Ok my step by step guide to fitting my Borden Connector, firstly you need to grind away the old cast borden so I whipped out my 'trusty' dremmel and fitted the smallest sanding drum, I then ground away about 75% of it leaving the last25% to be done by hand, I didnt want to risk sanding into the main part of the cheek
after its all sanded smooth I took a 7mm drill bit and drilled through, but before you go drilling through your helmet its important to make a 'spot' to guide your drill through, otherwise your drill may slip and either hurt you, or hurt your helmet, what I suggest is getting your drill bit and holding it over the center of the area you wish to go through, then apply some pressure and give it a few light twists, this should creat a small spot face where you can later position your drill, you will also find you are less likely to shatter your helmet unlike if you just drive a drill through with a lot of force
Lesson over
Anyway the diameter of the real borden is 9.5 mm so I file out the remainder of the hole by hand, I am not making it a size hole as I just want the borden to sit in the hole, not go all the way through, from what I can tell there is about 2.5mm of borden sticking out on the original helmet, the rest is glued through the helmet. Next step I got some 5 minute epoxy and fixed my borden to an M5 bolt, I held it in place with a small g-clamp until the epoxy had cured (see picture) Next up I reprimed my helmet where I had removed the cast borden and made my hole (see picture) The borden, now attached to the bolt now simply drops into the hole and sits in the slight recess, I then used 2 washers and a nut to secure it from the otherside (see picture) the helmet is now ready for paint and I can remove the borden at anytime during the painting process, hope this is of some benefit to you guys
Big thanks to Gav MojoFett for the real Borden