Angles to grind for 303 stainless

[paul1956Participant @paul1956]

I’m quite confident with the mechanical process of grinding HSS tools. What’s baffling me is the lack of consistency of naming the various facets of the tool faces, so knowing exactly what angles to grind starts to become a bit of a puzzle. I’ve several books, have looked on other web sites, and none of them use exactly the same terms for the faces.
In an attempt to get a decent answer for angles for 303 stainless steel I asked ChatGPT. A long text answer and when I asked it to clarify with an illustration of which face was which I got the image below. To my novice eye that looks wrong, anyone care to offer an opinion.

[JasonBModerator @jasonb]

I never bother to grind anything specificaly, generally the same tool does me for all metals so don’t get too hung up an grinding a tool for every material you come across.

[BazyleParticipant @bazyle]

Some of these ‘guides’ can get a bit precious and are really directed at production. Just do everything at 10 degrees.

[paul1956Participant @paul1956]

I was more interested in what people thought of the illustration.
The bottom right layout looks wrong and the tool ‘back rake’ seems to go the wrong way ?

More AI slop or am I reading it wrong ?

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Paul, I agree with what JasonB and Bazyle has said, the angles are not really critical for most work we do, and if mine look OK and are sharp, they will do the job.

Regards Nick.

[Pete RimmerParticipant @peterimmer30576]

I would not trust anything in that illustration that shows the direction of rotation as being away from the cutting edge. Go on archive.org and download some old text books and take your info from those.

303 is wonderful to machine and doesn’t readily tear up the surface like some mild steels but you don’t easily get a nice shiny finish on it.

[Howard LewisParticipant @howardlewis46836]

In my limited experience, as long as there are clearance angles, the exact value is less important.

As Jason says, 10 degrees will suffice for most purposes.

Whilst the optimumn clearance angle might be 8 degrees, disaster is unlkely to strike if it is actually 5 or 10 degrees. The essential thing is that the tool is on centre height, and there is clearance so that the tool does not rub.

FWIW, being me, Top rake is often zero, seemingly without problems.

Howard

[paul1956]

On paul1956 Said:

I was more interested in what people thought of the illustration.
The bottom right layout looks wrong and the tool ‘back rake’ seems to go the wrong way ?

More AI slop or am I reading it wrong ?

AI seems to have tied itself into a knot, it clearly hasn’t read Harold Hall’s “Tool and Cutter Grinding” as part of its Large Language Model.

Rod

[duncan webster 1Participant @duncanwebster1]

I find my eccentric engineering tangent tool works well on SS. Most important is keeping tool sharp and keeping it cutting. If it rubs the SS can work harden.

[JourneymanParticipant @journeyman]

Steve’s Workshop has some useful info on this topic. Including the poster below.

[old martParticipant @oldmart]

303 stainless is one of the easiest grades to machine, anything that works with mild steel will likely be fine. 303 is not the most corrosion resistant type, but I prefer it for it’s workability.

[duncan webster 1Participant @duncanwebster1]

We once had some large SS forgings machined by Peter Brotherhoods.  Can’t remember the exact material, but would have been austenitic. They found the best way to machine it was to use HSS, not too fast and keep it cutting. They knew what they were talking about and we had supplied test pieces for them to practice on. PB were a really good company to work with

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Duncan, now there’s a company name I haven’t heard of in a long time. When I was doing my City & Guilds, we had a visit to PB, to see and learn some of their welding and fabrication work, and what we saw was very good work indeed. The guy who was showing us around was very well spoken, and certainly knew his job, and there were quite a few top welder & fabricators working there.

Regards Nick.

[egaParticipant @ega]

I just completed a graduated resettable dial for my mill/drill in 303 and used the same tools as for MS but taking care not to get the work too hot. Unlike some steels, knurling was not bedevilled by the production of fine chips clogging the knurls.

[Howard LewisParticipant @howardlewis46836]

Peter Brotherhood are still in existence, having passed through several different owners.

Not too long ago, P S M E visited, and the website will probably show a group of members gathered round a turbine rotor.

Perkins, and Brotherhoods are two of the longstanding engineering companies in Peterborough to still remain and be thriving.

Howard

[jaCK HobsonParticipant @jackhobson50760]

Those chat GPT images… some have me confused! I think it gets some right but then starts hallucinating.

My limited experience suggests tip radius and ‘sharp’ edges are most important for surface finish. I think most of the angles are more critical for tool durability and maximum metal removal rates which don’t really apply to me – I have a wobbly lathe so only take light cuts, and I frequently touch up the edges on a diamond stone.

I often look at tools under magnification as my eyes and glasses alone are often not good enough to see when the tool is slightly dull, or to see the quality of the tip radius.

I guess alu and copper are more special – watch out for built up edge… but the steel cutters seem to work for me if sharp. Maybe if i used different back rake then my brass swarf might not fly so far.

But I guess if you can, then why not use the recommended angles – and Steve’s workshop seems a source for that – thanks.

[Michael GilliganParticipant @michaelgilligan61133]

According to Google’s image-search …. That ChatGPT illustration originates in this video:

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Can we judge an AI by the company it keeps ? …

MichaelG.

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Presumably linked from the comments …

I watched the whole video, but couldn’t take any more

[FulmenParticipant @fulmen]

What’s so bad about Artisan Makes? He’s a bit on the amateur side I guess but that’s not always such a bad thing. Sometimes it’s easier to follow someone on your own level than someone in a different league.

[Michael GilliganParticipant @michaelgilligan61133]

Mainly the absence of any guarding on his grinder !

MichaelG.

[FulmenParticipant @fulmen]

I see. Well, actually, I don’t. Or at least I haven’t noticed that so far. Maybe because I do the same all the time.

But fair enough, I’ll never criticize anyone for pointing out unsafe practices.

[Michael Gilligan]

On Michael Gilligan Said:

Mainly the absence of any guarding on his grinder !

He does mention that he plans to upgrade his grinder and it’s not best practice.
However how much do you trust someone prepared to demonstrate techniques on the internet with unsafe equipment ? I don’t.

“Sometimes it’s easier to follow someone on your own level than someone in a different league.”
The blind leading the blind isn’t a great way to learn.
There are plenty of people out there that are very experienced and can explain things clearly enough for novices to follow.

[Howard LewisParticipant @howardlewis46836]

Once the basics have been grasped and understood (Including safe practice) everything else soon follows.

Often, ABSOLUTE precision is not absolutely necessary. Fitness for purpose and all that.

A highly polished tool is unlikely to perform any better than one left dull, in many cases.

At least, in many cases a scrap component can be replaced / remade, limbs cannot.

Not a Health and Safety fanatic, but a firm believer in common sense and taking care.

Some times, realising the dangers involved, a machine can be operated without guards, just for that short time, not in perpetuity!

Howard

[paul1956]

On paul1956 Said:

On Michael Gilligan Said:

Mainly the absence of any guarding on his grinder !

He does mention that he plans to upgrade his grinder and it’s not best practice.
However how much do you trust someone prepared to demonstrate techniques on the internet with unsafe equipment ? I don’t.

 

Exactly my sentiment

MichaelG.

[Author]

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