Shaping on Metal Lathe

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ccs34x

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Looking for ideas on how to use shaping hand tools on a tool post on my metal lathe. I have a Grizzly G8688 mini lathe and need to shape the section on my fountain pen. Most of the videos I have seen show this being done on a wood lathe. Is there a way to mount something in my tool post to allow me to do this.
 
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bmachin

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There are a few ways to do this:

Since you mention mounting a tool in your tool post you can:

1. Set your lathe up to follow a pattern. Member More4Dan has done this and posted some pictures of his setup.

2. Make a form tool, i.e. a tool that has the negative profile of the shape you want and just plunge it into the work. It might work OK for something as small as a section, but nothing larger.

3. If you are really coordinated you can turn both the carriage and cross-slide cranks in unison to get the shape that you want. Sort of like patting your head and rubbing your belly. Brian Gray of Edison Pens told me that he actually did that on prototypes to shape barrels and caps with the aid of a metronome.

4. Convert to CNC.

5. If you keep your shape really simple (a straight taper) you can do most of it with the compound adjusted to whatever taper you want. Of course you'll still have some had work of some sort to do.

Two other alternatives:

1. Buy or fabricate a tool rest and turn with gouges and skews just as you would on a wood lathe.

2. My favorite option is files. you can use them to do the whole job or just for finishing, and they won't get away from you. They are really great for refining shapes.

Hope this helps,

Bill
 
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Dalecamino

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You use metal files. Pick up a set with different shapes. I got a set of Kobalt from Lowe's. A good friend sent me a combo file from Florida. I haven't been using it much. Slow speed with the file on top. The key to turning on a metal lathe is ridgity. Trying to use hand tools can be tricky. I suppose it can be done. But I won't try it again.

Just noticed Bill has faster fingers than I. But there you go..take your pick.
 
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More4dan

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The single bolt allows me to adjust the rest location side to side and toward the work. I did shorten the rest to better work for a single barrel now that I turn between centers.

Danny


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More4dan

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I extend the tailstock about 1-1-2” and just move the saddle/cross slide to the right up against the tail stock. These pictures were when I was just setting it up to use with a mandrel and there wasn’t room on my 7x10 lathe. Now I turn between centers and I can leave the saddle/cross assembly on the lathe.


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Woodchipper

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2. Make a form tool, i.e. a tool that has the negative profile of the shape you want and just plunge it into the work. It might work OK for something as small as a section, but nothing larger.
I did the same thing for turning cork grips for custom fishing rods. Piece of 2X2 cut and sanded to contour, double edge tape and a strip of sandpaper!
 
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If you want to learn how to shape on a metal lathe watch this guy, he is AMAZING.


https://www.youtube.com/channel/UCworsKCR-Sx6R6-BnIjS2MA/videos


Watch the older videos first.
Yeah, thanks for sending me down that rabbit hole. It killed the last half of my day pretty well. It's amazing that over 2000 years ago someone created this without the tools that we have today and did a damn fine job of it. Not only that, it was precise. The fact that it was precise relied on the observations of many people before them that observed the planetary alignments for who knows how long. Just so this person(s) would even have an inkling of the knowledge of how to build this, yet they did, with a precision that revels the technology of today. I was impressed that he attempted to make it as best he could to the ability of the person making the first machine. That's impressive.
 

rsieracki

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for those of you saying to shape with files... can you file alumalite, and PR, and all the other assorted styles of 'plastics' we use?

ive been strongly considering a small metal lathe also
 

Dalecamino

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for those of you saying to shape with files... can you file alumalite, and PR, and all the other assorted styles of 'plastics' we use?

ive been strongly considering a small metal lathe also
Sure. Just don't get too aggressive with it. :biggrin: I'm not sure you can file Titanium. anything softer than that is good.

Get your lathe and join the club. :wink:
 

rsieracki

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One other question.. is possiable to get a polished finish on the "plactics" by kicking up the speed and turning down the feed rate and turning to fonished diameter like you would on a piece of metal?

..im trying to increase consistency and speed up production and im essentially wondering if i can get a smooth enough finish like thst to skip some sanding steps

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Curly

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To a point yes. They are after all just more closely spaced grooves. If you use high speed steel, very sharp, with a radius on the tip and a light pass you will get a reasonably smooth surface that you can then start sanding in the 320/400 grit range. If you have flood coolant with a coolant that won't be detrimental to the plastic it will be better yet, just messy.
 

bmachin

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The only problem with slowing down the feed rate is that you won't be able to do it with the minilathe gear train without making some special gearing. With the 20:80:20:80 gear reduction on the 16 tpi leadscrew you're getting a little less than .004 inches of carriage travel per revolution which is not particularly fine. It's possible to add some sort of motor drive to the leadscrew, and lots of people have done it in various ways, but it's just another step.

That said, Pete is right. 320-400 is possible. Slowing down is not--at least with the gears that come with the machine.

FWIW,

Bill
 

More4dan

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I was able to do this with a pattern tracer modification. It only took an afternoon to make. For pens I first turn the barrel down to 0.10” larger than the bushing using the metal lathe in normal mode. I then shift the cross to the right with the tail stock extended. Install my tool rest and turn the barrel the rest of the way with hand tools. Then sand and finish. The tool test only took a couple hours too. You have a metal lathe, making your own tools is part of the fun and challenge. Let me know if you’re interested in how to make the metal lathe mods.



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RangeRat

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More4dan, I for one would definitely like to see your mini-lathe mods. I really like your tool rest idea. I’ve tried just locking a bar of square stock in the toolpost, but there is such limited mobility with the carriage assembly in place.
 

More4dan

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More4dan, I for one would definitely like to see your mini-lathe mods. I really like your tool rest idea. I’ve tried just locking a bar of square stock in the toolpost, but there is such limited mobility with the carriage assembly in place.


When I get back from the Holiday travels I’ll take some detailed pics and send you. It’s simple, would have to be if I came up with it.

Danny


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