# Curved slot using only a lathe and fabrication



## SignalFailure (Nov 2, 2010)

I've seen lots of engines especially wobblers that call for a curved slot on the reverser. I needed to make such an item for the current project with a 2mm slot within 1mm of the edge. Not having any fancy milling gear I tried chain drilling one but the result was very ugly and innacurate so I decided to fabricate one using only the lathe and some silver solder. Hopefully someone might find this useful.

Basically it consists of three discs - the main 'outer' disc (I used a 10mm end mill to make the 2mm deep recess... ), the central disc, and a ring with a sawn out section for the middle bit. I placed this ring carefully over the plans and marked off the part to be removed.

I made the two inner parts deep enough to stand a little proud of the outer ring so I could face it off nice and tidy after soldering. Hopefully the pictures explain all. Now I just need to drill another two holes and it's finished ;D

Paul


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## Deanofid (Nov 2, 2010)

Now that's a slick idea. Good thinking, Paul!


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## rleete (Nov 2, 2010)

Nice solution. A heck of a lot of work!


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## Lew Hartswick (Nov 2, 2010)

That looks a LOT easier than using a rotary table and a mill.  Course it has square
ends of the slot but I bet in 99 pct. of the time it doesn't matter.  
  ...lew...


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## SignalFailure (Nov 2, 2010)

Lew Hartswick  said:
			
		

> That looks a LOT easier than using a rotary table and a mill.  Course it has square
> ends of the slot but I bet in 99 pct. of the time it doesn't matter.



I can't say if it's easier 'cos I've never used a rotary table. You could have cosmetic perfection by using a round file on the sawn off ends I suppose but the practical difference must be miniscule (Marv will probably calculate the effect and tell me the error of my ways ;D)

rleete, it took me about an hour but that included making a piece of 3mm silver steel into a reamer


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## bearcar1 (Nov 2, 2010)

Yea, I'm likin' it. I'll have to store that one away in the archives for future use. Well done Paul. I really enjoy seeing rudimentary ways around a problem. Simple and effective and best of all, it did not require all sorts of setups and tooling to accomplish the task. Bravo! :bow:

BC1
Jim


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## mklotz (Nov 2, 2010)

Not to detract from your cleverness but is a curved slot really necessary? Most of the reversers of this type that I've seen manage with a straight slot. Many of Elmer Verburg's designs use straight slots. 

Regardless, the process of constructing oddly shaped voids by making solid pieces that fit together to create the void shape is still very clever. The classic example is constructing a square hole (e.g., for a tool bit) by milling out two U-shaped channels and soldering/welding together to form a square hole.

Artists talk a lot about the use of "negative space". Machining is something of an art so it's not surprising that we have to do the same.


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## SignalFailure (Nov 3, 2010)

mklotz  said:
			
		

> Most of the reversers of this type that I've seen manage with a straight slot.



Yes, I've seen some of those and it did cross my mind but not having a good grasp of the theory (if there is one!) I thought it best to stick to the original design. I suppose the effect of a straight slot would be to make the flow less 'tapered' when changing direction...

Paul


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