Mini Lathe Fuse

Hi

I thought it might be a good idea to keep a spare fuse for my son's 400W Warco mini lathe in stock, but don't know what type to get. The original fuse is 1 1/4" x 1/4" glass, 5A, 250V but I cannot tell if it is quick blow, standard or slow blow.

My inclination is to go for slow blow (time delay) to allow for starting current, but given the cost of replacement circuit boards I wondered if anybody knew better?

Thanks

Brian

Believe they're slow blow, but I sold my mini-lathe two years ago. I did buy a packet of the fuses over from Maplins for about £2

Slow blow fuses have a 'T' marked on them and look like they have a spring inside.

Neil

Thanks, apart from the certification stamps, voltage and current, the only marking is "ADL" which I assume to be the manufacturer. There is no T (or F) but the construction, with a spiral wire around a 1.5mm ceramic core running the length of the fuse looks like it is designed to dissipate heat, which suggested to me it might be a slow fuse.

Thanks

Brian

Having already paid for a replacement speed control PCB once, my mini lathe is now fitted with a 1amp quick blow fuse. This may blow occasionally, but replacing it is cheaper than a new PCB.

Regarding the fuse on your machine, a spring in the fuse would indicate it is a Slow Blow.

Edited By Anthony Knights on 01/07/2016 18:12:39

I used to have a Chester Conquest it used these fuses. I thought most of these mini lathes were the same but theres obviously a big difference in the electronics. these were 3.15A  quick acting and only 5x20 size.

Edited By mark smith 20 on 01/07/2016 18:33:12

I think I may have solved part of my problem, as according to RS, ADL is equivalent to MDL, (which has the same spiral around a ceramic core) and according to this **LINK** a 5A MDL fuse will sustain 200% current for up to 120 seconds. No sign of the usual solder lumps or springs seen on other time delay fuses though.

I'm not sure that helps me though as I'm not happy at the idea of putting 10A through a 400W motor (and more importantly its control board) for up to two minutes. Perhaps quick blow is the way to go, as a few blown fuses are many times cheaper than a circuit board?

Brian

Fuses in this sort of application are primarily intended to protect the supply wiring, not the load. Even with fast blow fuses the circuit is likely to be damaged orders of magitude faster than the fuse blows in the event of a fault. A fuse should carry it's rated current indefinitely, and will carry a 200% overload for many seconds. If you want it to blow quickly you need high currents, up to 10 times rated current or more.

Fuses work on I²T, effectively heating through a resistance. As can be seen higher currents have a disproportional effect on blow time.

If boards are getting damaged I doubt it is anything to do with the speed of the fuse, but more likely inadequate design.

Andrew

With the early mini-lathes the fuses are protecting the motor from sustained overheating, rather than protecting the board.

Neil