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
quote:
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
quote:
Originally posted by adithorp
quote:
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
This^^^ Generally it'll be slower than you think.
Plus a good cutting oil helps
Drill a small pilot hole first. 3mm? 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!
quote:
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!