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[DPRG] help making a dual threaded shaft?

Subject: [DPRG] help making a dual threaded shaft?
From: Earl Bollinger earlwbollinger at comcast.net
Date: Tue Sep 9 20:29:01 CDT 2003

Actually you'll need to do what I do, get a set of "rare" left hand
thread taps and dies for the thread size you want.
I am using 4-40 or 6-32 myself for a small gripper.
There are two ways that I see. 
One: Take a bras or aluminum or mild steel rod of the size you need.
   Cut it a little longer than needed. 
   Then thread one side right threaded, thread the other side left
threaded, leave a small unthreaded portion in the center. Then tap one
arm right handed and tap the other arm left handed.
Two: A bit less work, use a threaded rod for one side, then left hand
thread another rod for the right. Then drill and tap a short joiner rod
for both left and right hand threads and join the two threaded rods
together.

I intend to use a short piece of both L and R hand threaded rods to
screw onto the outer ends and use these as bushings or bearings on the
support truss for the grippers. I feel the raw threaded ends would ream
out the holes on the support trusses too quickly if I don't.

You can get the "rare" left hand taps and dies from
http://www.jtsmach.com/jtswebshop/asp/home.asp

Regards, 
Earl



-----Original Message-----
>From: dprglist-admin at dprg.org [mailto:dprglist-admin at dprg.org] On Behalf
Of rten at new.metronet.com
Sent: Tuesday, September 09, 2003 6:34 PM
To: Clay Timmons
Cc: dprglist at dprg.org
Subject: Re: [DPRG] help making a dual threaded shaft?

Clay:
If you rearrange the mechanical setup so that the screw pushes and pulls
>from one end. Then (for example) clockwise rotation of the screw opens
the
gripper; CCW closes it. Simpler constuction and software. Think about
it.
Ralph

On Tue, 9 Sep 2003, Clay Timmons wrote:

>
>
> Hey with 11 days to go I thought I would start on a gripper.
> I have a good start on a parallel jaw type that uses a dual threaded
rod.
> One jaw has right hand thread and the other jaw has left hand thread.
> When the shaft is rotated the jaws will close or open depending on
which way
> you turn the shaft.  Just like a self-centering vise.
>
> I have a very cheezy (spelling mistake intended) way to make the dual
threaded
> rod but I thought I would see advice from the collective DPRG
robo-wisdom.
>
>
>
> Does anyone know the correct way to make a shaft with both left and
right hand thread?
>
> I assume a lathe is the correct way to go.  I guess it could also be
done with two die.
>
> Anyone have both right hand and left hand 1/4-20 dies?
>
>
> The shaft I need is about 12" long with about 5" of 1/4-20 thread on
both ends.
> Material is not too important,  soft steel, aluminum, or brass should
work.
>
> Can anyone manufacture such a creature for me?
>
>
> Later,
>
> -Clay-
>
>
>
>
>
>
> _______________________________________________
> DPRGlist mailing list
> DPRGlist at dprg.org
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>

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