Mill draw-bar - Printable Version

Mill draw-bar - Printable Version

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Mill draw-bar - b4dyc - 05-01-2012

Hi

I am in the middle of making an imperial draw-bar for my mill and need to thread the end for 3/8 Whitworth for a Morse taper collet. Never had reason to use a Whitworth thread before I need to find out the diameter I need to turn the end of the draw-bar down to.
Had a look through the zuse book and came up with 0.3750 Does that sound right to you (I normally work in Metric you see Tongue

)

Thanks for any help

Andy

RE: Mill draw-bar - Tony Wells - 05-01-2012

That would be the correct OD. Here is a handy chart:

http://shopswarf.orconhosting.net.nz/bsw.html

RE: Mill draw-bar - b4dyc - 05-01-2012

I will create that tomorrow then!
Thanks for the chart link as well

Andy

RE: Mill draw-bar - doubleboost - 05-01-2012

Hi
Andy Drawbars are normally 3/8 unc (nearly the same as whitworth)
whit is 55 deg unc is 60 deg
John

RE: Mill draw-bar - b4dyc - 05-01-2012

Thanks John,
I was looking at getting the collets from Arc and they say `Drawbar Thread: 3/8" Whitworth` But what I will do is turn the bar and then check the collet thread when its in my mitts.
Best to make sure as even this simple draw-bar has taken a little shop time to make Blush

Andy

RE: Mill draw-bar - doubleboost - 05-01-2012

Andy
Just had a look at mine they are 7/16 unf
So i might have jumped the gun
Like you say best weight until you have them
John

RE: Mill draw-bar - Mayhem - 05-01-2012

Hi Andy - the easy way to get the decimal equivalent of an imperial measurement is the divide the numerator by the denominator.

So 3/8" = 3 divided by 8 = 0.375"

If there is a whole number, you just add that to the decimal.

So, 3 11/16" = 11 divided by 16 = 0.6875". Then we add the 3 = 3.6875"

This holds true for any fraction to decimal conversion. My math teacher will be so proud I remembered something :)

RE: Mill draw-bar - DaveH - 05-20-2012

Andy,

How did you get on with the draw bar you were making?

Got a pic ? Thumbsup

DaveH

RE: Mill draw-bar - b4dyc - 05-21-2012

Hi,
Yeah have progressed a bit further with it, lets see if i can add pictures here Ouch

Turned the bar between centres in the trusty Myford
[Image: 2012-05-02114819.jpg]

Arrived at the point where i needed the correct size of thread that i asked about
[Image: 2012-05-21115625.jpg]

Popped the thread on
[Image: 2012-05-21114332-1.jpg]

Now I try it on the new MT3 collet Success ! Rotfl

All that is needed now is my jig completing so that i can add the squared off end for the spanner to fit
[Image: 2012-05-21114419-1.jpg]

RE: Mill draw-bar - DaveH - 05-22-2012

Andy,

Good looking draw bar, nice job Thumbsup

Always good when things that supposed to screw together actually do! Rotfl

DaveH