drilling alloy...fast or slow

[steveo3002]

i need to drill a 14mm hole in some thick alloy

i have a cheap pillar drill that has a choice of maybe 3 or 4 speeds

should i select a fast or slow speed for the best results?

thanks

 

[Porschemaniac]

I think the recommended speed would be 1350 for 14mm in Ally.

If your drill press won't match that, I guess that I would match it as closely as possible - erring on the slow side if required.

 

[runnach]

14mm is a fair size hole to drill no matter what matl, I'm assuming you'll pilot drill, increasing as you go along till complete @ 14mm, fast to start, with say a 6mm drill, decreasing to slow speed as you progress, make sure you add ample cutting paste...

 

[steveo3002]

yes i plan to do several passes with increasing sizes ...whats a resaonble size to jump up each time 2mm or so?

i dont have any proper cutting fluid /paste...i have engine oil or 3 in 1 , im guessing that is better than nothing?

thanks all

 

[brookie456]

i need to drill a 14mm hole in some thick alloy

i have a cheap pillar drill that has a choice of maybe 3 or 4 speeds

should i select a fast or slow speed for the best results?

thanks

Without knowing what alloy (ali?) you're working, slightly slower speed, increased feed and "back off" ie increase angle/clearance on the drill bit - 10-15 degrees, paraffin helps the cut. If it is heat-treated proper alloy, constant pressure, plenty of lubrication and resharpening should get you there

 

[runnach]

Say 6>9>12>14 approx will be suffice, any kind of oil will be better than nothing.....

 

[wobblemonster]

Paraffin is good when cutting/drilling aluminium

 

[steveo3002]

righto will give it a whizz

no idea what it is exactly...its a cast part off a car gearbox, doubt its hardened

 

[Pete.]

Cast ally drills really nicely.

Re: stepping-up in size of hole - drill your pilot at 25% of the full size hole then go for the full size. Stepping-up too small can cause problems with snagging the drill especially in thinner materials.

 

[piman]

Hello Steve,

I agree with Pete, the purpose of the pilot hole is that the web on larger drills is quite thick so can't penetrate so easily if there is no pilot. You can do the old trick of grinding the point to thin the web but it is easy to get it wrong.
I just use a spray bottle of Duck oil as a lubricant in my home workshop.

Alec

 

[chap]

Well, i tend to split point grind drills (as mentioned), so i'd go in without a pilot.
I don't really understand why people like to start small and step up to the size they require?! I'd only see this as necessary if the drilling machine didn't have enough torque to go in at the finished size.

As for speed, i'd probably go in at 5-600 rpm, with a firm feed and cutting oil. Carefull incase it snatches when it brakes through (if not a blind hole).