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Thread chasing
March 22, 2013
10:20 PM
symesy
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March 14, 2013
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Hey lads, 

 

I was making something today and I decided to turn my first thread as part of the project. 

I have seen and read heaps about it, but not many people talk about thread chasing, tubalcain has mentioned it in his videos, but only briefly. 

Anyway I can't get it to work, and before I blame the lathe I was going to ask here as its probably second nature to you blokes. 

This is my method so far(which isn't working, lol)

Set up for the cut, 29.5deg on the compound. 

First tracing path, engage the halfnut lever at No. 1 on the thread chasing dial. 

Disengage half nut lever, cross feed out, traverse feed back to start.

Checked the pitch and it was spot on. 

First cut, cross feed back to 0. compound in 0.1 engage half nut lever at No. 1. 

This is where I noticed that it was not in line. So I tried a few more times, just with tracing paths on other stock and it won't line up when engaging at the same number, I haven't changed speed or anything, didn't even stop the machine once and it was off. 

 

What am I doing wrong? 

 

Sorry to bother you guys with this beginner stuff. 

 

Cheers, 

Symesy

 

 

 

March 22, 2013
11:00 PM
symesy
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OK so curiosity got the better of me. 

I remembered watching a review of a lathe and it had the wrong gear on the thread chasing dial, so I wondered if mine was the same. 

I decided to cut another thread and engage the half nut lever before or after the number I was on last time, and I fluked it. 

First cut I engaged on 6, second on 5, third on 4 etc and it worked! But I lost count somewhere and ruined it, haha. 

 

Anyway looks like I have to find another gear with the correct amount of teeth. 

 

Cheers, 

Symesy

March 23, 2013
5:29 AM
hucketn
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This problem depends on a lot of things. We need more info to sudgest fixes. What lathe are you using? Does it have an imperial or metric lead screw? What thread are you trying to cut? Metric or imperial?

 

Chuck

March 23, 2013
11:39 AM
Tyler
Seattle, WA
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Don't feel bad. I had the exact same problem.

On my G0602 I can't disengage the half nut when cutting a metric thread. If I do I can never pickup the thread in the right spot, even if I always engage the half nut on the same number. So I have to stop the spindle at the end of the threading procedure (before the threading tool collides with the shoulder if there is one), back the tool away to give clearance, and then reverse the spindle to the starting position. All the while keeping the half nut engaged.

With imperial threads I can use the thread dial just fine.

NOTE: I'm a single dad working two full-time jobs as a web developer and college instructor.  So if it takes me a few days to respond please don't take it personally. If it's urgent please send me a Private Message.

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March 24, 2013
1:51 AM
symesy
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The lathe is a Hafco AL320-G. How can I measure the lead screw to determine if its metric or imperial? I was trying to cut a 1.25mm pitch 8mm metric thread. Ill try and cut an imperial tomorrow see if its any better. 

 

Ill have to give that a go too tyler, wasnt keen to try as it is up to a shoulder and its a little tight, haha. 

 

Thanks for the help guys! 

March 30, 2013
11:24 PM
Tyler
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You can always stop the spindle early and manually turn the spindle the last rotation or two so that you don't hit the shoulder. that's what I do.

You probably don't have a thread gage suitable for the type of threads on your lead screw. Instead you can use a caliper to see how many threads per inch. If its a wonky number see if it comes out to an even number per millimeter.

NOTE: I'm a single dad working two full-time jobs as a web developer and college instructor.  So if it takes me a few days to respond please don't take it personally. If it's urgent please send me a Private Message.

TIPS:

  • Remember to subscribe to your posts so that you'll receive an e-mail update whenever a member replies.
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  • If you are having trouble viewing the forum posts, consider trying a different browser like Firefox or Chrome.
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