I think this is the project that was referred to...
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--- In 7x12minilathe@..., "MERTON B BAKER" <mertbaker@...> wrote:
I have a 2" x 24" boring bar, which I used to do the cannons. Still a reach
on a 12x36, & requires a jig. I had a friend with a 2.5" dia. gun drill to
ease the labor. Mert
-----Original Message-----
From: 7x12minilathe@...
[mailto:7x12minilathe@...]On Behalf Of "hanermo" - CNC 6-axis
Designs
Sent: Friday, October 14, 2011 7:51 AM
To: 7x12minilathe@...
Subject: Re: [7x12minilathe] Re: Finally, a project!
Agree 100% with Mert.
I could do it with a 7x - but would not.
It would involve building an external toolrest, and using a linear slide
to control the toolbit.
The linear slide, new, costs more than a 7x.
The work involved would be maybe 100 hours.. by my estimate.
I could do it with my 12x, but might not.
The bore is too deep for easy work.
Ie it IS doable, but far too big/heavy/hard/slow.
I would search for someone who has a 2" thick boring bar, and this is work
for industrial lathes in the 14x/3000 kg sizes, and above.
For my 12x I have a 1" one, and 1.5" ones are available.
Making one is not impractical, also.
Practical work sizes for a 7x are about 3" in steel, just like any lathe.
About half of nominal swing.
At a pinch, near nominal is doable, but very slow (everything is
relative.)
Boring that much metal on a big industrial lathe will probably take 3-4
hours.
12" deep means the cuts need to be light, maybe no more than 1 mm DOC or
depth, at a slow feed rate, to avoid excessive chatter.
If the total amount to be removed is say 6" or 140 mm, that means 70
passes at maybe 5 minutes per pass (could be a lot more, especially on the
later ones where rpm will be about 150).
You did not mention how thick the walls need to be, I guesstimeate at 0.5
inches.
That might be 350 minutes, or almost 6 hours.
Could be more.
Of course, the first 6" depth could be taken at 2-4 mm depths of cut, if
the lathe is a big enough one.
You will likely get your best price from a hobby semicommercial guy, who
will do it for 10-20-30$/hr.
They will take a full day, but wont be in a hurry, and the job might tax
their machines.
An industrial shop is likely to want 60$/hr x 3-4 hrs ..
Let us know how it goes, pics please ..
Rome was no built in a day. I was not the foreman on that job though,
and I
have advice. Keep your 7x12 for a while, buy a few books, (I'm making a
list, but there are some out there already) Play with your lathe, and
make a
few projects. Find something to make that turns you on, and if it's too
big
to fit on your 7x lathe build a working model that will. After 60 years
in
this game, I can say that if you are really interested, nothing can stop
you.
Mert
