Simple Auto Retract Thread Cutting

[olderdan]

Needing to make new frame to engine studs for my latest motorcycle build (it came with all thread) it is important to me that the threads only go through the fastening and not the parts being fastened. This involves accurate run out when screw cutting without an undercut. I have got pretty good at manual manipulation of the controls over the years but that means threading at much slower speeds than are ideal. To speed things up and to be able to single point thread at at least 350 rpm with no undercut I needed some help so came up with this idea which gives plenty of time to drop the half nuts. I already had a plate along the rear of the bed originally for copy turning from templates, this plate clocks true in both axis to the bed and has two precision ground riser blocks to take a ½ inch round bar or plate templates (It mostly gets used for a DTI) mag base. So with a ground bar and a simple 45 deg collar I have a way for the tool to retract the at the right moment, the slide is disconnected from the feed screw and retracts by the needle roller follower meeting the collar. At the moment thumb pressure on the cross slide is used and works well enough for me and is very fast to use, I have a means for spring pressure or air ram to be used but so far not needed. Depth of cut is by the flank method from the top slide. Obviously when threading to a shoulder I have to resort to the traditional method. I can imagine some chuckles from the CNC guys but this cost me nothing to make.

[dagrizz]

Ask the CNC guys how long it would take to program the threading into the machine, then we'll see who's laughing. BTW, great use of available resources.

[mdhatter3]

That is a truly neat idea. Nice. Very nice !!!👍👍👍👍

[tonyfoale]

Alan,

Very impressive.
Why do you avoid an under cut? As you can imagine I have made many such studs and I always have an undercut.

[tonyfoale]

Ask the CNC guys how long it would take to program the threading into the machine, then we'll see who's laughing. BTW, great use of available resources.

Actually it would not take long at all. There are pre-defined Gcodes for threading but most users would use a wizard with very few inputs needed.

[olderdan]

Alan,

Very impressive.
Why do you avoid an under cut? As you can imagine I have made many such studs and I always have an undercut.

Tony, I understand that a bolt or stud is only as strong as the thread root dia, if I use undercuts I use a radius tool. The reason for not is for originality, I am restoring a 1919 V twin AJS so I am making parts as close to OEM as possible. I bought this machine from an oil worker who brought it back from India and it was in poor shape although mostly complete having been used as a daily hack, the way these people keep things going is incredible. PIC.

Got my work cut out this time!.

[DIYer]

Thanks olderdan! We've added your Auto Retracting Thread Cutting Tool to our Tapping and Threading category,
as well as to your builder page: olderdan's Homemade Tools. Your receipt:

Auto Retracting Thread Cutting Tool by olderdan

tags: lathe, threading

[tonyfoale]

Alan,
Originality, yes I understand that. It has never been part of my own outlook but I understand its importance for tasks such as your current project, which looks to be a huge amount of work. My kids and friends would think that I was ill if I started worrying about originality. Keep us informed as things progress.

[slasher102]

i would like to see a YouTube video of tis in action Well done love it

[wizard69]

i would like to see a YouTube video of tis in action Well done love it

I have to second this! Your description is great and I do understand how it works but videos just make me chuckle. That is a good laugh or smile at a well done project.