Thread: Titanium Axles Advice needed

Hi guys,
In the continual pursuit of weight saving on my Superbike I am looking to make some titanium Gr 5 6AL-4V Wheel Axles.
The rear is 25mm OD and front 20mm OD each with a 4mm wall thickness.
Only solid rod is available to use as tube unfortunatley has a wall to thin(2mm)
The length of the rear axle is 360mm with 17MM ID My question is what is the best approach to successfully drill a 17mm hole right through I assume on the lathe but what tooling should be used?
The front will be 300mm long with a 12mm ID again similar approach?
Atm the axles are steel.
Many thanks

Well it goes like this mate Ti is a bear to machine successfully at home it has a nasty habit of galling / work hardening as you muck around with it, in my experience with it in an industrial nature you need CNC machinery appropriate speeds and feeds at high pressure coolant that does not allow the work piece / tool to rub

Ejector drilling either single tube or dual tube is what I required for that depth / diameter combination

I am having some work done for me by this company who may be able to help http://www.metaldrilling.com.au/

Good Luck with it

Bruce

The few small titanium machining jobs I've done, it's been a bit like turning aluminium. It depends on the alloy..

Here is some 20mm outer x 17mm inner, don't know if the grade is what you want however?

http://www.ebay.com.au/itm/1pcs-Tita...item2a3c85b284

Ray

Thanks Ray, I have seen these on ebay, Unfortunatley the wall thickness is too thin and not worth the gamble.
I did have an idea with the 25mm axle of getting two tubes 25x21 and a 22x18 and turning down the 22x18 to fit inside the 25x21 to form an interference fit and be pressed in.

I have made rear engine mount bolts with success. Using 12mm solid rod and drilled a 6mm hole right through for weight reduction from both ends on a 210mm length. Having said that I have noticed that it does work harden when it gets hot. I did go through a few drill bits. I have snapped drill bits in another one i was making, I used colbalt drills and lots of cutting fluid. Unfortunatley it does not disipate heat well at all.
Bruce thanks for the feedback, I will have alook at the website.

I am no expert at bikes. But aren't such bike axles supposed to be precision forged and heat treated before machining? If so, simply boring and turning (leaving away the forging and heat treatment steps) may result in a part too weak for the intended purpose?

I am no expert at bikes. But aren't such bike axles supposed to be precision forged and heat treated before machining? If so, simply boring and turning (leaving away the forging and heat treatment steps) may result in a part too weak for the intended purpose?

Edit: here a link to the various Ti alloys: http://en.wikipedia.org/wiki/Titanium_alloy

I am no expert on metals, however the Gr5 6AL-4V has similar properties to high grade steel. I think a very important thing is that the fit is precision for the wheel bearings with no slop just as the steel axle is. If it needs to be machine down that can be done on the lathe.
Basically I want to copy the exact same dimensions as the steel axle.

Have you heard "titanium" and "notch sensitivity" used in the same sentence?

Here is a link right up your ally...... thought you may already know all of this

https://www.highpowermedia.com/blog/...tener-material

Stuart

Originally Posted by Maxi77

I am no expert on metals, however the Gr5 6AL-4V has similar properties to high grade steel. I think a very important thing is that the fit is precision for the wheel bearings with no slop just as the steel axle is. If it needs to be machine down that can be done on the lathe.
Basically I want to copy the exact same dimensions as the steel axle.

the fact that Gr5 6AL-4V has similar properties to high grade steel is probably irrelevant

one of the things you need to know is: are steel axles turned on a lathe from bar or tube stock, deep drawn or forged ? I would think the one of the latter as deep drawing or forging should give better metallurgical properties and consistency.
Don't confuse machining to clean up a drawing or forging with machining from solid.

Which begs the question of whether a Titanium component should be turned, cast, drawn or forged

I turn steel stub axles for cars without issue, big loads and with sticky tyres too....not used on road though, bearing running on Ti, hmmm, maybe a lifing approach required?? If you do turn them, get a generous radius on any change of section.

When I was (more) dumb, young and full of c.., did have a set made for a MX bike in steel after changing a set of forks, axle had a nasty sharp radius.....still to this day don't remember what happened, but when I finally woke up with a crowd hovering, axle was in two pieces and my magnesium Marzocchis were broken.

I can only speak of my experience over the years as one who has made a lot of custom parts for my bikes and my friends ie never sold anything to anybody or had it engineered, by somebody with letters after there name but

Axles , Swing arm Bolts can in a production / price point situation appear to be forged upset heads etc but rub a file over them and they have the mechanical properties of cheese.

In high stress situations the best material is still 4140 with a nickel flash for plating make use of the high tensile properties of condition T at 13% elongation its strong and stiff take it down to a 4 mm wall in most areas and it will take a million wheelie hits on a front end or feed 60-80 hp through a back wheel of a KTM 1000 cc Adventure bike and take a full head on impact load.

Again its not the part that is the issue its the design and detail i.e. Fisher undercuts at bearing locations appropriate corner radius at transitions and watch the bearing corner radius.

Titanium has its place in the new world order but I question is use in these areas as these are critical in resisting the twisting toque load of a rear end and the impact loads of a set of forks

That's why ever motorcycle workshop manual has the TIR run out specified for axles, there is more weight to be removed from your Hub / Sprocket / Wheel / Brake Caliper which will have more impact on cornering due to reduced gyroscopic effect then remaking an axe out of TI

Good luck with it mate

Thanks Aussie Bruce for the reply,as far as I know the material is forged. I do get its about the grain structure not so much about ultimate strength of the material.
If you seen my bike the attention to detailed weight savings is second to none. I have got it down to 158kg with all fluids minus fuel ready to ride. If you know what a zx7rr weighs standard you will know that is no mean feet!
Gyroscpic effect is one thing and unsprung weight is another. The suspension reacts faster with more control and of course there is less weight to accelerate, brake and steer.
Its all getting very complicated. Obviosly a critcal component that I dont want to get wrong!