Kids wearing adult clothes~aka 5" mini lathe chuck & more.

Things have changed a lot in last couple of years. I don't know about anyone else but i've currently not a lot of free cash to spend on tooling or anything else for that matter.

I moved house 5 yrs ago & a lot of DIY was needed, so the machining had to take a back seat.

Now thouroughly sick of the DIY so Lathe & mill dusted off & enthusiasm re-kindled.

That as it may, a couple of years ago i was feling somewhat more flush & hankering after some machining. A few purchases made from Arc & other sources~ promptly dumped into a box & all but forgotten.

I found the box. Inside amongst other things were a SC4 faceplate & a 5" 3 jaw chuck from Arc.

Finally time to unbox.

Hope the following will be of use to someone.

If you've a mini lathe with a 100mm spindle & bought the face plate to fit, maybe like me you were slightly disappointed, the spindle flange makes for very short slots on the face plate.

The 80mm version looks a bit more useful to my eyes.

Pleased to report the SC4 face plate fits fine, Though there really is very little clearance between plate & bed.

It's a very massive item compared to the standard offering~ perhaps that's not such a bad thing for off centre work & the likely low speeds involved?

Worth your comsideration.

Now to the 5" chuck.

backplate, spindle & chuck all fitted together nicely, thanks Arc.

This thing looks slightly rediculous on the mini lathe.

Spun up, DTI readings taken, test cuts made.

A few things you might want to consider before mounting a 5" chuck on your mini lathe.

Runout was no better or worse than any 4" chinese self centering chuck i've tried bout 3 thou.. Yet to clean & re-lube the internals, so may get a little better,or not.

Nice 30mm bore, After investigating first, it may well be possible to bore out to 1.25". I'd be a happy camper, use 1.25" stock a fair bit.

Spun up to approx 1000rpm max, not sure i'd be happy pushing this up to 2500rpm , maybe i'm over cautious. No spurious noises, in fact the lathe seemed quieter than with a 4" chuck. Go figure??

A couple of vibration points @ certain rpm , but seems that way with my mini lathe whatever is mounted on the headstock..

Good as gold @ the low rpms i'm likely to use this for.

Some points for you to consider:

The chuck & backplate eats into your center to center distance, Probably not a problem....

I doubt many people mount foot long 4" dia work in a mini lathe.

I did once.thankfully the 4" chuck & a custom built center did the trick.

Typical swing over the mini lathe crosslide <4 1/2"

You will either need to have 100% concentration or maybe fit a suitable carriage stop otherwise you WILL crash the carriage into the chuck/ chuck jaws....sooner or later.

I don't think a 5" chuck on the mini lathe is a one size fits all, fit & forget solution. I will only be using when necessary.

I don't have the math but 5" chuck & high speed sounds like overloading something to me.

Maybe you know better.

Consider it a useful tool where conditions warrant. Looks like i;ll be able to turn 2" stock using inside jaws now.

Probably the extra mass will give a flywheel effect & a better finish pass~ one can but hope! Early days yet.

Sounds a useful upgrade for a small lathe.

Check with ARC or the manufacturer's data on the top RPM for the chuck you bought. Some have plastic retainers for the chuck key barrels,which limits the RPM before the heavy steel barrels fly out under centrifugal force. No idea what rpm that is though. My old banger Myford is flat out at about 800rpm so not an issue.

It is not so much how fast you run the chuck that will overload things but the initial start up load to get it and the proportionately larger lump of metal it can hold up to speed . Ketan has voiced his opinions on large chucks on "mini lathe" size of machine in the past and sells the parts due to demand not due to ARC recommending them, same with long tables on mills.

Edited By JasonB on 13/01/2023 07:08:24

I don't know better, I agree! Useful where conditions warrant, which we hope to be rare.

The problem is the extra weight. Chucks become disproportionally heavier with increasing diameter, and this loads the bearings, puts more stress on the drive train, and makes the motor work harder. This is before the job is loaded into the chuck, adding yet more weight.

A lathe fitted with an oversized chuck doesn't fail spectacularly. The effect is more subtle, for example bearings that would have lasted 20 years last 5; the motor eats brushes; and maybe the insulation eventually fails due to overheating. Mini-lathes are probably more prone to a spectacular failure than other lathes because their electronics are a little delicate. They're made down to a price, and the designer is unlikely to have allowed much headroom for an overload.

Doing oversized work on undersized equipment has always been part of Model Engineering. Just try to minimise how often the machine is overloaded, and don't thrash it. No different from towing a heavy caravan with a small car. Driven with skill a small car will cruise a big caravan at 50mph forever on a flat motorway. But expect trouble at 70mph and avoid hills and stop-start driving in town centres where brakes, clutch, gears, and engine all take a beating.

Dave

Hi Dave, the car you would use to tow anything will depend on what the manufacturer states, whether that is a big or small car and whether it is a big or small item you are towing, it's all to do with weights not size although there is a limit on the length of the item . Yes you can expect trouble towing at 70 mph, like blue lights on a vehicle behind you, as the maximum speed you are allowed to do while towing in the UK is 60 mph.

Regards Nick.

It's not just the speed you can tow at a small lightweight car will not be much use with a big load when you want to stop from 50mph

Yes, I'm guilty of misusing the language! However, before sentencing I ask the judge to remember small cars rarely have the qualities needed to tow a big caravan. Small cars usually have small tyres, small clutches, and small engines. Weight matters too:

Dunno if anyone else feels the same, but I won't buy a second-hand car if there's any sign of it having been fitted with a towing hook. I choose not to buy them because they risk needing early repair work and hauling heavy loads. legally or not, increases wear and tear.

Dave

Edited By SillyOldDuffer on 13/01/2023 10:49:34

Hi JasonB, I do agree with you, but my Astra Estate for instance is not not small or big, but the maximum weight the car can tow is 1000 Kg braked, but only 690 Kg un-braked, I can still tow a large trailer or caravan provided it's within those gross weights, but will also depend on what weight I have in my car, e.g. passengers for example, but you still have to take the whether and road conditions into account whatever vehicle you are using.

There are of course some cars, very often small ones, which you will not be allowed to tow anything at all, so unless the manufacturer has made points for a tow-bar to be fitted, you are not allowed to fit one.

Regards Nick.

Edited By Nicholas Farr on 13/01/2023 11:06:00

No spurious noises, in fact the lathe seemed quieter than with a 4" chuck. Go figure??

Geared headstock ? If so, the extra mass of the larger chuck is probably loading the gears & preventing chattering, where a lighter chuck oscillates through the gear backlash when under light load.

Doing oversized work on undersized equipment has always been part of Model Engineering.

Not just within the "Model" branch of engineering - a frequent occurence in "full size" engineering as well !

Doesn't seem to matter how big a machine a company buys, the first job that comes along is just that bit bigger than the latest aquisition's capacity.

No different from towing a heavy caravan with a small car.

Not a good analogy, Dave. Cars come with towing limits - usually given for braked & unbraked loads. These days the size of a car has little to do with it's towing limits - large ,heavy electric cars can have no towing capability. My medium sized Hyundai i30 estate has a towing limit of 300kg - a limitation imposed by the DCT transmission, I think, not the size or kerbside weight of the car. My manual transmission motorhome of similar power output has a towing limit of 2 tonnes, yet other (larger) models can have sub 1 tonne capability. Really pays to RTFM before commiting to a vehicle purchase if towing is a requirement - not something that is usually required when fitting a larger than recommended chuck to a hobby lathe.

Towed loads are also subject to "matching" recommendations - IIRC the unladen kerbside weight of the car is supposed to be greater than the maximum gross weight of the towed load. My brother has a large double axle caravan & requires a substantial towing vehicle of a miniumum unladen weight to tow it. Expect awkward conversations with insurers & the Police if something untoward happens when flaunting the rules.

Nigel B.

With small cars towing heavy loads like a caravan, it is possible to permanently stretch and distort the bodywork so the doors will no longer open.

Hi Dave, of course you need to know the maximum and minimum vertical coupling load of your coupling ball, which should be given by the cars manufacturer and also know what the download weight of the trailer is when loaded. I've bought two second hand cars with a tow-bar already fitted and neither have had any problems you have mentioned, but both were bought from reputable dealers.

Regards Nick.

Edited By Nicholas Farr on 13/01/2023 11:31:19

I bought two chucks for my 7 x 12 lathe because the originals were poor quality, an 80mm three jaw scroll which was a direct replacement and a 100mm four jaw independent which needed some machining for it to fit. The sizes are perfect for such a small lathe and the chucks, both Sanou make are much better made than the originals which had a Spanish name, but were made in China. Having another lathe which can easily hold 100mm made it easy to modify the four jaw to fit directly. The Smart & Brown model A at the museum is a 9 x 20 which is perfect for a 5" three jaw scroll chuck, we have a 6 3/4" Pratt with serrated jaws for it, but it rarely gets fitted because of the size.

As for the picture of the car and caravan, that is faked, you would have to put about 5 tons in the front of the van to get the car to tip up like that, and its front wheel drive to boot.

Edited By old mart on 13/01/2023 18:27:19

Edited By old mart on 13/01/2023 18:31:40

Point taken, and I've already pleaded guilty!

But buying second-hand, I suggest it's unwise to assume previous owners have read the manual or obeyed the law. If a tow-bar fitted car has always been driven and maintained sensibly, then I agree it's unlikely to be knackered. However, I've been overtaken by a caravan on a motorway by when I, ahem, might just possibly have been over the 70mph limit myself. The truth is not all caravan and trailer owners are sensible! Many ordinary motorists have a low opinion of caravan owners, because a noticeable proportion of them don't have consistent control.

I agree with Old Mart that the photo might be a fake or staged. But I have seen a car lifted off it's back wheels like that by a tipped over caravan. Burst tyre or uncontrollable snaking at speed maybe. Whatever the reason, the accident will have done the car no good at all; everything from a twisted chassis to shock stalled engine.

Persons selling cars used for towing might be happy no damage has been done, but buyers may not be so sure! In the good old days dealers used to remove tow-bars before selling cars on, because they put potential purchasers off.

My car might look like a better bet, but it suffers another damaging pattern of use, perhaps worse than over enthusiastic caravanning. My mileage dropped massively during the Covid lockdown never recovered. Now I only use it for short distance trips. Bad for IC cars; ideally they need to run for at least an hour, and not just pootled to the shops and back.

Dave

Hi Dave, if that person with the caravan overtook you in the fast lane of a three or more lane motorway, then that person would have broken two laws assuming they were doing over 60 mph, the other law would be towing in the fast lane.

Regards Nick.

Edited By Nicholas Farr on 13/01/2023 21:13:25

Old Mart It looks like a VW beetle to me and I can assure you that the engine is in the boot not front wheel drive.

Roy

This towing thing. It’s not just a matter of can the vehicle drag it along or even stop but dynamically can the vehicle control the load. With a massive trailer and a lightweight vehicle the ‘tail is going to be able to wag the dog’. Get the trailer snaking and it will take control of the car.

regards Martin

True. But it seems you're surprised that people would do such a thing?

I've ran a 5" chuck on my SC4 for years, so long in fact that I have worn out one chuck ( I do a production job on this lathe making stainless screws). It must have been started/stopped hundreds of thousands of times.

Never had any trouble.

Jim

It's one of the new style beetles in the photo not an old rear engine air cooled one.

It's not an SC4 that he is fitting it to it's a 7 x minilathe. Many of which have a 80mm chuck as standard unlike the SC4 which has a 100mm chuck as standard so less of a step up in your case.

He is also fitting the SC4 faceplate to a minilathe

One other point Dave said a larger chuck gets disproportionately heavier. This need not be the case, for example my 160mm 4-jaw is no heavier than the 125mm one that came with the lathe. As it is a slim bodied one which also has a lot of the material cut out at the back unlike the typical chucks supplied with the far eastern machines,

Edited By JasonB on 14/01/2023 07:00:14