Spotting Drill or Centre drill.

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Spotting Drill or Centre drill.

This topic has 50 replies, 28 voices, and was last updated 1 March 2018 at 22:23 by CHARLES lipscombe.

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9 February 2018 at 12:45 #340587
Vic
Participant
@vic
I was watching a Clickspring video on YouTube the other day and noticed that like me he used a spotting drill to start off a hole on the lathe and wondered how many others do this. Or do you use a centre drill instead?

Edited By Vic on 09/02/2018 12:46:24
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9 February 2018 at 12:45 #15990
Vic
Participant
@vic
9 February 2018 at 13:08 #340590
JasonB
Moderator
@jasonb
Spotting drill for me all the time in lathe and mill unless I particularly need a ctr hole
9 February 2018 at 13:10 #340591
FLguy
Participant
@flguy
Spotting drill. I'd like more sizes than I have too.
9 February 2018 at 13:18 #340594
Mike Crossfield
Participant
@mikecrossfield92481
I switched to using a spotting drill a year or two back, and only now use centre drill when I need a 60 degree centre for between centres turning.

I wish I could find a low cost source however. Spotting drills seem very expensive compared to centre drills.
9 February 2018 at 13:25 #340595
Hopper
Participant
@hopper
Five bob each way here. I often use a larger size centre drill but use only the tip of it to put a small divot in the job, as one would do with a spotting drill. This works real well for tiny size drills where if you use the appropriate tiny sized centre drill in wobbly ancient machinery (or is it the wobbly ancient operator?) it is soooo easy to break the tiny tip right off it.
9 February 2018 at 14:14 #340602
Vic
Participant
@vic
Posted by Mike Crossfield on 09/02/2018 13:18:18:

I switched to using a spotting drill a year or two back, and only now use centre drill when I need a 60 degree centre for between centres turning.

I wish I could find a low cost source however. Spotting drills seem very expensive compared to centre drills.

Yes, they do seem a bit expensive don’t they.
9 February 2018 at 14:16 #340603
Mick B1
Participant
@mickb1
I must've led a sheltered life in engineering – I'd never heard of a spot drill before I read this thread.

They're eye-wateringly expensive.

Although I've occasionally broken centre drill pilots, it's always been when I was impatient to drill the 60 degree cone in something difficult, not when I was spotting to guide a standard twist drill.

I think I'll stick with centre drills.
9 February 2018 at 14:44 #340605
Anonymous
On the milling machine I rarely use spotting drills and never use centre drills. A 4-facet drill starts accurately enough without needing either. When I do need extra precision, or the surface isn't flat, I use a carbide spot drill to start.

On the main lathe I use centre drills; they're way cheaper than carbide spot drills. On the Britan I use LH centre drills.

Andrew
9 February 2018 at 14:48 #340606
larry Phelan
Participant
@larryphelan54019
To Mike and Vic,

Look up a place called "Drills UK",They sell spotting drills,double ended,and not at all dear. I bought some MT drills from them a while back and am quite pleased with them. Along the way,I saw those spotting drills in many different sizes.I bought a pack of 10 5mm stub drills for £4 ,95.,are these what you are looking for?
9 February 2018 at 14:53 #340607
JasonB
Moderator
@jasonb
I just use 1/8 and 3/16 spotting drills, I like the Americam made Keo brand as they have the smallest "flat" between the webs that I have found. Don't think £2.42 inc vat from MSC is too bad though they are not stocking them anymore so just some left in the clearance except the 1/8" ones as I just bought their last 4 in stock

A lot depends on what I'm drilling like Andrew I will use a split point Dormer straight onto the metal in some cases particularly if I have got the stub length needed and I have most of the common sizes in those.
9 February 2018 at 15:15 #340609
Michael Horner
Participant
@michaelhorner54327
Spotting drill .

Usually I'm repairing a shaft by drilling and tapping. Go in deep enough so when I thread it doesn't pull the surface up.

1 less operation!

Cheers Michael.
9 February 2018 at 15:42 #340614
Vic
Participant
@vic
Posted by larry Phelan on 09/02/2018 14:48:39:

To Mike and Vic,

Look up a place called "Drills UK",They sell spotting drills,double ended,and not at all dear. I bought some MT drills from them a while back and am quite pleased with them. Along the way,I saw those spotting drills in many different sizes.I bought a pack of 10 5mm stub drills for £4 ,95.,are these what you are looking for?

I’m not looking for any at the moment as I have 6, 8 & 10mm spotting drills. They are not the same as stub drills.
9 February 2018 at 15:46 #340615
MW
Participant
@mw27036
I pretty much use centre drills for everything, but for some very soft materials I don't even bother as there's pretty much no resistance to the point when it goes in, provided it's a split point drill.

I honestly was never shown spotting drills when training and only discovered them through youtube and watching others on the forum, so i'll have to check them out one day.

Michael W

Edited By Michael-w on 09/02/2018 15:46:50
9 February 2018 at 15:51 #340616
Tony Pratt 1
Participant
@tonypratt1
Spotting drills

Tony
9 February 2018 at 15:55 #340617
SteveI
Participant
@stevei
For the folks using spotting drills are these 90 degree or 120 degree or another angle? I assume you follow up with a 118 degree or as near as regular twist drill.

Thanks,

Steve
9 February 2018 at 16:05 #340619
JasonB
Moderator
@jasonb
I just use the 90deg ones as they can give the hole a chamfer at the same time and as Michael says if tapping that little chamfer stops the area around the hole being raised up particularly if tapping softer metals. Regular angled drill follows OK.
9 February 2018 at 17:36 #340632
larry Phelan
Participant
@larryphelan54019
Sorry about that Vic,my mistake. I still have a lot to learn. I will look into that,I dont think I ever came across spotting drills but I did hear of stub drills,and I thought they were one and the same. I live and learn !
9 February 2018 at 17:43 #340635
Tomfilery
Participant
@tomfilery
90 degree spotting drill for me too!

I mostly use a 3mm one, even for tiny holes, and follow up with a normal 118 degree drill.

Tom
9 February 2018 at 18:51 #340639
Neil Wyatt
Moderator
@neilwyatt
All mine (which are in small sizes up to 3mm, came with those rotary tool accessory sets that contain lots of useful consumables and a few weird tips

Neil
9 February 2018 at 19:31 #340643
Mick B1
Participant
@mickb1
Posted by larry Phelan on 09/02/2018 14:48:39:

To Mike and Vic,

Look up a place called "Drills UK",They sell spotting drills,double ended,and not at all dear. I bought some MT drills from them a while back and am quite pleased with them. Along the way,I saw those spotting drills in many different sizes.I bought a pack of 10 5mm stub drills for £4 ,95.,are these what you are looking for?

Nah, still sticking to centre drills.

Those folk don't seem to be offering spotting drills unless they're the same as 'spot weld' drills – not double-ended either. Cromwell's spot drills seem to be around a tenner each, and they're not double-ended either.

Centre drill don't have cylindrical land and cut on the side as well as the point, so any eccentricity gets taken out. I've sometimes succesfully used the pilot as a tiny slot drill.

I can't see any substantial advantage in the spotting drill that's worth its price differential.
9 February 2018 at 20:57 #340664
Vic
Participant
@vic
I made a small turned part some years back and the hole ended up off centre when I used a centre drill to start the hole. I switched to using a spotting drill on the replacement part and I’ve used them ever since. I wouldn’t be without one or two now although I still use centre drills when needed. I’ve settled on using an 8mm on most jobs for some reason. Unlike centre drills you can’t snap the tip off so I’ve not needed to replace any yet.
9 February 2018 at 23:28 #340688
Nick Hulme
Participant
@nickhulme30114
Centre drills in the lathe, spotting drills on the mill if required (sometimes spot a layout to finish on the mill drill or drill press.

My centre drills have always self centred perfectly on the lathe, I can't imagine a way to stuff that up
10 February 2018 at 00:00 #340693
Fowlers Fury
Participant
@fowlersfury
Assuming there's no 'pip' left on the piece in the chuck and you are using a centre drill which either doesn't centre correctly or the tip breaks, there are several causes. One is a worn tailstock barrel. Another, peculiar to Myfords (only?), is that the hole in the back of the tailstock barrel into which that small, round dowel with its key fits, has become distorted. This can cause the barrel to "twitch" when you start drilling. Geo Thomas published a remedy in the M.E. some years ago. [I think it's also included in his Model Engineers Workshop Manual Vol 1].
When done on my original & well-worn Super 7, it cured the breaking of centre drill points.
10 February 2018 at 00:44 #340697
Muzzer
Participant
@muzzer
If you suffer from the problem of the loose / wobbly tailstock, centre drills are a risky proposition, so a spotting drill would be a good solution. The reason there is a small (brittle) drill on a centre drill is to give clearance for the point of the centre. One simple solution would be to use a spotting drill and grind off the very end of the centre. Pragmatic.

Murray
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