How to tell which drill bit & bolt is required?

[Mr. Clueless]

If you take a look at one of my recent threads i'm going to be looking at hanging the gate i put together.
I ordered in a hook & band hinge on the back of advice here. I'm just wondering how to tell what size bits & also coach bolts will be needed.

This is the hinge: http://www.toolstation.com/shop/Iro...sd2947/Hook+&+Band+Black+Cranked+Hinge/p84185 450mm.

So it has the square hole & then 3 circular holes.

I've found a #8 drill bit i have is the biggest that will go through the circular holes, however it'll only go through if i send it through with the end that connects in to the drill first as the end of the drill bit wont go through the holes - literally just the tip will not pass through.


As for the square hole, the largest drill bit i have is labelled up #10 & that easily passes through with room to spare.

If it helps any then the square hole measures 15mm-x-15mm.

I have a spade drill bit that is stamped up #12 & this rotates fine within the hole. The next size up i have is stamped up #16 but this is too large.


On to the coach bolts, i assume with the round holes since pretty much all the #8 drill bit passes through the holes that it'll be an M8 bolt needed?

And then whenever we work out which size bit for the square hole, it'll be the same number for the bolt?

 

[JohnD]

Well this is annoying

I look up "dimensions" for coach and carriage bolts, and the table is unreadable.


By eye, the square is "a bit" bigger than the shaft, so an M12 bolt might have a 15mm square (seems very big)

I don't know if I have any left over to measure.

It might be worth you buying one or two in sizes that seem about right and giving them a try.

Beware, many coach bolts are not fully threaded so can't be cut down much.

BTW I used hex-headed coach screws throughout for the building of my shed and gate, except for the hinges and Brenton bolts. You need washers under the heads or they will sink in when fiercely tightened.

Edit
Found one
http://www.avonstainlessfasteners.c...03-a2-and-a4?zenid=hurq2sgl61qjbe1fnheo5tl1p7

Sizes Available
b = < 125 16 18 22 26 30 38
b = > 200 22 24 28 32 36 44
f max 4.1 4.6 5.6 6.6 8.75 12.9
k max 3.3 3.88 4.88 5.38 6.95 8.95
d1 max 13.55 16.55 20.65 24.65 30.65 38.8

d M5 M6 M8 M10 M12 M16

L (mm)
16

20

Another page is
http://fullerfasteners.com/products/din-603-carriage-bolt/

or

http://www.fasnetdirect.com/refguide/Metcarriagelrg.pdf

includes Across Flats dimensions

 

[Burnerman]

Maybe the three round holes - as they seem to be countersunk - just have a slight burr on the edge which is fighting your drill? Either way it will be the right size as the next size bolt size down is 6mm and that's far too small.
As for the coach bolt hole, use the same - you can always go bigger later on if necessary.
One point to look for - if the pin which the bands hook onto is on the small size, the door will tend to droop......pack the door up with slips of timber and see that the gap at the hinge side is even.
John