Yup, just drill a undersized hole in a holding chuck, chamber the edges a little and your all set and centered.
Agree 100%
1 Like
Well he is trying to drill what is basically a 1/4" hole in a 1/2" Delrin sphere.
Acetal is very hard and has a pretty low coefficient of friction.
If he canāt clamp that sucker down he is going to spin it and burn his fingerprints right off.
Personally I think the easiest thing is a two piece jig with two holes. one piece is clamped to the table and has a hole on center. The other is a long strip with a hole near one end. Put the ball in the bottom hole, put the strip over the top, and put a clamp on the strip as close to the ball as possible. The lever action will help hold the ball in place.
3 Likes
I dunnoā¦is it really worth all that set up time and work? If itās a multiple item thing, then yeah, best to set up a jig / repeatable holder kind of thing. But if itās a one time thing, and wants to be safe and not wanna hold with his fingers, then he can just gets a pair of vice grips, pad them with some thick leather, or tape or pieces of rag; whatever, and hold it really easily.
Set the rpms to the minimum, make sure your drill bit is new and sharp, and it should go smooth as butterā¦
2 Likes
Well done. This sounds like something may dad would have come up with. Heās always finding interesting ways to use tools like this.
1 Like
Soā¦first - THANKS. Lots of great suggestions hereā¦
Let me add a few detailsā¦
Iām sliding the bead onto some line (aka rope) that is a āSoft Shackleā to hold the Clew of a Sail down to the boom (Itās for a Laser Sailboat if anyone knowsā¦) The balls reduce the surface contact and slide in and out of the boom to make adjusting it easier.
Here is a photo of the prototype.
I did wind up having a few of them spin in the original jig so bad the melted. Finally got through them with a really slow setting and the ball in a viceā¦but not optimal. My drill press isnāt exactly the top of the line either.
After I get a chance to test this concept (the soft shackle more than the balls) and dial in the actual diameter of the finished product, Iām hoping to produce these for sale. So with a little luck I will need to repeat this process.
I was thinking that with the GF I could basically set up a (wooden) tray of them, use 123D Make or Tinkercad to set up the cuts and save it as a ārepeatableā process. Which would allow me to turn it on and then do something else instead of aligning a drill bit and doing them one by oneā¦I suppose if I used @dan 's idea I could even just have two traysā¦one with the holes and one with the sticks.
I guess my last question would be how does it know how deep it is cutting? The GF specs says it will cut āVaries by material; can cut most 1/4ā³ (6mm) plywood and acrylic on one side;ā This stuff was pretty squishy and definitely not as dense as something like an acrylicā¦
THANKS ALL! Looking forward to getting mine soon!
Rob
3 Likes
So I have a silly question. Does it have to be a ball? If not, you could get a delrin sheet and cut out wheels. Or, you could you the greyscale function of the Glowforge and cut out donuts. i.e. 1/2" stock of delrin, cut half the donut, flip it, cut the other half of the donut. It might be cheaper to buy a sheet of delrin then the balls, but I didnāt look up the costs, so I donāt know.
1 Like
Not to discourage you from innovative use of your Glowforge, but you would seriously be better off with a good jig, and a sharp drill.
There are few technologies that can remove material from a hole as fast as a standard twist drill.
Spend a little time looking up proper speeds/feeds for Delrin, and thinking about how to hold those parts, and it will pay off big time when you can knock them out in seconds.
Take a look at a standard quick release drill press vise for instance:
https://www.zoro.com/wilton-drill-press-vise-1-516-d-4-1116in-open-13401/i/G8491524/?gdffi=047ada998cf641fa93e55ae8579df863&gdfms=33265877DAB940D692FCE299F9360998&gclid=CP-xlpmyjMsCFZeEaQodM_gE_g&gclsrc=aw.ds
Make some custom plastic or wood jaw inserts (on the Glowforge!) that hold the ball in exactly the right spot. You can probably drill a 1/4" hole in 1/2" of Delrin in 3 pulls of the drill press (donāt leave the drill bit in there too long, it will melt the plastic and grab). Then release the vise and toss in another ball.
Much better then burning tube time and ending up with off sized holes I think.
2 Likes
I wonāt tell you what this really looks likeā¦ 
But it does look funā¦
3 Likes
Ya might also want to look into this:
It could do the trick for ya.
1 Like
Thatās pretty cool!
By the way, a mini lathe will also work really well, if you happen to have one / can borrow one.
Yes, a lathe is a option, that is how I would do it, but I was not sure if OP had a lathe.
1 Like
OP, how many ya need done? Iāll do em for 10 cents each, plus shipping 
2 Likes
This one, too, which was inside the original one I postedā¦mentions using half round bits & how they work beautifully:
A variation on danās suggestion of using a peg to register would be a pin/bolt instead. Less total cutting. The initial pass is a 15/64" circle halfway through and a blind hole in the top for an m3 bolt (or something else smaller). remove from first jig, flip onto second jig, rezap.
By the way, my earlier point about the tilted hole sides was less about the beam angle - which is a factor, but on the small side - and more about the swarf. The ejecta from the cutting area (vaporized plastic and such) is hot, and will widen the hole on the way out.
5 Likes
Didnāt know that. Dislike not knowing stuff. Now I feel better.
3 Likes
@Dan, Is swarf a predictable function for a given material? In other words, if you say, hey I need a m3-clearance or m3-tap sized hole in this piece of acrylic, the CAM can say āoh, on a m3 hole x 1/4ā acrylic piece the swarf will widen my 0.5mm, so need to compensate"?
Hey Joeā¦Doughnuts would actually work wellā¦I donāt have my GF yet and I havenāt spent a whole lot of time looking at the different ways to get it to shape stuffā¦but if it works like you are describing that could be EZ! THANKS!
Is there a userās manual preview somewhere to look into the different functions?
Rob
No user manual preview that I know of, just information on this forum and around the interwebs. They have been talking about greyscale engraving for awhile, Iām not sure if it is working yet. Some at Glowforge will have to respond to that.