I would like to purchase my first mini-lathe but have one big remaining
question. I primarily model tanks from WW2 so my needs are turning gun
barrels and creating road wheels.
The complication I'm having is that I know I'm going to need a rotary
table to perform some of the tasks when creating road wheels (i.e.
cutting 7 holes perfectly spaced apart, among other things). I would
really like to not have to buy a mill, b/c of space and money. A lathe
is more realistic for my needs.
Since I know I will need a rotary table for some of my projects, my
question is can a rotary table be mounted vertically to a mini-lathe?
Thanks,
Kyle
Here's a suggestion which won't cost you any money. Reserve a copy of "Shop
Savvy" at your local library, and when it comes in, check it out. He has both
indexing attachment and shop-made milling attachment plans in there, all for a
small home shop lathe. If you're used to HSM type plans with real blueprints,
this will disappoint, but if you're any good as a model engineer you won't have
any trouble. Lots of other fascinating reading in there too. His indexing
attachment, like many others, uses a gear tooth and spring-loaded plunger to
effect the indexing. A 28 tooth gear would be pretty handy for indexing 7
equally spaced holes, for example.
GWE
Grant's suggestion is a good one. While a rotary table is good for
indexing any spacing, where they really shine is when you need to use
it for milling. If, for example, you need to mill curved grooves. Or
only partially around a hub. If you don't need the milling
capabilities then building an indexing attachment will probably be
better for you. If you build your own device then you can determine
where all the clamping holes are. With a rotary you are kinda stuck
with the T slots they come with. You can drill and tap other holes for
clamping, but not through. Through holes will allow dirt to get into
the works. But a faceplate for your lathe could be used as 1/2 of a
home made indexing setup.
ERS
I don't see a rotary table as a combination with a lathe. That's just
introducing too much shummy in an already unstiff set-up. Besides, that
would also imply a milling vice, and I can't see how to mount even the
smallest rotary table on the typical milling vice for a lathe.
But he doesn't need a rotary table. As Eric and Rex have pointed
out, it is a question of layout and indexing. I made a very simple, yet
effective indexing attachment (first for my 9" SB and later adapted to my
12" Clausing) lathe. I found/scrounged, some index plates with a 1.5"
center hole. I then machined a simple little plunger stop. The index
plate goes between the chuck and the spindle seat. This is okay since I
don't do any turning.
To make, say, seven holes evenly spaced on a wheel, say. Mount the
wheel in the chuck. Use a pointy tool (e.g., a scriber). First mark the
radius by holding the scriber against the work and rotating the chuck by
hand. Then go to your first hole position and mark the cross point by using
the cross feed. Back off, index to the next "7" position and repeat. Then
center punch the cross points and drill the holes in the drill press. No
problem holding it to a few thou accuracy. Better if you want to be really
finicky.
This is method is so easy and convenient that even though I have a
rotary table, mills, spin-indexers, etc. When I want to mark stuff that's
been worked on the lathe, rather than take it off the lathe and remount the
work on another tool (e.g., a rotary table), I index it on the lathe using
my cheapo indexer as above.
It's a lot, lot, easier finding various indexing plates at a used
machinery place than finding the right gears (pitch, bore, etc.).
Boris
I happen to have the cheap Enco spin indexer, and the minilathe. Here is
what I find:
What is possible if the cross-slide is removed, leaving only the carriage
base? The top of the dovetail on the minilathe cross-slide, to the spindle
axis, is about 2.6 inches. The bottom of the spin indexer to the collet
axis is about 2.75 inches. So apparently you could remove the cross slide
from the minilathe carriage, and bolt on the indexer, with the minilathe
axis about 0.15 inches below the indexer axis. So as long as your bolt
circle radiuses are about 0.15 or more, this ought to work. You'd put the
drill bit in the chuck, and hold and index the work in the indexer, and
feed the drill with the carriage wheel.
Consider making your own special workholding jig for the purpose.
Something that can be held in the toolpost, and index 8 holes in a given
size piece, or whatever.
As long as the spindle axis is with about 1/2" of the indexer CL, you
move the cross slide horizontally to get to the radius you need, then
lock it down and index away. Am I missing something?
For most applications you could mount it directly to the carriage, after
removing the cross slide. Or fashion a mount to the bed ways, perhaps
from a tailpost base. The indexer has enough axial travel that you could
use that instead of carriage travel to feed the work, for many
applications including that of the OP.
The spin indexer won't work for you. It indexes in even degrees, while
you said you needed 7 accurately spaced holes.
You'll need a rotary table or a dividing head. You may find a small
one, but I think that most of them will be a bit too large to mount on
the cross slide of your mini-lathe.
John Martin
He's only drilling through the side of a model locomotive wheel as I recall.
What, 1/4" travel? The $29 Enco looks to have a couple inches "for
cutting splines".
- -
Rex Burkheimer
Fort Worth TX
Richard J K>
7 holes is 51.428 degrees each.
This is not a high precision application, more of a "visual precision".
Could he not use the cheap indexer and extrapolate that half degree.
- -
Rex Burkheimer
WM Automotive
Fort Worth TX
John Mart>
"I happen to have the cheap Enco spin indexer, ..."
I doo, too, and these are MUCH more rigid and far better for milling:
formatting link
The index plate can be replaced with a home-made one or you could fit a
degree wheel since the split clamp on the other end holds the spindle,
much better than the thumbscrews on the spin index does.
You can use a Sherline 5C chuck instead of buying the collets.
jw
I would make an adapter plate with slots milled/chiseled/filed roughly
the shape of the ways, rig up a way to clamp it in place level and
square to the ways, then oil the ways and fill the space between them
and the plate with metal-filled epoxy. Based on considerable recent
experience making parts with the stuff I'd expect to trim the overflow
while still soft, let it harden and add more to fill the gaps, several
times.
jw
It could be as simple as clamping it to the flats between the V-ways.
But you may have to fabricate something. In an earlier message I
suggested you might want to buy a replacement tailstock base to make a
mount from.
As John Martin pointed out, 7 doesn't go into 360 degrees evenly. If
you decide you need the precision then the cheap indexer won't do. You
would need an indexer with a index plate that has a number of holes
divisible by seven.
It may be possible to get a replacement index plate for that Enco
that has the right number of holes. Anyone know if that is possible?
- -
Rex Burkheimer
Fort Worth TX
KN wrote:
The spindle does have a few inches of extra length, but it doesn't appear
to permit controlled axial motion. When you loosen the setscrew collar to
let the spindle travel axially, you have nothing holding the rotational
position. Attaching to the carriage bed would seem to be simplest method;
you'd also have the carriage wheel to control feed rate and pressure,
instead of just shoving it with your hand.
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