Expanding Mandrel for turning large tubes

[Frank S]

I like that grub screw expansion method, my smaller mandrels use a tapered shaft and nut to open up a sawn cylinder, but the grub screw method is almost like a Taperlok fitting, very neat and easy to adjust from the end.

The disadvantage to them were I had to make one for each ID hydraulic cylinder tube I machined. At the same time it proved to be nice to have so many sizes. We purchased our honed tubing from a supplier in Turkey in quantities of batch lots of 10 to 30 6 meter random lengths for each size at a time they provided honing inspection certs. to tolerances of -0/+.05 mm or less. so 1/4 turn of each screw went from slip in to fully locked in place and centered every time we had a dedicated lathe with a collet chuck and left either a 40 or 50 mm collet in it at all times