[jman4747]

Originally Posted by GeeTwo

I can't see the picture, so it's hard to be specific.

If the block is made of steel or another hard metal, and you have five threads engaged, you're getting as much holding power by tapping as you would by using a through bolt. Your block is 1/2" thick, so if you're using 1/4-20 bolts, the bolts would touch when each engaged 5 threads; this would not be optimal. If you're using finer thread bolts, it would just be a matter of trimming the bolts to the right length: no less than 5 threads engage, but less than 1/4" will enter the block. If using an aluminum block, definitely go with the through bolt.

That's what we don't know.

Are you using 1/4-20, 1/4-28, 10-32, 10-24, 8-32, etc ?

Also to Adams point, if you went with through holes that block could just be a spacer and wouldn't need the extra flanges on the top and bottom with the holes in them.