) but it was peculiar when I have used an auto shotgun - it throwing spent cases across me!

Apart from some semi-auto shotguns, I don’t think I have ever seen a completely left handed shotgun - the opening levers were always pushed to the right, even if the stock and triggers were set up for left handed. Ejection always seems to be biased to the right.

Then there are left and right handed cups and mugs….

I am right handed but my left eye is the master and shoot (or rather shot - not done any for years) with a normal right handed shotgun. A bit frightening for others to watch as I appear to be shooting at about 45 degrees to reality! Of course in the cadets at school I shot standard Lee Enfield rifles using my left eye as well which is my excuse for taking so long to get my empire test!

This different master eye to handedness is apparently called being cross lateral, whatever that means.

Using a 35mm film SLR was an issue as if you look through the viewfinder with your left eye there is a tendency to poke your right eye out with the lever wind. The answer was Exacta cameras which were left handed until an Olympus with motor wind took over.

Like S O D,I took Sparey,s advise and have never had any problem using HSS tools.

They are cheap, easy to shape, and easy to replace and they work.

What,s not to love ?

Buy a jewelers loup to use for tool inspection and get the edge as crisp as you can but don't get hung up on precise angles. If the book says 17deg ,14 to 20 will probably be ok 90% of the time . A tiny radius with a hand stone is as much as I ever do. Above all enjoy the day when you turn out a perfect finish with a tool that you made .

If you search Youtube for Oxtoolco Toolbit development 1 then you should find some useful videos on this. I learnt some good lessons from Tom Lipton by watching these.

The most important thing for a beginner is to stop thinking tool shape and grinding is in any way difficult or a black art. Starters get drawn into buying sets of carbide tools and QCTPs thinking it will provide some magic solution while in practice they usually make things worse. (bad shape, blunt, less rigid).
The reason books are full of it is because it is so trivial. The writer could knock off a quick chapter and get paid. Metalwork teachers liked promoting the waffle and diagrams in the books 'cos they could sleepwalk through a few easy lessons while filling in their pools coupon.
So forget all the faff, don't waste time of videos (the new incarnation of the lazy textbook author) just look at a picture and grind anything that isn't obviously 90 degrees to be roughly 10 degrees (well 90-10 = 80). Actual angles aren't important but try to have a simple simple simple grinding rest that allows you to repeat the angle for touch up grinding without having to take a load more metal off.