Really small tooling? Help!

[Chris64]

I'm trying to make a part for an RC car. I know this could go in the RC section but it's more related to tooling. The shocks are for the new losi micro-t which is a 1/36 scale full suspension race truck. The suspension is very good but has no dampening at all. I have a basic idea of what I want to build but it will involve threading the outside of a tube and the inside of a cap. It will also involve cutting some little grooves where c-clips could be attached.

I have a CNC but not a lathe. I figured I could thread it with a circle motion around the perimeter (and inside the cap) but where can I find a tool that small for cutting a thread. Maybe a dremel bit?

Also, any idea's on where I can find small sized o-rings and e/c-clips?

The tubing will only be about 1/4 in diameter and about 1 inch long.

[snowshovelbmx]

edit** sorry double post.. see below

[snowshovelbmx]

would it be possible to just use a tap and die to make the threads? might make things a lot easier.

[Chris64]

I don't think so. T&D's usually have a fairly gradual cut to them and with the size and space available I would need it to be threaded right up to the end of an inside pocket. I could possible use a Die on the outer sleave but it wouldn't look good and wouldn't leave a smooth surface for the spring to run on (coil-over design). Really I think a need a bit that could cut a thread type pattern but be around 1/8 diameter. Maybe 3/16 max.

[miljnor]

custom tooling man its your only probable source of tooling.

[Mcgyver]

you can get close to the bottom of a blind hole, use a bottoming tap and grind off the end point as much as is necessary. a 1/8 dia internal thread milling tool just doesn't seem practical, if with in one or two threads from a ground down tap isn't good enough (would like to understand why, might help with suggestions), change the design or maybe tap an open ended sleeve, silver solder or loctite into to the blind hole and then turn down. as far as male threads go, if you're not using a die or a lathe are they many other options than thread milling?

[Chris64]

I'll try to draw up a blue print so it's easier to see what I'm thinking.

[Chris64]

OK, here's a pic of what I'm talking about. The outer diamet of the sleeve is about .13" and the inner is .1" so we're talking real small. My machine seems to be pretty precise but I've never tried anything this small before. The gold parts would be e/c-clips, the blue would be teflon or nylon bushings, rubber o-rings. The shaft is still a bit of a mystery. Maybe stainless. Something stronger than alum that can be polished to a mirror shine.

As far as custom tooling goes...any suggestions where to start? I have a normal bench grinder but nothing that I would consider great for sharpening bits.

[snowshovelbmx]

I still say a tap and die might be easiest if youve got them rather than getting custom tooling which may be expensive... use a bottoming tap and run the die backwards so that it will cut a non tapered thread.

[Chris64]

I could try it. But what about the small channel on the shaft side to hold the c-clip in place? I was looking at Dremel tools and even none of those were small enough. I was thinking I could take 1 1/8 2 flute mill bit and just grind it into a t-slot cutter. I'm not sure if the mill would take to grinding though or if it would just explode into pieces.

For the cap I could even just make it a slide on fit with a set screw. Not nearly as easy to create a good seal, but much easier to machine. Maybe if I machined an angled channel for the set screw that would pull it down.

BTW, this is just a standard RC shock design I copied from various cars I've had in the past. Not necessarily my design so I am open to alternate design ideas. It does need to hold oil though.

[widgitmaster]

Necessity IS the mother of invention!
What you need is to learn how to single point a thread on a lathe, then your parts will be exactly as you want them, and look professional too!

A lathe is easy to learn, and most people start out making their own tooling to acomplish their immediate tasks!
If you run a die over tubing, you risk crushing it or distorting it, unless you fill it with a solid bar!

Eric

[NinerSevenTango]

Thinking out of the box, what if you made the tube out of a stainless steel bolt, bored thru, and for the end cap use a brass nut with a copper or brass plate silver soldered over the hole? Even better, you could machine the eye mount out of brass, leave a little pilot nub on the bottom to center it in the nut, and silver solder that on, instead of using a plate. That gets you your male and female threads, real cheap!

For the retainer on the other end, another nut with a plate brazed on, and a hole bored through the plate. Screwed all the way on, it'll function as a stop, that can be removed easier than a retaining clip. Or even fancier, thread thru a longer piece of round stock to go over the end of your shock tube instead of just using a nut. Machine the lip of your shock tube flat. Make another tube out of the same bolt stock as the shock tube, only make it shorter and bore it to guide the shock rod. Make a washer with OD large enough to rest on the end of the shock tube and ID the same as the shock rod guide. Then screw the shock tube and shock rod guide together into your new homemade nut, trapping the washer between the shock tube and the shock rod guide, with a piece of neoprene or teflon trapped in between the washer and the shock rod guide. If you make the washer with the right size hole, then you got your rod seal. Stack 'em up if you want.

A similar trick played at the end of the shock rod gives you your piston and seal.

Should be workable with a little fiddling around, and probably all do-able with tools you have (you'll need a torch, some flux, and some silver solder, though).

--97T--

Edit: Aw heck, I keep thinking up simpler ways to do it. To make it all smooth and professional looking, start with some stainless threaded rod. Then get some round stock, large enough OD to allow you to tap through it. Make the round stock longer than what your threaded rod cylinder bore piece is going to be. Tap it through. Then put your piece of threaded rod into it most of the way, and jam it tight with a nut. Then bore thru the center of the threaded rod; using the round stock to locate it will keep it on center. For the eye mount end, just machine the eye mount out of a piece of the threaded rod, and screw it in until it jams up against the cylinder tube. If you space it just right, it'll look like it was supposed to be that way. Same idea as before for the rod guide end and piston. Use the round stock to locate the rod guide end to keep the hole on center just like above. The shock rod you could make from drill rod, it comes right on size, you can run a die over it, then harden it and polish it up so it'll last. Sound like fun?