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Brian,
Most of my machining is done on a 5HP or
7.5HP engine lathe. Almost all the cutting is with carbide. You
can turn much faster and get a better surface finish with carbide.
I do have a smaller bench lathe. On a small
lathe it is more noticeable when material is harder to machine. Maybe
that's your situation. 1018 is a bit easier to machine then A-36 which is
what standard structural hot rolled steel plate, channel, I flat,
and rod is.
If your finding it a bit sticky and can use
coolant, you'll find it a little better.
Dan H.
----- Original Message -----
Sent: Monday, March 06, 2006 11:02
PM
Subject: Re: [PSUBS-MAILIST] viewport
surface finish
Dan,
Thanks for the heads up on the emery cloth ( and the self etching primer !),
I am aware of the problem but it's always good to keep in
mind
I'm very surprised to hear your comments on
the machinability of the A516 70grade, I have machined the
1018 with relative ease ( like butter !) and that was with a
standard machine tool steel. I couldn't cut the A516 without using
a carbide tool. Even with the carbide tool it has been very tough.
What size lathe do you have? The discrepancy could be with the
horsepower of the lathe, if your lathe is very large then maybe that
would explain your ease of cutting. I've been using the lathes at the
collage which are just medium size.
I have machined the stainless 316 and it is very
tough.
Brian
----- Original Message -----
Sent: Tuesday, March 07, 2006
13:46
Subject: RE: [PSUBS-MAILIST] viewport
surface finish
PLEASE PLEASE be
careful if you are going to use emry paper on the lathe, Cover all parts of
the lathe that could possibly get grit on it with newspaper (not rag). The
grit breaks off the paper and can settle on all you slides and bed and when
mixed with oil on the bed and or coolant you have grinding paste.
NASTY!
Newspaper is best
as rag has a high tensile strength and when caught around your arm and the
chuck = BAD
Newspaper will
tear.
Just some thoughts,
you hopefully know all this.
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Dan H.
Sent: Monday, 6 March 2006 7:34
PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] viewport
surface finish
A-516 shouldn't be
any more difficult to machine then standard off the shelf A-36 or 1018 steel
you find. There are some steels that are freer machining but not by
much. There are a lot of steels that are much tougher and sticker to
machine. If your machining any 316 stainless for sub parts, you'll
find that much more difficult.
I imagine you
could etch with acid but I've never heard of anyone doing that. It
would probably just give you a coating of corrosion under the paint.
All you need to do is, after your done machining, sand the surfaces your
going to paint a bit right in the lathe with some, maybe 180 grit emery
paper, or sand blast it after your done machining if you have a sand
blaster. Use a two part, self etching primer after that. The
primer will bite into the surface and hold the paint. Also, the primer
will protect the surface until your sub is all welded together and
painted.
You may want to
run some tests of how thick your paint will be when your finished. I'm
guessing one layer of primer and one layer of paint will average about .010
of an inch but it depends on how you put it on and how heavy you apply
it.
----- Original
Message -----
Sent: Monday, March
06, 2006 9:36 PM
Subject: [PSUBS-MAILIST]
viewport surface finish
I've got another couple of viewport questions for some of you savy sub
builders out there. I've been machining my first flat disk viewport
flange . That A516 grade 70 steel is really hard stuff !!
I was surprised how much more difficult it is to machine, in that
you can't take off as much metal at a time. Anyway I have been doing
some of the final cuts and facing and getting a very smooth
surface finish with higher speeds on the lathe and I have my
tolerences very close. But what I'm wondering is if those surfaces
are going to be painted with epoxy will the very smooth suface finish make
it hard for the epoxy to stick? Should I treat it with muriatic
acid before I paint it? And how many thousandths does the average
epoxy paint add up to?
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