How To Make A Self Centering Bit – Vix Bit Homemade Machines & Jigs
A self centering bit (also known as a vix bit) can be a handy thing to have if you are installing a few door hinges or other types of hardware that have screw holes. I generally do these by hand with an ordinary drill bit, since I have a lot of experience doing it and can get the bit centered reasonably well. And invariably, when I do that in a video, someone will point out that you can get those special bits to drill holes more accurately. So in a way, the viewers that make that comment are my inspiration for this project. I also thought it would be an interesting challenge, given my lack of precision metal working tools.
The easy way to drill a hole that is centered in a piece of round stock is to turn the stock while holding the drill bit steady, and to get started I need a 1/8″ hole through a piece of 3/8″ round bar. I’m using scrap I have in my shop to make this, and it’s all mild steel. The vix bits I’ve used in the past were made from aluminum, so any grade of steel will be more durable.
I have the stock mounted in my chuck on my wood lathe and took the Jacobs chuck from my drill press and put that in the tail stock. That chuck has a #2 Morse taper that matches the one on the lathe. To start the hole, you normally use a centering bit, but I don’t have one of those (either) and used a step drill instead:
The step drill is very stiff and won’t flex, much like a centering drill.
After I had the hole drilled, I used a coarse file to turn down the front end of this part (the nose piece) to exactly 5/16″:
It took about 10 minutes of filing, measuring and fine tuning to get it to the exact size. Patience is required to keep from going too far.
I then turned the nose piece around and parted off the other end. The part steps up from 5/16″ to 3/8″ at the end. The 1/8″ hole is for the drill bit, but I also had to drill in 1/2″ with a 7/32″ bit so that the spring would fit inside the nose piece part way:
I then turned it around again and beveled the tip to match the angle on the head of a screw:
I later shortened the nose piece by about 1/4″. Always better to have it too long and trim some off, rather than too short and have to make a new part.
The next complicated part is the outer sleeve and that’s made from 1/2″ round bar. I started with the step drill and then drilled a 1/4″ hole all the way through:
I then switched to a 3/8″ bit and drilled in 1-1/2″, sing the masking tape to tell me when to stop:
Flipping it around, I drilled the other end out to 5/16″ and beveled the end to make it look more streamlined:
The parts put together to check the fit:
The next operation is to drill and tap for a #8 – 32 set screw that will hold the sleeve in place and also clamp down on the drill bit and keep that from moving:
I filed a flat spot on the sleeve before drilling the hole.
The set screw installed:
After shortening the nose piece, I started machining out the relief hole in the side. This allows the wood chips from drilling to escape:
As shown better in the video below, I started doing this the hard way, by drilling a series of holes and then using a round file. A better way would have been to grind most of the hole with my angle grinder, then clean it up with a Dremel tool.
All of the parts:
Only the bit, spring and set screw were bought, and I already had each of these. I bought a bag of assorted springs a few years ago and have used them for many projects since. One was the wooden switchblade I made, and I also used several springs for vibration isolation in the wooden computer case I made.
The assembled and working unit:
One problem with these bits is that they tend to clog up fairly quickly, so opening the relief hole some more might help with that. When I’ve used them in the past, I got very frustrated with that and that’s the primary reason why I don’t use them anymore. To get around that, you could use the bit to mark the hole by drilling in just 1/8″, then finish drilling with a normal bit.
I took a few minutes and made the steel a bit shinier for the glamour shots:
Here’s the video I mad going through the build and features a short demo at the end: