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Internal Tube Sander

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75Plus:
Just a thought. Would not the proposed solution tend to change the taper? The pressure on the abrasive would increase as the diameter decreased causing the smaller part of the bore to be expanded.

A brake cylinder hone is spring loaded with the pressure applied at the center of each individual hone resulting in equal pressure on both ends.

JMHO

Joe

DMIOM:
Ant,

The conventional cylinder hone route should be OK I would have thought, if your mold has a constant draft angle, and you can get (or adapt) one with suitable length arms.

The hones are pivotted and will take up the angle (within reason) of the taper, In operation, the drive shaft needs to be on the axis of the cylinder; the stones are then kept in contact by the centrifugal force as the hone is spun up.

It won't do well though if you try to operate a smallbore hone set off-centre in a large cylinder - the independently-pivotted arms will just flop about, giving effectively interrupted cuts - but, if necessary, making a longer set of matched arms shouldn't be hard.

The hone assembly does need to be spun-up to get the hones out to their operating radius - unfortunately it won't for example, work by having the hone mounted in a tool holder or in the tailstock, and then spinning the work still mounted in the lathe.  Best would probably be to mount the hone in a mill or drill press with the work centred underneath and raise/lower the quill to work the hones.

If the diameter of your mold is too great to use a set of hones, another alternative would be some form of toolpost grinder (search on here); in which case you'll need to leave the grinder set at the same angle you had on the compound when you turned the original taper. If you are going with your reciprocating sander, as Joe/Ralph have highlighted, you'll need a smaller drum so it is only in contact with one wall at a time, and the action shaft will have similarly have to be set at the same taper angle.

Dave

ant...:
Hi Guys
Just because I love a laugh more as much as anyone, im going to show you my progress  :lol:

This device vibrates so much i had to screw it into a concrete slab, it worked and did a great job for about 60 seconds before it tore its mountings out.
The pole is made from steel which is too heavy and add vibration, its travel is too long (2cm) which make the vibration more violent.




After a mornings work and ruining one of the concrete slabs in my back garden patio, i finally made this:





The power internal sander could be modified to work, with lighter materials and better gearing, but ive decided to try your Cylinder Hone idea first.
This Cylinder Hone is onle £17 and it has 3 different grit levels.  If it does work it will hide away much easier than my mad contraption :smart:

Gadget:
Use a real light oil with the hone, it will do a better job. Let us know how it turns out.

ant...:
Thats the first time ive ever heard of using oil with an abrassive, dont get me wrong ive tried it but the fine ali dust turned the oil to a thick mud.

ill try oil though, thanks for the tip.

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