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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
Posted to rec.crafts.metalworking
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I apologize - Thread Guessing
Ok... I was kinda judgemental with somebody recently about figuring
out a thread. It bit me in the butt today. I was converting a belt drive Z axis on a CNC router to a direct drive with a helical coupler. I needed to replace the pulley on the ballscrew with a bushing to fit the helical coupler. The pulley was also the nut that puts pressure on the fixed bearings for the lead screw. Being a chinese machine I assumed it was metric, but after fighting with it I don't have a clue what it was. It definitely was not 8x1.25. I didn't have an 8x1 tap and I couldn't find my thread gage. My 5/16 x 24 tap threaded easily into the pulley about 7-8 turns, and then bound up. Got about 6 turns when I double checked with a 5/16 24 bolt. I figured it was just garbage around the set screw holes, so I made a set screw bushing to replace the pulley with a 5/16 24 center taped hole in the middle. It went onto the end of the ball screw about 4-5 turns and then bound up. I knew there wasn't a problem with burrs on my bushing as I triple chased each hole to make sure. The main bore and both set screw holes. Finally just on a whim I whipped out a 5/16 24 die and it went a 7-8 turns onto the end of the ballscrew and started to jam up. Getting a little frustrated I went ahead and ran it down. I can just barely see the tiniest little double ridge under my pocket scope, but its a good solid looking thread. No wrose than what a rolled thread looks like under the magnifier. I haven't a clue what thread it used to be, but its a 5/16 24 now. |
#2
Posted to rec.crafts.metalworking
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I apologize - Thread Guessing
On Tue, 12 Jun 2012 21:12:25 -0700 (PDT), Bob La Londe
wrote: Ok... I was kinda judgemental with somebody recently about figuring out a thread. It bit me in the butt today. I was converting a belt drive Z axis on a CNC router to a direct drive with a helical coupler. I needed to replace the pulley on the ballscrew with a bushing to fit the helical coupler. The pulley was also the nut that puts pressure on the fixed bearings for the lead screw. Being a chinese machine I assumed it was metric, but after fighting with it I don't have a clue what it was. It definitely was not 8x1.25. I didn't have an 8x1 tap and I couldn't find my thread gage. My 5/16 x 24 tap threaded easily into the pulley about 7-8 turns, and then bound up. Got about 6 turns when I double checked with a 5/16 24 bolt. I figured it was just garbage around the set screw holes, so I made a set screw bushing to replace the pulley with a 5/16 24 center taped hole in the middle. It went onto the end of the ball screw about 4-5 turns and then bound up. I knew there wasn't a problem with burrs on my bushing as I triple chased each hole to make sure. The main bore and both set screw holes. Finally just on a whim I whipped out a 5/16 24 die and it went a 7-8 turns onto the end of the ballscrew and started to jam up. Getting a little frustrated I went ahead and ran it down. I can just barely see the tiniest little double ridge under my pocket scope, but its a good solid looking thread. No wrose than what a rolled thread looks like under the magnifier. I haven't a clue what thread it used to be, but its a 5/16 24 now. was it 8mm x 1 mm ? (25.4 TPI) |
#3
Posted to rec.crafts.metalworking
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I apologize - Thread Guessing
"Karl Townsend" wrote in message
... On Tue, 12 Jun 2012 21:12:25 -0700 (PDT), Bob La Londe wrote: Ok... I was kinda judgemental with somebody recently about figuring out a thread. It bit me in the butt today. I was converting a belt drive Z axis on a CNC router to a direct drive with a helical coupler. I needed to replace the pulley on the ballscrew with a bushing to fit the helical coupler. The pulley was also the nut that puts pressure on the fixed bearings for the lead screw. Being a chinese machine I assumed it was metric, but after fighting with it I don't have a clue what it was. It definitely was not 8x1.25. I didn't have an 8x1 tap and I couldn't find my thread gage. My 5/16 x 24 tap threaded easily into the pulley about 7-8 turns, and then bound up. Got about 6 turns when I double checked with a 5/16 24 bolt. I figured it was just garbage around the set screw holes, so I made a set screw bushing to replace the pulley with a 5/16 24 center taped hole in the middle. It went onto the end of the ball screw about 4-5 turns and then bound up. I knew there wasn't a problem with burrs on my bushing as I triple chased each hole to make sure. The main bore and both set screw holes. Finally just on a whim I whipped out a 5/16 24 die and it went a 7-8 turns onto the end of the ballscrew and started to jam up. Getting a little frustrated I went ahead and ran it down. I can just barely see the tiniest little double ridge under my pocket scope, but its a good solid looking thread. No wrose than what a rolled thread looks like under the magnifier. I haven't a clue what thread it used to be, but its a 5/16 24 now. was it 8mm x 1 mm ? (25.4 TPI) Most likely. When the die and tap and bolt all thread on so far I guessed, and was wrong. LOL. It 5/16 24 now. |
#4
Posted to rec.crafts.metalworking
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I apologize - Thread Guessing
I think it's easier, particularly these days, to get tripped up by so many
variations of fine threads since there are so many in use. Machine parts ain't what they used to be.. now that there are often a mix of metric and inch fasteners, very commonly, it seems. It's not too difficult to distinguish 1/4, 5/16 and 3/8 coarse threads from 6, 8 and 10mm threads by eye and fine threads of each are a matter of recognizing the proportion between diameter and pitch.. but when the threads start getting finer, such as on machine parts, assumptions and guesses are more likely to lead to rework. Jumping around from general hardware to optics and electronic parts threads can get complicated. In addition to machine-formed threads, there are numerous applications where threaded parts are diecast, leading to more visual examples. Gilda - Roseanne Roseannadanna had it right.. -- WB .......... "Bob La Londe" wrote in message ... Ok... I was kinda judgemental with somebody recently about figuring out a thread. It bit me in the butt today. I was converting a belt drive Z axis on a CNC router to a direct drive with a helical coupler. I needed to replace the pulley on the ballscrew with a bushing to fit the helical coupler. The pulley was also the nut that puts pressure on the fixed bearings for the lead screw. Being a chinese machine I assumed it was metric, but after fighting with it I don't have a clue what it was. It definitely was not 8x1.25. I didn't have an 8x1 tap and I couldn't find my thread gage. My 5/16 x 24 tap threaded easily into the pulley about 7-8 turns, and then bound up. Got about 6 turns when I double checked with a 5/16 24 bolt. I figured it was just garbage around the set screw holes, so I made a set screw bushing to replace the pulley with a 5/16 24 center taped hole in the middle. It went onto the end of the ball screw about 4-5 turns and then bound up. I knew there wasn't a problem with burrs on my bushing as I triple chased each hole to make sure. The main bore and both set screw holes. Finally just on a whim I whipped out a 5/16 24 die and it went a 7-8 turns onto the end of the ballscrew and started to jam up. Getting a little frustrated I went ahead and ran it down. I can just barely see the tiniest little double ridge under my pocket scope, but its a good solid looking thread. No wrose than what a rolled thread looks like under the magnifier. I haven't a clue what thread it used to be, but its a 5/16 24 now. |
#5
Posted to rec.crafts.metalworking
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I apologize - Thread Guessing
On Wed, 13 Jun 2012 14:02:38 -0400, Wild_Bill wrote:
I think it's easier, particularly these days, to get tripped up by so many variations of fine threads since there are so many in use. Machine parts ain't what they used to be.. now that there are often a mix of metric and inch fasteners, very commonly, it seems. It's not too difficult to distinguish 1/4, 5/16 and 3/8 coarse threads from 6, 8 and 10mm threads by eye and fine threads of each are a matter of recognizing the proportion between diameter and pitch.. but when the threads start getting finer, such as on machine parts, assumptions and guesses are more likely to lead to rework. Jumping around from general hardware to optics and electronic parts threads can get complicated. In addition to machine-formed threads, there are numerous applications where threaded parts are diecast, leading to more visual examples. Standards are nice -- there's so many to choose from. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
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