03-01-2016, 07:45 AM
Hey Darren,
You can't depend on a dowel hole holding size or shape during heat treat. The normal approach is to ream the hole a thousandth under the finished dimension and then hone it to size after heat treat. All the die shops I've worked at had a Sunnen honing machine, but since you probably don't have one of those laying around, you'll have to lap it to size with some brass rod and lapping compound.
To protect the part from oxidation during heat treat (if you don't have an air tight furnace) wrap it in stainless foil with a piece of paper inside to consume the oxygen. A metal box sealed with fire clay will work as well.
Tom
You can't depend on a dowel hole holding size or shape during heat treat. The normal approach is to ream the hole a thousandth under the finished dimension and then hone it to size after heat treat. All the die shops I've worked at had a Sunnen honing machine, but since you probably don't have one of those laying around, you'll have to lap it to size with some brass rod and lapping compound.
To protect the part from oxidation during heat treat (if you don't have an air tight furnace) wrap it in stainless foil with a piece of paper inside to consume the oxygen. A metal box sealed with fire clay will work as well.
Tom
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