Very Small Drill

I need to drill some very small holes in the end of a shaft (# 71 drill, which is .026" diameter). The purpose is to allow the use of a split pin (cotter pin) through slits in the end of a nut (ie a Castellated nut) to prevent it from coming off the shaft.

The shaft diameter is 5/32" and the castellated slits are about 20 thou wide.

I propose to make split pins using some soft iron wire from the centre of plastic bag ties (It is about 12 thou in diameter).

I propose to make a drilling jig by drilling a hole for the shaft in a 1/2" square piece of BMS, and then at right angles drill a # 71 hole at an appropriate distance from the end.

Two Questions:

1. Is this a good way o do the job? Is there an alternative (better) approach. (I am not sure Loctite will work).

2. How do I hold the very small drill? None of my chucks will hold a drill that small, and my smallest collet is 2 mm?

All suggestions gratefully received

John A

Well I've done 0.5mm (0.020" splitins into 0.6mm (0.024" holes and just centred up the work under the drill axis, touched it with a spotting drill and drilled.

To hold the drill make a split collet buy drilling down the end of short length of rod with required drill, put a saw split down it slength to the middle and then hold in your drill chuck

I don't know why you are drilling 0.026" for a 0.012" pin or are you just going to use round section wire? I made the small ones by filing 0.5mm stitching wire to half round section and then bent to the shape of a split pin. The actual pin they went through was 1/16"

Edited By Katy Purvis on 08/02/2013 12:32:27

I made the split pins for the pins in the govenor linkage of the Stuart Turner S6 that I restored, I put the wite in my fretsaw frame to tension it, and filed it to half diameter.

To hold small drills in a chuck that won't close up enough, get some reasonably soft iron wire (some where about 24 SWG), and wrap it tightly around the shank of the drill, that way I can hold 1 mm drills in the 16 mm drill chuck on my mill drill, although I do have a 5/16" Jacobs, with a parallel shaft that was part of an old electric hand drill, the shaft fits in the bigger chuck, and holds right down to zero.

Ian S C

Use an Eclipse pin chuck, mine will easily hold a No.80 drill, the smallest I have:

I bought mine on Ebay, but they are available commercially.

Regards,

Andrew

John,

Far better than using a lash-up, buy a suitable drill chuck, such as the 0.4-4.0 mm one on this page (first item): **LINK**

Only £12 (plus a few £ for an arbour) and you will be able to use it again and again...

Concentricity is important with tiny drill bits, and this will give you the best chance. Withdraw frequently to clear the flutes, clogging of the flutes is probably the most common cause of breakage at these small sizes.

David

John A,

If at all possible drill your cross holes before threading the rod/bolt. You'll get far fewer drill dig ins or breakages that way round. If you have to drill into a threaded bar at least file a little flat where the hole will be to help get it started but beware the break out on the other side.

Bob D

I made the cross holes in the pins for these links using a No. 60 drill, and just made a tiny flat with a file before drilling. Just used my clarke pillar drill, but drilled teh pins before parting them off the stock.

The spring clips are from guitar 'e-string' - annealed so it will bend then re hardened and tempered. Looking at the picture perhaps I should have used heavier wire.

The heat treatment was a bit his and miss and I had one that stayed brittle and broke.

I like Jason's split pins.

Neil

Edited By Stub Mandrel on 06/02/2013 14:17:47

Hi, why not thread the shaft and put a lock nut on to it or carefully cut the nut horizontally half way through then close the gap made by the saw or slitting tool, this then makes a self locking nut.

Scroll down and see the pic of the small drill chuck for small drill in this **LINK**

But don't try that one in a drill press or mill as the lever will fly round!!

Something like this from ARC would be safer

Thank you all for your suggestions.

The problem with your first suggestion Jason B is that I need to hold the drill to drill a hole to hold the drill...........etc!

I like the second idea better, and the micro drill adaptor will be very useful as will the small chuck.

I have ordered from ARC Euro Trade in the past and their service is astounding. On both occasions I placed an order on Thursday night (Eastern Australian Standard Time) and the items were delivered on the following Monday morning to my Melbourne address. And the prices were about 60% of what I would have paid here, even after air freight of about $45 per kilo. And the delivery was quicker than when I ordered from a firm on the other side of Melbourne.

I have a number of pin chucks, and have used them in the past for small drills, but none are concentric and they can only be used with a hand held drill where they centre temselves. A bit too fraught for 25 thou.

There is insufficient clearance for locknuts, but the split nut is a thought. Any comment on that!

I had not planned to file or flatten the wire - I can barely see it, hence the hole twice the diameter, plus it's less fragile.

Thanks all of you.

John A

What sort of speed is necessary for very small drills in the 60 - 80 range? I was once told as fast as possible but I have since read that this is not the case.

Mick

Whether you use a positive locking device such as your castellated nut and split pin or a secondary lock such as the stiffnut suggestion depends on several things. Firstly the requirements of what you are making, a scale appearance for instance. Then there are the likelehood and consequences of the nut coming loose and then the difficulty of manufacture. Drilling the hole for a pin would seem to me to be no more difficult than making a clean looking slot in the side of a 5/32 nut. The easiest would be an appropriate grade of thread locking adhesive, again dependant on usage conditions and bearing in mind that once it is used disassembly and reassembly , although far from impossible, is not straightforward.

Jim

Seems a bit odd? I've used my pin chuck to drill several hundred 0.7mm holes 8mm deep in brass, on a Bridgeport mill, without breaking a drill.

I also found that, by just touching the small drill on the surface before commencing drilling proper, I didn't need to centre or spot drill first.

Andrew

I agree with Andrew, I have used 0.5mm drill in the Bridgeport without problems. Straight in the normal chuck as well!. The Bridgeport is hardly a sensitive drill either.

Perhaps it is easier to use a drill with a thickened shaft. Providing the hole you want to make is not to deep, removing most of the twist from small diameter drills (below 0.6mm) and that sharpen the left over bit again, gives a much stiffer drill. Niko.

drillspeeed? hss drill ms part 10,000 RPM /drill diameter (In mm)...

hence my pcb drill runs up to 36,000rpm..0.3 mm drills are my limit for hobby work

.smaller aperture for optics or gas bleeds use etching or sneaky technique.

The smallest drill I've ever used was 1mm dia. but I've been thinking, never a good idea. What happened to "spade" drills and the like ? seems to me to be a good solution to small holes, esp. when not very deep.

I use drills down to No. 70 in my cheap pillar drill at top speed for drilling PCBs.

It shouldn't work, but it does and the difference in accuracy, speed and reduction in breakage compared to a hand-held multi-tool is significant.

Neil