DIY Paper Tape Punch - Mechanism diagram?

Hugh Pyle hpyle at
Fri May 1 12:20:12 CDT 2020

Tony, maybe your collection can help me answer a puzzle:  which side is
"top"?  By my reading, for 8-level tape,
- ANSI and other US standards have three data bits / index / then five data
- ECMA has five/index/three... :)

On Fri, May 1, 2020 at 12:05 PM Tony Duell via cctalk <cctalk at>

> On Fri, May 1, 2020 at 4:48 PM Anders Nelson via cctalk
> <cctalk at> wrote:
> >
> > Wow, what a response! Really appreciate the docs and first-hand
> experience,
> > this is super helpful.
> I feel very greedy now. Looking arounds I have (not all working, but
> all could be got to work, it's things like drive belts I need to get )
> 3 Facit 4070s and an N4000
> A DEC PC04
> Two Data Dynamics units (1130 and 1183) which are 8-level punches
> 3 Teletype BRPEs
> A Trend Paper Tape Station (GNT 34 punch and Trend HSR500 reader in a
> rack chassis)
> A couple of Teletype Model 33 ASR's
> A Friden Flexowriter with punch/reader
> The punch from a Flexowriter on a rack chassis with its own motor.
> I think there's a couple of bare-chassis solenoid-operated punches
> here too but I would have to hunt for them.
> And that's the 8 level ones. For 5 level (only) I have a Creed 444
> teleprinter and a Booth-Willmott Model 44 Keypunch (totally mechanical
> between the keyboard and the 5 punch pins so not much use for computer
> interfacing).
> >
> > I'm also floored by the complexity of that Roytron punch! Looks like it
> > contains around one hundred separate parts. I'm convinced the punch parts
> > will have to be precision metal so while that's not quite "DIY" it might
> > still be a reasonable bit to CNC, mill or water-jet cut.
> >
> > It also looks like that punch has an escapement mechanism of some sort?
> > Seems like a simple way to keep regular spacing, but if course more parts
> > to buy from McMaster Carr or whatever.
> Some punches fed the tape with a sprocket wheel, one way to drive that
> is a suitably toothed ratchet wheel and drive pawl that moves it one
> tooth per punch cycle. As I said in another message, the Facit 4070
> uses an accurately-machined (right diameter) capstan and pinch roller,
> the capstan moves the tape one chracter spacing for a certain number
> of steps (it _may_ be just one step) of the motor. I have another
> punch unit here which has the crank-and-interposer mechanism to punch
> the holes but has as sprocket with its own stepper motor to feed the
> tape. Different manufacturers did it in different ways.
> >
> > Question: did all tapes have indexing holes separate from the drive
> Eh? The sprocket holes _are_ the indexing holes, surely?
> > sprocket holes? Also is there a source for tape with sprocket holes
> anymore?
> Every punch I've seen (and own) can punch the sprocket holes on
> totally blank tape. Some insist on doing it (there's no way to punch a
> character without a sprocket hole), for others the sprocket punch is
> just another pin operated by the same type of mechanism as the data
> punches and you have to fire the solenoid at the right time if you
> want a sprocket hole.
> -tony

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