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Old 10-11-17, 01:29 PM   #1
Join Date: Jun 2017
Location: North Wiltshire
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Default Die cutting phenomenon.

Not stricktly a stationary engine question, but I thought someone on this hallowed site might havs an idea why.

I'm in the shed making a new brake rod from 5/16 th mild steel cutting a B.S.F. thread 5 inches long. The first two inches are spot on, but then the thread seems to form a long amplitude helix (although the threads along the whole length are acceptable).

Now, why is this happening (or has happened)?:?:

Over to you knowledgeable people. Cheers, Tony.
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Old 10-11-17, 01:37 PM   #2
Lister M
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Are you backing off every couple of turns to clear the swarf as this could get trapped and force the die out of line.
Lister optimum melius quam ceteri, quid tibi pro vita.
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Old 10-11-17, 03:45 PM   #3
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I've seen exactly the same thing myself...

1st question - are you using a split die?
2nd question - is it a quality die (Presto, Golliath, etc.)?
3rd question - are you using a quality cutting compound?

I found that I needed to start with a nice sharp die, as wide open as I could get it in the die stock. Once the first, relatively shallow cut has run down the material you can tighten up a bit and go for the required depth.

A shorter answer is; I don't know why it happens (It's bloody annoying) but perseverance can make it better - once you've scrapped the wobbly thread.

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Old 10-11-17, 04:01 PM   #4
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I find that it's the way you apply the turning force to the handles that causes the issue, I try and do things like that in the lathe, or just buy a bit of threaded rod.

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Old 11-11-17, 11:15 AM   #5
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Thanks to all your knowledgeable answers,

I think I have hit the nail on the head. I did have the rod projecting quite a way up from the vice jaws. I cut another length with only 1 1/2 " out of the vice at any one time dieing down until I barked my knuckles only then lifting the rod higher by the same amount and the thread is spot on all the way down..

It seems as I was cutting the thread, the rod was twisting slightly (even cutting with the die fully opened up)

Take a sweety out of the jar Kleftiwallah
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