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Old 10-11-17, 01:29 PM   #1
Kleftiwallah
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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.
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Old 10-11-17, 03:45 PM   #3
martinpaff
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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.

MP
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Old 10-11-17, 04:01 PM   #4
listerdiesel
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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.

Peter
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Old 11-11-17, 11:15 AM   #5
Kleftiwallah
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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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