drilled for lightness...

degrees on

Do your step drilling process then apply a tapered reamer. Make the tapered reamer by chucking a suitably sized piece of silver steel, turn to the desdired taper, then mill it 'in half' so you end up with a 'D' cross section. Harden and temper and use cautiously with loads of coolant at low speed. Do a google on 'D bits' which work and are made the same way.

AWEM

Taper pin reamers, even large ones, have a taper of 1/4" per foot. Perhaps one would be suitable?

Wolfgang

Aust> one of the things I've been making recently is a 20mm steel axle, 124mm > long.

On or around Tue, 24 Oct 2006 13:45:23 +0100, "Andrew Mawson" enlightened us thusly:

now that's a thought. I'd not considered making me own tapered reamer.

presumably one could achieve as good or better results by turning the taper and then making suitable grooves in it? after all, a real bought tapered reamer is only a tapered round thing with (rather specialised) grooves.

now then, to hunt a supplier of 16mm silver steel bar...

loads

reamer.

grooves.

Try:

They go up to 15mm in metric but have Imperial sizes way over that. You'll find a D bit much easier to make than a normal reamer shape unless you have a T&C grinder.

AWEM

And also try J & L

Have a look at the 'browse sale flyers' - 16mm silver steel is in there for £4.06 for a 333mm length.

Peter

Rule of thump: Bore a bar with 50% of its OD to lose 25% of weight and 5% of stiffness.

Nick

On or around Tue, 24 Oct 2006 19:16:40 +0100, Peter Neill enlightened us thusly:

that's a thought - I get tools from them, never really looked at the materials bit.

a length such as that should allow of making a couple of suitable tools - I only have to make a few of these things, maybe up to 4 per month, so I don't need really impressive tooling.

On or around Tue, 24 Oct 2006 22:54:41 +0200, snipped-for-privacy@gmx.de (Nick Müller) enlightened us thusly:

ah, but this is cunning boring, with variable wall thickness... but useful rule of thumb even so.

for them as are curious...

it goes through a hub with 20mm ID ballraces, the hub is about 89mm end-to-end and the axle mounts on one side of a 20mm bore tube 35mm long. Hence the off-set "thick" bit, which lands nicely between the end of the mounting and the inner hub bearing - there's a spacer in there which I may look at getting rid of - technically, it'd be better if the bearing was up against the mounting...

Wouldn't it be as simple to fill a thin wall steel tube, your bearin surface, with a carbon fibre insert, that way you can really los weight but increase stiffness.

Of course the finished unit is sensitive to heat, but the bearing should not generate that much heat, should they?

Robi

-- rss

----------------------------------------------------------------------- rsss's Profile:

this thread:

Just sayd that that you have a ballpark of your weightsavings.

[snipped] You can make the part that is less loaded conical. But to be perfect, not a straight cone, but a parabel. If the distance is half the length or thickness it should be OK. Explanation:

. CenterLine

+-------+-------- | | | . | | | | | -------- < 50% of length | / | | / . | / | +---+------------ . | ^50% of wall thickness

Hope the drawing is clearer than my words. :-))

Nick

On or around Wed, 25 Oct 2006 10:10:05 -0500, rsss enlightened us thusly:

I doubt it, seeing as I'm not set up to play with Carbon Fibre. The current axle deign looks as if it will work OK - made out of better material than BMS it could doubtless be a bit lighter still - I might look into more impressive materials when I have a few more tuits.

no, they shouldn't.

On or around Wed, 25 Oct 2006 17:25:38 +0200, snipped-for-privacy@gmx.de (Nick Müller) enlightened us thusly:

hmmm. I think that's getting a bit technical.

I'm basing this on vehicle practice - typical stub axle has a taper and is larger at the mounting end than at the free end. In this case, the hubs I want to use are on 20mm bearings, so the taper is internal rather than external; I could, in fact, replace the outboard bearing with a different one and have a tapered stub axle, but that seems rather pointless.

That's how I draw it. Look where the CL is. I have left out the mirrored right half of the drawing and the hatching(?). I'm not an ASCI-artist. :-)

Nick