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