RE: 1/4-20 thread?

From: will pattison (
Date: Wed Mar 24 1999 - 21:08:27 EET

it's true, but how important it is depends on the requirements of the
prototype, as well as the skill of the person finishing it. it also
depends on the magnitude of the t.i.r. relative to the size of the desired
thread form. i may sound picky about this, but i put myself through grad
school by moonlighting as a machinist, so i tend to still use those methods
because they produce predictable results.


-----Original Message-----
From: Marshall Burns
Sent: Wednesday, March 24, 1999 12:42 PM
Subject: Re: 1/4-20 thread?

>he should absolutely make a pilot hole in the cad model,
>we all know that there isn't an rp hole out there that is truly round, so
>always opt for a finish drill.

    Yes, I stand corrected. Drilling into a pilot hole and then tapping is
still relatively easy and will give a better quality thread.

>drill the final hole before tapping (a male thread will present other
>challenges, obviously).

    But is this true? Can't we accomplish the same thing by fabbing an
oversize post in the correct position and orientation, and then cutting a
thread into it? Hopefully, the post will not be so off-round that a
threading tool (sorry, I'm not sure the technical term for this tool) can't
fit onto it.

Marshall Burns

Marshall Burns, President
Ennex(TM) Corporation
Fabbing the Future(TM)
10911 Weyburn Avenue, Suite 332, Los Angeles, U.S.A. 90024
Phone: +1 (310) 824-8700. Fax: +1 (310) 824-5185
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***** Copyright (c) 1999, Ennex Corporation

>-----Original Message-----
>From: Marshall Burns
>Sent: Wednesday, March 24, 1999 8:51 AM
>Subject: Re: 1/4-20 thread?
>>... you quickly run into resolution problems with features like a
>>1/4-20 thread. the beauty of sls, though, is that it machines so well.
>> so, save the hassle, not to mention the cad time to create the thread in
>>the first place, and just drill and tap that sucker.
> Wouldn't it be better to include at least the hole geometry in the CAD
>design so the fabricator can create the object with the hole in the right
>position and orientation? Then tapping can easily add the thread. If you
>both drilling and tapping manually, you are making the process of making
>object much more difficult and skill-intensive.

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