Question on how to make this extractor.

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TheGreenMan
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Question on how to make this extractor.

Postby TheGreenMan » Tue Feb 23, 2016 3:16 pm

One day I would like to make some extractors for the M95 and M95M rifles.
At the moment I do not have a mill, though I do have a lathe. I am planning to get one in a year or two and would like to know what steps (general) would be required to make an extractor. And specifically how to get the inside radius where the extractor travels over the bolt lug and how to cut the ridge on the extractor tail. I think I have a vague idea on the rest of the steps.

Thanks! :-)

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BadDog
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Re: Question on how to make this extractor.

Postby BadDog » Tue Feb 23, 2016 5:00 pm

That's a complicated piece beyond my experience. But I will say that it looks like many of the ID features were turned on a lathe just by the marks. Perhaps on a large lathe in a tubular fixture holding the parts in the ID? Marks could also be from a horizontal mill with mill cutter diameters selected as required, possibly custom made and ganged to produce most of the feature(s) in one plunge? That's my guess, I'll wait to see how that passes muster with those more experienced.
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Harold_V
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Re: Question on how to make this extractor.

Postby Harold_V » Tue Feb 23, 2016 5:05 pm

I'm not a gunsmith, so I may not understand which detail is of concern, but the bottom picture makes it obvious how the cuts were made. With the side cutter on center with the part, the cutter is plunged to proper depth. That means that the cutter must be the proper diameter, in order for the radius generated to be the correct size. For a production run, you can almost safely assume that several cuts were made at one time, so that means the mandrel was loaded with various side cutters, all of specific size and spacing.

For this type of work, a horizontal mill is almost mandatory, although you could cobble up a vertical to make similar cuts. It just wouldn't be as robust, and you most likely would have to address the cuts individually. A much slower process, and one fraught with the opportunity to make errors.

Making a part such as you've shown will require considerable skill, especially if you have any hopes of producing them in a timely fashion. Not for the faint of heart.

Harold
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Magicniner
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Re: Question on how to make this extractor.

Postby Magicniner » Wed Feb 24, 2016 3:36 am

I would make a fixture for the lathe to hold the work-piece, which replaced the tool post or bolted down to the cross slide.
Running an arbour between a chuck & centre to make the cuts in the way you would on a horizontal mill, probably only one cutter at a time, though, not with a ganged set.

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steamin10
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Re: Question on how to make this extractor.

Postby steamin10 » Wed Feb 24, 2016 5:53 am

For the complicated 'spoon' end, mass production would have this broached in a fixture. Other hot press and bend shaping would make a stick of metal into such a refined shape.
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TheGreenMan
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Re: Question on how to make this extractor.

Postby TheGreenMan » Wed Feb 24, 2016 3:29 pm

Thanks guys.

I read "horizontal mill" and went 'duh'. Sad that I missed the obvious.

Thanks for the tip on how to possibly try this on a lathe. Maybe I'll give it a try one day.

I'm not too worried about time as I only plan to make a few.

The extractor is totally machined and not pressed except to get the slight bend.

These were designed in the 1880s.


eta: Do you have a recommendation for an arbor that I could use?
I have an 8x12 HF lathe with a 5" 4 jaw chuck.

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Re: Question on how to make this extractor.

Postby Harold_V » Wed Feb 24, 2016 4:10 pm

While I'm not prepared to suggest this part can't be made on a lathe, it would be a nightmare, as the radius is tight---demanding that a boring bar be too slender to be functional. That would be particularly true for the larger radius, whereby the bar must pass through the smaller radius and have the ability to create the deeper cavity. The depth of the cut, alone, would dictate that it would border on the impossible.

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ctwo
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Re: Question on how to make this extractor.

Postby ctwo » Wed Feb 24, 2016 4:13 pm

Why? Could the part be mounted sideways and cross fed into the boring bar?
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Re: Question on how to make this extractor.

Postby Harold_V » Wed Feb 24, 2016 4:44 pm

ctwo wrote:Why? Could the part be mounted sideways and cross fed into the boring bar?

I should have been clear in my comments, which were intended to reflect machining by rotating the part, with the cutter held stationary.

If one is happy to take individual cuts, and has the ability to locate the cuts properly, sure, the cutter can be rotated, with the part plunged to control depth of cut. That, of course, would require the ability to mount the part on the cross slide, with the cutter held in the spindle. For the short cuts, that would work fine, even with a boring head (used to control the radius of the cut), but the cuts well away from the end will still present the same problem---a lack of support (you still face the same problem, as the target radius dictates the size of the bar in use), so the cutter would require tailstock support. That, more or less, sends you right back to what I described previously----a setup that rivals a horizontal mill.

I suspect the original parts were made from a single cutter---one profiled to match the part. With the tight radius, I expect there was no mandrel---the cutter was a single piece and was supported on the end to prevent deflection.

Sequence is everything when making a part such as this. If you machine in the wrong sequence, you may remove material that would be required to hold the part for one of the operations.

Harold
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BadDog
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Re: Question on how to make this extractor.

Postby BadDog » Wed Feb 24, 2016 5:24 pm

Something I hadn't thought of that Harold mentioned is the small radius meaning it couldn't be a standard cutter on a mandrel. And I think the ejector finger presents even more problems, unless that outboard portion of the cutter had a groove for clearance of the feature. It seems the small radius is the major problem, even for a horizontal mill op. Assuming a suitable fixture, it seems the larger radius could be formed without undue issue.

Using a lathe line bore type approach (mandrel with cutter bit between centers) with the part on a vertical support (angle plate, knee, whatever) still presents a major unpleasantness for that small diameter, but might actually be the easiest way? But you still have the ejector cartridge finger in the way of your tail stock and mandrel, unless maybe you locate it just to fit along the end of the mandrel. But then you couldn't use carriage feed, which means to use carriage feed the mandrel would have to clear the finger, making it quite small and subject to lots of flex/chatter.

So as Harold noted, that gets back to a custom cutter plunge cut for each part (which I guessed much of in my first post). But that doesn't help for the one off part.

But I've never done anything like this, so my posts are just a mental learning exercise for me.
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paulj84003
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Re: Question on how to make this extractor.

Postby paulj84003 » Mon Feb 29, 2016 11:30 am

why not lost wax cast in steel
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Re: Question on how to make this extractor.

Postby Harold_V » Mon Feb 29, 2016 3:35 pm

paulj84003 wrote:why not lost wax cast in steel

Fine for a shop with that capability, but it most likely would be impossible for the home shop, as the melting point of steel is well beyond temperatures that are normally achieved in small (fuel fired) furnaces. If one was equipped with an induction furnace, then, yeah, it most likely would be a good choice.

Harold
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