The Internal Mount of the PN 105mm f/2.8 "A Version&quo

Macro_Cosmos · Post by **Macro_Cosmos** » Thu Apr 04, 2019 6:28 am

The PN105 I purchased was modified to some weird M52 mount in a crude manner.

The seller was less than helpful, saying he doesn't know and refusing to ask the people that does such destruction... I mean adaption.

The M52 was neither x0.75, nor x1, nor SM2, I couldn't figure out what kind of thread depth it is. Don't care what it is. I want to throw this adapter away.

I measured about 48mm, compared the threads to an M38x0.5 adapter. It seems like M48x0.75?

Does anyone have any information? I appreciate the help!

PN105 had its original threading removed, cover cylinder removed, and converted via that crappy cheapo silver mount.

I think it's M48x0.75

Top: M38x0.5
Bottom: The crummy adapter
The thread pitch does look like x0.75 to me.

ray_parkhurst · Post by **ray_parkhurst** » Thu Apr 04, 2019 7:51 am

Only way to be sure is to measure it. Calipers for the thread diameter, and either use a ruler with fine scale for the pitch, or a male threaded adapter of the suspected pitch and see if the threads mate without gaps.

If you need I can check one of mine.

Macro_Cosmos · Post by **Macro_Cosmos** » Thu Apr 04, 2019 9:44 am

ray_parkhurst wrote:Only way to be sure is to measure it. Calipers for the thread diameter, and either use a ruler with fine scale for the pitch, or a male threaded adapter of the suspected pitch and see if the threads mate without gaps.

If you need I can check one of mine.

If you don't mind pulling a bit of metal off, I'd appreciate a check! It's not destructive, the seller told me the metal has been tossed away, way to destroy a lens, oh it focuses to infinity... hilarious...

The 48mm-ish number was obtained from a low quality caliper, my Mitutoyo one ran out of battery, waiting for coin cells to arrive.

Pressing two threads to see a fit is great idea, I just gave that a go. Tried a filter x0.75 pitch adapter with a 52mm opening, pressed it against the threads and attempted to gently "pull" the adapter, couldn't do it. The threads do seem to match, so my M48x0.75 speculation might be accurate. I tried an m542x1 helicoid, a gentle pull makes the tube dismount very easily, heard the typical clunky sound of thread teeth grinding against each other.

I'd say it's safe to assume it's a 48mm x0.75 thread. I would probably get one from Raf before ordering a dedicated tube from a machinist.

ray_parkhurst · Post by **ray_parkhurst** » Thu Apr 04, 2019 12:45 pm

I checked and indeed the threading is M48x0.75.