In updating a DTI base, I bought a snug and I made a snug. A beautiful find at a car boot. I actually bought two snugs for a couple of pounds, then they just sat there.
Snug: a universal adjustable joint you find with a magnetic base that allows the rods to be moved and angled.
I’ve had one of the cheap magnetic bases for holding dial gauges for some time. However, it kept stripping threads and needed significant force to lock the joints and unlock.
Hence after a while the plastic finger nuts broke, I replaced these with metric nuts. Then the threads stripped. It really was a mess.
When you compare these cheap snugs with the old units it is very obvious that the new units have no spring in them.
Then on one of my many trips to car boots I came across the snug seen in the image to the left. This was a very well machined old part that looked like it might have been an apprentice piece.
It has a lovely patina and operates very smoothly, but it has an imperial 3/8 inch hole through the main unit and the small hole was 1/4 inch.
One of the first jobs was to reduce the main upright on the magnetic base from 10mm to 3/8 inch. Machining the bar in the Warco lathe using a glanze tool holder and aluminium tips. The aluminium tips work really well with steel.
The main upright now machined to 3/8 inch, you can see the step out to 10mm at the bottom. I left the bottom section alone as it meant I could leave the thread that fits into the base. Also, the step allowed me to hold it accurately in the chuck and the other end with a centre.
The step does mean the snug won’t go right to the bottom, but as it is difficult to tighten it at that point is doesn’t matter.
Knurling the Thumb Nut
Knurling the tightening nut for the new snug.
Note: WD40 is not bad as a cutting fluid and as a lubricant for the knurling wheel.
The new snug was machined from mild steel and I hand reamed the hole 1/4 inch to get a really good fit on the main arm. The thumb nut was threaded M5 and fits onto a bolt machined again from mild steel. The snug was cut through using a cobalt slitting saw on the Sieg milling machine.
The new snug has quite a long lever between the 1/4 inch bar and the tightening nut, this means it really locks onto the 1/4 inch bar.
The dial gauge holder I made some years ago, but adapts well to this new setup of “old snug new snug”.
The adjustment on the new part is limited as it is rather simple, but I’m going to give it a go and see how well it works. The original snugs almost had too much adjustment and this made them difficult to tighten.
This is not a Starrett magnetic base, but I’ve taken an old snug and a new snug and I’ve been updating a DTI base to make it work for me. Also, I’ve recovered a poorly made part.