[Closed] machining 15mm thru axle hub caps down to fit 12mm spec thru axle?

I have a 29er wheel which has a 15mm thru axle.  I purchased the 12mm sleeve and thought it would just drop straight into my spec diverge fork.  Unfortunately, the 15mm end caps have an outer diam of 21mm whilst  the OD of the 12mm end caps is 19mm.

The hub in question is a SP Dynamo, which annoyingly does not have switchable end caps like a DT Swiss hub does.

Anyone had a similar issue which does not resolve building another wheel?