soligen
Member
Here are some pictures of a closed end mandrel I devised. I like it because for a new tube size all I need to do is make a new sleeve.
I made this from a 1 / 4 inch bolt, cutting off the threads and head to form a mandrel. I had to sand it a bit to get a 7mm tube to slide over it. I drilled a hole on the end (Drilled on lathe) and used a center bit to put a 60 degree chamfer on it so I could make the mandrel between centers. I epoxied a small piece if 7mm tube on the the end so I could create the taper to expand the sleeve.
Picture 4 shows how the mandrel looks without a blank mounted on it. Picture 5 then has a tube mounted on it.
Picture 6 – to expand the inside part of the sleeve, mount it in the collet chuck with a block of wood. Pull the block of wood away from the headstock which pushes the sleeve over the tapered brass part of the mandrel, thus expanding it.
To expand the other side of the sleeve (pic 7) mount the mandrel and remount with the expanding collar, then pull the wood piece to push in the expanding collar.
Pic 8: Ready to turn. The wood piece is removed. Push into the collet all the way.
The expanding collar is just a 7mm tube glued into a scrap of blank with the ends squared and a taper on the end of the tube.
For the sleeve, Glue in a 7mm tube. Be sure to get excellent glue coverage (CA not recommended). Turn until you have a free slip fit in the target tube size. Square the ends and chamfer the insides of the tube (make sure the chamfer is square to the tubes – Use a chamfer bit set up like you are drilling on the lathe. Cut the slots on a band or scroll saw. I made the sleeve 1.5 inches long
Total cost < $1. New tube sizes only require making a new sleeve.
Edit: To remove the mandrel, you have to remove the expanding collar and then push it in, so make sure there is room for this when mounting something with a closed end. Try it with an open ended blank first to get the feel.
I made this from a 1 / 4 inch bolt, cutting off the threads and head to form a mandrel. I had to sand it a bit to get a 7mm tube to slide over it. I drilled a hole on the end (Drilled on lathe) and used a center bit to put a 60 degree chamfer on it so I could make the mandrel between centers. I epoxied a small piece if 7mm tube on the the end so I could create the taper to expand the sleeve.
Picture 4 shows how the mandrel looks without a blank mounted on it. Picture 5 then has a tube mounted on it.
Picture 6 – to expand the inside part of the sleeve, mount it in the collet chuck with a block of wood. Pull the block of wood away from the headstock which pushes the sleeve over the tapered brass part of the mandrel, thus expanding it.
To expand the other side of the sleeve (pic 7) mount the mandrel and remount with the expanding collar, then pull the wood piece to push in the expanding collar.
Pic 8: Ready to turn. The wood piece is removed. Push into the collet all the way.
The expanding collar is just a 7mm tube glued into a scrap of blank with the ends squared and a taper on the end of the tube.
For the sleeve, Glue in a 7mm tube. Be sure to get excellent glue coverage (CA not recommended). Turn until you have a free slip fit in the target tube size. Square the ends and chamfer the insides of the tube (make sure the chamfer is square to the tubes – Use a chamfer bit set up like you are drilling on the lathe. Cut the slots on a band or scroll saw. I made the sleeve 1.5 inches long
Total cost < $1. New tube sizes only require making a new sleeve.
Edit: To remove the mandrel, you have to remove the expanding collar and then push it in, so make sure there is room for this when mounting something with a closed end. Try it with an open ended blank first to get the feel.
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