Need Help Making Knobs

[JR49]

So, I decided to replace the travel lock knobs on my PM 932 mill. Well hey, I'm a hobby machinist right? Why would I buy 6 knobs at about 65 cents a piece, when I can buy a 10 dollar 1.75" dia aluminum round bar and spend countless hours making my own? What an easy project this will be! Or so I thought. I guess if I had cut the round bar into 6 chunks 1" thick, I could have then made the star shaped outside dia., and the center hole on each piece individually, ( doing it manually, as I don't have a rotary table) but that would have been a lot of setting up, and I'm too smart for that, right? I decided I would shape the OD of the whole 8" long round bar, and then cut it into the 6 knobs approx. 1" thick. Then I had the realization that I have no clue how to set it up or even how to shape the OD into something like the pic I've included. Something like this sure puts me in my place as a complete newbe (been on this for 2 days and have nothing to show). Would sure like to hear some opinions on this--If you say I can't do it that way, then how would you do it ??? Thanks, JR49

PS. Have lathe, mill, horiz. saw, drill press fair amount of tooling incl. a boring head and bars

 

[PAturner]

Have you seen the YouTube channel click spring? Watch his videos on cutting pinions for his clock. Basically he does exactly what you're describing- cuts the profile of the part through a whole bar and parts off what he needs. If you got the right shape and size cutter I imagine you could probably set it up on the mill.

Edit- here's the link to the video:

Sent from my iPhone using Tapatalk

 

[mikey]

Not to even imply you can't find some way to do this, JR, but it would be easiest to use the stuff you don't have - a rotary table and tailstock support. Given the lack, maybe you would consider asking one of the guys who does own that stuff to do it for you? No shame in appealing to the community, I think.

That said, I suppose you might try setting the ends of the bar on V-blocks and clamping it down before taking light passes with a ball end mill. A healthy groove on each end would allow the cutter to get in behind the clamps. You would need some way to index the bar, some way to bolt the V-blocks to the table so each cut is aligned the same and some way to support the center of the bar so it doesn't move away from the cutter.

Personally, I would just make knobs on the lathe so its nice and pretty. I would live without the scallops. I'm sure the others will have some ingenious way to do this but my feeble mind can't come up with a better idea.

 

[JPMacG]

Funny, by happinstance I just made a knob for my Atlas mill. No scallops, all lathe work. I knurled the OD. It looks nice. The cutter marks left a kind of optical pattern on the face of the knob that looks attractive. Made it from an old chunk of 12L14 steel. I drilled and tapped all the way through and used a jam nut to lock some threaded rod in place.

I'm not sure the scallops have a function, other than to save material. I guess a scalloped shape is easier to grip, but the knurled OD works just fine.

 

[RJSakowski]

So, I decided to replace the travel lock knobs on my PM 932 mill. Well hey, I'm a hobby machinist right? Why would I buy 6 knobs at about 65 cents a piece, when I can buy a 10 dollar 1.75" dia aluminum round bar and spend countless hours making my own? What an easy project this will be! Or so I thought. I guess if I had cut the round bar into 6 chunks 1" thick, I could have then made the star shaped outside dia., and the center hole on each piece individually, ( doing it manually, as I don't have a rotary table) but that would have been a lot of setting up, and I'm too smart for that, right? I decided I would shape the OD of the whole 8" long round bar, and then cut it into the 6 knobs approx. 1" thick. Then I had the realization that I have no clue how to set it up or even how to shape the OD into something like the pic I've included. Something like this sure puts me in my place as a complete newbe (been on this for 2 days and have nothing to show). Would sure like to hear some opinions on this--If you say I can't do it that way, then how would you do it ??? Thanks, JR49

PS. Have lathe, mill, horiz. saw, drill press fair amount of tooling incl. a boring head and bars
View attachment 136870

You can make a fluted knob on a mill using a boring tool. Start by turning a disk; in this case 2". mount the disk to the mill and use the center of the disk as the 0,0 cordinate. The boring tool would be set for a 2" diameter and the coordinate given in the drawing would be the five centers for the boring operation. The points of the star could be broken with some light sanding or by buffing. Different patterns can be made by varying the boring tool diameter and/or center distance from the disk center. New cordinates can be obtained by using the sine and cosine of 72º and 144º and the appropriate multiplier or you can draw them out in a CAD program.

The blue is the resultant part, the red is the disk, and the violet is the boring tool cut.