[TomB_tx]

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For those who have Asahiflex lenses, using them on K-mount cameras has been difficult. The Asahiflex used an M37 thread mount, smaller than either the Leica M39 or Pentax M42 threaded mounts. Asahi did make an adapter to M42, but they are very scarce now.
A seller on eBay has made some M37 to M42 adapters that seem to work well:
eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices
Mine came today, and as you can see, it works nicely mounting on the K-5:


This adapter goes to M42 thread, so then use an M42 to K-mount adapter as well:

One negative is that the threads are not indexed relative to each other. That means the lens may mount in any orientation, so the focus and fstop index marks will not be on top when mounted.

[Trapezoid645]

One negative is that the threads are not indexed relative to each other. That means the lens may mount in any orientation, so the focus and fstop index marks will not be on top when mounted.

Appears, it depends on luck. Tak 135mm f3.5 (all silver M37) is spot on, on the top. It doesn't matter much anyway, since the focusing throw is over 360 on that lens (6ft - ~). But the price for this adapter is very nice and more importantly, the lens keeps INFINITY focus!