Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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  #1   Report Post  
KN
 
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Default Attach Rotary Table Vertically to Mini-Lathe?

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

  #2   Report Post  
Grant Erwin
 
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KN wrote:

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?


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
  #3   Report Post  
Rex B
 
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KN wrote:
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.


Why a rotary table? A spin indexer would be more appropriate, would it not?
  #4   Report Post  
KN
 
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I'm not familiar with a spin indexer. Could you explain or provide a
link?

Thanks,

Kyle

  #5   Report Post  
Eric R Snow
 
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On Thu, 29 Sep 2005 08:59:45 -0700, Grant Erwin
wrote:

KN wrote:

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?


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


  #6   Report Post  
Boris Beizer
 
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"Eric R Snow" wrote in message
...
On Thu, 29 Sep 2005 08:59:45 -0700, Grant Erwin
wrote:

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?


. 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.


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

--

-------------------------------------
Boris Beizer Ph.D. Seminars and Consulting
1232 Glenbrook Road on Software Testing and
Huntingdon Valley, PA 19006 Quality Assurance

TEL: 215-572-5580
FAX: 215-886-0144
Email bsquare "at" earthlink.net

------------------------------------------


  #7   Report Post  
Rex B
 
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http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3
- -
Rex Burkheimer
WM Automotive
Fort Worth TX

KN wrote:
I'm not familiar with a spin indexer. Could you explain or provide a
link?

Thanks,

Kyle

  #8   Report Post  
KN
 
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I'm not familiar with a spin indexer. Could you explain or provide a
link?

Thanks,

Kyle

  #9   Report Post  
Dave Hinz
 
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On 29 Sep 2005 13:28:14 -0700, KN wrote:
I'm not familiar with a spin indexer. Could you explain or provide a
link?


Not to be too much of a smartass, but the top hit on google for a search
string of "spin indexer" is a good one.

  #10   Report Post  
Richard J Kinch
 
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KN writes:

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?


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.


  #11   Report Post  
Rex B
 
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Richard J Kinch wrote:
KN writes:


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?



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.


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.
  #12   Report Post  
Richard J Kinch
 
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Rex B writes:

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.


Not the cheap Enco one.
  #13   Report Post  
John Martin
 
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KN wrote:
I'm not familiar with a spin indexer. Could you explain or provide a
link?

Thanks,

Kyle


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

  #14   Report Post  
Rex B
 
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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 Kinch wrote:
Rex B writes:


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.



Not the cheap Enco one.

  #15   Report Post  
Rex B
 
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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 Martin wrote:
KN wrote:

I'm not familiar with a spin indexer. Could you explain or provide a
link?

Thanks,

Kyle



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



  #16   Report Post  
 
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"I happen to have the cheap Enco spin indexer, ..."

I doo, too, and these are MUCH more rigid and far better for milling:
http://www.kalamazooindustries.com/i...5c21_alone.jpg

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

  #17   Report Post  
KN
 
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How would I mount this spin indexer to the lathe? I'm assuming it
would have to be attached to the bed somehow?

Thanks,

Kyle

  #18   Report Post  
 
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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

  #19   Report Post  
Rex B
 
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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:
How would I mount this spin indexer to the lathe? I'm assuming it
would have to be attached to the bed somehow?

Thanks,

Kyle

  #20   Report Post  
Richard J Kinch
 
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Rex B writes:

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".


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.


  #21   Report Post  
Rex B
 
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Probably could use some body filler for something like this.
Might even form some foil to the lathe bed first. You basically need to
model your fixture after the tailpost base.

Only complication here is you want to be able to locate it back and
forth or up and down so you can vary the distance radially from the
spindle, in which your drill will be mounted. If you cast a base to
follow the ways, you are not going to be able to move it across the
ways. You could probably get where you need to be by shimming the
height. So you would have, from bottom to top:

1 - Base molded to shape of bed and the size of the indexer base.
2 - shims vary the height
3 - indexer.

This sandwich would likely require a plate under the bed, so use the one
for the tailpost, since you don't need the TP for this op.
You will have to have a through-hole or two to hold all this together
and in place. It might be easiest to thread the bottom of the indexer
for a single bolt coming up from the bottom. You'll have to figure out
that from the bed, indexer, and lower clamp that you are working with.

Taking an entirely different tack, you might be ahead to build your own
fixture, based on a small angle plate in place of the toolpost, and
using a 28-tooth (or 21, or 35, 42 etc) gear to index, as someone else
pointed out. The only fabrication would be an arbor to accomodate your
wheel on one side of the angle plate, and the gear on the other side.
You just need something to engage the gear to lock it in place. Once you
build this once, I'm sure you will use it again for other parts of your
project.
Note that this could also double as a simple gear hobber. Google on
Gear hobber or gear cutting to get some ideas on this.

- -
Rex Burkheimer
Fort Worth TX

wrote:
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

  #22   Report Post  
Richard J Kinch
 
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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.


That won't do because there is no way to feed the work into the chucked
drill without loosening the clamp and losing rigidity. You either have to
mount a fixed workholder to the (movable) carriage, or have a motion
component on the workholder itself.
  #23   Report Post  
Rex B
 
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Richard J Kinch wrote:
Rex B writes:


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".



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.


Then the description is very misleading. Can't very well cut splines.

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.


I don't believe he has enough height between carriage and spindle, even
stripped down.
  #24   Report Post  
Richard J Kinch
 
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Rex B writes:

I don't believe he has enough height between carriage and spindle, even
stripped down.


I already addressed that, saying that there is about a 0.15 inch height
difference, which would be the minimum bolt circle radius.
  #25   Report Post  
John Martin
 
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Rex B wrote:
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


Suppose he could, depending on what his definition of "perfectly spaced
apart" is. It might not be the same as yours, or mine. Depending on
how large the holes are (i.e. how close together they are), you might
easily see the half-degree difference.

John Martin



  #26   Report Post  
 
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I haven't run these mini lathes, only the Sherline, Prazi and
Craftsman, so I don't really know what the ways look like and gave only
a general approach to fitting a plate to them. The milling attachment I
made for my 6" Craftsman lathe fitted onto the saddle dovetail but it
was done on a Bridgeport.

The usual way to bore offset holes on a lathe is to clamp the part to
the faceplate using some sort of alignment fixture, or center punch
marks placed by geometric layout techniques. Are the wheels are too
large for this?

You could attach a slotted angle plate to the base I suggested and use
the lathe like a drill press, although a real drill press is better.
The base could be held down at the edges the same way the saddle is.

The obvious answer is to buy a mini mill. See how much trouble milling
on a lathe can be?

jw

  #27   Report Post  
KN
 
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I appreciate everyone's comments and help. Unfortunately, this
discussion has gotten too in-depth/complicated for my level of skill.
Using the word "hobbiest" was misleading because when I meant
"hobbiest", I meant scale models, not machining.

While I understand some of the suggestions here about creating some
kind of attachment for the lathe bed, then mounting the indexer to it,
- it results in a catch-22. In order to create this attachment, I
would need a mill. Since I don't have a mill, I can't create the
attachment. If I had a mill, I would just go out and purchase a rotary
table and be done with it.

Thanks for all your suggestions. What I have learned from this
discussion is that there is no easy way to attach a rotary table to a
lathe. Guess I better find a plan B.

Thanks,

Kyle

  #28   Report Post  
Richard J Kinch
 
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KN writes:

While I understand some of the suggestions here about creating some
kind of attachment for the lathe bed, then mounting the indexer to it,
- it results in a catch-22. In order to create this attachment, I
would need a mill.


I was suggesting you simply mount the spin indexer to the carriage. This
only requires hand drilling.
  #29   Report Post  
James Waldby
 
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Default Attach Rotary Table Vertically to Mini-Lathe? / divide by 7

Rex B wrote:
....
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?


An earlier post ref'ed a webpage with Robert Bastow's comments
on ball-bearing-based divisions. He said the 20 millionths
tolerance of standard bearings was way too much, and the proper
thing to do is make precision toolmaker's buttons. Anyhow, the
idea is to capture a ring of n buttons between an inner cylinder
and an outer ring, all parts made to high accuracy.[1] It
immediately occurred to me that cylinder diameter is non-critical
if we use two rows of balls, rather than one. For example, rather
than making an inner cylinder of diameter .652382" and putting 7
..500000" balls around it and a 2.404286" ID ring around that,
put 7 .5000" bearings around a 1" cylinder, then a ring of 7
more .5000" bearings around that, and then a ring clamp outside
to hold it all together. This could be used to make a first-
generation index plate, which then could be used with a rotary
table to make a more-accurate plate, as he suggested elsewhere
in that page.
-jiw

[1] For n balls of radius b and inner cylinder radius r, let
angle g = pi/n radians = 180/n degrees. Then b=(r+b)*sin(g)
and r=b*k with k=(1-sin(g))/sin(g). For one row of balls,
ring radius p = b+r. For two rows and exact fit,
p = b + h + s where h = b sqrt(3) and s = sqrt(r^2+2*r*b).
Eg, for n=7 and b=.25, sin g =.4339, k=1.3048, r=.3262,
h=.4330, s=.5191, p=1.2021.
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