[modeleng] Re: Vari-speed motors
- From: "shep" <shep.28@xxxxxxxxxxxx>
- To: "Modeleng" <modeleng@xxxxxxxxxxxxx>
- Date: Sun, 11 Sep 2005 11:00:23 +0100
Dear Al
Thanks for this message.
If I cannot easily and economically acquire a vari-speed motor, giving a
good low speed torque, I would indeed use a single pulley in the headstock
(possibly with a tooth belt), driven by a countershaft with a cone of four
pulleys.
I am building this little lathe as a challenge, to see if my meagre
abilities will ultimately create a small, but heavy and accurate little
machine. I would wish it to be able to do all lathe work within its
capacity, including screwcutting. I have a 8mm watchmaker's lathe, which
I am planning to sell off, but retaining the 8mm collets - so the mandrel
will be desined to accept these collets. The nose will be screwcut to
accept the chucks etc used on the little Unimat lathe.
The tailstock will be bored to accept 0 MT centres, drill chucks etc.
I am aware that it will not be practical to slow down the lathe sufficiently
for screwcutting, using just belts (or vari-speed) and retain sufficient
torque.
I am avoiding the back-gear approach (partly because of complexity and
partly because I prefer not to have gears involved directly with the
mandlrel, as this tends to affect the quality of the finish). I plan to
place a commercially available compact geared speed-reducer, as an
alternative, between the motor and the countershaft. This will give the
back-gear effect, simply by changing belts on or off the speed reducer.
I even have distant plans of fitting a taper-turning device at the back of
the lathe.
All of this may be possible, if I hone my skills and live long enough! In
the meantime, it provides me with an on-going major project, which is
conveniently broken down into numerous mini-projects!
I am blessed with a cooperative tool-and-cutter grinder living in a nearby
village. He has kindly ground the ways of the bed and will grind the
cross-slide ways.
I am too old, too idle, too impatient and too unskilled to dabble in the
black art of scraping!
In Britain we are fortunate in having numerous (often small, independent)
suppliers of materials and tools, who are sometimes model engineers. One
such supplier sells superb cast iron in many shapes and sizes, cut to any
dimension.
Thanks for your interest and advice.
Cheers! Hubert
>
> Date: Sat, 10 Sep 2005 06:26:47 -0700 (PDT)
> From: Allen Messer <al_messer@xxxxxxxxx>
> Subject: [modeleng] Re: Vari-speed motors
>
> Hubert, being totlly ignorant of vari-speed motors, I
> would consider using a single pully on the lathe
> spindle, and vary the speed with a Jackshaft
> arrangement either behind or underneath with three or
> possible even four speed change pulleys. I'll be
> perfectly honest, if I understand you correctly, this
> lathe is to be used exclusively for thread cutting?
> If so, you won't need a lot of different speeds for
> threading, maybe two at the most.
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