Drill flute orientation

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Drill flute orientation

This topic has 23 replies, 13 voices, and was last updated 21 September 2017 at 09:12 by Mick B1.

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19 September 2017 at 11:01 #15959
Martin Kyte
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@martinkyte99762
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19 September 2017 at 11:01 #317681
Martin Kyte
Participant
@martinkyte99762
Hi Chaps

As you all like pondering odd subjects how about your thoughts on this one.

When drilling from the tailstock it is clearly posible to orientate the flutes of the drill any way one chooses. The question is 'does it make any difference'. The assumptions are that the drill is in perfect condition but the tailstock is slightly out in the lateral direction but is vertically on axis. The drill is small enough to flex slightly.

When starting the drill in a small centre hole is the the drill more likely to start true if

1 The flutes are horizontal.

2 The flutes are vertical

3 It doesn't make any difference what-so-ever.

regards Martin

PS The question arises because purely out of habit I mount drills with the flutes vertically.
19 September 2017 at 11:53 #317691
Gordon W
Participant
@gordonw
I was wondering also. I think of a drill in the tailstock as a boring bar, so if the tailstock is out in any direction a flute will be out. This flute edge then cuts a little more, assuming it's stiff enough.
19 September 2017 at 12:01 #317694
Speedy Builder5
Participant
@speedybuilder5
I don't think it makes any difference unless your tailstock is wildly out, in which case you should correct it or not use it for drilling (Unless Taper turning etc).
BobH
19 September 2017 at 12:35 #317701
Martin Kyte
Participant
@martinkyte99762
My thinking is that, as speedy says, for normal small errors you cannot practically notice any difference. However my thinking is also that for most reasonable lathes there is always going to be a side to side error rather than a vertical error. For small misallighnment the contact surfaces of the drill are going to be the two linear cutting edges. shaped like a V. If they are vertical and there is a small misalignment horizontally each flank will still touch the centre drilled hole at the same time. If they are horizontal and the tailstock is out in that direction one flank must touch first and be unsupported by the oppsite flank at that instant. So as it's as easy to mount with the flutes vertical as it is horizontal all other things being equal you may get a better start to the hole.

What I really wondered was had anyone ever heard of this being mentioned as good practice before. It may be that it's just a curiosity and of no practical value but I am if anything a curious person.

regards Martin

Edited By Martin Kyte on 19/09/2017 12:35:53

Edited By Martin Kyte on 19/09/2017 12:36:40
19 September 2017 at 13:07 #317704
Mick B1
Participant
@mickb1
I also tend to mount drills vertically – when it occurs to me to think about it – because I think the chips can clear a little more easily and evenly that way. But of course that only applies in the first diameter or so of depth, and may be spurious anyway.

It seems to me it's more important to give plenty of time to cut until the full diameter of the drill is engaged – so that if the drill is deflected by uneven lips, even by an invisible amount, you give it time for the elasticity of the drill body to spring it back nearly to truth, and so the full diameter enters a hole as near size-and-centre as makes no difference.
19 September 2017 at 14:35 #317710
Speedy Builder5
Participant
@speedybuilder5
And if your drill is slightly bent, drill chuck errors or made by "Back street China" etc, etc. – I think you worry too much Martin. If you want a really accurate hole, drill undersize and then bore it out, (then ream perhaps?).
BobH
19 September 2017 at 14:38 #317711
Martin Kyte
Participant
@martinkyte99762
I'm not worrying at all, as I said I've never noticed any difference, it was purely a whimsical question.

regards Martin
19 September 2017 at 15:00 #317713
MW
Participant
@mw27036
I cant say I've ever heard advice mentioned pertaining to their orientation. It's all rotating past the same points on the drill, I spose.

Michael W
19 September 2017 at 15:44 #317716
SillyOldDuffer
Moderator
@sillyoldduffer
Possibly a fourth alternative. If the tail-stock is off centre such that one tip acts a single point cutter, then the best solution might be to rotate the drill to minimise the effect. Not vertical, not horizontal, not random, but an angle related to the tail-stock's XY error. The position that makes sure there's flute space rather than tip at the outer point.

Actually, I doubt it makes any difference because the cutting axis is rotating. Whatever position the flutes are in, the drill cuts

along the axis of the rotating work. That being so the effect of any tail-stock offset will just be an oversize hole. I guess!

Dave
19 September 2017 at 16:52 #317720
Bazyle
Participant
@bazyle
Best solution is to rotate the drill too in a saddle mounted drilling head and then you can have auto feed at the same time, provided you sort the alignment issues.
19 September 2017 at 17:41 #317723
Andrew Tinsley
Participant
@andrewtinsley63637
Rather than think about the question, why on earth don't you fix your tailstock alignment. Then you won't have to ask the question!

Andrew.
19 September 2017 at 20:46 #317757
Howard Lewis
Participant
@howardlewis46836
Assuming that you have already centre drilled the work, the drill will tend to follow the pilot on the centre drill

Advocates of four, or six, facet drill grinding claim that centre drilling is no longer needed.

Unless the drill has been ground with equal length faces, it will cut oversize.

If the Tailstock is off centre, you will get an oversize hole even with an accurately ground drill, and a good, accurate (concentric) chuck

Howard
20 September 2017 at 09:45 #317810
Martin Kyte
Participant
@martinkyte99762
OK, it was just a whimsical question.

Judging by some of the responses some people perhaps didn't quite understand why I asked the question.

It arose because of late I have noticed that I habitually set drills with the flutes vertical and thought "that's strange I wonder if it makes any difference and if it does why".

So I was really talking about lathes that are in good alignment, but recognising that nothing is ever spot on. It could be assumed that horizontal alignment is going to be worse than vertical on amachine with low wear as there has to be some clearence so that the tailstock can slide. Clamping holds it down onto the bed but doesn't really ensure tight alignment horizontally on flat shears. The argumant does not really hold on prismatic beds. Therefor if generally the alignment assumed to be less good horizontally in general and if there is no time cost in orienting a drill one way as opposed to another and there is a preferrential orientation it probably makes sense to do it if you could be bothered.

In reality, I think the practical benifits are almost certainly un-measureable to the precision we are ever going to need which is why it was just a rhetorical question. I just wondered if there were any 'old wives tails' out there.

regards Martin
20 September 2017 at 13:04 #317839
Bazyle
Participant
@bazyle
If the flute is vertical then, if it is producing chips rather than a long spiral, those chips will fall away during the first mm but thereafter be lodged in the bottom of the hole just by the lowest cutting edge possibly blocking it and wedging it. However if the edge is horizontal the chips will vibrate down the sloping inner face of the cutting edge, out of the way.
20 September 2017 at 20:28 #317901
Robin
Participant
@robin
There is a notion that the lathe defines the centre line of the workpiece with the slowest moving material. It moves faster as you move away from the centre.

If there was any way to persuade the drill to follow that line it would be wonderful, but a Jobber bit has no cut in the centre so I thought it would shy away from that non-moving centre line.

Then I realised that there was no way the Jobber drill could tell it had shied because as far as it was concerned, it's own centre is always the slowest moving.

Then my brain imploded
20 September 2017 at 20:35 #317904
Robin
Participant
@robin
If you put the cutting edges horizontal you can apply a rigid sideways displacement to a wandering drill tip by running the cross slide up against it. This cuts a perfectly centred conical dent which guides the bit back on course as you release the pressure.
20 September 2017 at 20:41 #317906
mark costello 1
Participant
@markcostello1
I had a Boss that said to orient the cutting edges horizontal made it cut closer to size, seemed to prove out.
20 September 2017 at 20:51 #317907
Mick B1
Participant
@mickb1
Posted by Robin on 20/09/2017 20:35:46:

If you put the cutting edges horizontal you can apply a rigid sideways displacement to a wandering drill tip by running the cross slide up against it. This cuts a perfectly centred conical dent which guides the bit back on course as you release the pressure.

Yeah, yeah, but haven't you now actually got a truncated conical dent, with a flat at the bottom that's wider than the effective width of the chisel point of the drill, so losing any guidance to continue cutting on centre?

Apart from internal elasticity, that is. That's why I think it pays to pause and let it cut on springback to centre. Or maybe that's just another variant of what you're suggesting.

Maybe it's easier just to leave some mysteries alone…
20 September 2017 at 21:39 #317912
Robin
Participant
@robin
Yeah, yeah, but if the name of the game is remembering some way the flute orientation could possibly matter then I think I can claim a Brownie badge. There is no fun being a smart arse if there are no badges to collect you know
20 September 2017 at 22:11 #317916
Neil Wyatt
Moderator
@neilwyatt
You need Mozart drills, the ones with a magic flute.

Neil
20 September 2017 at 22:21 #317918
Nick_G
Participant
@nick_g
.

I know I am very much 'the new kid on the block' so far as engineering goes but I would think the quality of the drill bit and it's grinding have far, far more influence than it's orientation. – If it needs to be that accurate then a reamer would surly be ones best friend.????

Nick
21 September 2017 at 08:54 #317942
Robin
Participant
@robin
Mozart drills.

Made from Wolfgang carbide?

Robin

Edited By Robin on 21/09/2017 08:54:42

Edited By Robin on 21/09/2017 09:08:55
21 September 2017 at 09:12 #317944
Mick B1
Participant
@mickb1
Pun didn't work – deleted.

Edited By Mick B1 on 21/09/2017 09:16:26
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