Monotype Pneumatics: A new paper tower air supply connector

What with helping to get our daughter’s Hallowe’en costume finished in time, and trying to clean our store for the studio tour coming up this weekend, I have had little time to work on my Monotype. The current tasks are to get the air pins moving freely, and to fix the air leak where the air supply enters the paper tower.

It looks like I will be making my own connector to replace the ball-shaped one currently on the caster, with the replacement part having grooves to hold O-rings to make a proper seal. The top of the pipe rising from the caster table is threaded with a ¼″-32 straight thread—another non-standard combination—so I will probably replace the pipe as well rather than trying to match that thread.

The pipe is ¼″ outside diameter, so I should be able to use ¼″ soft copper tubing to replace it. The connection in the table has a rubber seal and a nut to compress it around the pipe, and I can make the connection of my choice where the pipe meets the connector at the top. I may put an S-bend in the pipe instead of the straight original one, to give allowance for a bit of positional adjustment (by bending) when I install it.

I was planning to use a flared connection from the pipe to the tower connector, but the smallest fitting I could find for ¼″ flare joints converted to ⅛″ male pipe thread. On adding the matching female thread to the drawing of my connector made it clear that there would not be much metal left in some spots, making for a weak part.

So, what I think I will try instead is to make the part out of brass, with a ¼″ diameter hole in the side, where I can solder the copper pipe into place. I don’t have much experience with machining brass so I will have to see how it turns out.

Maybe I’ll have time for it Sunday.

Posted in Equipment Acquisition, Repair, and Maintenance, Kevin, Monotype Composition Caster

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