Thread chasers

[4-6-4]

Greetings chaps. Down at Newport the other day I was handed a job to make a nut for the motion gear on the A2 locomotive. So I have posted a couple of pics on the job. My method of using external chaser is to place a platform on which the chaser is rested. This can be seen under the thread. The chaser is hand held and is allowed to move along the thread. It is only used after the thread has been mostly cut with a single point tool HSS in this case. The thread is 2 1/4 OD 6 TPI which is non standard thread. The second pic is the two chasers I will use The male thread I had to make because the bit the nut goes on is too big for the lathe. But it shows a method for external thread chasers. Hope this can be usefull. Yours 4-6-4

[Steamwhisperer]

Hi 4-6-4,
Can I ask why you used the chasers. Was it to achieve full thread form or is there another reason?

Phil

[4-6-4]

Hello Phil Yes the full form is the main reason but you can titivate the thread by slightly twisting the chaser. The last few thou on the thread are easy to achieve with a chaser. Sadly the hand chaser is a thing of the past. I had to weld an extension on mine so I could hold it firmly. It does need to be held firmly and it also has to be on center height. Yours 4-6-4