The threads are in the jaws not the casting I think, and its likely that the jaws are hardened so you'll be on a hiding to nothing trying to tap new threads
Just coming back to the original post.....
Expect the jaws to be carbon steel - they will tap but only with an HSS tap, not the carbon ones. The cast iron will drill quite well with HSS drills.
On a typical Record vice, the jaws are floating and the threads into the casting are BSW (as they should be). On this one, its anyone's guess but it looks like it's been tampered with previously.
John
It would be far easier to find a decent source of bolts, or carry the jaws and source a bolt to fit.
Re tapping an undamaged thread is a waste of effort
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local