7/32" BSW screw

Following up from my previous thread.
I am going to try and tap a 7/32" BSW countersunk screw 10 mm long
I have found the following dies:
'7/32 BSW dies' (http://www.tap-die.com/contents/en-uk/p516_7-32_BSW_dies.html )
'Rotagrip - 04) 7/32 x 24 BSW HSS Die 13/16\" Diameter' (http://tinyurl.com/pzecw2y )
A couple of questions:
1. Which blank can I use? 2. I have a 25mm die holder from a metric tap and die set. Do I need to get a 13/16" die holder for the dies above?
Thanks,
Antonio
--
asalcedo


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On 16/08/2013 16:21, asalcedo wrote:

What blank do you mean?
13/16ths equates to about 20m. You might get away with using a 25 die holder, but you wont have much adjustment. I'd be more inclined to get a smaller die holder to suit better.
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wrote:

You can't buy countersink screw 'blanks'
Holding countersink screws and machining a new thread on them is not straightforward so you need to machine from solid
What you are trying to do requires machine tools not a diestock and a die. At the very least a lathe, preferably a milling machine as well to cut the slots for the screw head. Think a minimum of 750 quid, a few months to learn, jigs to hold the blanks and part machined screws and quite possibly a shit end product.
A 13/16" die holder is needed for 13/16" diameter dies.
What is wrong with buying the as near as dammit 12 24 UNC screws off the shelf at 60p a piece?
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'The Other Mike[_3_ Wrote:

I have indeed ordered the 12 24 UNC screw from the place you pointed me to, a2stainless.com (they have been close for holidays and delivery will be delayed)
But I wanted to give a try as well to making a 7/32 BSW, if it were easy.
So, is it not possible to make the screw using the 7/32 BSW die from a tap and die set starting with an M6 slotted countersunk screw where I had removed the thread and holding it tight on a vice?
Also, and excuse my ignorance, other than to clean a thread or rethread a slightly worn out one, what use are the dies in a tap and die set for?
Thanks.
--
asalcedo

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wrote:

You need to remove the thread, keeping the bolt exactly round and parallel, reducing it in size to the major diameter of the thread you are trying to produce
7/32" BSW or 12 24 UNC are 0.216" or 5.48mm.
Given that an M6 x 1 thread is 6mm diameter and 5mm at the root you cannot produce a 7/32 BSW thread from this as by the time the M6 thread form is removed the diameter of the bolt is 0.48mm smaller than that of the diameter needed for the new thread.

For cutting new theads on usually round material, exactly what you want to do but you are starting from the wrong start point.
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I suppose he might be able to grip the counter sunk head in a *soft jaw vice*. I use off cuts of aluminium angle.

--
Tim Lamb

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On Friday, 16 August 2013 18:56:09 UTC+2, The Other Mike wrote:

A milling machine to cut screw heads? Seems like overkill! Broaching attachments that can cut - for example - hexagonal allen key holes in screw heads are an altogether simpler and cheaper solution.
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On Sat, 17 Aug 2013 07:06:51 -0700 (PDT), snipped-for-privacy@virgin.net wrote:

A hacksaw/needle file is cheapest but a bargain basement chinese mill with a slitting saw is a damn sight cheaper and quicker for a slotted screw head than buying a press, building a suitable fixture and making a broach
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