Author Topic: Thread Cutting Tool  (Read 3074 times)

Arbalest

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Thread Cutting Tool
« on: December 30, 2013, 11:38:37 AM »
At what angle from vertical would you need to "tip" a piece of square HSS over (toward the work piece) in order to get a 60 degree cutting angle for thread cutting. And, if you did make a tool to hold the cutter how well is it likely to work?
I'm wondering more about rigidity here not cutting to a shoulder, that's another consideration ...  :thinking:

It's the second picture here that got me thinking.  :naughty:

http://chaski.org/homemachinist/viewtopic.php?f=4&t=89950




Offline IanR

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Re: Thread Cutting Tool
« Reply #1 on: December 30, 2013, 01:34:02 PM »
You would need to have a piece of HSS with an equilateral triangular cross section to get the 60 degrees, so I don't think it's a quick solution.

Offline tangler

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Re: Thread Cutting Tool
« Reply #2 on: December 30, 2013, 02:34:34 PM »
I'm thinking out loud here - If the tip angle is 90 degrees when the tool is vertical and is zero degrees when horizontal then the tip is probably 45 degrees when the the tool is at 45 degrees.  This suggests to me that the tip angle will be 60 degrees when the tool is at 30 degrees to the vertical and 55 degrees when the tool is at 35 degrees.  However, I've never done any solid geometry so the above may merely be a function of the amount of sherry I have consumed.

Cheers  :cheers:

Rod
« Last Edit: December 30, 2013, 03:31:56 PM by tangler »

Offline DaveH

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Re: Thread Cutting Tool
« Reply #3 on: December 30, 2013, 04:16:01 PM »
Arbalest,

Unfortunately the more it is "tipped" the bigger the angle becomes, so it starts at 90deg. and gets bigger so the 60deg is not possible. I understand your thinking but if you sketch it out, it is easier to see.

Rod, you have definitely drank too much sherry  :ROFL:
 :cheers:
DaveH

Offline Hugh Currin

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Re: Thread Cutting Tool
« Reply #4 on: December 30, 2013, 05:01:43 PM »
Arbalest:

You mean to tilt the tool and grind flat? Something like a "diamond" tool holder also for square HSS blanks? If so, I think you need a tilt of 54.7 deg.



Hugh
Hugh

Offline Florian Eberhard

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Re: Thread Cutting Tool
« Reply #5 on: December 30, 2013, 05:21:21 PM »
If so, I think you need a tilt of 54.7 deg.

Seems right, I just got that with a slightly different approach.   :ThumbsUp:

Arbalest

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Re: Thread Cutting Tool
« Reply #6 on: December 30, 2013, 05:30:20 PM »
Arbalest:

You mean to tilt the tool and grind flat? Something like a "diamond" tool holder also for square HSS blanks? If so, I think you need a tilt of 54.7 deg.



Hugh

Yes, that's what I had in mind. Your maths looks a lot better than mine so 54.7 looks like a good starting point to me. Thanks for that! Sadly I'm not sure the setup would be ridgid enough. Still, I may give it a try when my workshop is up and running again in the new year.
« Last Edit: December 30, 2013, 05:39:54 PM by Arbalest »

Offline smfr

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Re: Thread Cutting Tool
« Reply #7 on: December 30, 2013, 05:41:55 PM »
Pretty close to what I got: sin(angle) = sqrt(0.5) / sqrt(1.5) (assuming bar has thickness of 1 unit) = 35.26deg: (90 - 35.26 = 54.74).



Simon

Offline tangler

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Re: Thread Cutting Tool
« Reply #8 on: December 30, 2013, 05:54:12 PM »
Well done chaps, good to see that some brains have survived the Christmas onslaught.

Rod

Arbalest

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Re: Thread Cutting Tool
« Reply #9 on: December 30, 2013, 06:14:00 PM »
Pretty close to what I got: sin(angle) = sqrt(0.5) / sqrt(1.5) (assuming bar has thickness of 1 unit) = 35.26deg: (90 - 35.26 = 54.74).



Simon

Nice graphic Simon!