C3 Minilathe Electrical Fault - Fixed

G'day all, just back after my gap year.

Today I set up a job in my C3 Minilathe and when I hit the power switch, no lights.

Checked the mains power socket, all was well so uplugged everything and decided to check the fuse,

When I unscrewed the fuse holder, it slipped out easily, but no fuse in sight.

So to cut a long story short, after removing the lead-screw and opening the electronics box I discovered the fuse sitting in the bottom of the box.

Next I spotted a black wire hanging loose with a silver contact soldered to it and closer examination revealed that the rear of the fuseholder had broken away from the body.

When I removed the broken fuseholder, many other pieces of the plastic body crumbled away.

The C3 is 15 years old and I have never had any electrical failures before.

The fuse is not blown, so I can only conclude that the plastic used for the fuseholder has deteriorated over the years. The Minilathe operated fine when I last used it in November.

At the end of the day I am relieved that it was not a more serious fault with the control board so I decided to post it here in case anybody else has a similar problem.

* Danny *

Edited By Danny M2Z on 16/01/2022 11:12:26

Edited By Danny M2Z on 16/01/2022 11:13:45

Edited By Danny M2Z on 16/01/2022 11:15:09

Was the minilathe new to you?

I have seen the same thing happen (not on a lathe but in the same type of holder) when a 20mm fuse has been replaced by a 1" UK plug fuse temporarily while waiting for the correct one to arrive.

The owner of the equipment confessed he had done this even though it kept going fir several months before finally failing.

There are a few possible causes of type of failure.
1\ It was over tightened and cracks propagated over time
2\ Plastic shrank due to loss of plasiciser or moisture.
3\ Contmination (oil coolant etc) affected the plastic.
It could even be a combination of these.
I have frequently found this style of holder where the nut could not be removed without the holder breaking. So my money is on 2\

Robert G8RPI.

Edited By Robert Atkinson 2 on 16/01/2022 12:51:35

Hi Danny,

The same happened to my Minimill a few years after I bought it. The bottom of the fuse holder had broken and I remember the loose wire. I had another fuse holder - same external dimensions - so I just replaced the broken one with the new one. Everything has worked without problems since, that is over a decade.

Thor

BTW Thor, thanks for the flag - you inspired me.

Minilathe was purchased new in 2006, it even came with a spare M205 3.15A 250V fuse.

Actually; it was instructional to look inside the control panel housing as the lead screw traverses though it and I wanted to see whether my home made swarf guard had worked over the years.

The swarf guard was lid of a 35mm film container which enclosed a disk of felt (from an old hat) with a hole a bit smaller than the lead screw diameter and which was secured to the outside of the control box using neutral cure silicon adhesive.

It was pleasing to observe that only one or two tiny brassy looking flecks could be seen.

Also made a mental note that the lead screw bearing blocks deserve a bit of a clean and lube.

Actually my biggest problem is locating a decent quality replacement M205 fuseholder. Diameter is 13mm, it also has anti-twist flats across the threads. I found a few candidates, cost about $4, shipping $10 -$15 ; -)

Such is life.

* danny *

Beware Chinese plastics.

Regards Ian.

There is also the tendency to place a lathe on a bench with window behind, over time the UV can make plastics brittle.

Just an update.

I located a decent quality fuseholder that fits perfectly so ordered qty 2 as I decided to replace the one in my X2 mill in case it suffers the same fate.

If the active wire had fallen across the control board or the leadscrew it might have been quite serious.

The replacements that I ordered arrived overnight from Sydney, NSW which was pretty impressive in these current times (I live in Victoria).

If anybody is looking for a replacement fuseholder The RS Components part # is 188-4630

* danny *

I've had this happen on European made kit as well.

It's caused by constant warmth for a hot fuse.

Neil

Another update.

I decided to remove the control box from my C3 minilathe to better undertake and inspect the repair work (soldering).

As a qualified electronics maintenance engineer it might seem a bit overboard to some, but I was trained that way.

After tagging the disconnected wiring another potentionally dangerous fault was discovered when I noticed that the green 'Power On' indicator had no source of illumination.

I discovered the remains 'hanging free' inside the control box. also of note was that the attached wiring was hard and noticeably heat affected

The plastic housing had also deteriorated just like the fuse-holder, so it had also broken and detached from the minilathe housing and as this is a neon indicator it also carries 240V.

As a safety issue I advise that anybody whom owns an ancient minilathe to inspect the relevant components and replace them if required.or get a qualified person to inspect them.

* danny *

I ran into the same problem when I relocated my fuse holder from the side to the front of the control box....It crumbled. I don't even like the location of the control box as I have to remove it to get up close to the spindle when I use my 3MT collets.

It appears that the original material is not stable over the years as your report confirms.

The replacement parts that I installed are made from a phenolic material and the data sheet indicates that they are made to a decent standard.

One thing that I had to do was to make a new 'flat' opposite to the original one. After wasting time with a file it turned out that a small drum sander in a Dremel rotary tool soon did the job. Alternately, one could re-shape the hole in the plastic control box housing as it is very soft and cuts easily with a sharp hobby blade.

Mini-lathe is now running smoothly, all lights,switches, tacho and controls operate as they should.

I have not re-fitted the lead screw yet as while it is out I plan to take the opportunity to drill the lead-screw pillow blocks and install some 6mm oiler fittings that I purchased a few years ago to pad out another order. 6mm oiler to suit mini lathe and mill

Just a question for anybody who has used these oilers, does one pack them with a wick/felt or just use them as supplied?

* danny *

As part of the work in making and fitting a Graduated Leadscrew Handwheel, I took the opportunity to derll the bearing blocks, deburr and fit 6 mm ball oilers.

At the same time, I removed the Apron, and drilled it to take another 6 mm ball oiler, As well, I .marked out a piece of acrylic which having been cut and filed to shape, was sealed to the Apron with Hylomar,

This has two functions. It prevents swarf finding its way into the gears, and acts as an oil bath for the gears..

Howard