We usually would only do a 4mm and then go straight to the 10mm drill bit so your using most of the cutting surface. Go slow with lube and pressure and if the bits are sharp should cut very easily.
Lucky you weren’t drilling stainless
Do you have access to a pedestal drill press? The right drill speed for bit size and the use of cutting fluid is important as you need a nice neat, straight hole so there’s no/minimal slop around thread - even more important if you’re planning to tap a thread...
A quick solution is to make a spacer out of timber. My top plate is a bolt down base for an outdoor umbrella so already had threaded holes. Anker screw bolts can be easily reused, I have taken my pier down a couple of times to repaint etc. and reused the same bolts.
Rick
ive decided to unbolt the pier and take it back to the fabricator. Ill get the 65mm recess deepened and flattened and the azimuth pin hole drilled. I might get a plate welded to reduce the 32 mm recess to end in a central m12 hole, to make mount bolting easier and more secure.
Just flattened the recess a little more with the Dremel. Not perfect but the mount sits stable. Tightened down with some heavy duty square metal M12 washers.
This is what it looks like...thank you all for your help!
Balancing is a PTA and required an additional counter weight. I think the ES102 is probably better mounted on top of the C925....not sure of how that is best achieved.
Last question is how to house this set up: tempted with another Telegizmo 365 due to its simplicity and cheapness. But while restoring the C925 was fun, don’t fancy the risk.
Other options include a rollaway scope shed, DIY obsy (shed etc) or a readymade dome (nexdome, skyshed etc).
I think I’m too lazy to set up and tear down each time anymore, especially when the conditions are so fickle.