Originally Posted by Snowflake
A wire can easily check for hole depth, but it can't easily confirm thread depth.
Didn't say it could but by running bolt in by hand will tell how far threads go. Then check with a tap will confirm it as to take out a small piece of material can be done with little force. That will tell if there is any hole left to tap other wise one could do damage by forcing a tape against the bottom of the hole. Been there done it many times that way during my years as a heavy duty mechanic.
And will add another thing that many don't do, blow the hole out with air as some times they are not cleaned after drilling and tapping, just an FYI for those who have never done this.