Member postings for Simon Williams 3

Hi Colin, your question doesn't have a simple and straightforward answer, but here goes.

The short answer is yes, the 10 amp switch will work OK, it'll stand the use for a time period which might be quite difficult to predict, but it's unlikely to go snap crackle pop immediately, so give it a try and see how you get on.

BUT>>>> (number 1)

Switch gear for controlling motors is rated to allow for the inrush current. When you start a motor, it accelerates from stand still very quickly, and while it is doing so it will take (if the supply will provide it) typically 6 - 9 times the "rated (full load) current". The rated current is the current while providing the full load torque relating to the power of the motor. Power equals torque times speed, so the rated current shown on the motor rating plate assumes that the motor has already accelerated up to the speed at which it runs at the corresponding load torque, But the switchgear has got to survive the shock of getting the motor onto its load curve.

This inrush current is brief, but severe. Most drum or cam switches are designed for switching a motor, so they have a rating for what is called AC3 duty - this is a number that allows for some de-rating of the switch. The start duty of using it upstream of a motor is only a brief torture, most of its life the switch will only have to carry no more than the rated motor current. But while it is carrying that start inrush current it has a hard life, and the "rated current" quoted for the switch has to allow for this. There is also something called AC1 duty - this is closer to the simple use of the switch to control a resistive (e.g. heating) load and will be a higher number that the AC3 figure specified. So which duty is the "15 amps Dewhurst switch"? Well, it is almost certainly an AC3 figure, because a Dewhurst switch's reason for being is to control a motor, but when you buy a 10 amp switch you need to be clear what the 10 amp figure actually represents. If it's a 10 amp push button switch, and the 10 amps is an AC1 duty then it is probably (guessing) only a 6 amp AC3 motor duty rated switch and the magic smoke will escape if you connect it to your 8.7 amp rated motor.

There is a complication here that the concept of AC3 only applies to 3 phase switchgear, and single phase motors are a quite different beast to start, but that's too complicated for this time of night!

Now, let's develop this a bit further. You have mentioned a push button type switch - and this also affects the answer. If your plan is to fit a forward/reverse selector switch AND a push button ON/OFF switch we're into a different can of worms. If the drum/cam forward/reverse selector switch is only ever going to connect the motor wires together without them being energised, and the switch of the inrush (starting current) is done elsewhere then you can over-rate the selector switch significantly. Nobody's going to commit to a definitive statement how greedy you can be, but your 10 amp switch controlling a 8.7 amp motor will be fine. The motor rated current is below the rated current of the selector switch, so all is well. The push button starter now has to make the motor inrush current, and break the motor voltage to stop it again, while the selector switch just has to carry the motor load current. It's the making and breaking reliably which is the arduous duty, by comparison any contacts carrying the motor current which don't have to make or break the circuit and carry current at the same time have an easier life.

However I'm bound to muse on "BUT" number two. My experience is that it is unlikely to be the switchgear that causes an RCD to trip, it is much more likely to be a fault within the motor. The current and voltage figures you quote say this is a single phase motor, and that rings alarm bells straight away. Single phase motors have a capacitor that'll happily go fault to earth, and if that's not the problem the centrifugal switch inside the motor which controls the start winding (if there is one) has a REALLY hard life, and splatters conducting metal vapour over its insulating mounting plate. So what leads you to believe that the drum switch is the faulty component? Has the switchgear been re-wired recently - and if so has the problem only arrived since something was changed? Have you had the insulation of the motor checked - it's a very easy and quick measurement for someone to do with an insulation tester that could stop you spending money on new stuff which doesn't fix the problem. My suggestion is to take it to a rewinder and get them to check the motor over before spending money on switchery. But maybe you already tried that.

Yada yada yada. Like I said, it's a simple enough question, but the answer is anything but!

But I sympathise with the aggro from SWMBO - I had to feed my shed with a separate RCD circuit for all the same reasons, though that was caused by the leakage currents of VSD's.

Hope this helps

Simon

My apologies if a pesonal recommendation is against the spirit of the forum, but I notice on lathes.co.uk for sale section several useful looking contenders for this. I bought my Bantam off Malcolm in Witney who's advertising here and I would recommend him to anyone.

The comments above about being able to do the job (to tolerance) in a fraction of the time is precisely why I love the Bantam over the Myford. If you've never had a production machine you won't know what your missing, but once you've worked on aa real lathe you never settle for tickling it wit the Myford again.

Rgds Simon

I'm with Phil above. I too have an elderly and much loved sorry much worn S7 that I bought 40 years ago (its older than I am, but only just), and a Bantam which I bought second hand about 20 years ago, and hardly touched the S7 since. You can't possibly compare the two machines, they're chalk and cheese. Myford's are lovely if that's all you can find room for, but a production lathe like anything with a Harrison or Colchester badge on it will knock it into a cocked hat. Can't comment on others -no experience, but buying the Bantam was the best purchase I ever made.

HTH rgds Simon

I looked at this and thought I recognised it as Osborn Titanic. Then I went out to the shed and got my old Titanic chuck out of its box and realised the collets I've got aren't one piece like this one, though I'm pretty sure this would fit. Looking on the web shows several different types of Titanic chucks, including one which uses the same collets as the Posiloc chuck I use all the time. So I 've decided I don't know enough about the different varieties of Titanic chucks to give an answer, but if you google Osborn Titanic you will see something very similar to this. I think there must be several different type of OT chucks just to complicate matters.

Anyone know any more /different?

Rgds Simon

For what it's worth I'd make a load of spacers with female threads each end. Now buy long grub screws and run them into the tapped thread. Side steps the taper at the heel of the thread problem, and is a whole lot quicker. You cam also be fussy about what grade of grub screw you use and control the stress point at the change of section.

There was an earlier thread about tapping in the lathe which is relevant.

Rgds. Simon

Cashier number 19 please...........

The H&S Police will love me for this, but it is a trick I was taught by a production machinist a long long time ago...

Take a suitable sized Jacobs chuck on a morse taper, and cut the tang off the back of the taper. Now clamp the tap as tight as you like in the chuck and pop it in the tailstock, leaving the taper just not quite home. Move the tailstock up to the work. With the lathe running , grap the tailstock chuck firmly and offer the end of the tap up to the rotating work. The lead of the tap will grab the hole, and bob's your uncle. If the tap binds or hits the bottom of the hole let the drive torque take the chuck out of your grip, and let it spin with the work.

The loose taper of the tailstock will guide the tap.to start straight with the axis of the rotating work, and anyway you can't tap it crooked if the work is rotating. Yes you can break the tap, and if you try really hard you can can your hand caught, but as a quick down and dirty fix it works for me.

I'm tempted to say "don't try this at home", but that rather spoils point of the story. I do ALWAYS take the tool out of the tool post (QCTP of course) so you haven't got a sharp pointy thing just in line with your thumb.

Best rgds Simon

Comments above bear out my own experience, and it cheers me up immensely that my experience in using this style of taper gismo has been that of others. I made a scratch one out of curiosity, but was completely unable to get it set to turn the same taper twice over. I suppose it depends on the reason for wanting to make something tapered - if it's to make a precision fit then this isnt going to cut the mustard, but if you just want to make a tapered end on something then this (and a big bag of patience) might be enough. Whether you use a boring head to achievethe same outcome probably doesn't matter in terms of results, but it is a.more cost effective thing to buy for sure. My parsimonious nature likes the idea of buying one accessory and getting two results, but if you want an accurate taper buy or make a taper turning attachment.

I know resetting the tailstock true is a pain in the vernaculars, but so is not being able to make two parts that fit together. For me, failing a TTA I'd take my chance with the tailstock every time!

Oops! My apologies, I think I've just committed the sin of trying to teach my grandmother to suck eggs, though in this case it's my grandfather to cook them!

But I'd love to see the results?

Anyone tried tig brazing a boiler?

Just for my curiosity, are there needle roller bearings up the centre of the pulley or are they plain bearings? It's a long long time since I had the "pleasure" of taking it all apart.

Rgds

Simon

This piqued my curiosity, so I've just had a furtle in the shed with my set of BOC nozzles. I have a set of the swaged copper nozzles to suit a BOC Sapphire 3 torch, and by dint of poking bits of wire and small drills up the orifice I've come up with the following:

#1 nozzle is 0.6 mm dia, #3 = 0.8 mm, #5 = 1.0 mm

#7 = 1.3 mm, #10 = 1.4 mm, #13 = 1.6 mm

#16 = 1.8 - 1.9mm (1.8 is loose, 1.9 won't go), #25 = 2.0 mm, 35 = 2.4 mm

It's hardly a precision measurement but it'll give a rough guide.

If anyone has got one of the sets of wire reamers BOC sold for nozzle cleaners these would give the sizes more accurately. I've always assumed that the numbering system, though peculiar to BOC, was the same for all their torches, but I haven't checked. Am I right in thinking the numbering system is related to the fuel gas consumption in some way?

As Fizzy says above, for silver soldering something as large and as heat-dissipative as a copper boiler you'll want a bloody big flame and I would think quite possibly a second torch - probably propane - to help with getting the whole thing pretty hot, then go in with the oxy-acetylene to trim the local temp' and get the solder to flow. Getting a structurally sound joint is a matter of getting on with the job, getting a structurally sound and pretty result is another stage of magic again. My Dad was a silversmith, and together we hard soldered some pretty crazy things (the broken antler on a brass statue of a deer was one) but you don't have time to hang around before the flux stops absorbing oxygen and you're knackered. That was with JM EasyFlo flux; I gather there are better fluxes around now, so good luck!

Do let us know how it goes. Rgds Simon

Hi Nick,, thanks for the response. Yes it's a lovely little lathe, hence I'd like to invest in keeping it that way!

As for the issue of the tailstock being low, my measurement is only in one position close to the chuck because that's where I can get a reliable repeatable measurement. Tthe bed looks ok, if that means anything, and it's induction hardened anyway. My impression is that the underside of the tailstock is worn, there is evidence of this if I remove the tail stock and turn it over you can feel the step in the casting. I was hoping to import some expertise to help optimise the adjustment. Not sure I feel competent to tackle this. I came across this forum googling articles on how to adjust the same.

The slack in the headstock adjusted out easily enough, but I note the injunction in the manual not to overtighten them. With what I've got here to measure the end float I can't tell the difference between just right and too tight, so I fancied hiring the expertise of someone who knows his (or her) trade and has the experience to know how the bearings should feel and behave when they are adjusted spot on.

Hello All,

Does anyone have any recommendations for a service engineer to give my Bantam a tune up - headstock bearings, shim the carriage, and the tailstock is about 7 thou low. I fiddle with most things but those Gamet bearings frighten me! The headstock spindle was loose when I got the lathe, I've adjusted them up but never got to the bottom of why they were loose. And dismantling it is beyond my comfort zone! It's a Mk 2 Bantam 2000 so it's the 6 1/2 inch centre height one originally with a two speed motor though now on a VSD.

I'm about 20 mile west of Gloucester, so someone based in S Wales or S W England would be ideal.

Thanks in anticipation of your help

Simon

I seem to remember that I had something similar happen to mine, and traced it to wear on (off) the outer surface of the clutch shoe. I found that the clutch shoe had got worn enough for it to be eccentric, and that I could either adjust the clutch to drive all the time, or not at all, but not both. I fiddled with it for ages before deciding to take a lick off the OD of the horseshoe so it was round and concentric with the countershaft, but then it was undersize and I didn't like to force the expander wedge that far. The horseshoe shaped bit is cast iron, so there's only so far it will bend before it goes ping. I bored out the corresponding bore in the side of the driven pulley, and lined it with a bit of bronze to bring it back to size. It's been working fine since.

I'd planned to make a replacement horseshoe out of Tufnol, but I've never been back to this project.

I seem to remember some complicated dance to be able to machine the bits of the clutch on the same lathe that I'd taken it off, just using it stop start. Maybe I made a dummy drive clutch, but I don't remember the details.

HTH, rgds Simon

Try your local electrical wholesaler. Most branches of City Electrical Factors or its local equivalent will sell CY control cable (copper/pvc multicore flex) in cut lengths. You might not get a lot of choice of what construction, but you'll probably find something that'll do. For an amp or two and say 5 - 10 metres you probably need a cable with 1.0 mm2 cores, though 0.75 mm2 will do. Even 0.5 mm2 will suffice just about if that's all you can get, but steppers like their current so more copper is better. That's the cross section area of each core. There are special end fittings (glands) for some of these cables, particularly the flex armoured (braided) kind known as SY cable.

Another possibility is to use 7 core trailer cable - it's not rated for 230 volts (CY cable will be) and might be a bit too chunky, but it's an easy thing to buy and will have plenty of copper in it. I think Maplin sell it, also B&Q. There will be a local auto electrician's wholesaler who will sell it, or buy a trailer board at the car boot sale and rob the cable off it.

Alternative 3 is to find an industrial control panel or switchgear builder (look under electrical motor control panel in your local yellow pages or google etc). They'll have all sorts of offcuts.

You can make a multicore cable from some suitably sized nylon tube (air line tube) and some pipe fittings (end fittings) to make a DIY plastic conduit. This can make a very robust assembly with some serious resistance to abuse, but it is a fiddle to find or make the bits to make a nice looking job of it. Threading the cores up the pipe can be fun, pinch the vacuum cleaner off SWMBO and suck them through, don't push as they will snaggle up and jam.

Have fun! Simon

Try RapidMetals in Redditch, but they also do internet sales. They'll cut almost any alloy or material to the size you specify, buy what you want when you want it.

It's a fact of life that once you've forfeited Womblers Grazing Rights to the company scrap bin, making things in metal can get a bit of an expensive past time. I agree with the post above - make friends with a local scrap bin! But don't forget TANSTAAFL!

Rgds Simon

And my apologies to all for the silly mistake over the date today - my calendar...

Here are some pictures of what I think is the relevant part from my TTA. The casting is 7 ins long by a shade under 3 ins at its widest. The web is 14 mm 9/16 thick at the slot. If you need any further info pls ask.

BTW has anyone else noticed the date anomaly on the "Latest Forum Posts" Window?

Hi everyone

Seems to me the original thread started with the understandable nervousness of tapping small threads into cast iron.

We've all bought one of those universal kits of every tap size and matching dies for £12.50, only to discover they're brittle as hell, and Murphy's Law applies (the more expensive the part, the more difficult it will be to extract the broken tap...) I have a theory that some of these sets haven't got any relief, so they just bind up, but when you're starting out it isn't clear that these sets aren't HSS and if you're new to the game what are you spending all that extra money on anyway.

Those of us who persevered past this first disappointment spent a fortune on HSS, blue wizard or some such, and anyway breaking a few taps taught us quite a lot on how to feel when it's all about to go horribly wrong. Once you've thrown those cheap and brittle carbon steel taps in the scrap - along with the work piece you just ruined - and bought some decent HSS taps you find there's nothing to it really, just a bit of practice.

In fairness to Tracy Tools, the grade of CS they seem to use has always delivered the goods for me, But I would be very nervous of tackling an M5 thread in CI if all I had to hand was a CS tap. Depends on the grade of CI, and how granular it is. Bigger threads, or M5 and smaller in (most grades of) brass with a CS tap by all means.

Cast Iron isn't difficult to tap, but it's got to be done with a sharp tap. Lubricant is irrelevant if the tap is sharp and cuts freely - hence my comment about relief on the cutting edges. And lubricant won't make a dull tap cut, but it might help you rescue the tap out of the hole just as is begins to bind up. A sharp good quality HSS tap won't break in CI unless you force it off axis or collide with the bottom of the hole (under power - don't ask, took me three weeks to dissolve the tap remnant out of a block of aluminium I'd invested a week's work in with battery acid, and tapping 4 x M5 holes was the last operation) And any metric (coarse) thread in CI is doing exactly what the designers invented metric coarse to do.

And spiral point taps are a dream come true, particularly in the sizes below about 6 mm.

So - to sum up - bite the bullet and buy at least one HSS good quality tap (is one allowed to say EUROPEAN?) , preferably spiral point but it doesn't have to be. Doesn't matter if it's a shiny polished one or a coated one for what we're looking at here, but if does need to be new (= sharp). Make an alignment block to ensure the tap starts true. Make sure you drill the tapping size hole the right size (4.20 mm for standard M5 x 0.8 pitch coarse) and that the drill you use actually cuts that size. There's a whole different thread about playing with the size of the tapping drill in other materials but that's irrelevant here. My recommendation is not to use lubricant, but if you feel you should use something thin but oily. Spit works well, as does butter.

I don't fancy a very fine thread in cast iron - if it's subject to movement it's going to strip sooner or later, and if it's not then a coarse thread is designed to give the optimum holding capacity (whatever than means) for the given size of thread. If you really want to put an adjustable thread into cast iron and make it as fine as 0.5 pitch then you're looking at an insert of some kind (do helicoils exist in this size?).

I used to work with a bloke who'd creep up behind you as you were just into threading a hole. He'd just lean over your shoulder and mutter "Give us a ping". Worked every time.

Best of luck, let us know how it goes!

Simon