开云体育

-----Original Message-----
From: 7x12minilathe@...
[mailto:7x12minilathe@...]On Behalf Of John Brookes
Sent: Friday, October 14, 2011 12:42 PM
To: 7x12minilathe@...
Subject: Re: [7x12minilathe] Re: Finally, a project!


I just jumped in here. The machining of the brass mortar barrel interesting.
I notice he made a cutting tool from heating and quenching ordinary CRS. Is
this generally possible?
Of course, brass is soft, and thats why he can get away with it.
If you were making a mortar with modern materials, wouldn't you just use
steel pipe? In WW2, the military used light weight mortars. How did they
overcome the problem of excessive weight which plagued these CW pieces?
JB



On Oct 14, 2011, at 11:16 AM, ralph_pattersonus wrote:

I think this is the project that was referred to...


--- 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

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