[PSUBS-MAILIST] Aluminum fine threads
hank pronk via Personal_Submersibles
personal_submersibles at psubs.org
Mon Mar 23 21:23:59 EDT 2015
Tom,
Where are you from, good to hear from you. Many machining questions arise.
Hank
--------------------------------------------
On Mon, 3/23/15, TOM WHENT via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Subject: Re: [PSUBS-MAILIST] Aluminum fine threads
To: "personal submersibles" <personal_submersibles at psubs.org>, "personal submersibles-request" <personal_submersibles-request at psubs.org>
Received: Monday, March 23, 2015, 8:22 PM
#yiv2939091083 p
{margin:0;}Hello! I am new to
browsing this mailing list, right now as a matter of
interest, not planning on building anything.. As a diver and
also as a professional metal worker I am intrigued by the
K-350 and also by the propane tank sub.
As a seasoned journeyman machinist I can say with confidence
that it is course threads which are meant to be used in
aluminum - primarily because of it's lower strength in
shear and it's higher ductility which effects the
cross-sectional strength of the thread at the pitch line. As
a matter of practice in my trade fine threads are never used
in aluminum due to the ease of stripping them.
That said, I look forward to learning more from this group
and am very impressed with the work displayed.
Cheers,
Tom
From: "via
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To: "personal submersibles"
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Sent: Monday, March 23, 2015 11:31:27 AM
Subject: Personal_Submersibles Digest, Vol 21, Issue
57
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Today's Topics:
1. Re: coarse vs fine thread
(Sean T Stevenson via
Personal_Submersibles)
2. Re: Specifications when ordering shell
(Andr? Eriksen via
Personal_Submersibles)
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Message: 1
Date: Mon, 23 Mar 2015 08:04:52 -0600
From: Sean T Stevenson via Personal_Submersibles
<personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion
<personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] coarse vs fine thread
Message-ID:
<6cf7f2e3-1d12-44ce-abc7-d5caf7cf81a5 at email.android.com>
Content-Type: text/plain; charset="utf-8"
Use 6061-T6 aluminum where possible. Hard anodize your
aluminium parts, and protect them with zinc anodes. Use
stainless fasteners coated in a corrosion inhibiting grease,
and use stainless helicoil thread inserts in blind tapped
holes.
Sean
On March 23, 2015 6:59:20 AM MDT, Alec Smyth via
Personal_Submersibles
<personal_submersibles at psubs.org> wrote:
>Ah, I have pondered something related for ages. I have
an aluminum bow
>dome
>retaining ring bolted to an aluminum seat. I used
aluminum screws, to
>reduce galvanic pair issues. And then I broke off one of
the screws by
>pure
>clumsiness. I will have to drill this out, as
there's virtually no
>stub,
>and will probably end up with one screw larger than the
rest if I need
>to
>re-tap. But my question is... would you guys recommend
using aluminum
>screws in this scenario? I am not really concerned about
their holding
>power, there's a large quantity of screws involved.
>
>Best,
>
>Alec
>
>On Sun, Mar 22, 2015 at 3:09 PM, Adam Lawrence via
>Personal_Submersibles <
>personal_submersibles at psubs.org> wrote:
>
>> Hi guys,
>>
>> There really isn't an appreciable difference in
performance between
>coarse
>> and fine threads. The more important questions are
bolt/nut
>> material, thread engagement and torque.
>>
>> The argument for sticking with coarse threads would
be that you
>reduce the
>> chance for cross threading the wrong bolt during
assembly, since
>coarse
>> threads are predominately used.
>>
>> Adam
>> ------------------------------
>> *From:* Personal_Submersibles [mailto:
>> personal_submersibles-bounces at psubs.org] *On Behalf
Of *Sean T
>Stevenson
>> via Personal_Submersibles
>> *Sent:* Sunday, March 22, 2015 1:13 PM
>> *To:* Personal Submersibles General Discussion
>> *Subject:* Re: [PSUBS-MAILIST] coarse vs fine
thread
>>
>> Helicoils are an option.
>>
>> Sean
>>
>>
>> On March 22, 2015 11:58:31 AM MDT, Rick Patton via
>Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>>
>>> Hank
>>>
>>> Fine is the only way to go as aluminum is a
much softer metal than
>steel
>>> so it will strip much easier so the more metal
you grab, the better,
>which
>>> fine threads will give you.
>>>
>>> Rick
>>>
>>> On Sun, Mar 22, 2015 at 5:55 AM, hank pronk
via
>Personal_Submersibles <
>>> personal_submersibles at psubs.org> wrote:
>>>
>>>> Help I need advice!
>>>> My new bow dome will be secured to the Al
mating ring with straps.
>I am
>>>> laying out the bolt holes to be threaded in
the AL ring. My
>question is,
>>>> should the bolts be fine or coarse thread?
What holds better in AL
>? The
>>>> threads will be 3/8 by 1 in deep.
>>>> Thank you in advance.
>>>> Hank
>>>>
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>>>>
>>>
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>
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Message: 2
Date: Mon, 23 Mar 2015 16:31:57 +0100
From: Andr? Eriksen via Personal_Submersibles
<personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion
<personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] Specifications when ordering
shell
Message-ID:
<CAMJapUYAXDcQwpr_qnr-TTUq+Hu=-jXUiKO6V-2JFk=vJAjFtw at mail.gmail.com>
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Thanks for the info guys! Made things abit clearer. The
company I`ve talked
to is in Germany, and I live in Norway so I can`t go and
measure the shell.
This is the tolerances they gave me on a OD1000x1500 shell:
OD +/- 2mm calculated out of >outside circumferential
length and real wall
thickness
Ovality max 4 mm, measured at both ends
Straightness 1mm/m max. 3 mm
Length - 0 / + 5 mm
Is the ovality tolerance good enough?
Regards
Andr?
2015-03-23 14:54 GMT+01:00 James Frankland via
Personal_Submersibles <
personal_submersibles at psubs.org>:
> Thanks for the clarification Steve.
> Regards
> James
>
> On 23 March 2015 at 12:18, Stephen Fordyce via
Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>> Hi guys,
>> The material certificate thing is all about quality
control and
>> traceability of exactly what is the composition of
the elements in
>> it. Ie. when the steel gets smelted and
poured into a block (or whatever)
>> at the mill, that particular batch gets analysed
for exact percentages
>> of all elements, and all parts poured from that
batch are given the "heat
>> number" of the batch. Since the
certificate is meant to trace back to the
>> original steel mill, it's often called a
"Mill Certificate".
>>
>> Each time the steel goes through a process (ie.
rolling into sheet, the
>> sheet formed into pipe or endcaps) there is a
chance the traceabilty to the
>> original analysed composition could be lost, if the
material gets mixed up
>> - and there are varying levels of quality control
that make sure of this,
>> and these are reflected in different types of
material certificates.
>>
>> The EN 3.1 cert is pretty high end (ie. good enough
for the SS304/316
>> cryogenic liquid ethane pressure vessels I'm
currently involved with at
>> work) and typical for most industrial applications
at least. I've not come
>> across requirements for 3.2 (which is even more
stringent), and we
>> frequently work with lesser requirements than 3.1.
>> Here's a good explanation of the difference:
>>
http://www.classicfilters.com/blog/materialcertificates/
>>
>> Tracing the material back to the mill is supposed
to be important in case
>> there is a failure in another part in the same
batch, so it can prevent
>> other failures. I've always thought the
whole certificate/traceability
>> thing was just a PITA and that so long as you get
steel or parts from
>> reputable suppliers who's QC practises you
trust, then that's just as
>> effective. Especially when you're
building a big system with hundreds of
>> welded parts.
>>
>> Cheers,
>> Steve
>> (Among other things - mechanical engineer in
Melbourne, Australia)
>>
>> On Mon, Mar 23, 2015 at 10:55 PM, James Frankland
via
>> Personal_Submersibles
<personal_submersibles at psubs.org> wrote:
>>
>>> Hi Andre,
>>>
>>> I was in this position some years ago.
Not knowing what to specify on
>>> the order.
>>>
>>> I believe the EN number is a certificate of the
material quality. Mine
>>> was done to EN10204.3.1.B but i never specified
it. I just asked for the
>>> material type.
>>>
>>> So just ask for your dimensions of shell,
material, percentage of round,
>>> bevel, weld.
>>>
>>>
>>> Example.
>>>
>>> Shell. P355 Steel. 10mm Thick.
>>>
>>> OD 1000mm x 2000mm length.
>>> Shell to be within +\- 3mm on diameter.
>>> Welded seam.
>>> 35 degree external bevel with 2mm nose.
>>>
>>>
>>> Something like that should do it. They
will send you a quote and should
>>> tell you what material grade it what code they
will be working to.
>>>
>>>
>>> Make sure you specify clearly the tolerance of
roundness you want and
>>> say your not paying for it if its not right.
They will probably need to
>>> re-roll the cylinder.
>>>
>>> Ideally go to the factory with a wooden
template and measure the
>>> cylinder before you accept it.
>>>
>>> Get the bevel put on, it will save you pain.
But. don't bother with
>>> grit blasting, you need to paint it straight
away after that or it will
>>> start to oxidise again. By the time
you've finished your hull, it will be
>>> all rusty again. Grit blast when
you've finished working on the hull.
>>>
>>> Someone else may have some other suggestions.
Comments.
>>>
>>> Hope this helps.
>>>
>>> Kind Regards
>>> James
>>>
>>>
>>>
>>> On 21 March 2015 at 22:30, Andr? Eriksen <
>>> personal_submersibles at psubs.org> wrote:
>>>
>>>> Hi,
>>>>
>>>> I`m in the process of ordering the shell
and tower for my submarine.
>>>> What specification should I ask for?
(Europe)
>>>>
>>>> I asked for EN10204 with 3.1
Sertificate (Not 100% sure of this, but
>>>> this is what I got when I ordered the
endcaps from another company. 3.2
>>>> Sertificate was a bit too expensive)
>>>> Told them I had no special requirements for
the plates and needed no
>>>> edge preperation.
>>>>
>>>> *They replied*: "this is not the
normal enquiry type, but we will not
>>>> ask any longer" (?)
>>>> And said the plates was going to be
EN10028-3 with certificate 3.2.
>>>>
>>>> I want to keep the cost down, but should I
ask that they grit blast
>>>> the shell after rolling?
>>>> Also I didn`t ask for bevel on the edges.
Again to keep cost down. But
>>>> maybe I should, to spare me the extra
work?
>>>>
>>>> May I ask what you tell your supplier when
ordrering?
>>>>
>>>>
>>>> -Andr?
>>>>
>>>>
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>>>>
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>>>>
>>>>
>>>
>>>
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>>>
>>
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>>
>
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>
--
Med Vennlig Hilsen / Regards
*Andr? Eriksen*
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