Front plate -batch rocket- studs

You folks have been excellent help on the last few remaining details before casting this 7" unit.

Perhaps my last question has been asked before, but couldn't locate an answer.

If using a fairly strong front of casting mold plate, (which I am) and (shown in photos) I can easily hold and locate 6 studs or 4, so that a head and some of the bolt are imbedded into the refactory mix. Pretty small in size most likely as the load would not be much on them.  These would be stainless, and only cost slightly more than non-stainless. and could be sticking into the castable 1.5-2" And then when the front mold plate is removed, they would remain in the casting to hold the front plate with door.  

Would expansion and contraction in this area cause the castable to break down around the studs? This end of the batch-box would slightly be cooler than rear end, but enough?  Or a touch of ceramic paper on the bolt before casting?  Or none at all?

That's a very interesting question Scott.  Usually, the door frame is mounted to the outer skin of the stove, be it masonry or cob.  That's not to say that what you propose wouldn't work, but I do agree that expansion and contraction may introduce unwelcome variables.  Mounting a door is one of the areas of construction that lead many to pause and forego building a batch box.  Maybe someone else here has some handy links that help illustrate how mounting a door is done in the traditional fashion?  Maybe we can get some more insight as to your proposed innovation as well?

The main reason that cast cores crack is due to expansion, as different areas will expand at different  rates.
Steel expands far faster that refractory cement so the chances are the areas around the bolts will form cracks.

Making split molds is a lot more time consuming but will reduce the risk considerably.

Have you read about burn out fibres and reinforcing fibres?
Your refractory mix might already have them but it is well worth checking.

Fox James wrote:

Have you read about burn out fibres and reinforcing fibres?
Your refractory mix might already have them but it is well worth checking.

Hello James, I have not read about these fibres, and will try to look this up. thank you.

Burn out fibres are made from low melting temperature nylon, when the refractory is heated they literally burn out leaving tiny channels within the mass. This in turn allows moisture to escape much reducing the risk of cracking, any moisture  can quickly turn to steam, a main cause of cracking.
Reinforcing fibres are made from high temperature material like carbon fibre or fibreglass, they offer stability to any cracks that do form.
Many of the more expensive mixes will contain  these  Ingredients but many others wont.
You can easily add your own.