the hobbs are new (mostly) there is a 48DP in the lot, another question is the pressure angle needed, most of the hobbs are 20deg
Chuck Harris <cfharris@...> wrote: lothar baier wrote:
i agree on the fact that hobbs are expensive but i have about 120 hobs that came with the machine,
That was a very lucky purchase. The hobs alone, if they are sharp and
any good, are worth easily 10 to 50 times what you paid for your machine.
Now, do you have any 48 dp hobs in your collection? If not, you will
be making, or buying some before you finish this project.
.... Any lathe has
threading capabilities
Begging your pardon, but that is not true. Most lathes used in
industry are second operation machines, and they can only cut a
thread if you have a die already made. A hob is way out of their
league.
The only other lathes used these days are CNC lathe centers. Manual
machines show up only in small model shops, and hobby machine shops.
.... and you need a lathe anyways to make the disks you cut your gears out of,
I included that in my guesstimate of the time to make a single gear.
Did you?
.... you wont need any
heat treating of the hob since you are only cutting plastic,
Plastics, such as delrin and nylon seem soft and buttery, but they are never-the-less
abrasive when you cut them. An unhardened tool steel hob will make quite a few gears,
but the sharp edge will be gone very early on. Plastics such as nylon and delrin
cut with a very ragged edge unless the tool is scary sharp.
If you are only going to make a couple for yourself, sure, you can take short cuts.
If you are going to make them for others, you don't dare.
a good quality toolsteel will do for that Apparantly you
havent been much around machining, i really dont know where you get the 5hours from,
Ever tried making a hob? I have made a few, and 5 hours is a good estimate for
one hardened and ground tool steel hob made on manual machines. If you have ten
identical hobs to make, you can take advantage of some economy of scale, but to
make one hob, will take you about 5 hours.
setup of your hobber takes about
1hr max and that includes calculating your index and feed gears, the cutting process in itself is depending on the
ammount of teeths on your gear and the feedrate you can run, if you use forced air cooling on delrin or PVC you can
generally run a good rate so the overall time to cut is about 10minutes 30minutes the most ! i have cut gears on
hobbing machines in the past helping out in my brothers shop, those were gears used in CASE harvesters and they only
took about 1hr/piece to hob, keep min mind that they were much larger in size ! There is no such thing as a manual
hobber either, all hobbers are automatic,
Really now? So, you have a stock feeder that puts the new blank into
your hobber, and removes the old? You just walk away, and the bucket
gets filled with gears?
No? Then you have a manually operated hobber. Someone has to be in
attendance during the entire operation.
-Chuck Harris
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