Bad Lag

I need to mount a gear shift lever to a new handlebar as part of a test. The new handlebar is larger in diameter than the hole in the lever's mounting bracket.

Handlebar diameter = 0.930" (23.6 mm)
Bracket mounting hole = 0.885" diameter (22.5 mm)
Difference = 0.045" diameter (1.1 mm)

I checked my few reamers, nothing is quite the right size.
A 1" diameter drilled hole would be too big.

Should I just grind/abrade/sand until the hole is large enough? If so, do I shim it back down to the original size when I put the original bars back on?

Any ideas would be appreciated.

zze86

I want to know what this project idea is! You can't just say you have a crazy idea and not share it!

I assume you are trying to put trigger shifters onto road bars based on the given dimensions. I also assume you have enough clamp material to grind away. If so, a few folks have used a dremel with drum sander or a OSS drum sander to enlargen the hole. Go slow and check often.

Trigger shifters are cheap enough that I would just replace them or get a cheap set to experiment on.

So wat'cha doin?

Bad Lag

So, you are after the undisclosed IP, whereas I am merely asking for help changing a hole size. Hmmm,...???

Anyone have a method to do what I am asking?

dabac

That's a mod that's fairly frequently done by people of a tinkering inclination.
If the clamp is beefy enough to tolerate the removal of material, the only remaining risk is the skill of the person performing the procedure.
Choice of procedure seem not to be critical, and mainly driven by what tools the tinkerer in question has access too or feel comfortable with.
Today, I have adjustable reamers, so that is what I'd use.
Prior to that, I wrapped sand paper around wooden dowels until desired diameter for smaller adjustments, like turning a 25.4 mm stem into a 26.0 mm stem.
With more material to be removed, I'd start out with a rat tail file, then go to the dowel method for finishing.
Once I stuck a file in a drill press to do the bulk removal.
A drum sander - the biggest you can fit/have available - together with the rotary tool of your choice can certainly work.
"Needs" more skill than the dowel method to create a hole that's tolerably round and aligned.
Shimming back is certainly possible.
Sometimes one can repurpose shims that come with cyclocomputers, front derailers, bells, or other bar mounted paraphernalia.
Sometimes one has to be creative.
Personally, I've never gotten a lasting result with tape, or bits of inner tube and other thigns like that. But some say they have. I prefer sheet metal as long as possible. Or a stiff enough plastic.

wschruba

...A bit stand-offish, don't you think? Most people like to talk a bit more than business.

But anyway, enlarging a hole is not rocket-science. Use an expanding reamer or, as noted, a file, sanding drum, or the poor-man's reamer--a slotted dowel with sandpaper stuck in it--depending on the amount of material to be removed and the desired precision. Some clamps, notably on high-end shifters, will not have enough "meat" left after removing .55mm all around.

u235

I have a great method, you pay me and I'll tell you.

Bad Lag

Thank you, I do think some abrasive method is what I will do. I can mount a mandrel in my drill press and make it progressively larger in diameter until I get the proper fit of the clamp onto the bars - an ersatz, impromptu oscillating spindle sander.

If I like the new bars, I am done. If I go back to the older bars, I will use a "liquid shim" or sheet metal to restore the original (smaller) diameter.

cyclintom

I strongly advise against opening up mounting bracket holes. That is asking to be stranded in the wilderness. Either buy the correct part or do not try this.

fietsbob

there are adjustable cylindrical multi blade reamers ,
but I only used a 1" +, one adjusted out in small increments

to go from a 27.0 ID frame, steel, to fit a 27.2 seat post.

not a /0.875" to 0.930" diameter ,

but the difference radially was 0.1mm ..

you are talking 0.55mm radius difference.. right?

cheap steel drop bars , and expensive ones from Germany,
that separate to fit a Rohloff grip shifter, by the stem,
are 7/8"-.875" /22.2mm.

"GMC" Denali sold with double (sram?)grip shifters, near the stem,
maybe you can find one of those bikes to cannibalize..




...

CliffordK

How expensive of parts are you dealing with?

Personally I wouldn't ream out a hole with the expectation that I would be shimming it back to where it was.

Just acquire a spare part... hopefully the right size, and keep the original for when you wish to go back.

Bad Lag

I removed the shifter and started abrading to open up the hole but stopped almost immediately. I started looking at how much material would be left when finished and recognizing that it is cast aluminum (brittle, full of defects), well,... it's not going to work.

I was only planning a test ride locally, not an adventure on dirt trails.

Perhaps I can rig the hub into a useful single speed mode and do the test ride that way. Perhaps, I can rig a temporary mounting bracket.

Compatible brifters are about $200 and I'm not willing to spend that much (yet). It's just for a test ride.

bbbean 

I read the title to this thread as describing an unpleasant person who was gaining weight.

CliffordK

One thing to note is that many cast bands are supposed to be a tight fit. I had a Campy front Derailleur that appeared as if it was far too large to fit over the tube. But, a little stretching and pressing, and it fit just fine.

On the other hand, circumference = pi*D. So a difference of about 1mm in diameter is equivalent to just over 3mm in circumference, meaning gaps get larger and holding stuff on get harder to fit.

TimothyH

I thought similar, that someone was an a-hole and becoming a bigger a-hole.

Best thread title ever.

Maybe he needs a bigass torque wrench.


-Tim-

Kapusta

Self Evident

Yea, I clicked on the thread just to see what the heck it was about...

Definately click-bait...

Cyclist0108

Don't talk about me like that.

Teamprovicycle

damn its tax paying season already ????

zze86

Ooooooo! Undisclosed IP! Curiouser and curiouser!

1) Rigging 22.2 "gear" shifter for 23.8 bars.
2) Rigging a hub into single speed mode and do the test ride that way
3) "compatible brifters are about $200"

What's he trying folks?!?!

The first two hint at a drop bar setup for an IGH, but the last doesn't match up with this theory.

The second also suggests an IGH but that the actual shifting function doesn't matter too much with for his "testing" so his undisclosed IP may not have nothing to do with the bars or shifters.

"Compatible brifters" suggest a more conventional drivetrain but I don't think this is the case as the op refers to the "shifter" in a singular sense multiple times. *Edit - Oh, I remember which ones the op refers to now. Yes, definitely a IGH on a drop bar I think.*

So I'm leaning towards an IGH setup with road-type bars. I actually have a perfect, cheap and previously disclosed solution that I developed but Enlargening A Hole and all. You're welcome to search for it op

WizardOfBoz

If you have enough beef on the original mounting bracket, I'm guessing that the Dremel with sanding drum (or a sanding drum on a drill press with a locking collar*) would work.

Using a reamer requires some sort of workholding solution. Creating a fixture may be more trouble than just patience and the abrasive wheel.

I DO NOT LIKE EXPANDING REAMERS. I view them as a pox on mankind. Never seen one that holds diameter adequately and is stiff enough for accurate work. But companies sell a lot of them.. Go figure.

Good luck.

clengman

Butt plug. Next question?

raria

Maybe the title refers to the OP?

Asking for help and then telling us not to pry too much?