hole size for 7/16th suspension bolts

[Discopotatoes]

Any one know what size hole to drill ( need to clear galvanising and powder coat ) does it need a tolerance?

[fausTVR]

7/16" dia equates to 11.11mm, add perhaps 0.3/0.4 for powder coat depending. I'm assuming this is a clearance hole you mean and not the tapping diameter?

[phillpot]

I'd start by popping a 7/16" drill through and see how it goes? you can always drill a bit more out but you can't put it back


I've always drilled holes the same size as the bolt thats going through and never had a problem.

[Discopotatoes]

yes its to clear all the extra material left by the galvanising and powder coat, i shall get a 7/16 bit and an 11.5mm and see how i get on

[Steve_D]

I think you will find it almost impossible to get a drill into most of the positions.

Even if you could I don't think it is advisable. You want to maintain the hole as tight a fit as possible to your new bolts so the best method is as large a round file as will fit and gently clear each hole, or pair of holes, by hand until the bolt just fits.

Steve

[portzi]

Steve_D said:

I think you will find it almost impossible to get a drill into most of the positions.

Even if you could I don't think it is advisable. You want to maintain the hole as tight a fit as possible to your new bolts so the best method is as large a round file as will fit and gently clear each hole, or pair of holes, by hand until the bolt just fits.

Steve

As recommended above. Don't waste all that time and money on galvanised and powdercoat only to chip it off with a drill bit. Nice and slowly with a round file, then finish the edges of the hole with some emery paper to remove any burrs. Better still rub down the area where the washer will sit as the powdercoat will crack underneath anyway and lightly smear some copper slip-on there.