machining procedure for gripping pattern

SimonvS · Jun 5, 2017

I would like to hear some ideas on how to machine the knurling like surfaces on the buttons of the camera below. I image machining a planar version of this pattern would be no major problem with a D bit engraver, but the concave curvature of the surface seems to be tricky to machine. :scratchchin:

I expect many ideas on how you would tackle such a quite difficult task.

Minox_Riga_with_Minostigmat_3,5_F=15_lens.jpg

KilrB · Jun 5, 2017

I suspect those were molded.

What do you intend to machine them from?

How many?

The curvature should pose no problem with CAD/CAM and a CNC machine but it's going to be very hard/impossible to get the detail right up to the edge like that.

If your material is conductive, make an electrode and sink it.

JRIowa · Jun 5, 2017

Those are molded parts (plastic). The mold was probably made with a sinker EDM. The electrode is much easier to make than making a part like on the camera.

I've done a few like that years ago with a Volstro head on a BP. If you don't have that, an indexer on a rotary table would work.
JR

L Vanice · Jun 5, 2017

JRIowa said:
Those are molded parts (plastic). The mold was probably made with a sinker EDM. The electrode is much easier to make than making a part like on the camera.

I've done a few like that years ago with a Volstro head on a BP. If you don't have that, an indexer on a rotary table would work.
JR

I don't think the 1938 Minox camera was made of plastic or that sinker EDM was involved. But I never owned one, so I defer to someone with actual first hand knowledge.

I bought the much cheaper Japanese Mamiya Super 16 in 1959. Minox was the original subminiature camera, designed so that everyone could keep a real camera in their pocket, ready for unexpected opportunities to take pictures. Now we have smart phones, fulfilling the same function.

Larry

Milland · Jun 5, 2017

If not molded, could they have been embossed? Master die stamping the surface into the part?

Dan from Oakland · Jun 5, 2017

Male die pressed into a blank prior to finish machining. If the knob is a soft material like 6061 it would work pretty well.

JRIowa · Jun 6, 2017

L Vanice said:
I don't think the 1938 Minox camera was made of plastic or that sinker EDM was involved.

Bakelite has been around since the early 1900s. But, being German, they probably machined an aluminum blank and used a forming tool to "coin" the part. I wasn't around in 1938. I did build a mold in the 80s for an alarm company that had a very similar knurled pattern on it. PITA to polish.
JR

L Vanice · Jun 6, 2017

JRIowa said:
Bakelite has been around since the early 1900s. But, being German, they probably machined an aluminum blank and used a forming tool to "coin" the part. I wasn't around in 1938. I did build a mold in the 80s for an alarm company that had a very similar knurled pattern on it. PITA to polish.
JR

I'll see your 1907 Bakelite and raise you a May 6, 1851 Nelson Goodyear patent for "hard rubber," commonly used to make buttons and other small decorative items.

Minox cameras were first made in Riga, Latvia in the period 1937-1943. The picture in post #1 is of a Riga model and was copied from the Wiki Minox article.
Minox - Wikipedia Two relevant quotes about construction:

"The original Riga-made Minox had a brass chassis covered in a stainless steel shell..."

"After World War II, production of the Minox II began in 1948 at a new company, Minox GmbH, in Giessen/Heuchelheim near Wetzlar, West Germany. The new camera very much resembled the original, but was made with a plastic chassis covered by an aluminum shell. This greatly reduced its weight and, to an extent, cost."

Based upon the above quotes, I think the knurled parts on the Riga Minox were either chrome plated brass or stainless steel.

Larry

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