This is particularly an issue with smaller type casters such as the Thompson. It seems that there is a basic human urge to walk up to a Thompson and turn the handhweel. Don't do it. If the Thompson is hot and operational, then you'd better be running it (not randomly turning the handwheel of a potentially dangerous machine you don't understand). If the machine is cold, you could break parts.
In most typecasting machines there are situations where if you cycle the machine, by hand or under power, you'll break parts. It's true of pivotal type casters, it's true of the Thompson Type-Caster, and it's true of the Barth. When can you, and when can you not, cycle the machine without damaging it?
(This addresses the safety of the machine, not that of the human operator. That's a different matter altogether.)
A No. 3 1/2 Barth is significantly harder to turn over by hand than a Thompson, so perhaps this isn't as much of an issue for random visitors. But it remains something that the operator of the machine must know.
The answer to the question "can the Barth be turned over by hand without damage to the machine" depends on a matrix of two factors: Whether the pot is in a hot (liquid) or a cold (solid) state, and whether the pot is swung in to operating position or is swung back/out away from the mold. Assuming that the machine is otherwise in good order, the following matrix describes the situations where you may or may not safely cycle the machine by hand or under power:
| Pot Cold/Solid | Pot Hot/Liquid | |
| Pot Swung In | NO | ok |
| Pot Swung Out | ok | ok |
If you do turn the machine over by hand, please note that the direction of rotation of the flywheel is top- away from the operator (that is, counterclockwise when viewed from the left side of the machine).
1. Pot swung in and cold (solid)
In this case, a cam is raising the pump lever against a piston which is frozen in a solid pot. There is no play in this mechanism, and parts could break.
2. Pot swung in and hot (solid)
This is simply state of the machine in normal operation.
3, 4. Pot swung out (back) and either cold (liquid) or hot (solid)
A. The Slide Cam oscillates the Slide and attached levers. All such motion is ok.
B. The Choker Cam just moves a detached Choker Lever slightly up and down. The downward spring pressure on either end of this lever is not strong enough to cause damage.
C. The Matrix Carriage Cam oscillates the Matrix Carriage in and out. All such motion is ok.
D. The Mold Body Piece Cam oscillates the Mold Body Piece up and down. All such motion is ok.
E. The Type Deliver Cam actuates the Type Delivery downward mechanism. All such motion is ok.
F. The Pump Cam barely touches the disengaged Pump Lever. The small motion it does give it against its spring is ok.
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