Drilling hole in HT bolt...help!

[Nick Allen]

We need to drill holes in some high-tensile bolts to take a split pin. One of the syndicate had a go, but so far has only managed to blunt some drills! Any advice on techniques/tools would be appreciated...

[Ken Fern]

Hello Nick

Best thing is the drilling jig sold by LAS part No MT001 and set it up in a pillar drill, with a good 1/16" drill you will have no problems, just take it nice and steady to save snapping the drill. Have used mine for many years no problems. Just a thought the LAS one is for UNF threads but a friend made me a similar one with BA, BSF threads as well.
Hope this helps
Ken

[Nick Allen]

Thanks, Ken. Much appreciated. Nick

[dangerous pete]

Nick,
I had some done by spark erosion, at an engineers on our local industrial estate. Not vey expensive.
Pete.

[Ian Law]

Slowing the drilling speed right down seems to help with hard materials/slightly blunt drills.

There is a sweet "spot"/speed at which the drill appears to bite more willingly - but you may well already know this.

Ian

[Trevor Harvey]

Use a centre drill first to stop the drill wandering, (unless you are already, in which case I apologise)
Use cutting compound (Rocol or similar) Run drill at ~500rpm & take it slowly, don't push too hard.

[Bill McCarthy]

Put a nut on the bolt first in order to get the hole central and in the right place. Drill a pilot hole to make life easier.