Tapping holes for the drag chains

Assembly questions and answers for the Shapeoko 3 CNC Mill
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ururk
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Joined: Sat Jul 16, 2016 4:25 pm

Tapping holes for the drag chains

Post by ururk » Tue Jul 18, 2017 12:45 am

I ran a few jobs this weekend and my VHB tape finally failed. Well... finally is not accurate. The tape failed earlier on but it always stuck back on. It no longer sticks, which tells me it's time to do something a bit more permanent.

I'd like to tap the X and Y gantries for the drag chain. Any suggestions on what size to use? I have taps for M4 on up, and the equivalent on up in SAE. I can purchase an M3, but figure it shouldn't be any smaller than that.

Is the aluminum thick enough to take threads? I'm pretty sure I've heard of people tapping the rails, but I couldn't locate any threads talking about it.

Thanks!

John

ururk
Posts: 6
Joined: Sat Jul 16, 2016 4:25 pm

Re: Tapping holes for the drag chains

Post by ururk » Tue Jul 18, 2017 1:44 am

Not to answer my own post, but...

https://www.shapeoko.com/forum/viewtopi ... 245#p49535

It looks like RawIndDesign used two M4 Phillips flat heads. Will post pictures when I finish this, hopefully tomorrow night.

CrazyBillybob
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Re: Tapping holes for the drag chains

Post by CrazyBillybob » Tue Jul 18, 2017 12:47 pm

On my Shapeoko 2 I used #10 and #8 on my drag chain. With your's being as S3 your mileage may very.

CBB

madhatter
Posts: 164
Joined: Sat Mar 21, 2015 1:33 am
Location: WA, USA

Re: Tapping holes for the drag chains

Post by madhatter » Tue Jul 18, 2017 5:35 pm

You could get some 3D printed brackets to hold your drag chain like these that I designed: http://imgur.com/a/SZGXq

If you have limit switches, one of the brackets interferes with the mounting brackets of the limit switches, so these specific ones might not be the best bet. I'll eventually upgrade to limit switches, and then I'm sure I'll re-design them, but for now, they work fine on my machine without limit switches.

If you have access to a 3D printer, the files are here:

https://drive.google.com/folderview?id= ... XJTbC1mQUU

The drag chain I have is the 30331-01 from Inventables.com
SO3 #0054
DWP611 - SuperPID
Prusa i3 MkII
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ururk
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Joined: Sat Jul 16, 2016 4:25 pm

Re: Tapping holes for the drag chains

Post by ururk » Wed Jul 26, 2017 2:07 am

madhatter - I was tempted after seeing your post to just 3D print the brackets, but I had already ordered the taps/screws/fluid.

I ended up using M3x8mm screws, rather than the M4. I bought a few M4's from the store, but they were too big to sit flush inside of the drag chain.

Since the VHB tape was still stuck on the alu extrusion, I figured it was a good reference for hole placement and left it on:
IMG_7971.JPG
IMG_7971.JPG (899.08 KiB) Viewed 653 times
Once the holes were tapped, it was a matter of screwing the end on:
IMG_7973.JPG
IMG_7973.JPG (985.16 KiB) Viewed 653 times
and the Y-axis:
IMG_7974.JPG
IMG_7974.JPG (657.79 KiB) Viewed 653 times
Last edited by ururk on Wed Jul 26, 2017 6:07 pm, edited 1 time in total.

ururk
Posts: 6
Joined: Sat Jul 16, 2016 4:25 pm

Re: Tapping holes for the drag chains

Post by ururk » Wed Jul 26, 2017 2:19 am

A few observations:

The aluminum extrusion is thin, but it feels thick enough to hold the screws. I didn't measure the thickness, but I'm guessing it was at least 1mm

The first hole I drilled I used a 2.5mm drill bit - for the remainder of the holes I used a slightly smaller bit. From the internets, it seems a #40 would have been more appropriate

My drill bit hit the screw holding in the controller board. Probably not the best thing to happen, but it won't interfere as I used a short (8mm long) screw.


All in all, I'm happy with this setup - I'm not entirely certain why the S03 comes with VHB tape and not a more permanent/consistent solution such as screws (cost?). I realize if something got jammed between the drag chain and the carriage, it would just pop off with tape only. With the screws the chain might get destroyed.

JohnManly
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Joined: Fri Jul 14, 2017 4:08 pm

Re: Tapping holes for the drag chains

Post by JohnManly » Fri Aug 11, 2017 3:04 pm

I realize the OP already solved this. But as info, a good rule of thumb for minimum threaded hole depth is three threads. So for an M3x0.5 screw, you would ideally want at least 1.5mm of wall thickness. In reality, for a steel screw threaded into aluminum, you'd want more if the connection was highly stressed. But for attaching plastic e-chain, you shouldn't have to worry.

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