lothar baier wrote:
Some things or actually a lot of things we do for a hobby have nothing to do with logic, sometimes you just do things
for fun, i have about $350 in the hobber including all acessories, i bought it not to make money but i figured that
its a nice complement to my metal hobby shop and $350 is a ammount that i can justify spending on a hobby !
I wouldn't argue against that, I have tens of thousands of dollars
in my machine shop. But I still won't waste my time hobbing a
gear that I can buy for $2. I would rather spend my shop time on
things that would be too expensive to purchase, if I could buy
them at all.
Why would
somebody want to fix testequipment or build a ham radio rig ? it cheaper to buy especially if you put in all the time
you spend - you do it for fun and to learn something, you gain alot of valuable skills by practicing - as it says
practice makes perfect, the other reason is that you have control over your parts and even if they are not available
anymore down the road you can still make them and fix your equipment, also you can make them better by using more
advanced materials. Plastic gears normally are not hobbed except if you use delrin,
You are in luck, the HP gears are already delrin on brass hubs.
Like nylon, delrin shrinks continually. Unfortunately, the brass hubs do not, so
given time, the gear will break at one of its roots.
PVC is a pain because it leaves a
I am not sure what PVC has to do with anything proposed.
bunch of burrs that need to be removed, the other side of PVC is that it becomes brittle over the years, normally the
gears HP used were made in a very crude way - injection molding which has a high yield and is cheaper in Qty. My idea
is to either use delrin or aluminum, the forces on the flanks of those gears are not very high and the rotating speed
is very slow so by far the specs are no challenge. All you need to know to make them is the number of teeth , the
diameter and the pressure angle, height and id of the gear.
And that information is what I was going to provide to the group.
If you hobb the gears, and make them available for sale, you
will quickly discover that you have to charge something for your
time, tooling and materials. Suddenly, you will see why metal
gears are so damned expensive... custom gears even more so.
If you are using manually operated machines (at $350, I think you are),
between blanking the gears, and hobbing the teeth, you will have several
hours in each gear you make.
US microwave engineers with experience are making what these days? $90K
to $130K? That works out to $40 to $60/hour paid to the engineer. They
cost their companies 2 to 3 times that much.
I don't think the guys that hang out on this group are going to be willing
to pay you $200 per gear. If you charge $5 per gear, your wife will divorce
you. I offered several gear *sets* at the cost of one broken 8640B OPT/1/2/3.
My price exceeded what the market would bear... even though I would essentially
be working for free.
-Chuck Harris
