View Full Version : expanding mandrel

02-01-2008, 02:49 AM
i need to make an expanding mandrel for a project. I can't afford to buy one right now, they're pretty expensive. Has anyone out there made one? Does any one know were I can find drawings? Thank you.

02-01-2008, 03:02 AM
Howdy. You don't say exactly what you're going to do with the mandrel or why it needs to be an expanding one instead of a tapered piece. A simple expanding mandrel can be easily made, but for specifics you need to state the diameter and length required for the mounting end. If you look at the sets in the Enco catalog, you'll get the general idea though.

02-01-2008, 03:21 AM
A quick and dirty small expanding mandrel can be made by turning your stock to the desired diameter, then drilling and tapping the end a short ways. Cut across the end with a hacksaw, deburr, slide on your workpiece and install a setscrew. By just threading a short way you'll tighten the setscrew into the tapered threads and expand the mandrel. I've used this to turn small pulleys and insure that everything is concentric. The mandrel had a 9mm OD and I used a 1/4-20 setscrew.


Forrest Addy
02-01-2008, 03:58 AM
I make expanding mandrels (actually spuds because they have a locating shoulder) the way I was taught by a dinosaur named Bill Shipley in 1962. Machine the spud to rough size, drill and tap though the axis for a pipe plug. Split the diameter into several sectors, run in a pipe plus just snug, and turn the reference features to final size. They repeat within 0.0005" if made right.

One thing: make a death grip prep on the chuck end of the spud and grip it in a four jaw. Three jaw chucks may be a bit slippery especially if the jaws are bell-mouthed

02-01-2008, 06:21 AM
I might add a NPT tap (as mentioned above) works better as it is Tapered, But if you use a regular tap , Don't use a bottoming tap for obvious reasons.

02-01-2008, 10:55 PM
Enco has a 1 inch x 4 inch long mandrel for $17.43 don't think you can make one for that price when you think buy stock, slit kerf, drill and tap. I make my own expanding collets but I make them 20 or 30 at a time. enco part # 240-3204

02-02-2008, 01:48 AM
Enco has their expanding sleeve mandrels on sale for less than half price. I just got a bunch of them (21/32 to 1 1/2). For Chinese, they're pretty darn nice and great for turning between centers. I just used one today and they're dead on accurate and hold tight. The larger ones (in 1/4" steps) come with two sleeves to cover the range.

Here's one example. For $31, I can't see trying make one and they're more accurate and secure than a spud.