Tuesday, February 26, 2019

The Ohto Uni Returning Duet

Here is the latest addition to the collection, the Ohto Piston Sharp SP-5. My birthday present to me :)
ohto piston sharp mechanical pencil

uni returns mechanical pencil

I first read of the Ohto Piston Sharp mechanical pencil in a Reddit post by 2nd_Astronaut. It immediately reminded of my Uni Returns M5-318 pencil. Unfortunately the Uni Returns has not fared well over the years. The elastomer grip is a sticky yucky mess. I have to store it wrapped in aluminium cooking foil to stop it contaminating its neighbours, and would have Kondo'ed the pencil long ago if it weren't for the unique mechanism. Well, after seeing the Piston Sharp I got on the sat-phone to contact 2nd in his space station and now I own another mechanical pencil with a returns mechanism, this time a much higher grade model, one that should last and not require aluminium foil... except of course for my hat which keeps the alien mind-control radio-waves at bay. The SP-5 I now have is metal and plastic, but there is also an SP-10 which is all metal.

So, to explain, the unique thing about this mechanism is that it both advances and retracts the lead via an otherwise normal push top ratchet mechanism. You do a small push or click to advance the lead, and a longer or bigger push or click to retract the lead. The Ohto Piston Sharp has clear markings on the barrel to indicate this - calling them Half Knock and Full Knock.
ohto sp-5 pencil mechanism

Once you understand the concept its not too hard to control the amount you push, and both pencils do have a partial resistance stop at the halfway point that you can feel.

The Uni Returns advances more lead per click than the Ohto Piston Sharp, so the Uni retraction mechanism will retract back 4 click advances worth of lead whilst the Ohto will retract back 3 clicks of lead.

Now, I'm sure this retraction mechanism must be patented by the inventor, so its use by two competing companies raises some questions. Did Ohto make the Returns for Uni? More likely I imagine would be that the inventor works for an OEM/ODM manufacturer which made both the Ohto and the Uni. Or the inventor has licensed both to use the patent. Or...???

The pocket clip attachment on the Piston Sharp is two spot welds to the body. Not particularly awe inspiring or aesthetically pleasing. But still, I am very glad to have added the Piston Sharp to the collection. Thanks 2nd.


Matthias said...

Happy birthday.
The idea of this mechanism is great. It's a shame this isn't available anymore. I wonder why (price, faulty, ...)? Thanks for explaining this to us.

Stefano said...

Happy birthday, Dave!
It's a beautiful present, indeed. When I first saw the Ohto Piston in action (on video), I immediately thought it had a really fascinating mechanism. I also think it's a pity that this retracting mechanism isn't featured anymore.

Anonymous said...

Happy birthday!
Where did you buy your Ohto Piston? I've been looking around for one and most of them are around the $100 mark, is this correct?

popossum said...

Belated birthday wishes, Dave!

There are three OHTO Piston Sharp variants that I'm aware of:
SP-5 500 Yen
SP-10 1000 Yen
SP-15(???) 1500 Yen

I don't know what the official model number of the last one is, but it was a 1500 Yen all metal pencil with an etched grip.
Here is an example: https://imgur.com/JnMqCag


Kiwi-d said...

Thanks for the info popossum.

2nd_astronaut said...

popossum, I didn't realize that the Ohto pencil in your picture link also features this mechanism ... The grip of that pencil is made of a garden hose like plastic and has a quite unique feeling :-)