Drilling small holes

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Drilling small holes

This topic has 24 replies, 14 voices, and was last updated 2 February 2012 at 18:14 by RobC.

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30 January 2012 at 21:28 #3632
RobC
Participant
@robc77385
How not to snap drill bits
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30 January 2012 at 21:28 #83499
RobC
Participant
@robc77385
Hello fellow clock makers and assorted engineers!

I am in the process of building my first clock and am having a lot of difficulty drilling small holes in plates with my pillar drill. Tonight I have managed to break four different types of drill, all less than 1.5mm diameter.

I do have an Eclipse pin chuck, but it doesn’t seem to hold the shanks of the drills quite vertically, which is no use at all. I also have some micro drills with larger diameter shanks, which did go into the main drill chuck better, but I broke them too.

It seems that whatever I do in the drill press, I either have too much or too little movement in the work to drill relationship.

I am currently drilling through three 3mm plates of aluminium, which I don’t think should be causing me this much trouble, but I guess there is either a technique or device that I do not know about. Once I have drilled these holes I am going to have to taper ream them and I really don’t want to bust the reamer too…

Any advice would be gratefully received!

Rob
30 January 2012 at 22:08 #83506
JohnF
Participant
@johnf59703
Rob, seems to me that your pillar drill is maybe to large and thus not sesitive enough for small drills? What type and size is it?

The Eclipse pin chucks I have found are not very accurate I would look for something better quality e.g. Albrecht or simmilar, I did buy a small Jacobs style chuck from Arc Euro and for the price very acceptable.

A smaller drill press might be best but an alternative would be a sensitive drilling attachment to use in you existing machine but be aware that you need much higher speeds for small drills.

Regards John
30 January 2012 at 22:45 #83507
Bazyle
Participant
@bazyle
Is the table firm and the work clamped to it? Is the quill when extended able to move sideways? Are you clearing swarf every mm?

Do you need to drill all 3 together? After drilling one spot through to the next and drill separately. 3mm is not a deep hole but 9 mm is in proportion to diameter so more risk of friction & heating.

Do you need to apply pressure or is the weight of the head enough to penetrate? The huge play in the feed mechanism of most pillar drills can cause snatching and sudden stress.
30 January 2012 at 23:02 #83509
KWIL
Participant
@kwil
No mention of a lubricant here either, paraffin is good on aluminium.
31 January 2012 at 05:15 #83513
Terryd
Participant
@terryd72465
Hi Rob,

Drill speed? You should be drilling at the highest speed that your machine is capable of with such small drills and as Kwil says, paraffin as a lubricant on aluminium is almost essential. I would also take Bazyle’s advice on drilling one plate and spotting through. A sensitive drilling attachment is also a good idea if you foresee having to do lots of holes.

You should also peck drill, a little at a time and withdraw to clear swarf regularly especially with aluminium, not so much with brass. Be as gentle as you can and let the drill cut but do not force it.

Good luck,

Terry
31 January 2012 at 10:08 #83526
NJH
Participant
@njh
Hi Rob

I agree with all the above advice but clock plates in aluminium? – I’ve not come across that before. What is the clock?

Regards

Norman
31 January 2012 at 13:12 #83538
Ian S C
Participant
@iansc
Maybe a dremel tool in a stand? Ian S C
31 January 2012 at 17:01 #83548
RobC
Participant
@robc77385
Thanks to all the commenters. I will try to summarise and answer what I can.

My answers to your questions

JohnF: Is the drill too large and un-sensitive – Yes Fobco Star 1/2″ chuck with a bit of a wobble to it.

Bazyle: The table is firm but the work was not clamped to it, although it was weighted down fairly well.

Quill extension was minimal, so no lateral movement.

No, I was not clearing the swarf every mm.

No, I was not using the highest speed on the drill (second highest)

I probably don’t need to drill all three together, although the job at hand is to drill, taper ream (1/16″) and pin the three plates together, so any tips here are appreciated.

I do need to apply pressure, since the return spring is fairly robust on the drill.

KWIL: No, I was not using sufficient lubricant (Trefulex)

Terryd: Peck drilling sounds sensible, I was probably being far too ham-fisted!

NJH: Aah, you spotted it! I am making a ‘trial’ clock in aluminium to make these types of mistakes, then a proper one from brass. This way I am scrapping chunks of aluminum and not being as unhappy with myself as I would be if I messed up with all the nice shiny brass. This way I get to practice the techniques and make the tooling/jigs I need before I get into the real thing.

Ian S C: Yes, I have thought about that. I do have a Dremel although I don’t have the stand for it. It may be simplest to source one of them.

My summary of the guidance so far:

Get a decent pin chuck

High speed on the drill

Peck drill into the work slowly, clearing the swarf frequently

Lots of lubricant – paraffin would be best

One plate at a time

Clamp the work to the drill table

Use a smaller, more sensitive drill for this sort of work (recommendations please)

Look at using Dremel mounted in vertical drilling stand as temporary solution

Phew, that’s a fair bit for a few hours of your time. Thanks guys

Rob
31 January 2012 at 18:20 #83551
NJH
Participant
@njh
Hi Rob

I’m a bit concerned about the ” bit of a wobble” on the chuck of your Fobco star – try a piece of (say) 1/4 in silver steel in the chuck – is this wobbling? If so are you able to measure how much wobble and discover why? As far as sensitive drilling goes (and if the silver steel is not wobbling) you might like to invest in one of these along with a suitable chuck That way you lock the quill of your Fobco and use fingertip pressure on the micro drill adapter so you will be able to ” feel it in”

Regards

Norman
31 January 2012 at 18:22 #83552
Richard Parsons
Participant
@richardparsons61721
Rob. Why not do as the old’uns (Graham, Harrison, Mudd, Breguet and the rest would have done. Do it by hand. Use a little Archmeanian drill and take your time.
If you are drilling by machine lock both plates together and clamp them down well. Use a high speed and take it slow. Pin chucks are not accurate they are for hand use. Get an eclipse 160 Pin Chuck this is what I use.
Do not get too worried about deadly accuracy on the hole size. You will have to broach it out to get the clock to run. Old clock makers have a saying it “If rattles it will run”.
Rdgs
Dick
31 January 2012 at 18:38 #83553
Stephen Benson
Participant
@stephenbenson75261
You could actually use ally and fit brass bushes then broach the holes to size or even use ball bearings as a growing band of modern clockmakers are

Edited By Stephen Benson on 31/01/2012 18:39:22
31 January 2012 at 19:16 #83558
blowlamp
Participant
@blowlamp
With a good chuck on your Fobco you should be OK, I think.

I use a Union pillar drill that’s about the same size as yours and I don’t get any problems with drills around 1mm diameter.

As has been pointed out already, a 9mm deep hole into aluminum with a 1.5mm drill is begging for trouble if it’s not cleared and lubed frequently.

Don’t make the mistake of believing you’ll have covered yourself by practising with aluminium for these movement plates, ‘cos brass is bad for snatching when the drill breaks through, so try on some scrap brass to before commiting to the real thing.

When it does snatch, the drill bit lifts the plate off the table at an angle and continues to cut a (now) slanted hole.

Have a look on Google for ideas to avoid the above snatching of drill bits.

Martin.
31 January 2012 at 19:42 #83563
Sub Mandrel
Participant
@submandrel
I have a cheap-as-chips Machine Mart pillar drill (I think it was £35!) and it quite happily drills PCBs using number 70 drills which are much less than 1mm in the standard chuck.

Neil
31 January 2012 at 21:56 #83585
Sam Stones
Participant
@samstones42903
Hi Rob,

Although I’ve only made one clock (in brass), here is my six penn’orth.

With regards to the quill and the spring arrangement in the drill head, a situation can arise (especially with small drills) where, as the weight of the quill becomes transferred onto the drill tip, feedback and sensitivity is reduced. In other words, the quill starts to `float’. At the point when the drill begins to break through, the quill can drop a short distance, depending upon how much clearance there is in the rack and pinion, and/or how the spring mechanism is arranged.

The risk of breaking a drill is reduced by having a (scrap) backing plate of the same material being drilled, or when you are spotting through to your next plate.

When drilling brass, carefully stone the two cutting edges of the drill to produce a negative (as opposed to a positive) edge. Not all that easy with tiny drills.

Although brass can be machined dry, aluminium needs lots of cutting fluid to minimise swarf build-up on the cutting edges etc.

Regards,

Sam

Edited By Sam Stones on 31/01/2012 22:06:38
1 February 2012 at 08:22 #83609
RobC
Participant
@robc77385
More great responses guys, I will answer a few of the questions too.

For clarity, I am drilling and taper reaming (1/16” ) locating holes to hold the three plates together with pins during the build process, so the fit is important in this bit.

NJH: Micro drill stuff looks good, I will probably go down that route if I can get to the bottom of the wobble on my drill. I have measured it in the past and it is not very pronounced at the taper above the chuck, but from the chuck it can be fairly large (I will measure again tonight). This leads me to think that the chuck may be knackered, although the bearings on the drill itself may also be past their best. I am not entirely sure where to go with this one, although I may just try replacing the chuck and seeing if that changes anything.

Richard: I did consider an Archimedes drill, but for the particular task I am performing, I thought it was not particularly suitable. It may be the simplest answer though, but I can’t imagine I will get a very perpendicular hole if I do. For regular clock elements, it would probably be ok, but probably not for the task at hand which is accurate location of the plates for the manufacturing process.

Stephen: At this point I am not making holes for pivots, although knowing that I could bush them in brass makes for interesting possibilities.

Blowlamp: Thank you for the vote of confidence in using a big lump of a drill to achieve this, I thought I should be able to, if I go carefully enough. I also appreciate that switching to brass will bring a whole new set of challenges, but at least this way I have tried a few before I embark on the more costly material. This is my very first project, so I am learning everything from scratch.

Stub: It sounds like the Machine Mart/Clark drills can be very good if you get hold of a decent one. I was warned off them by a fellow engineer, but maybe he was a bit hasty.

Sam: Thanks for the tips, I was definitely not using enough lubricant when cutting and was going too deep.

Thanks again guys, this is all a great help to a novice!

Rob

Edited By RobC on 01/02/2012 08:23:29
1 February 2012 at 10:03 #83611
Richard Parsons
Participant
@richardparsons61721
Taper reaming, are you using ‘Clock Makers Broaches’? These are normally hand tools. I have two sets. The 6-sided type for getting the hole close to size. I then use round smooth burnishing reamers to finish the hole.
Yes you can use ball bearings especially on those parts of the ‘Going Train’ where the ‘power levels’ are high. As the gearing ratio’s increase then ball/needle roller races are not advisable. You can get very low friction inserts, but in have never used them on clocks. I was using them on my tide computer where they worked well. That was until I received a ‘tribal visit’. The ‘Skilled Man’ dumped a large lump of a tractor engine on my instrument bench. As a result of my protest –he had crushed my multi-meter and the mechanical tide computer and other odds and ends. He then threw all the broken stuff into the barley field opposite –enough!
I normally drill my plates with my Startrite Mercuary pillar drill for the pivots or in my milling machine (using co-ordinate drilling) for the support pillars. I always use a slab of block board to drill on. This stuff is reasonably accurate.
Using the Archimedian drill you will find that with very small drills they will automatically become very close to the vertical. I have read that Cherry Hill uses them to spot the centres of holes to be drilled.
If you are drilling deep holes I have a rule of pecking which seems to work it is that the peck should be no deeper than 1 ½ time the drill diameter. I have drilled 1/16” holes 3.2” deep. It was slow work but successful.

Rdgs

Dick
1 February 2012 at 11:35 #83619
Cornish Jack
Participant
@cornishjack
Hi Rob

I also have a Fobco Star – superb bit of ‘old style’ quality engineering (and, surprisingly, still offering spares!). One of its problems is its sheer rigidity – with the table and column locked, if the drill isn’t EXACTLY on the mark, the drill will bend. Additionally, the chuck jaws are of a size to make central location difficult – I have lost count of the times I have got a small drill trapped between two chuck jaws , close to, but not on centre.

On the clockmaking side, I was lucky enough a few years ago, to be invited to John Wilding’s home and workshop (before his move). I was contemplating clockmaking and asked him about the need for, and method of drilling, taper pin holes. His reply was that he no longer used taper pins for plate location, preferring (IIRC) small BA bolts or screws. If that is good enough for ‘The Master’ who am I to argue?

Rgds

Bill
1 February 2012 at 14:47 #83626
RobC
Participant
@robc77385
Update – I have measured the ‘wobble’ on the drill chuck.

With a piece of round tool steel held in the chuck, I have movement of 0.30mm (0.012″) measured with a DTI at about 1″ below the chuck.

Removing the chuck and cleaning the scuffs off the taper itself, I have about 0.06mm (0.002″).

All of this assumes that I am reading my DTI correctly, that is to say that the overall swing covers the values I mentioned.

Is this amount of movement acceptable or do I need to try to sort it out?

Rob
1 February 2012 at 14:58 #83628
Anonymous
Hi Rob,

I would have expected the taper itself to be rather better than 2 thou, should be half a thou or better. I suspect that the 12 thou wobble is the main cause of your problems; I’d say it was unacceptable. If I get a chance later this evening I’ll measure my drill press and vertical mill and see what values I get.

As an aside I find that WD40 is pretty good when drilling aluminium alloys. You’re not really looking for lubrication, more to stop the swarf sticking to the tool.

Regards,

Andrew
1 February 2012 at 21:53 #83658
Sub Mandrel
Participant
@submandrel
> If that is good enough for ‘The Master’ who am I to argue?

Funny how model engineers chase spurious precision. I have seen so much about setting tool heights.

George H Thomas described a precision height gauge, to be constructed with extreme accuracy. Then near the end of the peice he says that if it is to be used for tool height setting, just set the gauge using a pip in the end of the work or a centre in the tailstock!

Neil
1 February 2012 at 22:12 #83660
Stephen Benson
Participant
@stephenbenson75261
Posted by Stub Mandrel on 01/02/2012 21:53:25:

> If that is good enough for ‘The Master’ who am I to argue?

Funny how model engineers chase spurious precision. I have seen so much about setting tool heights.

George H Thomas described a precision height gauge, to be constructed with extreme accuracy. Then near the end of the peice he says that if it is to be used for tool height setting, just set the gauge using a pip in the end of the work or a centre in the tailstock!

Neil

The Master in this case is John Wilding but he and Laurie Penman when they were both writing for Clocks Magazine used to disagree all the time quite often on fundamentals. In fact ask five clockmakers the same question and more often than not you will get five different answers. In clockmaking you need to pick your mentor and stick with him otherwise you will get very confused, I recommend Steve Conovor for clock repair but I very much enjoy John Wilding’s construction books.

Edited By Stephen Benson on 01/02/2012 22:13:07

Edited By Stephen Benson on 01/02/2012 22:13:37

Edited By Stephen Benson on 01/02/2012 22:16:58
1 February 2012 at 22:19 #83662
blowlamp
Participant
@blowlamp
If you want to see a true master from yesteryear, you could do worse than check out Thomas Mudge.

Martin.
1 February 2012 at 22:22 #83663
Anonymous
Here are the measured values for my machines. The measurements were taken with a piece of 1/2″ silver steel in a drill chuck, 1″ below the chuck jaws.

1) Pillar drill – Tauco, probably Lend-Lease – total run out 0.1mm

2) Vertical mill – Bridgeport, probably 1970s – total run out 0.07mm

I almost never use the pillar drill, but I have successfully drilled hundreds of 0.7mm holes 8mm deep in brass with the vertical mill.

Regards,

Andrew

PS: Funny thing, but I set my lathe tool heights by eye from a centre in the tailstock
2 February 2012 at 18:14 #83707
RobC
Participant
@robc77385
I think I have found one cause of my ‘wobble’ problem!

If I put my DTI on the taper of the drill and gently press the top of the quill, where it protrudes from the pulley, I can cause a deflection of just under 0.1mm to be shown.

I am guessing that the top bearings are either not seated well, or have seen better days.

Any ideas how I find out what they are so that I can replace them without having too much down time on the drill?

It is a Fobco Star and I do have the ‘manual’ from lathes.co.uk, but there is nothing in there about them that I can see.

Rob
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