On Sat, 1 Feb 2014 09:24:48 -0800 (PST), "
wrote:

On Saturday, February 1, 2014 2:56:33 AM UTC-5, F. George McDuffee wr


http://www.use-enco.com/CGI/INPDFF?P...MITEM=422-1674



cheap screw solution to locate off bo Clamp bar stock in

chuck. Turn to size. Drill and tap taper pipe thread in

end. Leave bar in chuck to minimize run out. cross cut end

of bar with hack saw and debur. taper pipe plug will expand

arbor enough to hold gear when torqued.


That is a good way to make an arbor to hold a part for machining. But in my case I want an arbor so a part can be rotated and any out of round can be seen. And I would like it to be useful for bores from a bit under 2 inches to bores of three or four inches.

On the current gear being worked on, the bore is now a bit over two inches. The final bore might be as much as 2 15/16 ths. So almost an inch bigger.




to locate of teeth faces use a plate with a taper hole

matching the taper of the bevel gear and three dowel pins to

locate off the teeth faces. Clamp the plate to the face

plate, bore the tapered hole with compound and leave

attached for minimum run out, clamp the gear in the hole

using dowel pins to locate off tooth faces. Bore hole to

size, then use expanding arbor to machine gear as required.

http://www.use-enco.com/CGI/INSRIT?P...PMPXNO=94517--

Unka' George


This might be useful, but I hesitate to use a plate with a tapered hole to hold the dowels. The little gear is a bit over a foot in diameter. The larger gear is more than two feet in diameter. So maybe use bungee cord to pull the pins into the gear faces. The problem is that the dowels do not fit snuggly, but may be good enough for a reference. Currently the thinking is to use the gear teeth as cast. We do not have a mill big enough to machine the teeth of the larger gear and I am not sure if the mill is big enough for the smaller gear.

Dan
====================

Given these are bevel gears, the best bet for a gear face
locator pin might be a round magnet.
http://www.allmagnetics.com/alnicorods.htm

Given the size of the parts relative to the machines, some
of the old time machining books will have some hints.
railroad and ship machining would be a good place to start.

One old time "arbor" kluge is a "cats head" mandrel
https://www.google.com/search?q=cat%...0%3B1024%3B768
This is not the cat's head that goes over irregular
barstock, e.g. hex, so it can run in a steady rest, but is a
mandrel with 2 sets of stout hex head screws set at 120 (or
90) degree angles that can grip the inside of bore. [Most
likely 3 at 120 is better as this gives more room to swing
the wrench to adjust the rear set] By adjusting the screws
the workpiece can be tilted and offset relative to the
mandrel. I've never used one, and they look to be a real
PITA to adjust, but would seem to do what you want, and
should be relatively cheap/easy to make.

Lindsey Books had many reprints, but is no longer in
business.
http://www.lindsaybks.com/
Your Old Time Book Store bought most of his inventory.
Their website is
http://www.youroldtimebookstore.com/category-s/2075.htm

try
http://www.youroldtimebookstore.com/category-s/1967.htm

also see
https://archive.org/details/textbookofadvanc00smituoft
https://archive.org/details/textbookofelemen00smitrich
https://archive.org/details/practicalmetalt00horngoog

sounds more interesting all the time. be sure to let us
know how things work out.


--
Unka' George

"Gold is the money of kings,
silver is the money of gentlemen,
barter is the money of peasants,
but debt is the money of slaves"

-Norm Franz, "Money and Wealth in the New Millenium"