How can I hold a spinner so that it can be machined inside?

[Kmot]

Hey guys,

I have this spinner hub, that is drilled and tapped already for a 1/4-28 crank. I would like to machine away about a 1/2" of the material on the inside, so that I can thread it onto the crankshaft and sit down flush against the propeller, and hiding the prop locknuts inside.

I cannot figure out how a spinner is held in chuck jaws. ???

Thanks!

 

[DICKEYBIRD]

I would turn a mandrel with a tapered section to roughly match the large part of the spinner, make a threaded drawbar with a clevis to engage the hole that's drilled across the spinner and hold the spinner tight in the mandrel with the drawbar. Harder to describe than make it!

The drawbar goes through the lathe spindle and pulls the spinner into a tapered "socket" in the mandrel which is chucked up in your 3-jaw (or 4 jaw.) Make sense?

 

[MachineTom]

Make an AL cup that fits the OD of the spinner, but slips over so the its edge will sit flush with spinner on surface plate, with 2 holes in the top, pour low melting point fixture metal (melts at 120-160°F) then machine the inside. Reheat to melt out the metal to be used again. $20 lb

For the next one you would machine the inside first then mount the spinner on a simple plate to turn the OD.

 

[steamer]

Another way would be a shellac chuck with a conical holder

All though shellac is an art form, you might be able to use 5 minute epoxy to hold on to it long enought to machine the inside. Its along the same idea as the low melting point alloy,


Or make a bucket chuck with a nut that clamps the spinner into a female conical hole, but only by the rim of the spinner, thereby leaving the center open for machining....that is a bit more involved to build, but perhaps easier to implement, and certainly more robust and available for other spinners if you have more than one

Dave

 

[stevehuckss396]

Get some cerrobend and cast it around the spinner. Put the spinner on a spit and turn the Cerro round. Then grab the Cerro and remove the spit. Machine the innerds and then boil it in water to remove the Cerro.

 

[steamer]

I like your idea better Steve!

Dave

 

[Kmot]

Thanks for all the great ideas!

 

[Stan]

I would screw it onto a long bolt, put the head of the bolt in the chuck and the nose in an inverted cone live center and machine it from the back.

 

[kvom]

Maybe a simpler plan:

Chuck a piece of aluminum round and bore a cavity that part of the spinner will fit snugly (taper the opening to give a better fit. Then thread in a bolt that has been center drilled and use a live center with enough pressure to secure the assembly. The spinner should now be held securely enough to machine the end using light cuts.

 

[Kmot]

More good ideas! Thanks!

 

[dgjessing]

How about leave that one for it's intended purpose and instead make a new one, inside first, then the outside on a threaded mandrel?

 

[rake60]

If it were me, I'd chuck it up gripping on the sharp corners at the large end.

Then I'd start a cut - then spend an hour looking for the spinner after throwing it
out of the lathe - then try one of the more reasonable suggestions offered here.


Rick

 

[Ken I]

Kmot, heres a slightly more mechanical approach using a "cup" and clamping ring.

Ken

View attachment DUMP1.zip

 

[Kmot]

Wow, Ken! That is awesome! Thanks!

That is something I can actually make, I am pretty sure.

All you guys are awesome! Thanks so much!

 

[Ken I]

Kmot, Drill the pilot hole through - if the spinner gets stuck you can tap it out from behind.

Ken