Monday, March 14, 2016

Modifying a Hanging Motor Mandrel.




A simple way to turn a rubber wheel mandrel into an adapter for different drill and burr sizes.


Every now and then I have to drill a long hole through something with my hanging motor.

This is a real drag if the piece cannot be clamped into a drill press or a vice.

Just such a piece came across by bench the other day.

A long very delicate bone carving that had to have a 2 mm hole through.

One of those, that if it was broken, it would be irreparable and also had a bucket load of sentimental value attached to it.

So I modified a standard rubber wheel mandrel that I buy at my jewellery tool supplier.


It's got a 1.5-ish mm screw that screws in to hold the rubber wheel.


So I ream it out using progressively larger ball frazers.

I do this on the bench using my hanging motor.

First 1.6 mm then 1.8 mm then 2.1 mm for a 2 mm drill.


Once it is reamed out, I file a flat on the ends and punch it.


I drill a 1.5 mm hole through both sides.

That is the correct size hole for a 2 mm tap.

I drill the hole right through so there is space for the tip of the tap to go deeper in.


Then I tap it.

Only one side needs be tapped.




I used a brass screw because I had them.

I thought they might be a bit soft but they work fine.

Stainless steel would be better but they are a mission to make, so brass it is.


The shortened screw.


Then I trim the brass screw off and cut a slot in it with my piercing saw.

Then I use a cup burr to make it domed and smooth.


I cut the mandrel shorter so the cone starts right up against the chuck.

I also made a flat section on the drill bit so that the lock screw holds the drill there.

I use a cut off disk for this.

That way the lock screw does not have to be tightened very, very tight


Locked and loaded.


I caught a dentist in the wild and tamed him, so now he gives me his old diamond burrs.

His blunt burrs are my sharp ones.

So I made a mandrel for those burrs as well.


The cone right up against the chuck so there is minimum wobble.

Any comments can be written on a 500EU note and posted to me.

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