Expanding Mandrels and Arbors

Topics include, Machine Tools & Tooling, Precision Measuring, Materials and their Properties, Electrical discussions related to machine tools, setups, fixtures and jigs and other general discussion related to amateur machining.

Moderators: Harold_V, websterz, GlennW

User avatar
Fender
Posts: 2831
Joined: Wed May 02, 2007 8:33 pm
Location: Chattanooga TN

Expanding Mandrels and Arbors

Post by Fender » Mon Mar 22, 2010 10:04 am

How effective are expanding mandrels or arbors in holding work in the lathe by a bored hole in the center? Which type is better from an accuracy and torque standpoint? What are the advantages or disadvantages to each? Here are examples of what I am talking about.

Expanding mandrel:
http://www.use-enco.com/CGI/INSRIT?PMAK ... TPG=INLMK3

Expanding arbor:
http://www.use-enco.com/CGI/INSRIT?PMAK ... TPG=INLMK3
Thanks,
Dan Watson

John Evans
Posts: 2166
Joined: Tue Jan 20, 2009 9:33 pm
Location: Phoenix ,AZ

Post by John Evans » Mon Mar 22, 2010 10:20 am

I have both and the expanding mandrels are what I use regularly, the arbors are good if you need to do allot of one size and machine to the needed size. The mandrels each cover a small range of sizes with no mods needed. I normally insert a mandrel in to the work piece and put the expanding section up against a stop and give the inner a tap with a soft hammer to lock it on. These work best with sharp tools and lighter cuts/feeds. Next time I feel flush I'm going to get the rest of the set above 1". Great for making short thin wall parts.
www.chaski.com

Jose Rivera
Posts: 3803
Joined: Wed Feb 21, 2007 9:21 pm
Location: Vallejo California

Post by Jose Rivera » Mon Mar 22, 2010 10:51 am

One type is to use between centers.

The other is to grab by a collet or chuck only.
There are no problems, only solutions.
--------------
Retired journeyman machinist and 3D CAD mechanical designer - hobbyist - grandpa

User avatar
GlennW
Posts: 6895
Joined: Sun Apr 15, 2007 9:23 am
Location: Florida

Post by GlennW » Mon Mar 22, 2010 11:39 am

One advantage of the Expanding Arbors is that you chuck it up, then machine it to the desired size, insuring concentricity. Sort of the opposite of saft jaws. If machined accurately to size/close tolerance fit, they hold very well and do not distort the part.

Very handy, and I always keep a new set in my "just in case" cabinet.

I also use similar 5C Expanding Arbors for larger sizes.

I also use the Expanding Mandrels, but the cheaper Import ones will turn a thin wall part into a polygon.

As Jose stated, they are usually used between centers with a drive dog, but can be gripped on the larger end with a chuck, and the other end supported with a tailstock center.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

User avatar
Steve_in_Mich
Posts: 1119
Joined: Sat Jan 04, 2003 4:14 pm
Location: Mid Michigan

Post by Steve_in_Mich » Mon Mar 22, 2010 12:43 pm

FWIW, How about option 3, make your own.

I have made a few assorted sizes for grabing objects by the id. In the photo the left end is threaded to the bolt and the right side is a slip/loose fit. The angle is whatever I'm able to hacksaw that looks reasonably close to that in the picture. The mating surfaces at the split are polished to promote sliding motion in that plane/point. Insert the split section in the bore and tighten the bolt. Good grip is acheived in sections both thinner and wider than the split width.
Attachments
Internal Expander 1 (Small).jpg
Just because you don’t believe it - doesn’t mean it’s not so.

JackF
Posts: 1572
Joined: Mon Jan 26, 2009 3:56 pm
Location: Caldwell, Idaho

Post by JackF » Mon Mar 22, 2010 3:28 pm

I have seen plans in the past to make your own but didn't make note of them. Does anyone here know where to find such plans? I have googled "Home made expanding arbors" and drew a blank.

JackF
Posts: 1572
Joined: Mon Jan 26, 2009 3:56 pm
Location: Caldwell, Idaho

Post by JackF » Mon Mar 22, 2010 3:29 pm

I have seen plans in the past to make your own but didn't make note of them. Does anyone here know where to find such plans? I have googled "Home made expanding arbors" and drew a blank.

User avatar
coal miner
Posts: 479
Joined: Tue Mar 18, 2008 6:19 pm
Location: Southern Illinios

Post by coal miner » Mon Mar 22, 2010 7:35 pm

Make your own works for me also . Use a 3 or 4 degree on the mating pieces and tap the inside piece to snug up in the taper ,letting the outside expand and grip the I.D. The first one is a part that had to have some knurling removed on the O.D. Used some delrin that I had , worked good and had a 15/16" turned on the end to put in a 5C collet to spin indexer for further mods in the mill .

Image

Image

The other one is a degree wheel for the spindle on the lathe . Same design , won't screw up the threads .

Image

Image
The more I learn , The more I don't know !

JackF
Posts: 1572
Joined: Mon Jan 26, 2009 3:56 pm
Location: Caldwell, Idaho

Post by JackF » Mon Mar 22, 2010 9:42 pm

coal miner,

Thanks.

Jack.

User avatar
Davo J
Posts: 365
Joined: Tue May 06, 2008 9:15 am
Location: Australia

Post by Davo J » Mon Mar 22, 2010 10:35 pm

This might help as well for some more ideas
http://madmodder.net/index.php?topic=2584.0
Rob (the author) has done some fantastic work.
One of them is his homemade taper attachment for his Myford
http://madmodder.net/index.php?topic=2353.0
and another is his cone centres
http://madmodder.net/index.php?topic=2479.0
Davo

JackF
Posts: 1572
Joined: Mon Jan 26, 2009 3:56 pm
Location: Caldwell, Idaho

Post by JackF » Mon Mar 22, 2010 11:25 pm

Davo J,

Thanks for the sites.

Jack.

User avatar
Fender
Posts: 2831
Joined: Wed May 02, 2007 8:33 pm
Location: Chattanooga TN

Post by Fender » Tue Mar 23, 2010 8:46 pm

Well, these certainly give me a lot of ideas! I like the idea of making my own arbor to just the right size. I think I remember a photo somebody posted that tapped the end of the arbor for 1/8" NPT, then cutting two slits at 90º lengthwise. Put the wheel on the arbor, then screw in a pipe plug to tighten.
Dan Watson

Post Reply