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I've been interested for quite a while in trying some thread milling, and recently bought a tool for this on eBay. Single-point thread mills can cut multiple pitches, and this one can do 13-32 TPI. For finer pitches these tools require a relief angle on the teeth to match the ramp angle.
Since I have a good supply of 5/16" brass rod, I decided to use this for my trial. For the g-code I used the thread-mill "wizard" in CAMBAM. It took a number of tries to sneak up on the proper cutting depth so that a nut would fit. Each tool needs some calibration since the tooth diameter can vary. Here's the video:
[ame]http://www.youtube.com/watch?v=ElbDMZeL4zM&feature=youtu.be[/ame]
Finding the correct feeds and speeds is an interesting exercise. I followed the guide posted here: http://www.harveytool.com/secure/Content/Documents/SF_71000.pdf
Basically you find the SFM recommended for a given material, convert to RPM given the tool's diameter. For the feed, find the chip load per tooth for tbe material, multiply by the number of teeth to find the feed rate. Finally reduce the feed rate by a factor that depends on the threads major diameter.
Although a single thread takes as long or longer than using a die, building a fixture to hold multiple stock can mean making studs less tedious.
Since I have a good supply of 5/16" brass rod, I decided to use this for my trial. For the g-code I used the thread-mill "wizard" in CAMBAM. It took a number of tries to sneak up on the proper cutting depth so that a nut would fit. Each tool needs some calibration since the tooth diameter can vary. Here's the video:
[ame]http://www.youtube.com/watch?v=ElbDMZeL4zM&feature=youtu.be[/ame]
Finding the correct feeds and speeds is an interesting exercise. I followed the guide posted here: http://www.harveytool.com/secure/Content/Documents/SF_71000.pdf
Basically you find the SFM recommended for a given material, convert to RPM given the tool's diameter. For the feed, find the chip load per tooth for tbe material, multiply by the number of teeth to find the feed rate. Finally reduce the feed rate by a factor that depends on the threads major diameter.
Although a single thread takes as long or longer than using a die, building a fixture to hold multiple stock can mean making studs less tedious.
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