Introduction: DIY Anti Backlash Nuts - Super Cheap and Simple
This nut can be used for any kind of linear motion. Weather it is on a 3D-Printer, a CNC or a camera slider. It only takes an hour to make and works amazingly well! Delrin is the perfect material to slide over metal.
There is very little wear and it fits the shape of your leadscrew perfectly. Therfore there is virtually no backlash. I´ve been using this nut on my large format CNC for 2 years now without any problems. The best part is that they are super cheap. This saved me 200$ over store bought lead nuts.
Things you need:
Step 1: Turn Your Lead Screw Into a Tap.
Use a hacksaw to cut some groves into your lead screw. This end can still be used in a coupling. The more groves you have, the more chips it can hold. (You can also do that with normal screws once you broke off all your taps. )
Step 2: Prepare Your Stock.
I am using Delrin which is also called POM or Acetal. You can get 1 foot long bars for 15$ on ebay. Just cut of a slice with any kind of saw and drill a hole in the middle that has roughly the size of the pitch diameter of your leadscrew. The dimensions are not critical.
Step 3: Heat Up Your Tap and Delrin Stock.
A blowtorch or hot air gun work. Heat it up so the lead screw has efficient thermal energy to melt the delrin stock around it. Make sure you melt the delrin around the plain part of the leas screw. Not the notches at the end. A hotter lead screw will contract more and cause a looser fit. If you heat up the delrin more, it will cause a tighter fit. However, attaching the lead screw with hose clamps allows you to deform them slightly. This causes contact in both directions which means there is virtually zero backlash. So the temperature of both delrin and tap are not critical. This is an easy project after all.
Step 4: Melt the Delrin Stock Around the Lead Screw.
Wear gloves and push the delrin stock around the lead screw. This will make the stock adapt exactly the same shape as your lead screw and cause a great fit. Most of the time there is a gap between the two halves, use some delrin chips and the torch again to fill the gap. Don´t breath this!
Step 5: Finish the Threads.
Move the nut up and down over the tap end of your leadscrew. (Not the one you melted it on.) A drop of oil helps. It can be difficult to make the nut move for the very first time. You can use a wrench to get it loose.
Use a brush to clean the chips out of the groves in the tap.
Step 6: Make It Pretty!
Clamp the lead screw in a lathe. Clean up all surfaces and add a channel in the middle of the cylinder to receive the hose clamp.
Step 7: Broaching - Create a Flat Side.
You need a flat side to stop the nut from spinning. Since this is only plastic you can simply broach it on the lathe. Turn of the power and lock the spindle. Then make very thin cuts with a flat and wide cutting tool. Works like a charm.
Step 8: Admire Your Work.
Appreciating your achivements is an important step!
Step 9: Mount the Nut on Your Linear Axis.
I found that the easiest and cheapes way to mount this type of nut is a hose clamp. The hose clamp has a enough force to derform the nut slightly. This will change the clearance. You want it just tight enough so there is no movement back and forth. (No backlash) The nut will wear, but very very slowly. Don´t worry. You can always tighten the hose clamp later.
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