[nowwhat]

I am cutting a 2 3/4"-6 acme thread on a hyundai hit 30s lathe and need to know how to blunt the first and last thread at 45 deg. from root to crest.

[WOLOG]

I do this all of the time on my Haas SL-30 BB. I use a grooving tool such as an Iscar Pentacut. You can do it a couple of ways. But the whole idea is to split the thread lead. Your start position for your thread clip should be half of your thread pitch. Meaning that if your Z start is Z.250, add .083" to your start position. this should put you in the middle of your thread. The rpms and the machine's rapid speed will change the type of clip you will get. Then all you do is run another threading cycle to clip the thread. Make sure you change your z length so that is just long enough to clip the thread. To get a real short clip, you have to lower your rpms a lot. This will mess with your lead though. If you have any problems understanding what I am trying to explain, I can email you a sample program.

To clip the rear thread, it is basiclly the same process.

[JPMach]

Wouldn't you have to use a upside down tool and run the spindle in reverse to do the rear thread so that the tool started in the groove at the end of the thread?

JP

[WOLOG]

I don't normally have to clip the rear thread, but that is one way to do it. I have heard of several people that plunge in the rear thread. That way takes some programming, several parts, a box of inserts and maybe a turret realignment. The majority of the time I use a die grinder with a scotchbrite wheel to clean up the rear thread.