Star Screws - smooth

I was looking through the CAD files for the DOGO robot and noticed that they are using smooth Start Screws as idle screws — that’s so nice!

Where do you find smooth cap screws?


This is correct, AMOGO and DOGO used smooth screws where threads aren’t seen because they are less resource intensive.

But, if you are looking for a screw with an unthreaded portion, you can find them on McMaster. Here’s a link to 8-32 partial thread screws.

Robosource also sells shoulder screws, link here, where the unthreaded portion perfectly fits inside of a square hole of a c-channel. This makes it easier to make sure your mechanisms are square.


Thank you! Are they also using hollow standoffs? Are these custom built?

That’s not the case — their CAD file shows both regular star screws as well as smooth star screws…

what are hollow standoffs??? whatever you mean, no, they are not custom.

I’m curious why you think vrc is wrong… he said the same thing that unionjackjz, the creator of the cad did. A “smooth” totally threadless screw has no use lol, it doesn’t exist in real life.


Commercially, standoffs that are 1" and under are “fully threaded” and would be “hollow”, while standoffs over 1" are drilled/tapped only on the ends. Cf: McMaster-Carr

These would be rivets! :slight_smile:

In general, CAD models rarely use detailed threads, as they generally don’t serve any purpose but tying up computing time to generate the graphics. Most CAD software give the option of using “cosmetic threads” on a model where it is desirable to show where threads are located, but not to actually model them. The CAD system uses a graphic image to show where the threads are.


to add on to what @djavaisadog said if the standoff was threadless it would no longer be a standoff. You could consider it a hexagonal spacer ig- but, regardless, a spacer is not what the model is intended to represent.


They can be used as pins. I had a team a few years ago that had a part that unfolded. They were using a screw to hold it in place and it would scrape on the way out. A minute in a lathe with a file they had a smooth bore screw. Threads were left intact at the top to fasten it onto the flange. The lower part of the screw was smooth.

(thread three nuts all the way to the head, mount into the chuck. File off the unwanted threads. Then back off the nuts to clean the wanted threads out. I had recommended just using a shaft and some collars, but this was a “much more cooler Mr Foster” design. )


I guess they are just normal standoffs


Hi Jess, I am not sure if your re involved with the team that published the CAD files — but much appreciated if you are. I have a new 6th grade team who never built robots before, so I am hoping to have them build these two robots as part of their learning curve - and from there, figure out how to make a robot of their own (they have built the original VRC claw bot, and the hero bot).

Plus, I have learned a few things myself looking through the CAD!

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These robots were used at a summer camp where we had students with no experience build them and compete with them, we’re glad to see others using them for the same purpose :slight_smile:

All screws on these robots were the RoboSource colored screws (some screws were shoulder screws). All hardware (besides thin lock nuts from RoboSource) are normal VEX hardware. Both 0.375 and 0.5 OD spacers are used.


I can’t say how much these are the greatest thing since sliced Wonderbread and Kraft individual wrapped singles. Teams love them, I can snatch the right length screw out of the box, it’s awesome!

Well except for the unicorn team that wants all the screws to be purple ( 1.5") Oh my library teams …


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