Small diameter turning tool with 360 degree travelling steady

[thehomeengineer]

Hi All
I made this tool several years ago for making BA threaded stock diameters for my modelling. It doesn't get used that often but I had to make some M1.4 x 0.3mm (0.055" diameter) aluminium studs for a job at work from 2.4mm TIG welding rod. So I thought I would share the tool with the community on HMT.

The tool fits a standard tool-post holder and has a micrometer barrel to finely adjust the HSS tool bit to the desired diameter. Under the tool bit is a grub screw to adjust the centre height of the tool relevant to the brass button. This is important as the brass button needs to be on centre and true so the HSS can be adjusted to lathe centre height. The brass button supports the shaft diameter while the lathe carriage travels along the bed. This brass button gives 360 degree support on the stock material outer diameter allowing the tool to maintain a constant turned diameter. The cutting tool is set to cut the required diameter in one pass to size.

There are commercial available tools which are very expensive without the fine adjustment of the micrometer barrel or the traditional roller box as used on capstan lathes.


Main body in standard tool holder


Selection of buttons with different hole diameters. The 5 buttons to the left are spares which can be drilled to suit the external stock diameter of the bar to be cut. The buttons can be made from other materials to suit the stock being cut.


Back view of tool without button in place


£/32" button in place ready to be set to cut the TIG welding rod


Short test cut to correctly adjust/set HSS tool bit to required finished diameter.


Cutting the Tig welding rod to 1.4mm diameter (0.055")


Checking finished diameter for size.

Thank you for taking the time to view and I hope you have found this of interest.

The Home Engineer

[DIYSwede]

Thank you for taking the time to view and I hope you have found this of interest.

-I most certainly did! Clever design, nicely made and versatile!
Q: -How do you retract the cutting tool? It seems to me that the micrometer screw just pushes the tool into the work.
Aren't there any chances of the threading tool digging itself into the turned piece?

Cheers
Johan

[thehomeengineer]

Hi Johan

Thank you for your comments and interest.

The micrometer screw is only used to set the HSS bit to the correct diameter. As the button can only support the stock diameter. Once the diameter is cut the lathe is stopped and the tool retracted along the Z axis so it doesn't damage/mark the turned diameter.
The HSS tool bit is not a screw/threading tool it is ground as a standard turning tool, purely to make the TIG welding rod the correct diameter to be threaded. The rod is then cut to the desired length and a split die used to cut the thread on one end of the rod in this case.

I did design and make a retracting one for a college HNC project (many years ago) using the same method 360 degree travelling steady for screw-cutting small diameters. I will post over the weekend so you can view it.

It is a lot more complicated than this one as you have to be able to, not only retract the tool, but also advance it to put the next cut on while still maintaining the brass button position at centre height and reliant to the main spindle. Once setup it works a treat.

Many thanks again
The Home Engineer

[Frank S]

And I thought I had problems the time I prototyped a 3mm x 5 cm stem for a poppet valve with a 15mm long turned down section in the center to 2.1mm

[thehomeengineer]

Link to roller box that can be used for screw cutting.
Roller Box with adjustable in feed for screw cutting
The Home Engineer

[DIYer]

Thanks thehomeengineer! We've added your Small Diameter Turning Tool to our Machining category,
as well as to your builder page: thehomeengineer's Homemade Tools. Your receipt:

Small Diameter Turning Tool by thehomeengineer

tags: threading, cutting tool

[greenie]

A Box Tool does exactly the same thing, only far less complicated.

[thehomeengineer]

Hi Greenie
Thank you for your interest. I am unsure what a box tool is. I have Google and can only find storage tool boxes when putting box tool in the search engine. I would be very grateful if you could post a link of the box tool so I can understand what a one is.
Many thanks
The Home Engineer

[olderdan]

Hi Greenie
Thank you for your interest. I am unsure what a box tool is. I have Google and can only find storage tool boxes when putting box tool in the search engine. I would be very grateful if you could post a link of the box tool so I can understand what a one is.
Many thanks
The Home Engineer

Commonly known as a roller box, mostly used on turret lathes for batch work.


I think your idea is better suited for the small sizes you need, when I saw your post it occurred to me that it could also house a button die for making studding.
Regards
Alan

[threesixesinarow]

Hi Greenie
Thank you for your interest. I am unsure what a box tool is. I have Google and can only find storage tool boxes when putting box tool in the search engine. I would be very grateful if you could post a link of the box tool so I can understand what a one is.
Many thanks
The Home Engineer

Here’s a small box tool, meant to use in a turret but I sometimes stick it on the carriage in a boring bar holder. Bigger ones can have things like screw adjustable roller supports and retracting cutters.

https://babel.hathitrust.org/cgi/pt?...iew=1up&seq=63

I’m terrible at setting mine and would have a much easier time with a tool with guide bushings like yours. Nice work and thanks for posting it!