I have a 15x100mm fork I'd like to use with a 12x100 front wheel.

Does anyone know of a source for an adapter?

A 15 mm through axle will not fit in a 12 mm hole
The other way around might be possible

What hub?

Really? Dang, I missed that in my engineering classes.

I'm thinking of something like a heli-coil insert.

the "adapter" will be the correct 15 x 100 thru axle and matching hub.

the problem is the threads on the thru axle.
and adapter would be a threaded insert, and then a bushing for the lever end of the thru axle...
the threaded insert can not be made since the threads on the outside would cut into the threads on the inside, leaving a mess of metal chips instead of a sleeve.

get a correct 15mm TA axle and hub, bub.

Yes, there is a company that makes adapter inserts for popular forks. I think they are on eBay. Quality stuff.

you seem to have also missed thread depth specifications, and basic math.

instead of engineering.. take Machine Shop Technologies next time.

it covers most of what Mechanical Engineering does, plus it applies the knowledge to real world situations and materials

do you know the thread pitches involved, yet?

heli-coils are great at tensile loads, but terrible for pivotal load resistance... they chisel into softer materials.... and they require an interference fit on the external threads.

It's a Fulcrum Rapid Red Carbon Front Wheel - 700c, 12 x 100mm, Center-Lock Disc, Black.

Try this bunch- they make a variety of adaptors, including, I think, a 15mm fork to 12mm axle adaptor. They're legit - I have an excellent threaded-to-threadless headset adaptor from them

Awesome - exactly what I'm looking for - thank you!

Machine Shop Technologies would be a great course!

Looks like Fulcrum has adapters for what you want to do: https://adapters.fulcrumwheels.com/?id=1

it is... and well worth the effort.

the Rockshox 409 fork i have here uses an insert into a plain bore.... it's a 20mm thru-axle type.
if yours is a similar design, just in 15mm, then an adapter could be used.

and no matter what you find available.. you'll need to know the pitch of any threads involved.... most axles have the pitch on them.
i recall a list of at least 9 "common" pitches for 4 diameters of thru-axles.
that site 13ollochs linked looks promising.
ebay only shows a bunch of "other way" offerings.

personally, i'd still get the correct hub, and do it right.

Do you have me set on ignore?

I flunked industrial engineering so I could take the lab course twice. Okay, actually I slept through an exam. But taking the lab course twice was awesome. Among other treasures, I ended up with two Virginia Tech ashtrays. Those were different days.

I'm glad someone is making those adapters for the fork. I have some 15mm dynohubs I want to use on a 12mm fork, and that's not always possible. I guess I'm going to have to make some endcaps.

https://www.amazon.com/HQPARRTS-Fork...s%2C112&sr=8-1

this might be an option.

Can you knock out the bearings & go this route?
https://www.amazon.com/Corki-Adapter...%2C112&sr=8-23

Some hubs can be switched between 12 and 15mm simply by switching end caps. Don't know about your particular wheels.

I think these can. 🤞