The objective is to flatten the Welch plug so that it spreads out and jams in the hole:
1. Ensure the block is squeaky clean.
2. Coat the block with Loc-Tite before installing the disk. (Permatex #2 is good too)
3. Use two ball peen hammers - One as a buck to achieve a flat hammer strike and minimize the possibility of striking the block.
4. The edges of an installed plug may be staked to improve retention.
5. Again, the goal should be an installed plug that is visually flat.
6. Use brass Welch plugs if you can find them. They are 1 3/16" diameter.Alternative Solution