Insert threadingtools

Male thread 1. Turn your bar to the required OD 2. Calculate what pitch and lead are required and how many starts you want. 3. Set the lathe to cut the required lead 4. Using a threading tool touch the work and zero the cross feed 5. Using slow revs begin cutting the threads 6. Use a thread gauge to check that you have the correct lead 7. Continue cutting the thread* 8. When the thread has been finished advance the top slide by the pitch of the thread. So for a 1mm pitch thread the top slide would be advanced 1mm 9. Repeat 5-9 until all the threads have been cut.

So if I had wanted a thread with a lead of 5mm and I wanted 4 starts using the formula P=L/S so P=5/4 Therefore the pitch would be 1.25

Threading insertsize chart

Female thread 1. Bore a hole to the required dimension = OD – pitch 2. Thread the hole using the same steps as for the male thread. Using steps 3-9

Once the part was turned to size, the backgears were set for 2mm threads. The threading tool was offered to the work and zeroed when it just touches. Then I ran the tool with an in-feed of 0.05mm in order to determine if I had the correct settings for threading.

Insert threadingmachine

I next made the nut. As this was just a practical exercise the nut was just made from a scrap bar. The bar was turned to have a bore of 23.5mm. To get that diameter I deducted the pitch (0.5mm) from the OD of the male thread (24mm) resulting in the ID for the nut being 23.5mm.

The finish on the thread isn’t fantastic. I was running the lathe at high rpm. So here are two pictures of the parts mated.

Insert threadingchart

The remaining two threads follow the same pattern of advancing the top slide 0.5mm making the thread then advancing again to make the final thread. It is worth noting that this is done while the top slide is set perpendicular to the cross slide so that as you advance it, the tool moves parallel to the work.

Insert threadingsizes

I wanted a 24 x 0.5 mm thread with a lead of 2mm this will give me a thread with four starts. If you remember that number of starts is equal to the lead divided by the pitch. Use this triangle to help.

* To calculate how much infeed to use multiply the pitch by 0.6134 For example the infeed for a 0.5mm pitch is 0.5 x 0.6134 = 0.3067mm For a 1.5mm pitch we need 1.5 x 0.6134 = 0.9201

I caught the thread indicator on the “1” line and for all of the remaining passes I used this number. I finished this thread and when I was happy with it I advanced the top slide 0.5mm.

I wanted to have a go at doing some multi start threading. This how-to will be in two parts. The first section will be a demonstration of sorts of how I made my thread and the second will be a step by step how-to.