Drilling and tapping M50/S50 oil return...

[jaistanley]

Just a quick one..

I'm at the stage of the S50 swap where I have to prepare the E34 M50 sump. First job is to drill and tap the oil return. I have a 10.5mm drill bit and the required M12x1.5 tap. My drill chuck is rather pants and it's been a while since I've been in a machine shop. I noticed when making my servo bracket that I've been getting a lot of drill bit chatter and making triangular holes regardless of how many pilot hole stages I go through..

How can I prepare the aluminium for a perfect round drill. I'm going to get a better chuck, clamp the sump down, use some light oil on the drill bit and drill a 2mm then 8mm pilot. Sound OK?

Bit of a basic question from a supposed engineer!

Many thanks.

Jai

[jkarran]

Has the 10.5 been sharpened? I find with re-sharpened bits unless I grind them perfectly symetrical they tend to chatter especially with big drills in thin material.

Check the table is level on your drill, my crappy B&Q £10 'bargain' doesn't stay level for long.

If the drill cutting edges are good then your plan sounds ok to me, I'm assuming since you plan to tap it the material is at least 5mm thick so it should drill better than a thin servo mount anyway.
jk

[jaistanley]

It's a nice new HSS bit. Unfortunately I don't have a pillar drill...

I'm drilling the aluminium sump from an M50 (from an E34) so it should be about 5mm thick. Luckily it doesn't need to be torqued particularly high, worse comes to the worst I can always bond it in with some chemical metal I suppose.

Many thanks..

Jai

[DanThe]

Drill slowly and square on. 5mm pilot then straight to 10.5