Cutting Involute Spur Gears with a rotary table and mill. Possible??
rrme...@storm.ca
Just curious if it's possible to cut gears using a vertical mill,
preferably with a rotary table mounted with the axis horizontal.
I will need to make some gears in the future, spiral, bevel, etc, but
let's stick to the simplest, spur gears for the moment. I'd like to
know if you can take a blank and with an end mill of the proper shape,
cut out the valley between 2 teeth, then turn the gear blank to do it
again, until all the teeth are made. Of course an indexing head would
do this too, just as a cnc rotary table would.
My concern is based on a moderate amount of knowledge about involute
gear tooth form. If you look at 2 teeth, is the valley between them
undercut at all? If it is, I can see a real problem trying to plunge
any kind of custom-shaped milling cutter radially into the gear blank.
It might work if the end mill was fed into the blank sideways. Again,
al this is assuming that I can buy/make an end mill to match the shape
of the valleys between the teeth. Or, I can even see using something
like a shaper, if the valley is not undercut.
So anyone done this? With a mill is there a better way to make gears
of various types, as I mentioned previously? I'd always be in fovour
of buying gears, but I really might need custom sizes and shapes of
gears to install into the scale Rolls Merlin I'm doing. There are
OODLES of gears in the wheelcase, just behind the crankcase.
Thanks anyone who dives in. Tom Kay, Ottawa Canada.
Tom Martin
Forget the endmill idea. Endmills don't exist like that.
You need an arbor that takes proper gear cutters or a flycutter
that you can fit a ground to profile, bit.
Cutting helical gears needs a universal mill: one that the table
can be set at angle.
Spiral gears require a drive between table & indexing device.
As for the bevel gears, a milling machine cannot make a true
bevel gear, cuts need to be taken from both the inside & outside
diameters of the teeth and the intersection of those cuts merged.
Having, in another life worked on the real thing, I can empathise
with your task ahead!
Contact Boston gear before,getting carried away, they have a
tremendous range of small stock gears that might be persuaded to
fit......
Tom
M/shop info & old machine tools.
http://shopswarf.orcon.net.nz
DoN. Nichols
>Hi all
>
>Just curious if it's possible to cut gears using a vertical mill,
>preferably with a rotary table mounted with the axis horizontal.
Before I dive into the answers, I would like to warn you that I
have never actually *made* any gears -- just considered how to make
them, and read discussions on the subject.
>I will need to make some gears in the future, spiral, bevel, etc, but
>let's stick to the simplest, spur gears for the moment. I'd like to
>know if you can take a blank and with an end mill of the proper shape,
>cut out the valley between 2 teeth, then turn the gear blank to do it
>again, until all the teeth are made. Of course an indexing head would
>do this too, just as a cnc rotary table would.
There are gear tooth milling cutters designed for use with a
horizontal spindle mill, though you might get away with using them with
a vertical spindle, you would be lacking the support at the other end of
the arbor. These cutters come in sets for a given pitch, each one cuts
the tooth form for a particular (fairly narrow) range of teeth per
cutter (because the different radius on each gear requires a different
tooth form to fit with all other gears of the same pitch (and the same
pressure angle).
Now -- it is possible to make a single-point cutter by grinding
a HSS tool bit for use in something resembling a flycutter. This saves
money, but slows the rate at which you can cut the metal.
>So anyone done this? With a mill is there a better way to make gears
>of various types, as I mentioned previously? I'd always be in fovour
>of buying gears, but I really might need custom sizes and shapes of
>gears to install into the scale Rolls Merlin I'm doing. There are
>OODLES of gears in the wheelcase, just behind the crankcase.
Now what I have discussed above is for only straight-tooth
(spur) gears. For the angled teeth, you need a way to angle the travel
of the tableExpires:
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In article <3c1d19f6....@news.storm.ca>, <rrme...@storm.ca>
wrote:
>Hi all
>
>Just curious if it's possible to cut gears using a vertical mill,
>preferably with a rotary table mounted with the axis horizontal.
>
>I will need to make some gears in the future, spiral, bevel, etc, but
>let's stick to the simplest, spur gears for the moment. I'd like to
>know if you can take a blank and with an end mill of the proper shape,
>cut out the valley between 2 teeth, then turn the gear blank to do it
>again, until all the teeth are made. Of course an indexing head would
>do this too, just as a cnc rotary table would.
There are gear tooth milling cutters designed for use with a
horizontal spindle mill, though you might get away with using them with
a vertical spindle, you would be lacking the support at the other end of
the arbor. These cutters come in sets for a given pitch, each one cuts
the tooth form for a particular (fairly narrow) range of teeth per
cutter (because the different radius on each gear requires a different
tooth form to fit with all other gears of the same pitch (and the same
pressure angle).
Now -- it is possible to make a single-point cutter by grinding
a HSS tool bit for use in something resembling a flycutter. This saves
money, but slows the rate at which you can cut the metal.
Also -- it is common to do this with an index head and a
matching center, with the gear blank mounted on a (very slightly)
tapered arbor.
>So anyone done this? With a mill is there a better way to make gears
>of various types, as I mentioned previously? I'd always be in fovour
>of buying gears, but I really might need custom sizes and shapes of
>gears to install into the scale Rolls Merlin I'm doing. There are
>OODLES of gears in the wheelcase, just behind the crankcase.
Now what I have discussed above is for only straight-tooth
(spur) gears. For the angled teeth, you need a way to angle the axis of
the index head/center pair relative to the path of the table, and
ideally, you need to be able to rotate the gear as it passes under the
cutter, so you don't wind up with variable depth teeth. (The wider the
gear, the more critical this is.)
When you start talking about bevel gears, you would probably be
better off cutting those on a shaper (with the proper fixtures and index
head).
Of course, the really *right* way to make them is on a hobbing
machine, in which the workpiece and the hob (consider it to be a strange
looking threaded milling cutter) rotate at the proper rates to produce
the necessary shapes.
There are books on making gears, including (I think) one in the
Lindsey site. His books are quite affordable.
Good Luck,
DoN.
--
Email: <dnic...@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
Ed Huntress
much trouble.
The easiest way is to buy commercial milling gear cutters. One cutter will
cut a range of gear sizes. If you look up "milling gear cutters" on the web,
you should find enough information to get you going.
I've done it, back when I worked in a shop. My biggest problem was setting
the indexing table correctly. I remember one really nice, big gear I made,
which was supposed to have 40 teeth, but which wound up with 39. <g>
Ed Huntress
<rrme...@storm.ca> wrote in message
news:3c1d19f6....@news.storm.ca...
Robert Swinney
I would get a good book on gears (library, maybe?) and copy the profiles of
gear types you are interested in - preferably enlarged. Study the profile
very carefully, reduce it to size and and make a gage from it. Grind the
profile on a single point cutter for cutting the teeth one at a time. Cut
with a fly-cutter.
Bob Swinney
<rrme...@storm.ca> wrote in message
news:3c1d19f6....@news.storm.ca...
JWDoyleJr
>Just curious if it's possible to cut gears using a vertical mill,
>preferably with a rotary table mounted with the axis horizontal.
>
There is a small book which covers the art and science of gears called "GEARS
AND GEAR CUTTING" by Ivan Law. There is a section on making single-tooth bits
to be used in a fly cutter. It is doable by any HSM, and my EMCO mill is
running on a home-cut gear.
The book is listed in the Campbell Tools Company Catalog for $21
Campbell Tools Company
2100 Selma Road
Springfield, OH 4550
1-800-878-8562
eberlein
proper tools and equipment.
Basically, I used a horizontal mill with appropriate shaped gear milling
cutter, and a dividing head. First you turn a gear blank to the
appropriate dimensions, diameter, thickness, etc. on a lathe, bore or ream
an appropriate center hole, press onto an arbor, and mount between centers
with the dividing head on one end of the arbor and a dead center on the
other. The gear milling cutter has the involute shape ground into it.
Take passes with the cutter, indexing the gear blank 1 tooth for each
pass.
The advantage of the dividing head is that you have accurate indexing
plates that you can select whatever number of teeth you need, so no
calculating is required, you don't have to worry about mis-indexing the
dial of the rotary table, etc.
The downside is that you need access to lots of different cutter shapes.
A specific cutter only does a narrow range of teeth, and you need
different cutters for a rack, for 8-12 tooth, 12-16 tooth, etc.
Additionally you need different cutters for different pressure angles. If
you are working on a project that has lots of different types of gears,
you will need lots of cutters.
I made a series of gears for my 10 inch Logan/wards lathe in 1991
(pre-Internet for me. I didn't know who made the lathe back then and the
spindle gears, bull gear and back gear train were virtually destroyed). I
was lucky in that I was taking the weekend advance machine shop course at
a community college in Cedar Rapids, IA, and had an understanding
instructor who knew how to make gears. The class room had all the cutters
I needed (fortunately, Logan uses pretty standard gear sizes), and I got
the headstock gears built. I learned my lesson though, as I bought 7
missing change gears from Browning, reamed appropriate hub hole diameters,
put in the key ways and faced to thickness on a lathe.
It was a worthwhile project in that I re-learned the gear design stuff I
studied in college and actually got to make gears that worked, and are
still working in my lathe. I wouldn't want to do it again, though. There
is no reason you couldn't do the same fabrication method in a vertical
mill using an indexing device of some sort.
Buying the gears will be the simplest approach. See:
http://www.bostongear.com/ for bigger sizes and
http://www.sdp-si.com/Component_Cat.htm for smaller sizes.
Hope this helps
Regards,
Mike Eberlein
The Baron@flash.net
not often involute. The Boston Gear Co. is only interested in selling you
a 1000 gears, never been much help to me.
I use a small , 2nd production Hardinge horiz. mill, with about a 4''
diameter capacity. I have found it is not productive to use a dividing
head, too much wear and tear on my hands and fingers so I made index plates
, 10 ranges per plate, and mainly use only 3 plates.
I have cut gears on a vertical mill, with dividing head, when they were
larger diameter, or 1'' plus thickness, such as you would find on a tower
clock.
Have not CNC'ed my machines but am getting pressured to do so.
MSC has involute milling cutters, in the Diametral Pitch system very
reasonably priced just decide what pressure angle you want. If you need to
make a fly cutter for something special then go ahead but the cutters are
much faster. My cyclodial cutters, Module system, come from England and
cost US$ 70 each.
<rrme...@storm.ca> wrote in message
news:3c1d19f6....@news.storm.ca...
Peter Verbree
Go to Busy Bee and get yourself a copy of Gears and Gear cutting by Ivan
Law. It's worth the $$
Cheers
Pete in Sudbury
Walter West
7/8" hole and my Sheldon horizontal had only a 1" arber.
I wanted 18 DP- 14-1/2 PA gears for metric conversion of a 9" SB. 18 PA
gears are not available from Boston Gear but 20 DP are. When I priced the
100 tooth gear 20 DP, I found you can just about buy a whole set of 8
cutters from Wholesale Tool ,20 DP for $89 shown on pg 140 in there 2001
cat. I don't think these cutters are listed on the internet cat.
Although if I changed all the end gears to 20 DP I could get the $89 set and
do them all( not quite as strong, but OK) But for not too much more money
Wholesale Tool had 30 & 40 % discounts on many of the 18 PA cutters which I
bought, ( all 8).
If anyone is interested and can't get the 2001 cat before the end of the
2001 year I can give you the price & cat no. if I know the PA & DP.
Walt West
<rrme...@storm.ca> wrote in message
news:3c1d19f6....@news.storm.ca...
The Baron@flash.net
DP to a 20 DP knowing that they have different center distances? Or do you
mean that you changed the pressure angle from 141/2 deg. to 20 deg. and kept
the same DP?
"Walter West" <ww...@netonecom.net> wrote in message
news:3c1e0eb1$0$95064$45be...@newscene.com...
Randal O'Brian
a rotary table using the method described in:
MAKING YOUR OWN SPUR GEARS THE EASY WAY,
by F.E. (Pat) Loop.
Generating gear teeth and gears using a hob.
Issues # 40 ....$6.25ea.
See www.Strictlyic.com under special interest articles
The "hob" is a homemade cutter in the form of a rack and generates the teeth
rather than shaping them directly. You do need a lathe to make the cutter
and some expertise in heat treating a tool steel like 01 or W1. The size of
the gears is somewhat limited because the cutter has no out board support
but for gears less than 1.5" it works pretty well if a bit slow.
<rrme...@storm.ca> wrote in message
news:3c1d19f6....@news.storm.ca...
Doug Goncz
shows making 120 beveled teeth in a six inch four jaw chuck using a collet
indexer, cross vise, drill press, arbor, and gear cutter.
Yours,
Doug Goncz
Replikon Research
Seven Corners, VA
To email a copy of your post, remove dot net.
http://users.aol.com/DGoncz/index.htm
http://groups.google.com/groups?as_q=DGoncz
Favorite Conversion: 1 Joule = 1 Watt-sec ~ 0.75 foot-lbf
Engineman1
head (could have been a rotary table) and used a flycutter with a toolbit
ground to fit a gauge with an involute shape produced by drawing a large
diagram of the necessary involute shape and reducing it to the required size
with a pantograph.
Later in my career I worked for a company that produced high performance gears
for driving fire engine pumps. They machined gears by various methods and
finished them with a gearshaver which used a gear of the tooth no. that the
gear being finished would mesh with. This gear was hardened and had sharp edged
grooves cut in the faces of the teeth and was run at high speed with the gear
being made. The edges of the grooves acted as cutting edges and shaved off the
irregularities of the faces of the gear teeth.
Engineman1
Walter West
headstock to the QC box or leadscrew and the adjustments are all adjustable,
as long as all the gears have the same DP & PA any gears will work that will
fit. A 16 DP 127 tooth gear is so big it gets difficult to fit it. 20 DP is
smaller and fits nicely.
Walt West
"The Ba...@flash.net" <theb...@flash.net> wrote in message
news:%xpT7.22051$fy6.200...@newssvr16.news.prodigy.com...
James Wilkins
>
> ... I'd like to
> know if you can take a blank and with an end mill of the proper shape,
> cut out the valley between 2 teeth, then turn the gear blank to do it
> again, until all the teeth are made.
I suppose theoretically you could, if the end mill was tapered to cut
a rack tooth of the same pitch. You would have to readjust the x axis
between crosswise cuts to make the end mill imitate one tooth of a
rack running across the top of the rotating gear. You are effectively
hobbing the gear.
If you unrolled a tape measure horizontally off a pitch-diameter disk
attached to the blank, you could realign a pointer that represents the
spindle axis to a mark on the tape every time you turned the index.
I would first rough out all the teeth using the index divisions, since
the tape will give you an accumulating error. You could drill an index
hole for each tooth in the pitch diameter disk and pin the blank to
it, so you only move the disk and tape back and forth across one tooth
space.
Sorry my description isn't too clear yet. Gotta stop re-re-editing now
and go back to work on a long & messy communications-link program. Is
anyone familiar with the I2C protocol?
> ...So anyone done this? With a mill is there a better way to make gears
> of various types, as I mentioned previously? I'd always be in fovour
> of buying gears, but I really might need custom sizes and shapes of
> gears to install into the scale Rolls Merlin I'm doing. There are
> OODLES of gears in the wheelcase, just behind the crankcase.
>
> Thanks anyone who dives in. Tom Kay, Ottawa Canada.
I've made a gear shaped-broach with a flycutter bit. It was very hard
to get good overall fit because neither the tool bit nor the splined
motor shaft would hold bluing. Since an interference fit was OK in
this case, I put thin plastic-backed sandpaper in the tooth groove and
sanded the bit to fit it.
jw