Hints and tips

[Jim GreetheadParticipant @jimgreethead]

Neil.

To go the other way, divide the figure in mm by 25.4 and multiply by 64 to get the imperial dimension in 64ths which is probably about as small a fraction as you would need.

Then just simplify: 32/64 = 1/2 etc. You could go to 128ths the same way.

 

Might need to round off a bit when you get 32.2/64 it is probably 1/2 or close enough.

 

Jim

 

[Jim GreetheadParticipant @jimgreethead]

Neil,

Sorry about that, I still have most of my marbles but sometimes it takes a while for them to roll into the correct holes.

 

Conversion to and from metric is most easily done with a conversion chart. I have one such chart laminated and conveniently displayed in my workshop. Apart from other information, the relevant column headings are: millimetres, fractional inches and decimal inches.

 

It is low tech but faster and much more convenient than calculation.

 

Jim

 

[jomacParticipant @jomac]

Hi, an old method for sharpening files and rasps is to, first do what Ian SC does with a piece of brass or copper tube, then wash them with detergent, rinse off properly. Then put them outside in the cold nights, sometimes also wet them with weak acid ie lemon juice or vinegar you might need to do this a couple of times. But the ensuing rust has left a sharper edge, finaly brush and oil them.

Good luck John Holloway

[Ian WelfordParticipant @ianwelford58739]

A Really good source of large donut shaped magnets is the Magnetron found in any kitchen microwave oven.

Just ask SWMBO if you’ve got a burnt out microwave anywhere ( usually is one in our house but maybe that’s just my better half and children making bits for dady !).

 

Cut the plug off, leave it a bit ( got big capacitors in ’em these days and they hurt !), then open up and look for a strange fin covered bit attached to one side of the oven bit. That’s the magnetron. pull off the find and CAREFULLY ease the magnets off the central spindle. Carefullt dispose of the unnecessary bits and you shoudl have a nice matched pair of 3″ dia magnets.

 

Now if you add a length of broom handle though the centre of one of these, attaching with epoxy and put it in a plastic container with thye handle sticking through the top. You then have a magetic pick up for swarf etc which keeps your hand out of the way.

 

To get the swarf off pull the handle up to the top of the container and the swarf drops away.

 

This gadget is also really good at retrieving the “lost nut, screw or thingumy ” that’s gone under the bench or even dropped in the grass in the garden ‘cos you can roll it around and if it gets wet- so what!

 

Chris and Bogs thanks for the interesting links and comments !

 

 

[Ian WelfordParticipant @ianwelford58739]

Oh one more thought.

 

Always worth asking shops what they do with their plastic window banners when they’ve finished with them.

 

The plastic makes really good spacers to place between cutters in storage. It stops epoxy sticking to the bench or indeed anything else.

 

You may get a few funnly looks when you ask but then again….

 

You may just get funny looks anyway!

 

 

 

 

[Sub MandrelParticipant @submandrel]

Hi Jomac,

 

In an old ME there was the advice of pickling files in old battery acid. Obvious precautions i.e. don’t do it, or if you do don’t blame me if your hand falls off and you pollute most of Rutland …

 

Neil

[blowlampParticipant @blowlamp]

I recently fitted my Clarke CL300 lathe with a DRO kit from Arceurotrade.

For those unfamiliar with them, these readouts fit directly to the feedsrews of the top slide and cross slide so don’t measure actual movement of the axis, but as the provided screws are accurate, the system works well.

They only have 3 buttons, which are, On/Off, Zero and inch/mm and very little in the way of instructions on how to use them, but they do read to 0.001mm!

This could be another one of my “well that’s obvious” tips, but I messed about for a day or two and you never know who else is out there that can’t see the wood for the trees.

Anyway, to my tip:

 

Take a light cut along your workpiece and carefully measure the diameter. Move the carriage clear of the job and zero the cross slide DRO. Use the DRO to then wind the slide forward a distance equivalent to exactly half the distance you’ve just measured (the radius).

Press Zero again and you’re done!

 

All readings from now on will be of the radius of the part  (ignore the minus sign), which I find much less confusing than zeroing at say 10mm diameter and having the readout display 1.375mm once I’ve reached 7.25mm diameter.

 

I find I’m using my vernier and micrometer much less after fitting this kit as it really is accurate – far better than I expected.

 

Martin.

[KWILParticipant @kwil]

It all depends upon the backlash of the leadscrew nut and  bearings.

[blowlampParticipant @blowlamp]

It works identically to conventional feedscrew dials. As long as you allow for the backlash by winding back a little too far before applying the cut it works perfectly.

 

Martin.

[ChrisHParticipant @chrish]

This is a copy of a tip I got on another thread regarding a welder that kept tripping the MCB.

 

Connect the welder to the socket via a long meaty extension cable, it limits the inrush current I am informed and stops the MCB from tripping.

 

Worked for me!

 

Chris 

[Chris TriceParticipant @christrice43267]

I’ve got a Makita cut off saw which keeps tripping when plugged into the domestic ring main. Haven’t tried running it through an extension cable but found that simply plugging it into the higher current cooker socket stopped the problem.

[Steve GarnettParticipant @stevegarnett62550]

Posted by ChrisH on 11/01/2011 17:08:13:

This is a copy of a tip I got on another thread regarding a welder that kept tripping the MCB.

 

Connect the welder to the socket via a long meaty extension cable, it limits the inrush current I am informed and stops the MCB from tripping.

 

 

Okay, here’s a tip about your tip. With any extension cable that you are drawing significant current through, make sure that you have uncoiled it before you run it like this for very long. If you don’t, it will get hot – the resistive cable acts just like a coiled electric fire, and in extreme cases you can easily finish the job off by having it burst into flames!

 

I must admit that I was a bit dubious about this until I tried it just to see what would happen – and the coiled cable got a lot hotter in the centre than I’d expected it to. Just goes to show…

 

 

[Chris TriceParticipant @christrice43267]

Most reel extension cables have thermal cut out buttons now to counteract the problem. I found the worst culprit was the workshop electric heater which would have the cable cut out tripping in half an hour or so if you didn’t unreel it. And yes the cable was uncomfortably hot.

[ChrisHParticipant @chrish]

Steve – have heard about uncoiling the extension cable before use to avoid it overheating, and always do.  Words like “inductive current” return to the little grey cells when I think of this, the wire when left in a coil with a good current flowing through it induces a much higher current in the coil which causes the overheating, I seem to remember.  I hope that is the correct explanation!

[Anonymous]

ChrisH: Err, I don’t think so; the cable can’t ‘magic’ current out of nothing. The current in the wire is determined by the source and the load. Anyway, the cable coiled on the holder is not a simple inductor. Think about it; assuming that we’re talking about mains cable, the current flows out along one wire, and back along an adjacent wire. What is the effect of that? It minimises the inductance, as the magnetic fields around each wire tend to cancel.

 

In practice the cable coiled up will probably have a slightly higher inductance than a straight piece of cable, as the cancellation is not perfect and there will be stray magnetic coupling between turns.

 

The current rating of mains cable is generally set by a specified temperature rise in free air. If the cable has restricted cooling, buried in a wall or wound up in a tight coil, it will get hotter for a given current. The advice to unwind an extension cable before use at higher currents is sound, but it based on simple I^2R heating and temperature rise. Nothing to do with ‘magic’ inductance.

 

Regards,

 

Andrew

[ChrisHParticipant @chrish]

Andrew,

 

If what you say is correct then I bow to your superior knowledge, although I never claimed to have sarcastically described inductance as ‘magic’.

 

I am not an electrical person, I was merely repeating what an electrical person described to me many years ago.  Inductive current or lack of heat dispersion, the former would lead to the latter anyway, so the end result could and probably would be the same in most cases, overheating of the cable on high current loads, which is all you really need to know.

 

Chris 

 

Edited By ChrisH on 12/01/2011 14:50:46

[John HaineParticipant @johnhaine32865]

If the field cancellation wasn’t perfect (or if for example it wasn’t twin cable but a single strand), any series inductance would decrease rather than increase the current as it (sort of) adds to the series resistance.  The only way there could possibly be an increase in current is if there is also a significant distributed capacitance that resonated with the inductance at the frequency of operation (even then it isn’t apparent how it would actually increase the crrent in this configuration).  At mains frequency and with the dimensions of ordinary cable this is very unlikely.

[Steve GarnettParticipant @stevegarnett62550]

Posted by John Haine on 12/01/2011 16:19:15:

 

At mains frequency and with the dimensions of ordinary cable this is very unlikely.

 

Absolutely.  As I mentioned in the opening salvo, the losses are definitely resistive, as Andy also has noted. The heat build-up is based on a combination of better heat insulation and very poor cooling. I’m not sure exactly what level of derating you’d have to apply to the cable, but I suspect that it’s more than most people might think.

 

Doesn’t matter what the mechanism is really, though, because the message is still the same – don’t do it!

[peter walton 1Participant @peterwalton1]

You should uncoil extension leads if used at the maximum rating of the cable as its rating is for a flexible cable in free air rating.  Coil it up and should be derated or just get a higher rating unit(more money more copper)

 

peter

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, a good number of commercially made extension leads that are coiled up on a drum of some type, will give up the maximum ratings allowed if it is used coiled up. It is normally very much lower than when it is uncoiled.

   I’ve seen a 110V 16A one burn with just a small vacuum cleaner and a lead light attached, just a moment or two after I advised the chap using it to uncoil it fully. He first  looked at me as if I was from another planet, and then jumped up to pull the plug before he had a fire in a “Hot Work Permit Zone”, outbursting with surprise, words I cannot print here.

 

Regards Nick.

[John HaineParticipant @johnhaine32865]

So, I just measured the resistance of my 10 metre extension lead.  Each core has about 0.5 ohms as far as I can tell (quite hard to measure low resistances as the probe contact resistance is significant).  So let’s assume each one was 1 ohm, total 2.  At 10 amps (this lead is rated 13A) the loss is “IsquaredR” which is 200 watts, two old fashioned light bulbs, so it will get quite hot especially since cooling inside the drum is minimal.  But typically you might be running a 100 watt inspection lamp (0.4 amps) and an electric drill intermittently, so if the average current was 1 amp (which it won’t be) the power lost will be 2 watts which would hardly warm it.  The lamp on its own will result in 320 milliwatts loss which you can forget about.

 

Message – be sensible, if you’re just doing some work in the loft with a light and a drill don’t worry, you’re more likely to break your neck tripping over the excess cable than setting the house on fire.  But if you’re running a lead to the shed an running your lathe and a convection heater then rollout all the cable.

[Author]

Posts