It’s a fairly tiny effect. The picture is very exaggerated. The thicker the material the more noticeable it will be. Might notice the effect on thicker homogeneous material like acrylic. The charred edges on wood are likely to mask most of it until you get above 1/4".
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We have issues with cuts being angled from industrial shops. We have micron level tolerances, though. So a <1deg angle will still have a relatively big affect. But that angle is determined by the focal length of the lens. The Glowforge has a 0.5" focal length (I believe). Industrial machines are bigger, so they can have a longer focal length, which decreases the angle.
From looking at Epilog’s page, there standard lens is 2". http://support.epiloglaser.com/article/8205/42831/focus-lens-101
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How about doing it one size smaller and then use that for a pilot hole for standard drill?
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Does GF really have a 0.5" focal length? That seems impractically short. I thought it had a 0.5" focal range, which is a different thing.
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I’m not sure. From the Tech Specs:
Work Area: Focus range: 0.5″ (13mm)
Autofocus: Completely Internal — Lens moves internally up and down inside the head by 0.5” (13mm)
I took this to mean that the focal length was 0.5", but its position in space can be moved up and down. But, from reading it again right now, both points could be saying the same thing. So I’m going to stick with my “Not Sure”.
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50 mm focal length. ~2"
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Ah, there we go. I guess the Focus Range is just the movement of the lens up and down.
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If you have a drill press, you can try the following method:
- Put the bit into the chuck upside down (so the flutes are in the chuck - not too tight!)
- Put a heavy vise under the press and center it under the bit
- Lower the bit down into the vise and clamp it tightly in the vise
- Clamp down the vise if necessary
- Loosen the drill press chuck and raise it up. The bit will stay in the vise and it will be centered on the chuck
- Put the delrin ball in the chuck (hopefully you have a 1/2" chuck!) It should be centered in the chuck. Tighten as much as needed.
- Start the drill press and slowly press the ball down onto the fixed bit. If everything is tight enough, you’ll drill a nice centered hole.
Conceptually, you’re using the drill press backwards, with the bit fixed and the part spinning. But the result is the same.
Here’s an illustrated guide to doing something similar (drilling a hole in a rod instead of a sphere) but the method is the same: http://k0lee.com/2010/12/using-a-drill-press-like-a-lathe-to-make-a-center-hole/
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@pdobrien I love that!
But if you don’t have a 1/2" chuck…
Use the glowforge to cut a jig to hold the ball under the drill press.
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Why is it hard using a drill press? You mean to hold the ball perfectly centered? That’s easy; just drill a 1/4 hole in some hard wood (or metal / aluminum) to hold the ball steady, and it will be perfectly centered. You probably have to hold the ball to keep it from spinning, but some gorilla tape should work just fine if you don’t want to risk injury to your hand.
Piece of cake, really…
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Good idea! I have put a drill chuck in the tail stock of my lathe to center a hole.
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Yup, just drill a undersized hole in a holding chuck, chamber the edges a little and your all set and centered.
Agree 100%
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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 can’t 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.
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I dunno…is it really worth all that set up time and work? If it’s a multiple item thing, then yeah, best to set up a jig / repeatable holder kind of thing. But if it’s 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 butter…
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Well done. This sounds like something may dad would have come up with. He’s always finding interesting ways to use tools like this.
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So…first - THANKS. Lots of great suggestions here…
Let me add a few details…
I’m sliding the bead onto some line (aka rope) that is a “Soft Shackle” to hold the Clew of a Sail down to the boom (It’s for a Laser Sailboat if anyone knows…) 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 vice…but not optimal. My drill press isn’t 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, I’m 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 “repeatable” 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 one…I suppose if I used @dan 's idea I could even just have two trays…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 “Varies by material; can cut most 1/4″ (6mm) plywood and acrylic on one side;” This stuff was pretty squishy and definitely not as dense as something like an acrylic…
THANKS ALL! Looking forward to getting mine soon!
Rob
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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 didn’t look up the costs, so I don’t know.
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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 (don’t 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.
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I won’t tell you what this really looks like… 
But it does look fun…
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Ya might also want to look into this:
It could do the trick for ya.
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