drill bit specifications
Turbo Mini Forums

well, after a frustrating evening of progress on the metro last night, I spent 3 hours to end up slightly behind where I started. How I managed it, I don't know, but I sheared both the screws that hold the choke mechanism onto the carb.

Having spend a good couple of hours drilling out and sorting that, it was apparent that perhaps my drill bits aren't the greatest. While trying to do the precision work in the pillar drill, even some of the larger bits were flexing and running off centre at times.

The current set is similar to this (although bits are black/blue steel appearance - got to love my technical terminology!) http://www.screwfix.com/p/combination-dril...piece-set/88149 - absolutely fine for most things but I'm wondering if there is something more suitable/ appropriate for 'precision' work.

so, has anyone any guidance or recommendation for me?

cheers

Go to an engineering supplier being careful not to run out of diesel on the way and buy yourself a set of Dormer TiN coated (Titanium Nitride) drills. Use them only for precise work (e.g. not for boshing a 8.5mm hole through a panel to mount something) and they will last you years.

Edited by Tom Fenton on 25th Jan, 2016.

+1 for set of proper dormer bits, they dont need to have fancy coatings or anything just dont abuse them.

(AND learn how to resharpen them properly so when you do blunt one you can reuse it.)

cheers guys; i'll do a bit of fishing based on your suggestions

I wish someone could teach me to re-sharpen a 1/8" drill !

I just bin ,em and use a new one.

I never re-sharpen a drill I intend to use in the mill or on the lathe because they rarely drill a true hole afterwards.

Also I like a nice tungsten bit for pilot holes, although it should be a central drill really I spose.....

For bashing general holes in sheet I pretty much totally use step drills.

You are probably destroying your drill bits by running them too fast and not feeding fast enough.

Are you using a spotting drill too?

But for precision work a jacobs chuck is dreadful. For anything other then clearance I wouldn't be using jacobs chuck.

A neat trick to use if you are really having problems with accuracy is to drill the hole say 0.2mm undersized then use a drill with the corners rounded off at the appropriate size. You'll get at least a h7 fit out of it.

Or even split point drills. I used to use them when pushed for time

Yes, jacobs chuck. As for speed, i'm not sure what i've got the drill set at - its not particularly fast though, i could probably count the revolutions if i tried but its something to take note of.

Not using a spotting drill but giving the comments by Joe, i've been looking at them as well.

The smaller the bit, the faster the required speed. You might be surprised at the difference in recommended speed as the bits get bigger. There is probably a chart on the net somewhere detailing it.

Always use a centre drill first and the drill bit won't wander. If it's wanders off with a pilot hole, then it's likely that the drill tip isn't sharpened in the centre. The main thing that blunts drills is heat, especially on smaller drills, so cutting fluid is your friend here.

I've always find that some of the drill speeds ridiculously high. I quite often have to drill 1mm holes in cam followers etc.. And trying to drill them at say 2000rpm is crazy, and doesn't cut any faster.

Another one for Dormer drills here, they last for ever! Most of my drilling is on stainless and they are the only ones that really last, and even when they go blunt the flute clearance is always good enough to resharpen it.

Edited by matty on 25th Jan, 2016.

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1/4mile in 13.2sec @ 111 terminal on 15psi

Double post!

Edited by matty on 25th Jan, 2016.

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1/4mile in 13.2sec @ 111 terminal on 15psi

I find cobalt are the best for what I do, nice and slow with cutting fluid from tool Station.

I have started posting on Instagram also my name on there is turbomk1golf

Nothing is impossible it just costs more and takes longer.

I've got a bottle of this stuff, make no mistake its MEGA

http://www.lawson-his.co.uk/rocol-53003-tr...CFYvpwgod6KcE5w

Not sure where the cutting fluid i use comes from. I generally borrow it from nicks bench at the other end of the shed!

Whats the problem anyway. Are your holes the wrong diameter or in the wrong place? (Or wandering?)

also as a side note,

if your countersinking holes especially by hand... get some zero flute countersinks,

I was trying to drill a steel screw out of the alloy body and bit was wandering. I've managed to fanny it up so it will work but not my best work to be honest. Was using small bits to be fair but I've noticed on some of the larger elements of work, the bits can wander too. No apparent play in the spindle or chuck so I'm putting it down to the bits and perhaps poor start prep on how I go about it

How about the DeWalt Extreme 2 sets? They have a self centering tip design.

I have the 29 piece set and have been very pleased with them. I also buy 4mm bits in bulk 10 packs for general use.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Too late for you Rob, But I use a centre drill to mark the job when drilling steel out of alloy
And I have the benefit of a mill and collet chucks to hold the drill rigid.

It is the only certain way I know to do the job.

If you're drilling a bolt out, you need to look to see where the thread ends and offset the centre drill the thread depth towards that side. As you look at the broken bolt/stud what looks to be the centre of bolt actually isn't,and you'll end up with a half moon shape left on one side and drill the thread out on the ally part on the other, when you get to the core size of the thread...if that makes sense?

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1/4mile in 13.2sec @ 111 terminal on 15psi

get where you are coming from and I did try to mark the top of the screw but to be fair, my centre punch was really too blunt to get a fine point. Bear in mind the screws are perhaps equivalent to an M2 or 2.5 so the bits I was using were 2mm and 3mm so it was fine work

its all a learning curve and I simply want to get myself prepared for the future

try something like this maybe?

https://youtu.be/fqZYgReuywM

this guys a bit clever and kinda funny to listen to. If you get time to look through his stuff, he's got a few useful videos.

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1/4mile in 13.2sec @ 111 terminal on 15psi