View Full Version : [Question(s)] Servo bolts

11-13-2008, 11:56 AM
Hi everyone,

I started my first robotics project, and i'm a little stuck trying to connect my servos (HS-422 for example) to... anything.

on the servo, the plastic circle that spins (does it have a more 'technical name'?) has holes all around it. my problem is that in order to connect anything to the rotating circle, i need bolts small enough to fit through those holes! i figured M2 bolts do not fit, so i probably need M1 in size. does anyone know where i can buy those, or any other bolts i can use to connect to the round, plastic, rotating disc of the servo??

11-13-2008, 12:15 PM
Check out mcmaster.com.


11-13-2008, 12:19 PM
The "technical" name is "servo horn"

Naw, you don't need screws that fit - you need a drill-press. #4 screws fit just fine after a little convincing on the drill press.

And I'm not alone on that - The CrustCrawler SG5 arm kit instructions call for the holes to be drilled-out too. I've never built a project that I didn't drill out the servo horns...

11-13-2008, 12:55 PM
I believe the standard hole on a servo horn is designed to accept a #2 sheet metal screw. However, as others are saying, a drill press (or a drill) and a tap (a tool that makes threads) will get it to accept larger machine screws.

11-13-2008, 01:18 PM
Why tap it? That nylon won't hold a thread for a metal machine screw under any kind of load. That's why they made nuts. Bonus points for Nylock-type locking nuts...

If you are going to tap it, make sure you use nylon bolts.

11-13-2008, 01:32 PM
Also depending on what you are connecting to the servo horn these discs are designed to be used with the Model clevis, which is a control horn used in model aircraft to link to the control surfaces. A metal two pronged clip with a pin that fits through the servo disc and is retained by the other prong. But this is only for a push/pull type scenario, not for direct load bearing on robots. Just another option. But in general I replace the nylon servo horn with metal/alloy discs much stronger.

11-13-2008, 02:31 PM
Thanks for the ideas guys! yea, i thought to make bigger holes by drilling, but i guess i didnt want to 'scar' my new servos... i suppose as long as it works its a good idea.

11-14-2008, 10:10 PM
You'll need to get used to 'scar'-ing brand new things if you're going to build robots!

01-28-2009, 05:03 PM
i have a ? that kind of goes in hear? I have a MG995 servo and wanted to know if (any) servo horn will fit? http://www.trossenrobotics.com/images/PImages/M-200-RS-HMSH-02.jpg (http://www.trossenrobotics.com/store/p/5509-Hitec-Spline-Metal-Servo-Horn-Tapped-.aspx)
Lynxmotion (http://www.trossenrobotics.com/m/lynxmotion.aspx) Hitec Spline Metal Servo Horn (http://www.trossenrobotics.com/store/p/5509-Hitec-Spline-Metal-Servo-Horn-Tapped-.aspx)

I was looking at this but wanted to know if its the size?

01-28-2009, 10:50 PM
The above Hitec splined (24 count) metal servo horn should not be used with a Tower MG995 servo, as that servo is appears to have a Futaba spline (25 count). See this RC servo info post (http://www.rcgroups.com/forums/showpost.php?p=8523025&postcount=9).