Can anyone shed some light on the best speed to drill metal? Are low speeds or high speeds better?

I am drilling out a snapped bolt on a 2012 VW Golf with a cordless drill (it holds the diesel injectors in place) but wanted to make sure i dont mess it up and ruin the drill bit.

Any pointers?

Cheers all

N1

Hi,
From experience, low speed and a sharp drill bit is what you are looking for.
High speed will overheat and damage the drill bit which will come useless very quickly.
Also, if it is a big diameter, start with a small hole (2-3mm), and drill bigger and bigger.
Hope that will help

You need to know that the 'best' cutting speed varies by metal being cut and the material being used to do the cutting.

This looks like a reasonable guide: Cutting Speed Advice

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Originally posted by JAG
You need to know that the 'best' cutting speed varies by metal being cut and the material being used to do the cutting.

This looks like a reasonable guide: Cutting Speed Advice

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quote:

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Originally posted by adithorp

quote:

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Originally posted by JAG
You need to know that the 'best' cutting speed varies by metal being cut and the material being used to do the cutting.

This looks like a reasonable guide: Cutting Speed Advice

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This^^^ Generally it'll be slower than you think.

Plus a good cutting oil helps

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I'm lazy, I've set my pillar drill to the lowest speed and just use that all the time for everything ..........

Tends to be ok.

Controlling speed when you're applying pressure I find very difficult, good luck.

I've very often found using a centre punch to mark to spot where you want the drill bill to start helps.

As does starting with a centre drill, before a normal drill bit.

https://www.amazon.co.uk/Youmeng-Centering-60-Degree-Countersink-Metalworking/dp/B09ZTSS8SG/ref=asc_df_B09ZTSS8SG/?tag=googshopuk-21&linkCode=df0& amp;hvadid=697257156448&hvpos=&hvnetw=g&hvrand=11344433040747448955&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvloc int=&hvlocphy=9045741&hvtargid=pla-1679688962543&psc=1&mcid=a4ec1c9d57d938de847c60b527750df2&gad_source=1

...also, what size is the bolt you need to drill out, M6?

https://play.google.com/store/apps/details?id=com.beta.fswizard_lite

Surprisingly accurate and has rarely let me down.

Has the bolt / stud broken above the surface of the cylinder head ? If so my method would to be place a washer over the remains and weld a nut onto the end of the bolt , the heat from welding and being able to fit a socket/ spanner over the nut and apply slight pressure back and forth will often shift it. If below the surface try using L/H drill bits which often wind the remains out. Do not use easiouts, the best place for them is the dustbin!

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Originally posted by rusty nuts
Has the bolt / stud broken above the surface of the cylinder head ? If so my method would to be place a washer over the remains and weld a nut onto the end of the bolt , the heat from welding and being able to fit a socket/ spanner over the nut and apply slight pressure back and forth will often shift it. If below the surface try using L/H drill bits which often wind the remains out. Do not use easiouts, the best place for them is the dustbin!

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Thanks for the replies chaps. Sorry for the late reply but only just seen the notifications

The bolt was like a stretch bolt that goes through a bracket that then holds down 2 diesel injectors. It was a mates car. Long story short.....we couldn't get it out and it went to a garage and is now sorted.

However....... I am now in a similar position as i have snapped a 4.5mm chrome vanadium allen key in a grub screw in a Lotus elise rear brembo caliper!!!!! I bought a new set of Draper drill bits and its not even touching it. This is using a dewalt cordless drill.

Im ordering some cutting agent and considering buying a used bench pillar drill but what drill bits are the best for it? Ive read solid carbide or cobolt? Any ideas?

Thanks

N1

For bits like this i'd use a Cobalt drill bit, low and very slow but is just chipsaway at really hard metals. Can be used on Titanium if used correctly.

I've used on snapped studs before and I use a 1.5mm to drill out holes in nuts and bolts for wirelocking. Light pressure and slow speed 20/30 rpm. Also a good lubricant to keep the heat down, I use some thick engine or gearbox oil.

[Edited on 11/7/24 by tims31]

Agree, slow and lots of torque. I once snapped an easyout in a upright. Tried the usual "fast and lots of smoke" and didn't work. Got a low rpm 12v cordless hand drill, hot wired it to a car battery and used loads of lube. Quick work.

Buy a bench grinder (Screwfix sells them for £25) and learn to sharpen your drill bits, it will save you a lot of money...