Milling SFM or RPM

[chris stephensParticipant @chrisstephens63393]

Hi Kwil,

Thanks for the info but I can’t say that I have any pressing need right know, but the details will be filed away.

chriStephens

[chris stephensParticipant @chrisstephens63393]

Hi Kwil,

Thanks for the info but I can’t say that I have any pressing need right know, but the details will be filed away.

chriStephens

[mgjParticipant @mgj]

As I said, I have no experience of screwcutting with tips, and I get very good results with HSS. OK I’m not so red hot with tip radii – I just break the tip with a stone but still work to .64 is it of the pitch for depth. The alternative being .8 something of p. Its an accurate pich neatly cut thread, perhaps a bit functional WRT to depth, but as always its better to be approximately right than exactly wrong.

 

I have to say I have never worried about the potential of carbide tips to shift metal, though at those speeds operating life is often in modelling terms, uneconomically short.(15-20 minutes in some recommendations.) I accept I “under use”, but I just use them interchangeably with HSS. I can take shaving cuts if I need to, (in 220M07) though I am aware of Sandviks reccomendation that the final cut should always be =/> the tip radius, and I do try to organise it that way if I feel like it.

 

What is handy for me is that, as a person who doen’t have a lot of modelling time, I can (at a price) spend time making rather than sharpening. I still have specialist tools to sharpen, and drill bits of course, but they are a lesser task.

[chris stephensParticipant @chrisstephens63393]

Hi MGJ,

Do you know you are beginning to persuade me that I ought to spend a little, or at least some, time model making instead of tool making. For me though there can never be too many tools. You have to agree that tools are useful and while models can be things of beauty but once you have proved they work they tend to be left on the mantle shelf for others to admire. Traction engines excepted but a little out of my price range at the moment or the foreseeable future.

Anybody know next weeks winning Lotto numbers?

chriStephens

[Anonymous]

Chris,

 

I do have an Ainjest unit lying on the bench. But I think they’re specific to a given lathe, so unless you have the same lathe as me you will not be able to try it out.

Secondly, because I was an idiot and made a stupid mistake when using the unit, it is now damaged and awaiting repair, when I get my enthusiasm back.

Before I damaged it, I found it difficult to engage the half nuts correctly. Once running it was fine and dropped out instantly in the same place. I was being cautious and running at about 550rpm, cutting a 1.5″ diameter 12tpi thread. To be more precise, when I tried to engage the half nuts when it wasn’t set up to cut an actual thread, everything worked fine. When it was set to take a cut, it didn’t always seem to engage properly. Finger trouble on my part probably.

 

Regards,

 

Andrew

 

[mgjParticipant @mgj]

Young Christopher…

 

For years I made nothing but tools. Let me loose in a tool shop with someone elses credit card and I go weak at the knees with pleasure. I love tools.

 

BUT,

 

I don’t think that the person with a full time job can really do both satisfactorily. Ours is just not a hasty hobby, and if you take 3 years to knock up a traction engine, its going to take a lot longer, with a lot more forgetting of bits and potential loss of motivation if you have to do all the ordinary tooling, as well as the specialist stuff related ot that job.

 

Probably accidentally, I went about it the right way, in that for many years I made tools, and though I could yet make a lot more, by the time I started “modelling” there wasn’t a lot I needed, other than a ball turning tool. Boring head, mill, rotary table, dividing head, decent coolant systems, machine vices – I had them all at reasonable cost and great accuracy.

 

For me its all about what one wants to do and what one enjoys. Tools, there is a great satisfaction in making the next one more easily using the one you have just made, but it does stop there.

 

A TE or a loco, you can tow kids, contribute at open days, burn coal, get dirty, and discuss engineering and the worlds problems for hours in a very relaxing atmosphere, once you have finishied a longish project. Metre Maid – she is running on air in 7 months, and I hope to have her tested and on track by the autumn, so that will have taken about 15months or so.

 

However, I found that, despite having loved and worked on the development of IC engines for a lot of my career, I just couldn’t get excited about making one – not because it doesn’t require skill though a single cylinder 2 stroke is hardly taxing either to make or design, but because they don’t do anything on their own. You have to build an aeroplane or a boat to go round it and a lot of commercial people do it a lot better! The trouble is that, once you have run it, its done all its ever going to do. They don’t have a life of their own, you can’t watch all the bits work, and spectators get bored quickly. So they don’t have an added entertainemnt value – for me.

 

I might make a stationary steam engine -a beam engine say, but much of the above applies to them. In model aircraft terms I can quite see why they could become a hangar queen as you suggest . But a loco or a TE – there IS added value, and a shed load of subsystems (pumps water lifters, injectors, overfilled boilers, cold fires etc etc)and you need to use all of them with some skill to keep the whole going. As you will discover when you drive the Little Samson soon – even the steering is rather feminine and prone to spite.

 

However, to go full circle – you ain’t going to get a loco, even a simple one like Speedy or Pansy or Metre Maid/Sweet Pea, ready to a decent standard in 15-18 months if you have to stop for tooling.

 

So you makes your choice. Whichever you enjoy, this not being a rehearsal.

 

(What next  – a 4″ Little Samson, and then a Duchess)

 

Edited By mgj on 26/02/2011 23:17:54

[chris stephensParticipant @chrisstephens63393]

Hi MGJ,

You know it’s only jealousy on my part. Given the same credit card in your opening para. I would quite possibly buy a set of TE material and castings, but it ain’t goner happen!!!

chriStephens

[chris stephensParticipant @chrisstephens63393]

Hi Guys,

As some of you might remember I was milling some HSS , well I have loaded a photo or two of what it was all for. You can see the HSS in its holder, it looks a bit untidy but I only used an oddment for the experiment. Before you lot ask, yes I honed the milled surfaces on a diamond plate to get rid of machining marks and the top cutting face was ground.

chriStephens

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