Don’t even think about getting the lisle set mentioned above without considering the risk of using it. Read from post #13 on in thread I’ve linked to below.
http://www.garagejournal.com/forum/showthread.php?t=7437&page=2

Below is photo of what I use. The fork is made in USA by Old Forge.

I don't think the cheaper ones hit very hard. The better ones have fews BPMs, blows per minute, like 1500 to maybe 2000. The point of the air hammer is to hit it hard and not keep tapping on it.

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