Choosing the right die

[phantomshtter]

Hello, I'm a novice machist with zero experience threading materials. I have a project here building some 1/20 scale dual rate coilovers and I want to thread the aluminum shock body for a functional ride height adjuster ring. The tubing is 4mm OD x 3mm ID so the threads must be very shallow cut. Is this even gonna be possible? I'm totally clueless as to choosing a die for the job. A link to a die that will work would be wonderful if even possible. Thanks and happy holidays!

 

[DAT510]

A few questions..... Do you know what Thread Dia and Pitch you are looking to cut? Are the treads on the outside of the shock housing for the Treaded Collar and Spring Height Adjustment?

 

[phantomshtter]

A few questions..... Do you know what Thread Dia and Pitch you are looking to cut? Are the treads on the outside of the shock housing for the Treaded Collar and Spring Height Adjustment?

Oh jeez, my bad, I'd want to cut male threads onto the aluminum, not female. So the diameter would be 4mm. I can use a simple piece of styrene plastic tubing that will thread itself over the male threads. As far as pitch I guess .5mm would be good.

 

[Bob Korves]

A standard thread is 4-0.7mm, very common. If the material is that large it would probably be the best idea.

 

[DAT510]

A metric 4mm fine thread with a 0.5mm pitch has a Minor Diameter of 3.387, which would leave a 0.19mm wall or about 0.007", which is getting pretty thin. https://www.newmantools.com/tech/threadmf.htm

The 4mm x 0.7mm pitch has a minor diameter of 3.141mm, which would leave an even thinner wall.
https://www.newmantools.com/tech/threadm.htm

Since you mentioned letting the Styrene "self thread", there's no reason you need to cut the threads to full depth (if you were to cut the threads on a lathe verses using a Thread Die.) If the ID could be smaller than 3mm? Say, 2.5mm, you would have more wall thickness and using a 4mm x 0.5 Die would probably be fine.

 

[phantomshtter]

A metric 4mm fine thread with a 0.5mm pitch has a Minor Diameter of 3.387, which would leave a 0.19mm wall or about 0.007", which is getting pretty thin. https://www.newmantools.com/tech/threadmf.htm

The 4mm x 0.7mm pitch has a minor diameter of 3.141mm, which would leave an even thinner wall.
https://www.newmantools.com/tech/threadm.htm

Since you mentioned letting the Styrene "self thread", there's no reason you need to cut the threads to full depth (if you were to cut the threads on a lathe verses using a Thread Die.) If the ID could be smaller than 3mm? Say, 2.5mm, you would have more wall thickness and using a 4mm x 0.5 Die would probably be fine.

I'm always working with these stupid low tolerances in this hobby. lol These will have to be functional and do some work but they're built for 1:24 - 1:20 scale r/c crawlers, not high speed or high abuse applications when used properly. That said, less than .25 mm wall is just REALLY thin. I might have to see about starting over with a thicker wall tubing. Otherwise just using shims for ride height adjustments. Not a very high cool factor.

 

[RJSakowski]

M4-.5mm is a standard thread which will give you a little more wall thickness if you're cutting a standard profile thread. Since you are making both parts though, you could use a non-standard thread profile. It would require a custom ground tool. Here is an example:

The thread is an M4-.5mm but truncated at the root on a thin wall tube with an O.D of 4mm and I.D. of 3mm. Single point thread on the lathe. The tool profile to cut this thread is shown in red. Minimum wall thickness would be .35mm.
For the mating part, the tap drill size would be 2 x 1.85mm or 3.7mm or slightly larger and the part would be tapped with an off-the-shelf M4-.5mm tap.

 

[Billh50]

You can always make your own size thread since it is a one off of your own design. Many manufacturers have their own threads for things like that.

 

[mikey]

Since you mentioned letting the Styrene "self thread", there's no reason you need to cut the threads to full depth.

This, and this:

You can always make your own size thread since it is a one off of your own design.

There is no reason to use a known nominal thread in this instance. You can make it whatever thread you want on whatever OD you want, to whatever thread depth you want. As long as it allows your styrene tubing to do what you need it to do then you're fine.