Modifying Flex Shaft Hand piece Mandrel



A simple way to turn a rubber wheel mandrel into a drill bit extender or an adapter for different drill and bur shaft sizes such as dental drill bits to be used in your flex shaft motor handpiece.



Every now and then you have to drill a long hole through something with your hanging motor.
This is a real drag if the piece cannot be clamped into a drill press or a vice.

Like a long delicate bone carving that has to have a 2 mm hole through.
One of those, that if it was broken it would be irreparable and also had a lot of sentimental value attached to it.

So here we will show you how you can modify a standard rubber wheel mandrel.


Select a 1.5 mm screw that screws in to hold the rubber wheel.


Ream it out using larger ball burs.

Do this on the bench using your hanging motor.

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



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



Drill a 1.5 mm hole through both sides.

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

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



Then tap it.

Only one side needs to be tapped.




You can use a brass or stainless steel screw.





Then trim the screw off and cut a slot in it with your piercing saw.

Then use a cup bur to make it domed and smooth.



Cut the mandrel shorter so the cone starts right up against the chuck.

Make a flat section on the drill bit so that the lock screw holds the drill there.

You can use a cut off disk for this.

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



Drill bit fitted and locked.


You can make a mandrel to fit your diamond burs too.



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


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