Cheap Magnetic Flexible Holder for a Test Indicator or Dial Gauge

I recently bought myself a mini metal lathe and have been adding some useful accessories to it. Instead of just going out to buy the accessories (some I have to buy) I decided to make what I could. I particularly like free or as close to free as possible. You can buy a magnetic flexible gauge holder on eBay for around $40 or so but some of the reviews I didn't like. Anyway, why have a lathe and not make some of the accessories yourself?

One of the 1st needs I have is to check the accuracy of the lathe parts themselves and to be able to check if a part in the lathe chuck is dead centre etc.

I found a similar project on the Internet and I made this holder in a similar way.

There were 4 things I had to source The flexible base, the steel rod(s), some 10mm x 10mm square bar (or similar piece of mild steel) and a good magnet. Oh, 5 things, and a coupling nut to join the camera mount to the round rod.

For the rod I also pinched the idea to use the steel rods found in old inkjet printers - they are nicely polished and accurately ground. And they are FREE.

For the flexible base I bought a $6 mini camera mount from eBay and I got a strong round magnet from the local hardware store.

I had a length of square steel bar and cut a piece from this. Any scrap metal that will be able to be drilled to take the rod and the bolt sizes will do

An independent 4-jaw chuck in the lathe is best to face off the 6 sides of this bar (yes there are 6 sides). A 3-jaw chuck will battle to hold the piece well.

In fact - I think a 4-jaw chuck (with independent jaws) is essential to add to your lathe accessories

It is not essential to get all the sides perfectly square for this project.

This is, in fact, a very good exercise for you to get used to the lathe and cutting faces on all 6 sides.

Now cut the bar in to two equal length (that's through the middle :-) )

We need two pieces to make the joint.

I am actually going to make up another joint like this to be able to extend the holder through a second round rod (the other half of my round rod) to give even more flexibility.

You can see from this image that each half of the square bar is drilled to accommodate the round rod size (6mm for my rod from the printer) and also for the 5mm (or whatever)size bolt at right angles.

The nut could also be a wing nut to make the clamping easier. I am busy sourcing a better plastic or knurled metal thumb screw for this.

As you can see each half is also split (with a hacksaw or grinder and metal cutting disc) to make a small spring action which will clamp the round bar in place.

If you are using a test indicator gauge, as I am, it comes with two sizes of connections - my 6mm hole fits their connector perfectly.

Note: The hole(s) being drilled for the bolt have a small detail not seen in these images. The starting hole for the bolt (the left half of the joint in this image) is threaded up to the slot. So, I drilled the hole up to the slot with a 4mm drill bit and the second half back to the slot with a 5mm drill bit. I then tapped the 4mm section with a thread for the 5mm bolt. The other right hand half of the joint is drilled right through with a 5mm drill bit. I did this so that it would make the tightening and untightening of the nut easier. ie. the bolt would not turn in the hole.

I bought this mini camera mount from eBay for $6. It has the standard 1/4" threaded hole in the bottom to fit on a tripod and a threaded 1/4" coupling for camera on top. I removed the locking collar.

I found a nice strong round magnet at the local hardware store. These magnets have a steel top and side cover and have a 5mm hole drilled through the middle of the top plate. Fortunately, the hole through the magnet itself is bigger and will allow you to enlarge the hole through the steel top plate for a 1/4" bolt.

NB These powerful magnets are ceramic and don't like being drilled - they will probably shatter! So the pre-made holes are important.

Find a small flat headed (round in my case) 1/4" bolt and fit the magnet under the camera mount. The bolt head must be below the surface of the magnet so that it can sit flat on surfaces.

I also bought a 1/4'" coupling nut from the hardware store. The top of the camera mount fits the 1/4" standard hole in most cameras. I threaded the end of the round rod for 1/4" too to fit into the other end of the coupling nut. A bit of locktite will help if the nut doesn't tighten up well.

As you can see the steel joint you have made can slide up and down the round rod and the gauge therefore angled in any position.

I cut the steel rod from the printer in half so that I can make another joint to extend the gauge's reach and to give it more flexibility.

You now have a useful magnetic gauge holder.

One thought which I'm still considering. The magnet picks up any chips, metal dust and shavings so cleaning it off is a bit annoying - so I'm going to find a plastic cap to glue over the bottom. I might have to turn one on the lathe. A smooth cap will make the removal of dust and chips much easier.