They do it before hardening the axle.

I was waiting for that.

Offseason here is both cruel and entertaining.

Make sure you heat treat those.

Because I dont have one in my junk box.

Unless the spindle is marked cro-mo or something to that effect, it's possible that it's just case hardened and made out of a lower quality steel.

A lot of Japanese spindles were made that way, especially Sugino Maxi style spindles with end nuts instead of bolts. The dark areas on these hardness test specimens show the depth of the case hardened surfaces which range from ~.005" (0.127mm) to ~.050" (1.27mm) deep.



They're about 60 Rc on the surface while the center can be a lot softer.


The size of through holes in BB spindles is ~7mm. The spindle is probably 110mm - 116mm long. The hole depth is 16 to 16.5 times the drill diameter deep.

Standard style drills going that deep tend to wander off center so the drill could come out the other side as much as 2mm off the center line, weakening one side of the spindle. Also removing chips from a hole becomes a problem.

There's a possibility that the drill can grab and break too.

Back in the 1970's most bicycle components were machined on old low tech equipment. Older and/or less expensive spindles were drilled from both sides leaving a mismatch in the middle.

High quality spindles were/are machined on modern CNC equipment with high performance drills.


Here's a neat example, this is a 9/16" (14.27mm) high performance carbide drill going 4.5" (114mm) deep in 28Rc 4140 alloy steel.

Total drilling time 6 second! When this video was made that drill had already done 3500 holes!

https://www.youtube.com/watch?v=-E4te5stFmg

PS. I'm involved with these products.


My recommendation is get a hollow axle that fits your BB if that's important to you. You'll be hours ahead and not have to be concerned about spindle breakage... (think Fignon)

But... who am I to discourage someone from experiencing the pleasure of working with your hands. I still like to fix or modify bike goodies. When possible safety issues are a stake, that's when I butt in with my 2 centimes worth...

verktyg

Chas.

It's '88 Shimano Cro-Mo. Interesting info on case hardening. Thanx, I'm learning about metals.

both unsafe and gross?

B^)

To keep the crank-bolt holes centered, drill only 1/2-way from each end.

Also most of the load is on the skin of a tube. You don't lose much strength or rigidity when it's hollow.

That's why stiffness goes up by the 4th power of diameter.

To quote a legend:

the drilling is done for function and weight reduction. if drilling is slightly off a rider would never be ble to feel it. you ride a bike with your legs, not your eyes. noone has ever won a Tour De France using their eyes. this is not for old men trying to create a museum type bike that they always wanted. this is for a person to need to reduce weight and to be FAST!

This crankset is not for the older man who is trying to recreate something ORIGINAL that he always wanted and say "i finally got it after 4 decades!". this is for the person who is actually riding and getting a good deal on a very good crankset."DONT BE AFRAID TO STEP OUT OF THE BOX!" If you fall down and break your hip it just means your rode to the very end of your life! That is called passion!! and you have Obama care! THE WEIGHT IS VERY CLOSE TO SUPER RECORD 11. I KNOW MANY BABY BOOMERS MAY NOT HAVE NOT HAVE THE PRIVILEGE TO OWN SUPER RECORD 11. BUT THE WEIGHT IS VERY CLOSE. AT ONLY 10% OF THE COST! THIS IS A DEAL! YOUR WHITE HAIRED WIFE WON'T GET ON YOU FOR SPENDING TOO MUCH! EVERYONE IS HAPPY! ask her for permission to bid.

I have a cheapo 3p nutted spindle that I stripped the threads (applied the crank arm extractor somehow with the nut still on - Doh!)

And in my best money saving mode was musing every time I see it in the bin if it is possible to maybe have it drilled to convert it to a bolt - guess not!

Thanks all!

I wouldn't think that a spindle would be hard all the way through. The surface needs to be hard for bearings but hard also becomes brittle and the constant slight flexing that a crank spindle would see would certainly cause failures often. Case hardening on shafting gives the best of both, wear resistance on the surface and the toughness of being "strong enough to bend".

Are you talking about a standard square taper spindle?

HA!

May I quote you?

If I had to hazard a guess, OldsCool, I'll bet boring the through bore was the first operation that the machinists at Campy did on those parts. Before turning the profile in between centers. To try to do it after the fact will be very difficult, I would think. How would it be held? Maybe in the center of the shaft in a four jaw chuck. Only a project for the seriously bored or the whacky, in my view.

Evidently you have much more experience than I on this, but the spindle is already drilled for the bolts, about 15mm each side, so if it's a 110 actual hole depth is 80mm, 40mm from each side. That doesn't look too much.

You really oughta have those laminated too. :€

Someone get this man a hollow spindle...please.
Before he hurts himself.....

I think a well lubricated and cooled carbide drill bit from both ends would make short work of this. As far as strength is concerned, if you're not embiggening the tap drill hole diameter then it should be as strong as the original section which has a larger effective unsupported bore. Make an aluminum split bushing to hold the center section if you need to. A carbide bit is not going to be too cheap though.

My thoughts exactly. There is a lot of beef outside of that thread cut diameter. When first handling the spindle it felt more like a railroad spike than a bike part.

Yes, please! From time to time, you are hearby annointed as my voice of reason, and can stop me from doing something stoopid.

I think it is OK to line bore out a CrMo spindle, if you can do it. IIRC, two of my BB'S have hollow CrMo spindles (one Bador and one Edco), and they have not given me any problems....but then I am no TDF Pro rider either....

Maybe it time to take up another hobby.......

A lot of repliers (replicants?)got bits of this right. I am a trained professional machinist and here is what I think. Once you get past the case hardening you get to the soft, chewy center and you can buzz away with a HSS drill. Carbide is not required here. Carbide drills are expensive and brittle. Since you are drilling through the tapped hole you would likely be away from the hardened area anyway. I would do this with an electric drill in a vise! Drill half way from each side.

So how many weenie points might one get with doing this???
20 to 30 some grams, maybe?? Plus possibly a few broken drill bits along the way....
Mehhh..... just find a BB that has one already..... apparently they are not that rare, as I found out....

You're probably right about not needing a carbide bit, but you never know how tough these grades of hardenable steels are. Alternatively, I would not expect the case hardening to be anywhere near the tapped hole bore. FWIW, I am an engineer with over 30 years working with steels, mostly surgical stuff, though. I've worked on lines using carbide tipped gun drills for boring titanium about this size.

All 3 of my main bikes have hollow spindles. But again, I am curious and a bit of a weight weeny.

Not likely.