Long, thin (3mm-ish) drill

[gregmcateer]

Hi Folks,

I have been asked to make some light pulls and the only 3mm drill I have is about 5 cm long. I have reversed the piece and drilled from both ends, but it does go off centre and I am concerned that when turned, I may get some breakout on the thinner sections.

Are there long drills of this sort of diameter? Or is there some sort of sleeve that could give the drill body some support, at the non-business end?

Or am I going about this wrongly and there is some cunning method I've not yet sussed out?!

Thanks in advance for any advice.

Greg

 

[nev]

PM me your address Greg and I'll stick one in the post. I bought a pack of ten when I first tried light pulls and I think I can spare one

 

[Paul Hannaby]

Tilgear and other suppliers do long series drills.

 

[gregmcateer]

Thanks, Nev and Paul.

Greg

 

[nev]

... Are there long drills of this sort of diameter? Or is there some sort of sleeve that could give the drill body some support, at the non-business end?

Or am I going about this wrongly and there is some cunning method I've not yet sussed out? Greg

The drill WILL wander, so the trick is to drill the hole in your (square?) blank then use the holes to mount and support the blank on the lathe sort of guaranteeing that the hole will be central. Do you have a light pull mandrel? they do make life a little easier.

 

[chipmunk]

Hi Greg,
I like to use an engineering centre-drill with a 3mm tip to create the knot hole. Then continue right on through the blank with a 3mm long series drill (Toolstation).

You can create your own drive using a piece of metal rod (or tube) of the same diameter as your knot hole with a few teeth filed in the end like a mini Steb centre. Put a 60 degree live centre in the 3mm hole and away you go.

A neat trick to stop scoring your live centre with either your gouge or skew when you trim the top of the light pull is to grab hold of the live centre and turn it into a dead centre for a few seconds as you cut the last few fibres - if that makes sense. You need to make sure you haven't got too much pressure on the tailstock and you can only trim a small amount. Then finally screw in the tailstock a bit to take up the slack again.

HTH
Jon

 

[=Adam=]

Hi chipmunk!

Can you go through the drive idea again please, I'm not sure what you mean about filing teeth into the metal rod. Do you then hold this metal rod in your drill chuck at the headstock?

I like the idea of this as I don't really want to spend £10 (plus p&p) on the axi model! I know, I know, I'm tight! But I like to use things that I have made

 

[=Adam=]

... Are there long drills of this sort of diameter? Or is there some sort of sleeve that could give the drill body some support, at the non-business end?

Or am I going about this wrongly and there is some cunning method I've not yet sussed out? Greg

The drill WILL wander, so the trick is to drill the hole in your (square?) blank then use the holes to mount and support the blank on the lathe sort of guaranteeing that the hole will be central. Do you have a light pull mandrel? they do make life a little easier.

Nev are you saying to drill the hole before turning and then to mount the drilled blank on your mandrel? That seems like a logical approach! I drilled mine after turning, it turned out ok but the hole could have been a bit more central.

 

[nev]

Nev are you saying to drill the hole before turning and then to mount the drilled blank on your mandrel? That seems like a logical approach! I drilled mine after turning, it turned out ok but the hole could have been a bit more central.

yes, then stick the tailstock drive/point in one end of the hole and the drive in the other.

 

[chipmunk]

Sorry Adam, of course.

If you use a centre-drill the knot hole it will be tapered (countersinked) at the end where the diameter goes from big to small and so teeth in the end of a rod or tube can grip this sloping section.

The teeth can simply be a series of roughly filed nicks with a triangle file (saw sharpening file) or even a hack saw around the edge to produce a set of points that'll bite into this section inside the knot hole.

If the rod and hole are the same size then you can even make a rough two-prong drive by filing the rod to a blade like shape (think flat screwdriver).

I think this is more positive than the Wilkie drive Axminster sell which is just relies on friction. I think you can buy a tiny steb centre along the same principles but it doesn't have a sprung point.

Either hold this rod/tube drive in a Jacobs chuck or better still mount it into a blank-end arbor (drill hole and then araldite it in or put in a grub screw through the side). Blank end arbors only come in MT2 and MT3 though like this one...

http://www.arceurotrade.co.uk/Catalogue/Blank-End-Arbors

This makes it a real drive centre like your others for a fraction of the cost.
HTH
Jon

 

[gregmcateer]

Great help. Thanks guys
Greg

 

[=Adam=]

Sorry Adam, of course.

If you use a centre-drill the knot hole it will be tapered (countersinked) at the end where the diameter goes from big to small and so teeth in the end of a rod or tube can grip this sloping section.

The teeth can simply be a series of roughly filed nicks with a triangle file (saw sharpening file) or even a hack saw around the edge to produce a set of points that'll bite into this section inside the knot hole.

If the rod and hole are the same size then you can even make a rough two-prong drive by filing the rod to a blade like shape (think flat screwdriver).

I think this is more positive than the Wilkie drive Axminster sell which is just relies on friction. I think you can buy a tiny steb centre along the same principles but it doesn't have a sprung point.

Either hold this rod/tube drive in a Jacobs chuck or better still mount it into a blank-end arbor (drill hole and then araldite it in or put in a grub screw through the side). Blank end arbors only come in MT2 and MT3 though like this one...

http://www.arceurotrade.co.uk/Catalogue/Blank-End-Arbors

This makes it a real drive centre like your others for a fraction of the cost.
HTH
Jon

Sorry but I dont quite understand the principle, from what you are saying I assume that you mean to use a 3mm metal rod for a 3mm hole, if I am right in what I am saying then wouldnt the rod slide through the hole and not grab anything? or are you suggesting using say a 4 or 5mm bar for the 3mm hole so that the 'teeth' grab on to the countersunk section?

Sorry for my ignorance, I just cannot picture it.

Thanks

 

[chipmunk]

Hi Adam,
If you look at a picture of a centre-drill it may be clearer.
http://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Centre-Drills

It has a wide section (think knot hole ~8mm) and a thin end section (think ~3mm string hole) and a countersink section..

The rod/drive then fits into the wider 8mm knot hole and the teeth bit into the transition/step/countersink between wide hole and narrow hole. Any dents in this are well inside the light pull and hidden by the knot and so won't show.

Is that easier to understand?
Sorry - My wife reckons I'm rubbish at explaining anything.
Jon

 

[=Adam=]

Hi Adam,
If you look at a picture of a centre-drill it may be clearer.
http://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Centre-Drills

It has a wide section (think knot hole ~8mm) and a thin end section (think ~3mm string hole) and a countersink section..

The rod/drive then fits into the wider 8mm knot hole and the teeth bit into the transition/step/countersink between wide hole and narrow hole. Any dents in this are well inside the light pull and hidden by the knot and so won't show.

Is that easier to understand?
Sorry - My wife reckons I'm rubbish at explaining anything.
Jon

Thanks Jon, what size rod would you use to 'Drive' it? would it be an 8mm one or just anything larger than the 3mm pilot hole?

 

[chipmunk]

I use an 8mm diameter drive.

Mine's made of 8mm tube (B&Q in 1m lengths) with teeth filed in the end and drilled out to accept a 6mm rod up the centre (B&Q too) to reinforce it. The end of the 6mm rod is also shaped to a point on the end and so when inside it makes something that looks like a baby Steb but the point is fixed rather than sprung.

But an 8mm diameter rod sharpened to make a two-prong drive would almost certainly also work if the knot hole is deep enough.

HTH
Jon

 

[gregmcateer]

Great help, everyone.
Thnaks for taking the questions and explanations further than my original post - Very helpful
Greg