Welcome to Part 2 of the granite plate drill blog. I hope you enjoy.

Offering up the granite enable me to position it correctly and mark the location of the holes to be drilled in the granite. I wasn't looking forward to drill these holes. They had to be 38mm Diameter and 130mm deep so i knew it was going to be a hell of a task with a hand drill.

Taking an initial measurement before bolt down gave me a feel for how far off the maximum peak was off from the bed of the surface plate. I also offered up the other side granite piece and compared the two heights to give me a feel for which side was sitting high. This is useful information to take note of when it comes to beginning the levelling process. It was close on the first side showing only a 0.08mm difference from the front the the back. This was reassuring, but i fully expected this figure to change whenit was torqued up. Obviously bolt position is reliant on accurately drilled holes in granite and the centre alignment of the inserts. Anyway i knew it was pretty close.

I marked up the holes for the first side using silver spray paint blown through the holes. This worked very well. This was the first time i have drilled granite significantly like this and I was nervous again about creating fractures in the base. It quickly became obvious with the base that this is highly unlikely assuming the piece of granite is not floored internally.

It is possible to drill the granite holes relatively quickly. The problem is that it will kill your core drill in a hole or two. Oh yes. i have forgot to cover that part. I chose to use diamond tipped core drills. For these larger holes, I used the ones supplied to me by Odlings. I don't know of the brand. For all the other M8 & M10 inserts i purchased them from Golz (UK) Ltd. They were about £25 each and if i remember correctly I got about 80-100 holes at 16mm diameter and 100mm depth before they were worn out or more likely that one of the teeth snapped off. Highly reccomended from Golz. They make to order and their service is impeccable. On my second order, the drills were delivered and in my hand before i had even received the invoice. Of course I paid immediately for service like that!! To get that sort of life out of a core drill you need to be applying a constant feed of fresh water to keep the bit cool and to clear granite dust.

I created a basic jig for aligning the core drill to ensure that it was within a degree or two squareness. You will struggle to achieve anything better with a hand drill. Especially because you almost instantly become fatigued. God the nightmare flashbacks i am having right now!! If you choose to do the drilling outside and use a hosepipe feed, expect the whole place to be flooded leaving a granite powder sludge that is horrible to clean up. The cost of doing business I suppose. Below is a short video of some of the drilling.

When you are drilling by hand you really cannot see any progress in realtime. It is such a slow process. Later on when there are parts i can drill with a bench drill, the mechanical advantage you get with the depth mechanism enables you to apply more pressure. That said, you can only cut so fast otherwise the hole becomes blocked with dry granite dust. You really need to apply a significant amount of pressue that you feel you can maintain for probably 1 hour per hole.

If you are fortunate enough to leave the core intact for the entire depth of the hole, you will probably be able to break off the centre core in one full piece. I did this my inserting a thin but strong flat head screwdriver into the groove and tilting it until you feel the granite shear off. It is actually quite brittle when it is in this situation. I highly reccomend that you drill you holes at least 3~5mm deeper that you absolutely require to fit the insert inside without it protruding from the surface. The reason for this is that the granite does not tend to shear of directly at the bottom of the hole. As you can see from the collection of hammers and heavy duty screwdrivers and chisels, for some of the holes I had to try and chisel out little end pieces and they can be very reluctant to shear off. It can also be a nightmare the get broken pieces of granite out, especially when drilling vertically down into granite that you can't flip over.

It quite literally took me a full 10 hour day to drill the full 8 holes, and even longer to clean up the mess left behind over the next few days.

Right, I one more part to this section will finish off the job where I cover how i cemented in the inserts and what product i used.

Thats all for now Folks! Keep an eye out for Part 3 coming shortly...

Please take some time to leave us some comments and lets try and get some conversation going,

Continue to Part 3 of the Surface Plate Prep & Drill Blog (Coming Soon!)

THIS BUILD DIARY IS ONLY HOSTED ONLINE BY EMG PRECISION LTD. IT IS A PRIVATE HOBBY PROJECT BY MYSELF, JONATHAN GEE. THIS PROJECT BLOG IS ONLY A DIARY OF EVENTS WITH SOME IDEAS FOR HOW I FELT THE PROCESS WENT WITH SOME TECHNIQUES I FOUND USEFUL. THIS IS NOT AT ALL AN OFFICIAL GUIDE OF HOW TO DO THINGS AND YOU SHOULD SEEK PROFESSIONAL ADVICE FROM COMPETENT PERSONS AND CONDUCT RISK ASSESSMENTS BEFORE UNDERTAKING ANY OF THE TASKS SHOWN IN THIS PROJECT BLOG DIARY.