How would you design a extra mini lathe (Adept size)

[Neil WyattModerator @neilwyatt]

> And same with most SIEG machines too. Is it possible that your Bridgeport is 55 deg.

Do you just mean the mills? Saddle on my mini-lathe is 60-degree, I know because I made a replacement cross slide using a 60-degree cutter and it works

Neil

[Ketan SwaliParticipant @ketanswali79440]

Posted by Neil Wyatt on 20/09/2015 14:31:37:

> And same with most SIEG machines too. Is it possible that your Bridgeport is 55 deg.

Do you just mean the mills? Saddle on my mini-lathe is 60-degree, I know because I made a replacement cross slide using a 60-degree cutter and it works

Neil

Yes the SIEG mills Neil,

Ketan

[RainbowsParticipant @rainbows]

Posted by bodge on 20/09/2015 03:01:30:

I guess thats a yes to both parts of the question , i have not seen a lathe made that way ,but that does not mean its not been done , I dont think its a good idea mechanically, if the poppet head was running between the shears as usual, if it were to be locked ,the action of the dove tails would be to spread the shears .

Maybe you are thinking of the old Drummond 5&6 inch lathes they had a double deck bed arrangement .

bodge.

No it wasn't that. Maybe I just made it up because the Super Adept I once owned had a T slot running down the middle to locate the tailstock. That drummond is new to me but I'm not sure that design would transfer well

 

 

Well I can't find 55 cutters that happen to have a threaded shank to fit the mill. If Sieg use it on their lathe I might just use a 60. It can't be that cataclysmic

Edited By Rainbows on 20/09/2015 19:14:39

[jaCK HobsonParticipant @jackhobson50760]

Posted by Roderick Jenkins on 19/09/2015 20:34:11:

I think of toughness as being a resistance to both fracture and bending- hence tempered steel, although less hard, is tougher than as quenched. So toughness is a trade off between hardness and malleability.

Rod

That is fine for general English use but not the engineering definition. Just like lots of words in physics have more precise meanings than every day use e.g. work, energy, charge. 'Bending' in engineering probably just implies strain – less specific than your use meaning preserved strain after the load is removed. It is possible to imagine a tough material that isn't malleable – rubber bands?

[Michael GilliganParticipant @michaelgilligan61133]

jaCK & Rod

This might help

MichaelG.

[Roderick JenkinsParticipant @roderickjenkins93242]

Posted by jaCK Hobson on 21/09/2015 08:13:34:

Posted by Roderick Jenkins on 19/09/2015 20:34:11:

I think of toughness as being a resistance to both fracture and bending- hence tempered steel, although less hard, is tougher than as quenched. So toughness is a trade off between hardness and malleability.

Rod

That is fine for general English use but not the engineering definition. Just like lots of words in physics have more precise meanings than every day use e.g. work, energy, charge. 'Bending' in engineering probably just implies strain – less specific than your use meaning preserved strain after the load is removed. It is possible to imagine a tough material that isn't malleable – rubber bands?

Agreed. I think we are both struggling to put the technical definitions that we know into general terms, where strength and toughness are often confused.

**LINK**

Kind regards,

Rod

[Ian S CParticipant @iansc]

Here's what the Collins English Dictionary says, "anneal"(1) to temper, or toughen (something) by heat treatment. (2) to subject to or undergo some physical treatment, esp. heating, that removes internal stress, crystal defects, and dislocations. (3) (tr) to toughen or strengthen (the will, determination, etc.). (4) Physics, to disappear or cause to disappear by a rearrangement of atoms; defects anneal out at different temperatures (5) an act of annealing from old English to burn.

I know what I mean when I use the term, ie. anneal copper to relieve work hardening when working the metal, that's all I need to know.

Ian S C

[AjohnwParticipant @ajohnw51620]

I agree Ian – it is a bit of a yawn.

John

–

[jaCK HobsonParticipant @jackhobson50760]

Posted by John W1 on 21/09/2015 11:40:31:

I agree Ian – it is a bit of a yawn.

John

–

Got to be at least as interesting as bodge vs botch or begging the question? Well, the above definition of anneal has sparked an interest in me OK, so probably the wrong thread, but I think annealed copper is softer because of the presence of increased number of dislocations that are free to move. However the Collins' definition, and even respected references like Wikipedia, suggest that annealing removes dislocations. Maybe both are correct – annealing removes dislocations that are not so free to move but introduces dislocations that are free to move? I do need to find out the answer.

[Neil WyattModerator @neilwyatt]

Well work hardening is caused by dislocations forming so that crystals jam up against each other, so in copper at least annealing must be removal of these.

Tempering is not the same as annealing though, here's an extract from the excellent article by Richard Rex in MEW 224 January 2015:

Hardening carbon steels

Roughly speaking, the hardening process today is only a refinement of what I learned back at the forge: heat then quench. The back story is a little more complicated. First, the metal must be in the all-austenite state, meaning above the UCT. Second, you need to know that quenching forms an entirely new phase called martensite. Yes, another ‘ite’ word. There are at least eight in the steel literature; this article talks about only five. Martensite is responsible for tool steel's useful qualities.

Consider the case of an ordinary tool steel like O1 or W1. Looking at the Fe-C phase diagram, which depicts equilibrium conditions, we know that the metal must be entirely austenitic above the UCT, with all of its carbon (say 1%) dissolved into the wide-open spaces of FCC iron. Slow cooling through the UCT and below changes the composition to a mix of austenite and cementite. With further slow cooling below the LCT this is transformed again into cementite and pearlite. These processes take time.

But what if you don't allow the time? Suppose you quench it, cool it very rapidly, such as 2000^OF (1100 C) per second. Unsurprisingly, this causes a violent, near-instantaneous transformation from austenite to something else entirely, namely martensite. Theoretically, martensite is all there should be in just-quenched steel at room temperature; in practice the martensite content may be as low as 60% or so, the remainder being austenite that didn't make the cut.

The change to martensite is dramatic indeed, like the shattering of safety glass. In a fraction of a second we have gone from the 14-atom FCC austenite to a stretched version of the 9-atom BCC, yet without losing any carbon, thus preventing the formation of pearlite. The new ‘martensitic structure’ is called a Body Centered Tetragonal, BCT (Fig.6).

Martensite is indeed a phase, but it is highly unstable and therefore doesn't appear on the phase diagram. It is a very hard and brittle form of steel with a hardness close to 65 R_C (Rockwell ‘C’ scale), about the same as high speed steel. Martensite comes with a lot of internal stress and strain which, as you've guessed, we can relieve to the desired degree by cooking at a low temperature – in other words, by tempering.

What does tempering actually do?

This is a question that gets evasive answers, if any, mainly because the metallurgy is very complex. At the practical level we know that tempering makes the workpiece a usable tool, trading its hardness/brittleness for toughness. Tempering is a slow process, taking an hour or more in the oven. The short version of the story is as follows. Tempering stabilizes the steel in three stages: 1 By forming in the martensite very small ‘intermediate’ carbides (relatives of cementite, but not quite the same), then; 2 By decomposing retained austenite into ferrite and intermediate carbides, and; 3 Finally, by replacing the intermediate carbides with their more stable counterpart, cementite, Fe₃C.

Now, back to the shop

Do you really need to know all that austenite, cementite, martensite stuff for practical heat treatment? No, but it helps to talk the talk when your project calls for additional background.

 

<oops – I missed out the important bit>

Neil

Edited By Neil Wyatt on 21/09/2015 19:02:46

[Ian S CParticipant @iansc]

We had to know all the states of steel after heat treatment, and the effect of heat treatment when I did my School Certificate exams at school. Even helped my teacher to prepare samples to put under the microscope.

Ian S C

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