Pile Preparation
A. Concrete Piles:
1) Drill the top hole using 3/8-in bit (Hammer Drill)
2) Remove the drill bit to use Auto Punch - this is the best punch (do NOT use hand-held hammer with Auto Punch).
The old way of using "manual punch" is not as good.
3) Fasten the "Aluminum template". Drill the 2nd hole thru the big circle of this template. Remove the template. Finish drilling the 2nd hole to required hole depth.
Repeat step 2 for 2nd hole.
Note: In USA, bolt is 1/4-in size, coarse thread.
To buy bit + auto punch combo: hilti.com #2112762 for $91
To buy auto punch only: https://www.tcsportcharlotte.com/diabst25-sds-plus-drop-in-anchor-power-setting-tool/ for $16
In this sketch:
"Best" anchor is flushed with pile surface.
"OK" anchor if you accidently drill hole a little bit deep. Still OK because you can use longer bolt.
"Bad" examples: will cause sensors to be bent (and pre-strain them)
B. Steel Pipe Piles
Bit size has to be at least 0.8-mm smaller than threaded tap, so that the thread has enough depth.
USA: tap (thread) size = 1/4-in, then bit size = 7/32-in is good (in USA, bolt is 1/4-in size, coarse thread).
C. Steel H Piles
Bit size has to be larger than bolt size (in USA, bolt is 1/4-in size, then bit = 9/32 or 5/16 or 3/8)
D. Timber Piles
Drill pilot hole (very small pilot bits, such as 1/8-in).
Use lag bolts.
Video:
Video shows to re-punch with a handheld hammer, but re-punch is really NOT necessary. The auto punch is perfect: https://www.youtube.com/watch?v=Abm627_s2Jw