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Tubal Cain : 0.5mm holes : spade point bit needed ? why ?

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BW16/02/2019 09:22:47
194 forum posts
31 photos

Hello,

Following success with a couple of very simple little steam engine models, I have been reading "Simple Model Steam Engines" by Tubal Cain.

On one of his builds he recommends Jewellers Spade Point Drill Bits for drilling 0.5mm holes.

Do you always need this sort of drill bit for tiny holes ?

Bill

And PS - If any novices want easy engines to have a go at try these .     Mikes Workshop Wobbler and HMEM EZ Engine .........  fairly easy to make, forgiving of my various inaccuracies and terrific sense of satisfaction when you see them moving round and round.

 

Edited By BW on 16/02/2019 09:27:25

Michael Gilligan16/02/2019 09:43:11
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12699 forum posts
551 photos
Posted by BW on 16/02/2019 09:22:47:

I have been reading "Simple Model Steam Engines" by Tubal Cain.

On one of his builds he recommends Jewellers Spade Point Drill Bits for drilling 0.5mm holes.

Do you always need this sort of drill bit for tiny holes ?

.

When he first wrote that, it was doubtless a wise recommendation [check the date]

... Times have changed: So, no ... not always.

MichaelG.

.

According to Wikipedia, he graduated in 1934

https://en.m.wikipedia.org/wiki/Tom_Walshaw

Edited By Michael Gilligan on 16/02/2019 09:53:31

pgk pgk16/02/2019 09:51:07
1229 forum posts
278 photos

I'll have a crack at speculating on the answer here (but it is just guesswork). According to tom's techniques the problem with tiny twist drills breaking is having a drill that can run fast enough. And of course any twist drill has a thinner core than it's cutting diameter which essentialy makes it weaker still and more prone to bending and wandering. A spade end is also going to be less challenging to sharpen and easier to hone without losing temper.

I've never tried drilling such tiny holes in steel but I have used tiny bone pins like that for orthopaedic fragment repair and as pilots for wire holes..less prone to wandering on starting the hole and can be used in a hand chuck (into bone). If the hole wasn't of any great depth then I have popped bur-holes that size through orthopaedic steel using a high-speed water-cooled dental drill bit but at 1 to 300,000rpm it's a different ball-game.

pgk

Weary16/02/2019 12:25:35
266 forum posts

To answer your question:

"On one of his builds he [Tubal Cain] recommends Jewellers Spade Point Drill Bits for drilling 0.5mm holes.

Do you always need this sort of drill bit for tiny holes ?"

 

No.

I would suggest 0.5mm PCB Tungsten Carbide drill bits in the appropriate collet as the modern equivalent.

If you are unfamiliar with these drill-bits then a search on ebay will illustrate the sort of thing which is available from many suppliers in a range of sizes.  I tried to link to a suitable ad' but was unable to do-so successfully.

You do not have to drill at fantastic rotational speed, but if drilling at slow rotational speeds then you must proceed very gently with extremely frequent withdrawal and clearing of the flutes.  You may find the bits perform better without 'suds' which, depending on the material you are drilling into, can slow debris clearance - in my experience anyway.  A bit of experimentation may be in order.

Regards,

Phil

 

 

Edited By Weary on 16/02/2019 12:32:15

not done it yet16/02/2019 12:55:00
2651 forum posts
11 photos

His is of a similar ‘time warp’ to the ETW era plans, where all(?) were centred around hand tools - and a lathe as the only main mechanical aid required/expected. Perhaps an electric drill, of some description, might be added, but most certainly not a milling machine.

Joules Beech16/02/2019 12:59:34
34 forum posts
7 photos

They are however fun to make and use out of piano wire. Give them a go, learn some new skills it’s never wasted time.

Neil Wyatt16/02/2019 14:58:40
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15589 forum posts
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No, but they work very well.

roy entwistle16/02/2019 15:09:58
933 forum posts

On a Horological course we made them out of sewing needles,  very effective too

Roy

Edited By roy entwistle on 16/02/2019 15:10:27

BW16/02/2019 22:39:39
194 forum posts
31 photos

Thanks for the tips,

If anybody else stumbles across this thread ....................

I found this how to make a tiny spade bit article which seems useful

http://www.wirralmodelengineeringsociety.co.uk/Articles/spadedrillbits.pdf

and this youtube video  - most of it is talking, the guts of the method is demonstrated in the end of the video,  it seems sensible. I am vaguely aware of a watchmakers technique where the operator simply pushes a drill in a hand held pin vice into the spinning workpiece. Is that a standard watchmakers technique ?

https://www.youtube.com/watch?v=PqU5wS0J4MU&t=611s

..... and I finally used the link tool so somebody doesnt have to do it for me ...

 

Bill

 

 

 

 

 

Edited By BW on 16/02/2019 22:43:13

lfoggy19/02/2019 00:10:53
31 forum posts
5 photos

A few years ago I had to drill a number of small holes (0.3 - 0.5mm) in brass and steel for a project. Although you can buy twist drills in this size you need very high speeds to make them work properly. I ended up buying a micro drill press with a speed range of up to 30,000rpm. At high speeds these small drills cut very well, rarely break and last for ages as well.

**LINK**

Its proven quite useful in the worshop for any drilling under 1.5mm or so.

Ian Newman 126/02/2019 09:27:55
11 forum posts

Hi,

The method of making very small hole by hand holding the drill bit is a "standard" trick. I use a graver to catch the hole/rotation centre rather than a centre drill (which is generally too large for the job). See the videos below for my take on it:

Gravers:

https://m.youtube.com/watch?v=lZ7PP4KgzmU

Catching a centre:

https://m.youtube.com/watch?v=f8IDhos0Qtw

Drilling:

https://m.youtube.com/watch?v=maUtJ2UBuMs

The finished hole:

https://m.youtube.com/watch?v=hiXwU0qn9s0

(The last video includes the workshop cat and the little kid from next door who always came round when he heard the "Grumpy Old Man" doing stuff in the workshop)

The reason the method works is simple physics:

If you have a rotating drill and a fixed work piece, the drill has an axis of rotation and there are cutting forces on both lips of the drill bit - the forces are not equal (the drill bit will not be perfectly symmetrical) and so as the force on one side of the drill bit is greater than on the other, the drill bit gets pushed off axis and the hole "drifts"

If the work rotates, the same physics applies and the drill bit will move until the forces on each side of the drill are equal - this happens no matter how deep the hole is, the drill bit is always forced towards the axis of rotation of the work piece

Holding the drill in a fixed (i.e. tailstock) chuck results in a conflict between the path the drill bit wants to follow and the path being forced on it by the chuck - this can result in a small drill bit snapping. With very small diameter bits, it is best to hold the bit by hand to allow it freedom to "float" - it also allows you to let the drill "slip" in your fingers if/when the drill grabs, or something else goes wrong

I've been using lathes for 50 years and have broken loads of things in that time, but I've never snapped a small drill using the above technique

All the best,

Ian

Steve Crow27/02/2019 17:44:13
96 forum posts
21 photos

I can recommend these drill bits. I've drilled over 100 0.5mm holes through ground flat stock with one of these without breakage. This was using a small bench drill at about 3000rpm.

lfoggy27/02/2019 19:53:01
31 forum posts
5 photos

Ian,

Some good tips and videos there.

Most of the small holes I need to drill seem to be in workpieces that can't be rotated in a lathe chuck though, so I end up having to resort to the drill press.....

Ian Newman 127/02/2019 20:45:14
11 forum posts

Hi Ifoggy,

<SNIP>

Most of the small holes I need to drill seem to be in workpieces that can't be rotated

</SNIP>

Ah yes, the difference between the beautiful ideal of the perfect world, and the brutal reality of the real world

All the best,

Ian

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