How do you Drill?

[vcutajar]

John

Thanks for all the info. I have learnt many things from this thread, primarily the use of the spot drill. Now to get hold of some spot drills. I doubt I will find any locally but there is nothing wrong in hoping. Thanks for sharing your knowledge as I have started this hobby with no machining knowledge and have learnt things hands on and by reading.

Vince

 

[Blogwitch]

Just to make things a little clearer, I have been out to my shop and had a root through my drill boxes. So here are a few pics to show what I was on about.

On the right are the older style of spot drill, almost a flat plate drill, but still with four facets, and on the left, the normal type of spot drills, these are all 90 degree ones.

I now hope you can recognise these ones as 60 degree protected centres, clearly showing the outer cutting edge that forms the recess. The left hand one has an angled bottom recess cut, and the right a flat.

These are my pair of old and well used radius centres, for when doing between centres taper turning.

Now a couple of ones I have never used, and doubt I ever will.
First a 90 degree centre drill. Where and when it will be used, I have no idea.

This is one I really need help with, it is almost a standard protected 60 degree centre, with an angled recess bottom, but what is the bulge for?

John

 

[mocaquita]

I use stub length drills without spotting almost all the time. With a little care starting, they're plenty accurate.
For critical positions, I'll use a spotter. For really close positioning I'll drill an undersized hole and bore it in postion and usually to size.

 

[wongster]

Hi John,

I'm wondering what sizes of spot drill I should get if I usually drill holes between 2 to max 10mm diameter?

Regards,
Wong

 

[rake60]

I have spot drills in my toolbox but the center drills are at the lathe within arms reach of my mini mill.
I do use the center drills in place of the spot drill, but I only use them to spot!

I do not drill deeper than the the end angle of the center drill.
That is all you need. Drilling deeper than a spot can cause your drill bit to grab.

Rick

 

[AlanHaisley]

John,
To make a guess about

This is one I really need help with, it is almost a standard protected 60 degree centre, with an angled recess bottom, but what is the bulge for?

John

I wonder if someone ever developed a ball end center for more radical taper machining?

Alan

 

[Blogwitch]

Wong,

I have a set that goes up to 8mm, and like Rick has stated, you don't need to go the full width or start to penetrate with the side flute. I just use enough depth so that I clear the width of the flat face of the drill tip, that ensures that it is the cutting faces of the drill than are starting first, and they guide the drill perfectly straight. The only time I would use the large 8mm one would be if I was using say above 1" drill bits.

Alan,

I should really get it mounted up and drill down the centre between a couple of plates mounted on the mill, just to see exactly what shape it does give.
But even then, I don't think it would be of any use in my shop.

Just curiosity really.

John

 

[wongster]

Thanks John. That mean that I don't have to go grab a full set but a few pieces and vary the depth from there. Good stuff! I'll go get some when I happen to be around the tool shop.

Regards,
Wong

 

[Smifffy]

The spot drills I ordered arrived on Thursday and are a pleasure to use.

So much nicer (and with no fear of a broken tip) than using centre drills.

Cheers

Smifffy

 

[robcas631]

I've done that John and it works but I now use a center drill.

 

[robcas631]

If a drill is incorrectly sharpened what will happen? Will it drift? In my opinion this is a important question.

 

[aonemarine]

For me it seemed to cause a slite drifting problem and also excessive pressure to drill as it wasnt center cutting well.

 

[robcas631]

Aone, on youtube there was a training video. A center drill was used first then of course a drill. What was interesting was the emphasis on not using lube as that might cause drifting. What do you think of that?

 

[aonemarine]

Rob, I dont have the experence to make an honest comment....But to not use lube to stay on track?? sounds a bit hokey...

 

[robcas631]

smitty, How many flutes?

 

[robcas631]

Aone, I never have as well. I believe if a drill is cutting at proper speed, drifting should not be an issue. The reason I brought the no lubrication topic up is because I observed it on a youtube lathe training video. I wish I could find these videos.

Rob

 

[goldstar31]

If a drill is incorrectly sharpened what will happen? Will it drift? In my opinion this is a important question.

A drill with two lips of unequal lengths will certainly drift. Again, if a drill chuck is inaccurate in holding a perfect drill- it will also drift or cut an oversize hole. Again, if the chuck is 'out' of alignment or worn or whatever, and the drill is similar, the fault will remain.

You MAY get away with using a thinner drill but the words are 'you May'

This is only 5 lines of reply to what is a very long, difficult but fundamental subject. I can say that 'some' of my drill chucks perform more accurately than others. They were made to more exacting standards and consequently performed better. The others are worn or cheap and nasty and are kept for woodwork, drilling holes in bricks and garden gates.

I have no doubt that someone will tell me that I'm wrong. So be it.