Fluted Knob Fail

[Bill Gruby]

It's called a learning curve. You are rounding the curve very easily. Congratulations.

"Billy G"

 

[bfd]

where I worked years ago I did the same thing unscrewed the the knob I was making unscrewed off the mandrel and ruined it then I was able to find a left handed endmill in the tool crib. onewhich cut in the opposite direction so the handle tightened as it cut worked much better Idont know if left handed endmills are still around bill

 

[brino]

Lots of great simple solutions above, I'll add one more.
A hex collet block would work nicely and is less expensive than a spin indexer.

http://littlemachineshop.com/products/product_view.php?ProductID=4105&category=

I find collets grab threads quite securely and without damage to either.

-brino

 

[willthedancer]

Try grinding up a radius tool, turning it so that the top faces the chuck, and slotting the od by moving the lathe carriage. You have to lay out where you want the flutes, but it works pretty well, especially on softer material like Al and plastics. Cut to depth a little at a time, and index the spindle to the next one. You can get it precisely.

 

[Inflight]

Left handed cutter would solve it too.

 

[woodchucker]

Thanks for all the comments/suggestions. What I ended up doing was making a v-block out of some scrap aluminum. I scribed a line on the block to use as an index against the points on the nut.View attachment 108902

Then I was able to bring the end mill in from the side to make the groove.
View attachment 108904
It came out pretty good, although I had a little trouble with keeping the knob vertical in the vise.
View attachment 108903
The next one I'll take the advice and use locktite to hold the shaft in. That way I can use a jam nut (or group of them) to clamp and index.
It hadn't occurred to me how easy it would be to use heat release on the locktited joint.

regards,
Leon

Whats the point of that v block?
Usually you use the v to secure the part. In your use a square block would have done the same as your v block

 

[chips&more]

I would get oversized material. And then drill and ream 6 nice and smooth equally spaced holes as needed. Then turn the OD down to the size needed, bada bing bada boom…Dave


Using a ball end mill leaves a funny pattern in the center of its cut. And plunging with an end mill is hard to control the side cutting parameters. Drilling 6 holes can be done using just the X & Y dials on a mill and math/trig. You could even use a boring head on the mill during the same set-up, to finish the OD on the knob. Instead of going back to the lathe.

 

[MikeinFresno]

cut a slit all the way thru in the "locknut" with a saw or dremel. Then when you clamp it in the vise it really grabs the threads.