Requesting suggestions on how to accurately locate an offset hole

[mofosheee]

Depends on the equipment you have. I would cut a slot with an endmill. Otherwise, I would put a blob of weld on the steel part and punch a hole with and endmill. No need to make a plug for such a small hole. Use a chunk of aluminum or copper to cover the back of the hole while you're welding. Honestly, I'm having trouble imagining the situation you are trying to solve. If you could add any details...

Aligned and "tig'd" a 0.25" washer where I wanted the hole to be then milled through the washer using a 0.25" endmill.
A broken endmill was inserted through the holes to confirm proper alignment.

How to best fill the void? I'm not the best welder...............
Will a 1/4" aluminum pin inserted in the hole allow me to fill the void with steel tig rod?
You guys bailed me out again. Thank you

 

[Jake M]

I see the hole is done, and quite satisfactorily it appears, so this is for "future projects". Because me, and tacking washers dead nuts on square is a gamble on the best of days......

You're able to confirm the diameter of the holes, and you've confirmed that it fits in a mill or drill press. My preferred way to do this is to take a round "anything" and (depending on hole size), neck down some (not in this case), so that you can get it fit into said drill (or mill). Then on the "part end", grind a flat half way across.
If it's the same diameter as the hole, then when you line up "part of the hole" on one side, the other half is inherently lined up as well.

Perfect? No. But pretty danged close enough as long as you're not flying this thing to the moon.

 

[mofosheee]

How to best fill the void?
thanks again

 

[pdentrem]

Bore the hole over size and sleeve it.