Have you ever wondered what a Shimano Hollowtech crank looks like cut in half?

Over the weekend, to satisfy my curiosity, I cut a Shimano Hollowtech crank in half. This is what it looks like (please excuse my lack of skill with a hacksaw):
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Shimano XT Hollowtech II Crank[/url] by eddkh[/url], on Flickr

For reference it is a Shimano Deore XT M760 non-drive side crank, 170mm long. If anyone desperately wants it I could send it for the cost of postage.

Interesting.
I want to know how they make them now.

Interesting.
I want to know how they make them now.

They get Edd to post them to them, and sugru them together. Et voila…!

DrP

Looks like a tube that’s been squashed flat, and if you look at the tip of the pedal end there’s a line in the metal that could be the join*

* Looking at my cranks, not the photo

Was it knackered? I’ve been after a 170mm NDS XT crank arm for a while 🙁

MidlandTrailquestsGraham – Member
Interesting.
I want to know how they make them now.

I think that oldnick has it. I believe that they are cold forged in a multi stage process from an aluminium tube. Then machined to produce the splines, pedal threads etc.

woody2000 – I had stuffed the pedal threads and, rather than using a HeliCoil, I replaced it with this: (Granted it looks a bit weird with one side XT and the other SLX but it works.)
http://www.chainreactioncycles.com/Models.aspx?ModelID=41814

Some of them are tubes forged around a core that’s then removed and the end squished flat. Others are hydroformed and have a little hole somewhere to let water out. From my memory of some cutaway ones Shimano had on a stand at a show…

Nice. I’d be tempted to sand that down to s smooth finish & hang it in the garage. Might take a while though…!

How ‘flat’ is the cut or is it wibbly wobbly?!

I might be interested in it, if no one else wants it?!

I reckon it’s worth polishing up the cut faces and getting some close up shots, I want to see the grain structure and if there’s any indication of how the material behaved when formed in different areas, it’s a pretty complex form for forging .

I’ve got a pair of 170mm hones with a frigged Driveside pedal thread I think, I was also going ot look at helicoiling that, but now I’m tempted to cut up the driveside arm for a look… Hmmm.

Anyone want the Non-drive arm if I do chop it up?

Do you have any XTRs you can cut in half?

I’d like to see how they differ.

Could be that its inflated in a semi-solid state – in the same way that some turbine blades are made?

stumpy01 – Member
…
How ‘flat’ is the cut or is it wibbly wobbly?!

I cut from each end so where I “met” in the middle isn’t that pretty.

cookeaa – Member
I reckon it’s worth polishing up the cut faces and getting some close up shots, I want to see the grain structure and if there’s any indication of how the material behaved when formed in different areas, it’s a pretty complex form for forging.

You’re welcome to have a go (and I would be very interested to see the results) but I’ll leave it for someone else to do.

beefheart – Member
Do you have any XTRs you can cut in half?

I’m not made of money. 😉

In a similar vein, I took apart an old brake caliper the other day to see what was inside. I was quite surprised how little there was to it…

Was it knackered? I’ve been after a 170mm
NDS XT crank arm for a while

Think I may have one knocking about!

IIRC some of the Hollowtech cranks were made by welding a plate onto the back of the forging – though I understand they’ve used a variety of different methods.

@twohats – if you have one, drop me an email. It’s this generation (760) I’m after 🙂

Perthmtb – which areas did you actually cut on that caliper ?

Nothing cut, its a two piece caliper, just dis-assembled. In fact its back together now as a spare.

The caliper is just bolted together isnt it?

So you were expecting more from XTR – More branding and more money is all you get

Anyone want the Non-drive arm if I do chop it up?

Can I have the outside half – Mine is all scuffed

Actually its an SLX, the XTR caliper is a single piece.

Wow even less bits!!

its a two piece caliper

I thought as much when I inspected my XT, though I suspected they’d use some sort of ‘weld’ to stop folk having a prod about.

Thanks for clarifying…

@woody2000, aye that’s what I’ve got, need to double check when I get home later.

I thought as much when I inspected my XT, though I suspected they’d use some sort of ‘weld’ to stop folk having a prod about.

Thanks for clarifying…

If your XT is the M785 then the caliper is identical to the SLX above (except painted a different colour and with those magic letters ‘XT’). There’s nothing other than two bolts holding the two halves together. The long bolt in the picture goes through the top hole (in the top picture), and the banjo bolt which attaches the hose to the caliper goes through the bottom one. The banjo bolt has the ‘O’ ring pictured to seal the two halves (note the recess for it), but the top one doesn’t even need that as there’s no oil around it.

Very simple to take apart, just make sure you force the pistons out as far as you can while its still attached to the lever, as they’re a bu@@er to get out otherwise (learnt the hard way 😳 ) Re-assembly is even easier, but needs a good bleed to get air out of the small oil passages drilled through the caliper body (see bottom picture – the passage on the left goes to the bleed nipple, and the one on the right to the banjo bolt).

Thanks, man. Good shout on the piston, too.

wowsers! so that’s why they call it Hollowtech 😉

ndthornton – Member
Wow even less bits!!

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Could have saved you the trouble:

Legs of iron, me.