What bolts to use on stove rebuild?

[AlanS]

Vermont Castings Encore....I removed the inner side walls and the upper fireback. Broke some bolts (drilled and re-threaded the holes)... Do I need to get 'special' bolts to replace the old?
They are 1/4- 20, but should I get Stainless Steel? Do they have to be a certain hardness? I have a well stocked hardware store near by, so I will get what you suggest. I see that one of the old bolt heads has three dashes on the head...anything? I want to get this thing together already

 

[WES999]

The dashes on the head indicate the grade or strength of the bolt, 3 hash marks = grade 5
(broken link removed to http://www.unified-eng.com/scitech/bolt/boltmarks.html)

I expect grade 5 should work just fine. You may want to put some never seize on the threads to make removal in the future easier.

 

[Dune]

Three dashs is a grade 5, not the strongest bolt possible, but a hardened bolt nonetheless. Replace your bolts with grade 5 (three marks on the head), or grade 8 (six marks on the heads). Stainless would be a waste of money. Incidentaly, when I have rebuilt old stoves in the past, I used "stove bolts", which are grade 2 (dead soft steel).

 

[Corey]

Why stove bolts of course! You can shell out money for the stronger grade 5 or 8's but the heat from the firebox will temper them all back to grade 2 anyway.

 

[Dune]

Why stove bolts of course! You can shell out money for the stronger grade 5 or 8's but the heat from the firebox will temper them all back to grade 2 anyway.

Not nessasarily. For a hardened bolt to be "tempered all the way back" (anealed), it must be heated to above the critical temperature of the metal (1375F) for low carbon, higher for medium carbon. It is unlikely that all the bolts in a modern stove will ever be exposed to these temps. For the cost of two or three dollars more, it is not worth the risk of re-engineering the stove's construction.

 

[daryl]

Three dashs is a grade 5, not the strongest bolt possible, but a hardened bolt nonetheless. Replace your bolts with grade 5 (three marks on the head), or grade 8 (six marks on the heads). Stainless would be a waste of money. Incidentaly, when I have rebuilt old stoves in the past, I used "stove bolts", which are grade 2 (dead soft steel).

A soft bolt sure makes it easier to drill and re tap because you forgot to put the anti seize on the first time around.

 

[BrotherBart]

Replace them with 304 stainless, the ones in the bin at the hardware store, and put copper based anti-seize compound from the local auto parts store on the the threads before reinstalling them.

Good as it gets.