# Fluted Knob Fail



## lcorley (Aug 15, 2015)

I'm trying to make a fluted knob as shown in the left picture.  My plan was to use  the hex bolt head (right pic) as an index in the mill vise and cut the flutes with the edge of a 1/4" mill.  I would rotate the assembly to the next bolt head flat after each cut. I was very pleased with this plan till I tried it.  The torque from the end mill happily spun the knob off my "fixture". 

Hmph.  

I guess my next approach is to make an aluminum v-block to hold the knob and index the points of the hex bolt against an index mark on the v-block.  Any other suggestions? Comments welcome.

regards,
Leon


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## Bill Gruby (Aug 15, 2015)

Keep the bolt as short as possible and use a JAM NUT instead of the one you did. Get the knob as close to the edge of the milling vice as you can. This will eliminate almost all vibration. Tighten the vise as tight as you can and try again. The regular nut  is why it spun off. You have a sound plan, just the wrong stuff.

 "Billy G"


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## John Hasler (Aug 15, 2015)

Another approach: start with a piece of hex stock.  Mill flutes in the flats. Turn the piece down on the lathe leaving just the flutes.


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## jpfabricator (Aug 15, 2015)

Apply the feed from the other side of the knob. On the left side of of the knob so the rotating force is trying to screw the nut/knob on insted of off.

Sent from somewhere in East Texas Jake Parker


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## TTD (Aug 15, 2015)

lcorley said:


> The torque from the end mill happily spun the knob off my "fixture".


I had the _exact_ same thing happen to me when I made the knobs for some indicator holders (3/8" end mill). I switched to a ball nosed end mill and turned the workpiece like you see in pic below and it worked perfect...just make sure the knob is good and snug first.


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## Round in circles (Aug 15, 2015)

Bill Gruby said:


> Keep the bolt as short as possible and use a JAM NUT instead of the one you did. Get the knob as close to the edge of the milling vice as you can. This will eliminate almost all vibration. Tighten the vise as tight as you can and try again. The regular nut  is why it spun off. You have a sound plan, just the wrong stuff.
> 
> "Billy G"



Billy , I'd try and not only use the jam nut principle I'd also fill the whole thread with nuts to stop movement in the chuck jaws , turning down a nut or the bolt length  to make the final quality fit  if needed. ( basically making the bolt into a hexagonal bar to fit the chuck jaws ) .

Then take it to bits put some Loctite on the threads , reassemble and make the flutes when the Locktite has set  .

The six flats of the nuts will give you six flutes on the knob or make a thinner nut so you can  rotate the knob 30 degrees & then you can get 12 flutes on it .

Once made , a bit of dunking in boiling water will see the Loctite loosed enough to undo it .


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## Round in circles (Aug 15, 2015)

TTD said:


> I had the _exact_ same thing happen to me when I made the knobs for some indicator holders (3/8" end mill). I switched to a ball nosed end mill and turned the workpiece like you see in pic below and it worked perfect...just make sure the knob is good and snug first.


Hi Todd ,
Did you make a packing washer to get the knob,s  45 degree positions accurately set/held or turn some off the base of the knob?


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## TTD (Aug 15, 2015)

Round in circles said:


> Hi Todd ,
> Did you make a packing washer to get the knob,s  45 degree positions accurately set/held or turn some off the base of the knob?



Hello David,
I'm pretty new at this whole machining game (about 1 yr) so I'm probably not the guy to be following any kind of advice from, but yes, I used some shims from a 3000psi regulator rebuild kit I had. Had to play around a bit before I found the right combination of shim thickness to "index" the knob the right amount, but finally got it "eyeball" close by lining up a line scribed in center of fixture with corresponding lined scribed on knob ....it sucks not having all the proper tools yet!

I won't clutter Leon's thread with my inexperienced jibber-jabber going into detail, but can show you here (just scroll down near bottom of page): http://www.hobby-machinist.com/thre...-first-project-with-milling-attachment.37673/


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## kd4gij (Aug 15, 2015)

I have a piece of 1" hex stock with a 5/8" hole bored through it and made inserts with different thread sizes that I use for that type work. And as said run the mill on the right side so it tightens it.


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## lcorley (Aug 16, 2015)

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.
	

		
			
		

		
	




Then I was able to bring the end mill in from the side to make the groove.


It came out pretty good, although I had a little trouble with keeping the knob vertical in the vise.


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


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## Bill Gruby (Aug 16, 2015)

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

 "Billy G"


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## bfd (Jan 26, 2017)

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


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## brino (Jan 26, 2017)

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


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## willthedancer (Jan 26, 2017)

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.


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## Inflight (Jan 26, 2017)

Left handed cutter would solve it too.


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## woodchucker (Jan 27, 2017)

lcorley said:


> 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.
> 
> 
> 
> ...


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


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## chips&more (Jan 27, 2017)

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.


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## MikeinFresno (Jan 30, 2017)

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.


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