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Posted by Amateur machinist on November 19, 2008, 8:57 am
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Now that the stepper controlled dividing head (qv) is commissioned
I need to manufacture a milling spindle to cut the clock wheels and
pinions.
I purchased the cutters 4 years ago (thinking then that I was much further
advanced than I even am now!) from Thorntons and both the wheel and the
pinion cutter have a 7 mm bore.
Therefore it seems that all I will need is a 7 mm shaft with suitable means
to clamp the cutters, mounted in ball races (and I just happen to have 4
races with a 7 mm bore in a box of junk) with a pulley on one end, the
whole thing to be mounted on a vertical slide or even the topslide mounted
vertically.
My question to the NG is, can I just turn up a shaft from mild steel or from
brass, both of which I inherited quite a bit in the junk box I was given, or
do
I need to use tool steel and then harden the shafts? it seems to me that in
the first instance because I only have one clock to make, that a mild steel
shaft would be more than sufficient and that if I then get the clock-making
bug still further then I can think again about a more sophisticated shaft.
Certainly I could suck it and see, but I have an in-built neurosis not to go
several weeks down a path and then to have to start again.
So, is mild steel OK for this, please?
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Posted by Tony Jeffree on November 19, 2008, 9:52 am
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On Wed, 19 Nov 2008 13:57:42 -0000, "Amateur machinist"
>Therefore it seems that all I will need is a 7 mm shaft with suitable means
>to clamp the cutters, mounted in ball races (and I just happen to have 4
>races with a 7 mm bore in a box of junk) with a pulley on one end, the
>whole thing to be mounted on a vertical slide or even the topslide mounted
>vertically.
A 7mm shaft sounds a bit on the light side to me for that application
- you would probably find that it isn't stiff enough, particularly for
pinion cutting. I would go for something more substantial than that
and machine the end to take the 7mm bore.
A good option for a "ready made" milling spindle would be to buy one
of the Taig headstocks and a matching pulley set; they do an ER16
collet version for their mill which would be just the job.
Regards,
Tony
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Posted by Dave Baker on November 19, 2008, 10:02 am
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> Now that the stepper controlled dividing head (qv) is commissioned
> I need to manufacture a milling spindle to cut the clock wheels and
> pinions.
>
> I purchased the cutters 4 years ago (thinking then that I was much further
> advanced than I even am now!) from Thorntons and both the wheel and the
> pinion cutter have a 7 mm bore.
>
> Therefore it seems that all I will need is a 7 mm shaft with suitable
> means
> to clamp the cutters, mounted in ball races (and I just happen to have 4
> races with a 7 mm bore in a box of junk) with a pulley on one end, the
> whole thing to be mounted on a vertical slide or even the topslide mounted
> vertically.
>
> My question to the NG is, can I just turn up a shaft from mild steel or
> from
> brass, both of which I inherited quite a bit in the junk box I was given,
> or do
> I need to use tool steel and then harden the shafts? it seems to me that
> in
> the first instance because I only have one clock to make, that a mild
> steel
> shaft would be more than sufficient and that if I then get the
> clock-making
> bug still further then I can think again about a more sophisticated shaft.
>
> Certainly I could suck it and see, but I have an in-built neurosis not to
> go
> several weeks down a path and then to have to start again.
>
> So, is mild steel OK for this, please?
The issue is one of rigidity and all types of steel have the same modulus of
elasticity i.e how much they bend under a given load so mild steel will be
as good as anything else. However that's not to say that a 7mm shaft of any
type of steel will actually be strong enough. I have no idea what you're
making so I can't say.
--
Dave Baker
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Posted by Amateur Machinist on November 19, 2008, 10:39 am
Please log in for more thread options > The issue is one of rigidity and all types of steel have the same modulus
> of elasticity i.e how much they bend under a given load so mild steel will
> be as good as anything else. However that's not to say that a 7mm shaft of
> any type of steel will actually be strong enough. I have no idea what
> you're making so I can't say.
I'm making (or intending to make) some clock wheels in brass
and steel pinions, both of 1 modulus.
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Posted by Dave Baker on November 19, 2008, 1:33 pm
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>> The issue is one of rigidity and all types of steel have the same modulus
>> of elasticity i.e how much they bend under a given load so mild steel
>> will be as good as anything else. However that's not to say that a 7mm
>> shaft of any type of steel will actually be strong enough. I have no idea
>> what you're making so I can't say.
>
> I'm making (or intending to make) some clock wheels in brass
> and steel pinions, both of 1 modulus.
I'm not talking about the end product you're making, which is irrelevant to
the problem, I'm talking about the device you're making to make that end
product. How big it is, how big the cutters are, what cutting forces it will
encounter etc. Without knowing those things no one can tell you if a 7mm
shaft will do the job. Obviously how that shaft is mounted and what overhang
the cutters have on it is yet another variable in the problem. A good
engineer can just look at a device and know in his gut if it's sturdy enough
to perform its intended function. If you can't, or don't know someone who
can for you, you could very well make something which won't cut butter and
will just chatter like crazy every time you try and remove metal with it.
If in doubt make everything much more sturdy than you ever thought you
needed. You can't go wrong making something bigger rather than smaller. If
you want to post a pic or a scale drawing of what you intend to do maybe we
can advise you better.
Personally a 7mm anything sounds very weedy for a machine tool. If that 7mm
was just the last few mm on a 1 inch bar rigidly mounted between good
bearings it would be a different story.
Back to you.
--
Dave Baker
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>to clamp the cutters, mounted in ball races (and I just happen to have 4
>races with a 7 mm bore in a box of junk) with a pulley on one end, the
>whole thing to be mounted on a vertical slide or even the topslide mounted
>vertically.