[GreenKeys] [External] Re: BRPE punch blocks

[Jones, Douglas W]

On Jan 24, 2020, at 3:22 PM, John, W9DDD wrote:

> I wondered about that adjustment.  Wouldn't you need to add one on the other side as well?  Going from 5 bit tape to 8 bit tape don't you add one hole on one side of the feed holes and 2 holes on the other?

I've got a "universal" photoelectric paper-tape reader in my junk pile that has a knob you turn to rotate the tape guide to set the 3 tape widths.  The sprocket is always in the same place.  If you use big O for data and little o for sprocket, the 3 tape formats are:
  OOOoOO
  OOOoOOO
  OOOoOOOOO

> However having a example, one could drill and tap some more holes and fabricate another show.

Punch blocks are made of tool steel, hardened and tempered.  You can machine them using tungsten-carbide tooling, but they are impervious to the more common steel tooling.  If you want to machine new holes, the old-school way to do it would be to anneal the block (bring to near red heat, then cool slowly), machine, harden (bring to red heat and quench) then temper (350 degree oven for 30 minutes).  That almost always risks oxidizing the already machined surfaces unless you do the heating in a way that excludes oxygen (for example, do all the heating submerged in a cup of fine refractory powder (fireclay, for example).

		Doug Jones
		jones at cs.uiowa.edu