- Joined
- Oct 19, 2020
- Messages
- 158
Well, I've given up for the day on cutting my first threads on my South Bend 10K. My objective was a 1/4 20 thread in a piece of brass stock. I took my OD down to 1/4 inch and set my lead screw speed.
![IMG_3016.JPG IMG_3016.JPG](https://www.hobby-machinist.com/data/attachments/314/314742-f04506cee3c6497c90a1e202a8a5022a.jpg)
I put my drive into back gears and set the RPM to about 150.
![IMG_3015.JPG IMG_3015.JPG](https://www.hobby-machinist.com/data/attachments/314/314743-d99b7aa3825c106ad82666a62f9b8632.jpg)
My compound was at 29 1/2 degrees. My tool is ground to 60 degrees. My first pass looked OK and measured 20 threads per inch as expected. But after several passes of about 5 thousandths, I kept coming up with a mess that looked like this.
![IMG_3017.JPG IMG_3017.JPG](https://www.hobby-machinist.com/data/attachments/314/314744-9379269270075d5e1d05b82125c14841.jpg)
The threads were rough and read at 40 TPI, not 20. I tried to engage my half nut on any of the 8 lines on my thread gauge since it was an even number of threads.
![IMG_3018.JPG IMG_3018.JPG](https://www.hobby-machinist.com/data/attachments/314/314745-d4e38174c7fcc3733942683f8475f5b2.jpg)
I did notice that my gauge does not allow me to engage exactly when the lines are on the mark. I can go a little before or a little after. Maybe that is where where I am making my mistake. The next time I can try always going a little before the mark. Does anyone know if I can adjust the threading gauge to engage closer to the mark?
Anyway, any advice is appreciated.
![IMG_3016.JPG IMG_3016.JPG](https://www.hobby-machinist.com/data/attachments/314/314742-f04506cee3c6497c90a1e202a8a5022a.jpg)
I put my drive into back gears and set the RPM to about 150.
![IMG_3015.JPG IMG_3015.JPG](https://www.hobby-machinist.com/data/attachments/314/314743-d99b7aa3825c106ad82666a62f9b8632.jpg)
My compound was at 29 1/2 degrees. My tool is ground to 60 degrees. My first pass looked OK and measured 20 threads per inch as expected. But after several passes of about 5 thousandths, I kept coming up with a mess that looked like this.
![IMG_3017.JPG IMG_3017.JPG](https://www.hobby-machinist.com/data/attachments/314/314744-9379269270075d5e1d05b82125c14841.jpg)
The threads were rough and read at 40 TPI, not 20. I tried to engage my half nut on any of the 8 lines on my thread gauge since it was an even number of threads.
![IMG_3018.JPG IMG_3018.JPG](https://www.hobby-machinist.com/data/attachments/314/314745-d4e38174c7fcc3733942683f8475f5b2.jpg)
I did notice that my gauge does not allow me to engage exactly when the lines are on the mark. I can go a little before or a little after. Maybe that is where where I am making my mistake. The next time I can try always going a little before the mark. Does anyone know if I can adjust the threading gauge to engage closer to the mark?
Anyway, any advice is appreciated.