Stirling Mini Fan first build question

[GregW]

I'm starting the Stirling Mini Fan as my first engine project. What is the best way to cut the fins on the head? They need to be spaced .04, so I'm thinking either a slitting saw on my mill, or a parting tool on the lathe? I'd rather do the operation on the lathe, but don't know if I'll be able to find a tool that small.

 

[Cogsy]

I'm not familiar with those plans so I don't know how deep the fins need to be, but you should be able to grind a hss tool to cut them as long as they're not too deep.

 

[Boot]

I made the Super Stirling by Jerry Howell and I used a long HSS tool to cut the fins. They are .041 wide spaced at .093 apart cut into a square piece of 1.5 aluminum approx .220 deep on a side. It's a long skinny tool ,but it worked.
I think I hand ground it from a 1/4"sq. Circle C HSS tool blank. Just take your time plunging it into the cylinder. I used a 9" South Bend lathe to do it. Boot

 

[doc1955]

I made the Super Stirling by Jerry Howell and I used a long HSS tool to cut the fins. They are .041 wide spaced at .093 apart cut into a square piece of 1.5 aluminum approx .220 deep on a side. It's a long skinny tool ,but it worked.
I think I hand ground it from a 1/4"sq. Circle C HSS tool blank. Just take your time plunging it into the cylinder. I used a 9" South Bend lathe to do it. Boot

I also built that fan several times. I agree grind up a tool or take a part off tool and grind the end of it down you can get them down to .05 wide. Here is a vid of cutting the fins on the super

[ame]https://www.youtube.com/watch?v=wROXzesbfX8[/ame]

 

[GailInNM]

A "P" typecutoff blade works well. The P1N is 0.040 wide x 1/2 x 3-1/2 long. They have lots of side clearance. If you have an AXA quick change tool post the 250-107 universal cutoff blade holder will hold it but you should put a shim behind it about 5/16 or 3/8 tall to align it vertical to get all the clearances right. Align the blade with a dial indicator so it it parallel to the cross slide travel and only let the blade project out as much as you need.

The P1N blades are easily available from most industrial supply sources at prices ranging from about $7 to $15. Little machine shop has them for about $8.
Gail in NM

 

[GregW]

Great, thanks for all the info.

 

[Blogwitch]

If I could give you a little advice.

Imagine you are parting off many many times, as that is all cutting fins on a lathe is.

People get scared of parting off, but the golden rule is don't faulter or hang about. Start the cut and just keep feeding in until you reach depth, otherwise you are liable to get a snatch or dig in occuring.

This isn't BS, I have cut many thousands of fins with hardly a single tool failure, in all materials. Mind you, I always use my own ground tools with no side relief, just a chip breaker on the tip. The advantage of possessing a surface grinder.

Cast iron

Bronze

Brass, this grooving tool, as far as I can remember was 0.025" wide.

And lots of them

On the other hand, RT and slitting saw on the mill can overcome certain problems if you are an uncertain parting off modeller. If you can gang up on slitting saws, you can get the job done in one quick swipe.

I hope this helps a little.


John