I'm looking for opinions and options. for expanding mandrels.
I've seen some cheap sets on ebay that have set screw in one end to
expand the mandrel. I've also seen the sliding taper version which
could be mounted between centers if needed.

Trying to keep to a small budget, but will spend enought o get the right
tools that I need. Tired of using threaded rods nuts and bolts.

Plus and the parts I need to make don't have any tight tolerances except
of the center shaft hole.

I want to hold stainless steel, aluminum and plastic (PVC, UHMW PE ,
Delrin) Inside ID 1/2" and 1".

Making parts for packaging machinery. Part would be no bigger than 4"
od and 2" wide.

Please point me in the right direction

Thanks
Mike Miller

On Sun, 02 Apr 2006 22:35:05 GMT, Mike wrote:

I'm looking for opinions and options. for expanding mandrels.
I've seen some cheap sets on ebay that have set screw in one end to
expand the mandrel. I've also seen the sliding taper version which
could be mounted between centers if needed.

Trying to keep to a small budget, but will spend enought o get the right
tools that I need. Tired of using threaded rods nuts and bolts.

Plus and the parts I need to make don't have any tight tolerances except
of the center shaft hole.

I want to hold stainless steel, aluminum and plastic (PVC, UHMW PE ,
Delrin) Inside ID 1/2" and 1".

Making parts for packaging machinery. Part would be no bigger than 4"
od and 2" wide.

Please point me in the right direction

Thanks
Mike Miller
Greetings Mike,
The ones with the sliding expanding sleeve are better than the ones
with a screw in the end. If you can rough the parts first and then
slip onto a mandrel for the finish pass I have a suggestion for making
these parts fast. Rough the parts first by holding in the 3 jaw chuck
and turning 1/2 the length. Turn the part around and repeat. Leave
..015" or so for a finish pass. Since the through holes will be sized
accurately you will only need two mandrels, 1.000" dia. and .500"dia.
We'll use the 1.000" mandrel as the example: If the chuck runs true
then use 1.000" diameter stock. If not then use oversize material and
turn to size. Mark the mandrel so that it goes into the chuck the same
each time. Assuming oversize stock put the stock into the chuck
sticking out a little longer than the length of the part to be turned.
If the mandrel is longthen center drill the stock. Use a live center
to support the outboard end and turn the stock down to the desired
size. Depending on how long the mandrel is you may want to turn it
undersize in the middle to make it easier to slide the part onto. Now,
with the stock marked so that it will go into the chuck the same way,
remove the mandrel and clamp it in a vise on your mill. Mill a flat
close to the chuck end that is just over 1" long and either .128 or
..191 deep. Make a mark on the un-turned part of the mandrel in line
with the flat is so you will know where the flat is when the part is
on the mandrel and covering the flat. Now put the mandrel back into
the lathe chuck exactly the way it was when you turned it. Rotate the
chuck so that the flat is on top. Slide the part onto the mandrel
almost to the flat. Depending on how deep the flat was milled, place
either a .125" or .1875" dowell pin centered on the flat . Slide the
part over the flat and the pin. Rotate the chuck away from you about
45 degrees. Rotate the part on the mandrel away from you and the pin
will become wedged between the part and the mandrel. Turn the part
with the outboard end of the mandrel supported by a live center. Now
that the part is finished rotate the chuck so that the flat is rotated
toward you a few degrees from top dead center. Grasp the part and
rotate toward you and the pin will become free and you can slide the
part off of the mandrel. If the part can be supported with a
bull-nosed live center then all you really need is a stub of a mandrel
long enough for the pin. Whoops! I see that the parts are only 2"
long. In that case you only need to make a short mandrel. Be careful
with the UHMW parts because the stuff is so soft the pin may leave a
dent inside the part. Also, depending on how much material needs to be
removed, you may find it faster to make all the cuts on the mandrel.
The drawback of taking heavy cuts with this method is the risk of
making a slight dent inside the part. To insure that the pin makes
contact for the full length do this: Rotate the chuck away from you,
then rotate the part on the mandrel toward you, then rotate away from
you to lock it. Finally, instead of milling a flat you can mill a
groove that will trap the pin. Just make sure the groove is wide
enough for the pin to wedge. The above method works very well.
Cheers,
Eric R Snow,
E T Precision Machine

"Mike" wrote in message
om...
I'm looking for opinions and options. for expanding mandrels.
I've seen some cheap sets on ebay that have set screw in one end to expand
the mandrel. I've also seen the sliding taper version which could be
mounted between centers if needed.


Make one, or two in your case!
Machine a slightly larger diameter shaft than the hole size of the part. In
your case, 1" & 1-1/2" shaft would do it for each part. Machine the shaft to
a tight slip fit into the bore of the part, no deeper than the thickness of
the part. Drill and tap the end for a tapered pipe plug. Remove your new
"mandrel" and saw cut two radial slits about 1" from the end. Insert back
into the lath, add the pipe plug, insert part over the mandrel and tighten
the pipe plug securely.
Easy, cheap, and disposable. We machined many parts using this setup when I
worked at a shop years ago.
Greg