Hemingway Quorn Mk3

So I bored it out to 1.4", figuring I can bore a sleeve to fit on the column, and then possibly mount it on a mandrel, and cut the OD to fit the 1.4" bore.

In terms of Aluminum, steel, or cast iron, I have been back and forth on whether to paint the castings or clear coat them after they get a patina. These modern castings do not look as smooth as some of the ones I have seen from the folks builds who grab castings from a guy that bought them in the 70's or 80's and never got around to it, plus they have some burr demurring marks near the seams of the casting so I am leaning on paint. Seeing as the aluminum would be painted over, I am seriously considering just going that route. I have probably over 1000 pounds of aluminum bar stock. It would be encapsulated in machine paint forever.
 
Let's just say that I am INCREDIBLY happy that I went the extra mile to bore out the casting to 1.4" and then make a sleeve. I went with Aluminum, because I have a butt ton of it, and here's what I did. I chucked up a piece of aluminum and faced. Flipped it and faced and marked the length I need. Cleaned up the outside, and then drilled it to an inch. Then start boring it out. I have these polished carbide inserts for aluminum and they do a really nice job. Got to 1.2 roughing and then took a measurement and took. a 20 thou and 3 10 thou passes to finish. Took a final spring pass, and the bar fits perfectly. It is difficult to get started, but once its in about 3/4" it slides right in.I did not drill the aluminum slug through so the fit was so good it was acting like an air shock.Pulling it out gave an incredibly satisfying plop sound.

The riser bar for the Quorn Mk3 is already machined with the spiral, and the end already has a center point, so I decided what better way to beat resonance while machining the outer diameter to 1.4" than insert the bar, and use my live center for tail support.

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First few runs were annoying long skinny strands of aluminum, but I dialed in RPMs, feed and depth of cut and the chips start breaking. Great for roughing. 60-80 thou DOC at about 5-600 RPM was working great for roughing, and once within 50 thou I slowed down the feed and lightened up on DOC. This time went 20-20-5 and 5 thou, and needed to spring pass another 3 thou to hit my 1.4"

I tried to fit the casting to the sleeve while it was still on the lathe, and it got stuck half way. Decided to press it home with my vice. That sieve is NEVER coming out. Column bar still fits perfectly as well. Drilled and tapped the casting for grub screws that lock the column, and these pieces are pretty much done with major machining.

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As a brand self new learning budding hobby machinist, today is the best day I have had in the shop to date. Everything came together better than I could have hoped or expected. Best lesson I have learned past few weeks with this project is:

Precision is intentional, it is a process, there is no luck involved and it MUST be planned., Changing your process because you think you don't need to follow it each and every time you are performing a procedure will ruin a part QUICKLY.

Second lesson. You are a machinist. Do not just move on with "good enough" Make a plan and fix your mistakes.
 
Last point on this part of the project. I wanted the horizontal bars to be centered on the casting as best I could get them. After doing that, the vertical bar hole is not centered on the casting after measuring the center from the center of the rear most horizontal bar. I decided to go this way as that part of the casting had the most meat on it to work with. That is why that bored hole is so far off center for the column.
 
From what I've seen of the drawings from Hemingway, the book is hopeless by comparison. The drawings are so tiny they're almost illegible. All the descriptions of the machining ops are geared toward a time when literally the only machine tool in the shop is a 6.5" swing lathe, so they aren't much help apart from making you say "awww, cute" out loud. I redrew everything in CAD and more or less threw the book in the bin.

What are you struggling with?
 
Lo-Fi said:
From what I've seen of the drawings from Hemingway, the book is hopeless by comparison. The drawings are so tiny they're almost illegible. All the descriptions of the machining ops are geared toward a time when literally the only machine tool in the shop is a 6.5" swing lathe, so they aren't much help apart from making you say "awww, cute" out loud. I redrew everything in CAD and more or less threw the book in the bin.

What are you struggling with?
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Small contextual things.

Most recently, I finished up major machining on the 2 base castings. I mocked everything up and the rear bar (that I assume is just for support and rigidity as I don't think it moves) will need to be locked into the castings so the front bar with spring and micrometer can work without fear of the rear bar moving. I do not see anything in the plans, nor in the assembly document that shows how that rear bar is secured. Loc-tite? I was thinking maybe making brass grubs to clamp the rear in place within the casting. How are you supposed to lock the rear bar into the castings so it provides a rigid framework so the front bar can be adjusted with repeatable accuracy?

Edit - I guess IF the Quorn was mounted to a base, this would not be an issue.
 
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I used brass tipped setscrews on mine. I sorta think Chaddock suggested loctite.

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Weldingrod1 said:
I used brass tipped setscrews on mine. I sorta think Chaddock suggested loctite.

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Did you come up through the bottom void of the casting at an angle or from elsewhere?
 
Christianstark said:
@Lo-Fi any input?
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Yeah, loctite is what the book suggests. To be fair to it, it's helpful for those little kinda nuggets. I don't think there's anything wrong with set screws, but personally I'd worry that they'll work loose over time with vibration, though that's possibly unfounded.
 
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