Retractable internal screw cutting tool

Retractable internal screw cutting tool
Hi All
Over the last couple of weeks, I have been designing a retractable internal screw cutting tool.
The reason for this post is to judge what interest there would be in purchasing a set of drawings once I have manufactured a prototype to prove the concept. If all goes to plan would like to make the drawing available via the Homemadetools.net. tool plans area. I will be making the prototype over the next few weeks (time permitting) and will keep you update on my progress.
I have designed the tool to be used in conjunction with my Colchester Student 1800 Lathe. But I am sure the drawings could be scaled up or down to suit the individual’s needs. The drawings have been constructed on Auto Cad and I am going to create a diary on the manufacture to support the build with photos and a bill of materials.
The plan, if there is any interest, is to sell the drawing for around $10.
I have posted a G.A. of the concept as a taster, the finished drawings will be fully dimensiond and a boarder and title block will be set.

Attachment 21642

I would appreciate any feedback or comments about selling drawings/plans/designs etc.
Thank you again for taking the time to view.
The Home Engineer

Go for it. I just love new tools especially those I can make my self.

Ralph

Subscribed

Scaleable prints make your project applicable to all. I have a small retracting slide I use occasionally; tight external threads, it's ideal for O-rings, and a few internal threads over the years. I'd use it more often but the size [centerline height] restricts it to larger lathes. It was originally from a toolmaker or small turret lathe, unknown name but likely Rivett, Hardinge, etc., I use it in place of a standard toolpost.

Yours would be a welcome addition.

I'd be very interested to see what you came up with. In fact I was just recently collecting articles & links of this very issue - how to mitigate the nail biting 'fun' of threading towards the headstock towards a raised shoulder or the looming rotating chuck itself. Yes, I know you can invert the tool, reverse the chuck & traversing direction from HS to TS. That involves a few more tooling considerations & only works with cam lock (non-threaded) spindle. Also metric threading on IMP machine means not disengaging the thread lock so this kind of mechanism would be particularly welcome.

I've seen the 'auto flip up' style but just cant get my head around suddenly reversing the motor direction being hard on electronics. I have the book Model Engineers Workshop Manual G.Thomas where such a retracting mechanism is described. It looks quite slick but I think was orientated for the machines (meaning cross slides & tool posts etc.) popular in that day.

I would consider your design even more beneficial if it considered or integrated:

- typical cross slide / dovetail tool post / tool holders found on more current hobby machines

- holding insert threading tool shanks which are becoming quite inexpensive (Asian knockoffs). If it relies on custom HSS bits & pieces, that's not the end of the world, but just one more thing to grind & prepare & properly dress. I'm on uncharted waters here.

- I'm not sure how/if this could be similarly utilized to ID threading operation. I guess it would be a similar issue using a RH tool inside a bore, providing you have overbore allowance. Or else I guess its a LH tool starting in the thread relief traversing out to TS in reverse direction.

Anyway, looking forward to what you come up with!

My experience has been that I always learn things from Mark I prototypes that makes the design of Mark II much better. Ideas don't become designs until they've been been actually reduced to practice and shop or bench tested.

I like the tool. I will what and see.
allenz

I am also interested in the drawings.

Hi All
The drawings have been modified and updated for a third time today, as I keep coming up with improvements (that’s before I have even started to cut any metal) I am sure this will be an ongoing theme. This afternoon I started sawing the material (As I think I am happy with the design?), so after a couple of weeks designing and many years thinking about it, it is now on its way.

It is amazing that you think you have covered every based then BANG a better idea comes in to your head, so you go back to the drawing board (well the computer).

Thank you to all, for the positive response and once finished I am sure there will be further ideas and improvements by you and myself. Is there such a thing as the perfect tool?

The Home Engineer

excerpted

Quote:

---

Originally Posted by thehomeengineer

Hi All
The drawings have been modified and updated for a third time today, as I keep coming up with improvements...sure there will be further ideas and improvements by you and myself. Is there such a thing as the perfect tool? The Home Engineer

---

Sure there is; just hasn't been built yet. There is a related quote; attributed to those who make gunstocks. "In this blank is an ideal rifle stock; you just need to remove the extra wood".
Easier said than done.

Since so few retracting holders have appeared over time, fact you are cutting materials is already significant progress. Hooyah for thehomeengineer!

Looking forward to seeing the completed tool.
Cheers, JR

Material cut and ready for machining. I hope to get it made within the next 3/4 weeks, work and family life permitting.
Attachment 21764
The Home Engineer