3D Printed Bolt Knob - A testament to half an ounce.

apohlo

Lil-Rokslider
Joined
Jan 26, 2021
Messages
138
Location
Wisconsin
As the snow flies here in WI I start to reflect on my hunts from the fall and how to improve/change my gear for next season.

I had a rigorous, yet successful western elk hunt this fall and it got me thinking about trimming down some weight on my trusty north American game rifle, the Springfield Waypoint chambered in 6.5 PRC. I carried the thing a lot of miles and it treats me very well.

So, as one does, I went down the road of unnecessary reinventing the wheel, to save the weight of a toothbrush .... but to gain a custom, warm to the touch, rifle accessory. I 3D printed a R700 pattern bolt knob.

Before you continue to read this - I want to agree with everyone on the potential concerns and risks involved with replacing aluminum with thermoplastic polyester. Will it survive harsh hunting conditions, wear and tear, freezing temperatures... I'm going to find out. But my choice of material on hand (PETG) has been tough in my testing.

I have some plans to reduce another few ounces which I won't get into on this thread, but I felt the need the showcase my cheap way to save almost .5oz because I haven't seen it done before. After all, it's fun to tinker.
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Pictures showcasing the print and comparison to the solid AL knob featured on the Waypoint 2020.
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A whopping 13 grams! (.46oz)

But I changed the profile to more of an intermediate bell. Gives me a bit more scope clearance with this 90 degree action.
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I tapped the printed hole to "I" tap drill size for 5/16-24 TPI which is .2720". Then ran a tap through and the threads ran clean and tight. I think it looks nice...
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If it cracks at all (doubt it) you can try printing it solid in TPU (moderately stuff when solid) which is tough and won't crack on impact, etc.
Hasn't shown any sign of cracking - even in sub freezing temps here. But good to know! I printed a similar part with the same material at solid (100% infill like this knob) and tried to break it... Took crushing it in a vice to win that battle. So far so good!
 
Hasn't shown any sign of cracking - even in sub freezing temps here. But good to know! I printed a similar part with the same material at solid (100% infill like this knob) and tried to break it... Took crushing it in a vice to win that battle. So far so good!
Yeah it'll be pretty solid in PETG which is why I said I'd doubt it'd have issues since there isn't much leverage in your design to crack it.
 
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