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Seeking method to turn square stock round

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auto.pilot

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#1
I would like to make some small threaded inserts similar to the attached picture. I can buy them but not in the size that I need. The square section is three eighths of an inch in the total length is a little over 1 inch. I'm really not looking forward to setting up the 4 jaw Chuck on multiple pieces. It occurred to me that a square collet might be the best approach. I'm also very concerned about the interrupted cutting necessary until the square stock becomes round. These parts will be either mild steel or brass. They will also be threaded through the entire length. Would appreciate any advice

Thank you in advance.

Jim
 

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Ulma Doctor

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#2
so long as you don't try to get too aggressive in your DOC, you should have little problem holding it a collet
12L14 steel cuts like butter, brass would be easy to machine.
6061 aluminum may also be a consideration- easy to machine and inexpensive too
 

RJSakowski

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#3
You could borrow the technique used to make a cube in a cube. Bore a hole in a piece of round stock with a diameter equal to the diagonal length of your square stock. Then cut a lengthwise slit. Insert your square stock with one side straddling the slit. When you tighten the assembly in your three jaw chuck or collet, it will securely clamp the square stock.
 

fradish

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#4
A slightly more wasteful option would to turn this out of round stock,
thread, etc, then part off and put your part in a 5c collet block and square off
the head in a mill. Asuming you have a mill...

The other thought I had was, once you center up the first part in a 4 jaw, if you
loosen 2 jaws at right angles say one full turn of the chuck key, how far off will
you be if you tighten up those same two jaws one full turn?
 

tomjaksa

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#5
what if you setup your square stock in 4 jaw long enough to make several parts? Cut the rounds leaving square pieces in between rounds. Then you cut the pieces on bandsaw or hacksaw. Then for rest of the operations you just use 3 jaw.
That way you only use the 4 jaw once for several parts.
But hey i am a self taught noob so my theory probably sucks.
 

Chipper5783

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#6
What is the issue with using the 4 jaw chuck? You said the issue was that there were multiple pieces - are you making lots of them? If it is <50 items, that wouldn't be a big deal - loading in/out of the 4 jaw.

The other thought I had was, once you center up the first part in a 4 jaw, if you
loosen 2 jaws at right angles say one full turn of the chuck key, how far off will
you be if you tighten up those same two jaws one full turn?
Fradish is right, just working two jaws puts you pretty close (I find I am within 0.005" on the first try - it won't come back the same when the next piece goes in, but it will be close). Use a wide tip on the plunger of the dial indicator and it will likely ride right over the corners.

An interrupted cut on a little piece like that is not going to be an issue to the machine. The tooling may not be too happy (start with HSS and don't get too aggressive on the depth of cut).
 

Frank Ford

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#7
I do this kind of thing routinely, so to make these in quantity I'd start with square stock and use the square collet, and turn the round section in one pass with a sharp insert working up close to the collet. Then I'd shove the stock farther out, part off the piece a bit overlength, repeating until I had as many as I need.

It would be a quick process, and there would be sufficient support to turn the round section without difficulty. I'd then switch to a round collet, grip the part right at the shoulder, and quickly face them off to the same length without moving the lathe carriage. Then back in the collet for drilling and threading I'd drill all of them first, then thread them.
 

Frank Ford

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#9
Hopefully the round part is a collet size. If not might have to use an emergency collet or ER series.
Ah, that is a point - I assume too much sometimes. Natcherly, you'd check that before proceeding.

It wouldn't be a problem for me because almost all of my work is in collets, so I have FULL assortment of 5C - 64ths, metrics, #drill 1-60 , square, hex, and even some rectangular, along with all the ones I've bored for specials like tapered or eccentric stuff. I also find it handy to have duplicates of common sizes, for use when I need to move repetitively to the mill to use the spin index or collet block.
 

tomh

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#10
This is not going to work for the op, however at times like this a 4 jaw scroll chuck is well worth looking into and a good investment to have on hand.
I have one and leave it on the lathe all the time in place of the 3 jaw, the only time I go to the 3 jaw now is for hex stock.
 

Charles Spencer

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#11
I'd probably do it in a 4-jaw chuck with a process like I've sketched below. By turning the second part before you cut off the first you would be able to use a parting tool without an interrupted cut. The square end could be cleaned up on a sander or grinder. If you have a tail stock turret or capstan it would save tool changing time.

drawing.jpg
 

Silverbullet

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#12
Perfect job for collet, if you had a turret box on your compound , 4 tools set up . Face and rough turn , finish turn , center drill , drill , chamfer, tap, then cut off . Turret LATHES are made for this type work. You will want the bar length through the head stock , not a bunch of short pieces. It makes holding in the collet easier. And the material being tubing when parting is easy. Looks like a gravy job , you'll do alright . Get the collet , my vote
 

Wreck™Wreck

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#13
Put in lathe and turn, drill, tap and part off, that easy. Don't worry about the interrupted cut, use a roughing tool then a finishing tool if the finish is a priority, you should be able to make hundreds of such parts with one tool if you are not in a hurry.

If you really want to enjoy yourself single point threads on the corners of square steel bars.
About 15 years ago I made a dozen or so parts in 1 1/2" square cold rolled steel bars about 30" long, 15" of which were threaded on the corners, such a racket this made. These were parts for the restoration of some manner of historic canal lock controls built in the late 1800's when it appears that time meant nothing. The deburring of threads with 4 interrupted cuts is a nightmare as you can imagine.

Good Luck
 

kd4gij

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#14
First never pass up an opportunity by new tools. But that would be easy in a 4 jaw chuck. If the square stock will fit through your spindle. Make first part part off losen jaws 1 and 2 advance stock and tighten. you should stay pretty close that way.
 

auto.pilot

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#15
Thanks very much to everyone for your excellent and detailed responses. My plan is to buy the square collet and make sure that I have a round collet in the proper size for the 2nd procedure. I will post follow up results in the next couple of weeks.

Jim
 

benmychree

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#16
You could borrow the technique used to make a cube in a cube. Bore a hole in a piece of round stock with a diameter equal to the diagonal length of your square stock. Then cut a lengthwise slit. Insert your square stock with one side straddling the slit. When you tighten the assembly in your three jaw chuck or collet, it will securely clamp the square stock.
Also available are square hole sleeves made by the Sturdy Broaching Co. that are made to be used for making boring bars and other tooling by drilling and reaming a round hole and silver soldering or loctiting the sleeve in place. For holding square stock, they can be slit along one corner and clamped in a 3 jaw chuck.
 

bfd

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#17
what I do is to use my Jacobs rubber collet chuck. find the size collet that fits over the square stock but find one that has metal inserts that is a multiple of 4 say 8 or 12 metal inserts then I line up the square points on the metal inserts and tighten the collet down and lock it in place works well to turn the end of square stock down to round. but not everybody has a Jacobs rubber collet chuck this method is very fast and accurate bill
 

Catcam

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#18
I'd probably do it in a 4-jaw chuck with a process like I've sketched below. By turning the second part before you cut off the first you would be able to use a parting tool without an interrupted cut. The square end could be cleaned up on a sander or grinder. If you have a tail stock turret or capstan it would save tool changing time.

View attachment 231767
I recommend parting before "turn 2" otherwise ok
 

GK1918

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#19
I was probably 14 yrs old, one of my first tests in school was giving one piece of square stock and one
piece of round stock.. We were instructed to make the square round and the round made square. No
books no nothing and no talking. Pick your lathe, I want these parts at the end of the school day. Any
way only two of us managed this, I was brought up in grease and oil and gears so at least I had a little
brain. Till this day I always thought the teacher had us do off the wall projects because he was
weeding our thinking levels . Some kids couldn't even operate a crescent wrench. This was 55 yrs ago
and I now realize I rather be the student than a teacher kids must have drove him to a bottle of Jack
when he got home. Picture a 60 yrs old gold rim glasses about 5' 5'' always wore one of those knitted
hats with a ball on top (you see Christmas time).............. Just rambling again you can do it.......sam
 

auto.pilot

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#20
Thank you for sharing that story. What a great way to learn! Quite frankly at my age with no instructor, I approached almost every project the same way. If something looks like it's possible I go ahead and try to do it. The major difference of course is without the internet I would never be able to accomplish these things!
 
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