cross-posting to alt.machines.cnc as that is one of the most
knowledgeable groups on the web as their contributors have an extensive
traditional machining backgrounds in addition to cnc.
I am hosting more than teaching a community college class in basic
manual machining to a small group of very dedicated and enthusiastic
students. This class is stressing traditional machining techniques
emphasizing ingenuity rather than attachments. While I do have one
student that is taking the class from a hobby or home shop standpoint,
the others are looking to change careers (gun-smithing) or are involved
in maintenance, generally involving obsolescent equipment for which
parts are no longer available or available only with unacceptably long
In an end of semester discussion about what topics were of interest for
the spring session, production of one-off gears came up. I have made a
few simple spur gears using a dividing head and an involute gear cutter
on a Van Dorne horizontal milling machine with both the cutter and gear
blank on arbors.
The class has available two V-10 Emco lathes, one of which has the
vertical milling attachment.
From a review of the literature including Milling Operations in theLather by Tubal Cain and Gears and Gear Cutting by I. Law (Work Shop
Practice series) [see for US source] and
Gingery's book Delux Accessories [see
] it appears
that we can use a fly cutter and hand ground bits to cut the gear teeth
(spaces) to the proper involute profile, so no problem here.
However we do lack a way to index the gear blank.
Money is very tight and we need to stay under the Administration's
It appears the least expensive alternative (other than a one-time ebay
buy) is the Cen-Tec 6 inch rotary table with indexing from Harbor
Freight [see SKU 47824-0VGA] for $169.00.
I have been unable to get Harbor Freight to tell me what hole
patterns/divisions are on the indexing plate that comes with this unit
so I can tell what gears it can cut. I am therefore asking the
newsgroups the following questions:
(1) If anyone has one of these units, what are the hole patterns on the
(2) What has your experience been with this unit?
(3) Can you do compound indexing with this unit? I came across this in
an old edition of the Machinery's handbook. In addition to turning
the crank/worm so many holes, you also turn the index disk so many
holes on another ring of holes in either the same or the opposite
direction. This gives the same effect as differential screw threads.
Effectively you multiply the number of holes in each of the two
patterns you are using.
(4) Has anyone done gear cutting with one of these units using a
flycutter? For the class project we will be cutting additional Emco
V10 change gears (M1 module) from 1/2 inch thick 6061 T6 aluminum
Thanks for any hints, advice, etc. anyone may care to contribute.