[PSUBS-MAILIST] coarse vs fine thread

[Vance Bradley via Personal_Submersibles]

Helicoils w/SS hardware. And not machine threads, which are guaranteed to pack solid with salt, rust and jam, or cross thread. Take your pick.
Vance

Sent from my iPhone

> On Mar 23, 2015, at 7:59 AM, 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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