[time-nuts] Machining some aluminum help!

[Lincoln]

I agree, tapping that depth in aluminum is just asking to gall the threads. If you have a decent alloy (6061 7075) you only need 1/8” to hold what ever is save to hold with a #4. If you need more strength then it would be best to use helicoil inserts. 

Where are you located? There are a number of hacker spaces across the country / globe. If you are in the US, there is also "The Tech Shop”. If you are in the SF Bay Area I would take a look.

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> On May 18, 2017, at 11:16 AM, Tim Shoppa <tshoppa at gmail.com> wrote:
> 
> I'm very dubious that you need a tapped 4-40 hole to be threaded any deeper
> than 0.25". If you work with the machinist I'm sure you can come up with
> some reasonable spec that does not require a bottoming tap and will save
> you a lot of money.
> 
> I bet you went to 0.25" wall square tubing only because you want to tap the
> walls for 4-40. Alternative designs can let you use much thinner material
> and a very different flange on the ends, but the costs will likely move
> towards welding/brazing rather than machining.
> 
> Tim N3QE
> 
> On Thu, May 18, 2017 at 12:54 PM, <cdelect at juno.com> wrote:
> 
>> Hi,
>> 
>> I have a square aluminum tube 5" X 5" with a .25" wall it's 8 1/2" long.
>> 
>> I need 20 holes in each end tapped for 4/40 and 1/2" deep.
>> 
>> This is for a Rubidium project.
>> 
>> The local machine shop want's $360.00!!!!
>> 
>> Anyone have a machining setup that could do the work a bit cheaper?
>> 
>> If not I'll give it a try myself.
>> 
>> Please contact me off list.
>> 
>> Thanks!
>> 
>> Corby Dawson
>> 
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