Member postings for Nigel Bennett

Could you not open up and then thread the existing eccentric hole in the piston and then "let in" a piece of threaded brass or gunmetal into the enlarged tapped hole - and then drill and thread it concentric to the OD? Something like an oversize Helicoil, retained with Loctite 270.

Taking part of a statement out of context and calling it "tosh" isn't really helpful. ER collets were designed for toolholding, and workholding is only a by-product that happens to suit our needs. If you read back in EIM in 2003, you will find that I described how to make an ER32 collet for the Myford lathe, so I can hardly be accused of preaching Thou Shalt Not Use ER collets for other purposes!

I think it unlikely that anything short of an ER40 size collet would do - ER32 has a maximum diameter of 20mm. If your 25mm head is very short, then an ER collet would not be a good plan as it would distort badly and not grip well - unless you fitted a short 25mm disc in the far end as well.

I don't think ER40 collet chucks are readily available for mini lathes. (ER collets really are for cutting tools only, not material, despite what people - including me - actually use them for.)

In your case, I would fit a piece of material in the 3-jaw chuck and BORE it out to 25mm. I'd mark it against jaw No. 1 and remove it, cut through one side of it to make a split collet and then use that to hold your parts.

Cast Iron usually wears less and is much to be preferred for heavy use. Brass is not the best material to use for cylinders. However, it's quite easy to do what I did and fabricate cylinders from bits of brass tube and plate and then fit cast iron - or gunmetal - liners. Making them from mild steel is also an option - but you'll need to line these for certain, and to take care to squirt WD40 or similar into them after a run.

Using cast iron piston rings in cast iron cylinders is also an excellent idea; making them has been described several times.

Good luck with your Tich, Kevin. I run a little 3.1/2"G 0-4-0ST that is a tad bigger than Tich and a bit smaller than Juliet. It's older than both those designs! It goes like stink for a while (until it gets choked up) and it does need to be thrashed a bit to take two round the track at Eggborough, but it brings a smile to my face, and it can also serve as a mantelpiece ornament when not in use... Your 5"G version should be a lot less difficult to keep going, too.

Hex socket countersunk screws can be very prone to the hexagons rounding off - you need well-fitting Allen keys of the right size, and a good fit in the socket. Remember that one way to remove a hex socket screw with a rounded-off socket is to batter in a suitably-sized Torx driver and unscrew it with that. Done that a lot with chewed-up screws!

I'd forget about using BA sizes unless you happen to find a convenient source of supply. Metric are much easier to find now, and eBay will usually throw up a number of suppliers in the small quantities needed.

It all rather depends on whether you've tapped the holes in your engine already!

There was a supplier at the Doncaster show who sold stainless steel metric fasteners from about M1,6 upwards at about a quid a bag. (Turbo Trade UK 07926 256551, www,turbotradeuk.co.uk according to my programme).

My last couple of locos have all sorts of fasteners both metric and BA, because that's what I happened to have at the time. I've often tapped out BA nuts to the next larger metric size as this often gives a good "scale" appearance.

I dispensed with my topslide and mounted my toolpost on the cross slide, using a chunk of steel of the appropriate thickness (i.e. a little thinner than the topslide). It gives a much more robust mounting for the toolpost, and I've only used the topslide two or three times since in several years. I think there was an article in ME about it by somebody. (Oh, all right, it was me. ME No. 4366 (2009) p717.)

Edited By Nigel Bennett on 30/07/2016 12:05:28

I've made several backplate registers on my lathe undersize by 0,5mm or so. That way you can nip up the securing screws on the chuck/collet holder and bop it to run true using a DTI and a soft hammer.( I will leave it to you to decide how these implements are used...)

Nipping up the screws tightly should ensure it stays reasonably true - but the DTI/mallet system does allow you to make adjustments to any job you have, a bit like a cheap Griptru.

Only thing to watch is if you have a big dig-in, which might cause the chuck to slip slightly and hence eccentric running. You just have to get the mallet out again and take shallower cuts!

(Jason got in before I'd finished typing!)

Edited By Nigel Bennett on 23/07/2016 11:34:23

Dave

Cast iron is the usual material, but steel would be a reasonable alternative. If you've access to a milling machine then you can chew it out of solid. Fabricating it from a number of steel sections screwed together is a method used by a number of DIY lathe builders in the past.

Short Myford cross- slides are sometimes available when users fit long ones instead, but I've no idea if they will fit the Grayson.

Determination. Like anything else you do, if you're determined to do something, you'll find a way of doing it. Lots of people seeing things I've made say, "You must have lots of patience!" but they haven't seen me, with steam coming out of my ears, jumping up and down on the bit that's just turned out wrong...

Neville Shute's quote on the cover of "Trustee from the Toolroom" :

"An engineer is someone who can make for five bob what any bloody fool can make for a quid" pretty well sums it up for me.

Bernard, that's an excellent piece of work! To return to Chris' original problems, having ground the jaws back using one of the methods described, it's quite possible that the chuck won't now grip truly concentric. Don't forget the simple dodge of turning a few thou off the chuck backplate register diameter and then bopping the chuck to run true with a mallet - a cheap and cheerful alternative to Bernard's Griptru solution.

It's possible that it was put there during manufacture. A fitter would have assembled parts together, and perhaps they were then sent away for further processing such as painting. The marking would enable the correct assembly to be reunited with the lathe to which it was fitted. Look under the tailstock and see if there's another G7 there.

You should be able to determine roughly what size of tooth you're dealing with by measuring the tooth depth. If it's a metric gear (Module), then the tooth depth is a little over twice the Module - e.g. if the tooth depth is 2,25mm or so, it's possibly a 1 Module gear.

If you're dealing with a DP gear (perhaps more likely in Model Engineering) then the method is similar. Full depth of tooth on a DP gear is 2.157/DP. So if your tooth depth is a little over 1/8", then it's probably 16DP.

Once you've determined the approximate pitch size, then you can use the David Brown Base Tangent method, whereby you use a vernier caliper to measure over 2 or 3 teeth (it depends on the number of teeth in the gear) and you can then decide whether it's (say) 8DP or 3 Module.

Be aware that there are two standard "pressure angles" for gears - 14.5 degrees and 20 degrees. This affects the shape of the teeth and hence the Base Tangent measurement. Older DP gears may well be 14,5 deg, most module gears are 20 deg.

Machinery's Handbook gives dimensions for BTM, but in my 1957 edition they hadn't invented millimetres.

I've now had two IMO Jaguar Cub inverters from Transwave, who advertise on this site and in the magazines.

My first purchase was a 3A unit, a couple of years ago for a Super 7, which also included a new motor and the Remote Pendant affair, which works brilliantly. The help and advice from their MD Pete Moss has been excellent. He was able to diagnose a problem I had with it and to guide me through changing one of the parameters on the inverter, which cured the problem completely.

The second and more recent installation was a 5A unit for a Boxford 280, where rather than using their Pendant, I wanted to use and therefore rewire the existing lathe controls. Again Pete was very helpful in advising on components for this - even to giving me the Maplin part numbers.

Usual disclaimer - but it's good to be able to give some positive comments and to be able to recommend one of our suppliers.

(Editid 4 spelin)

Edited By Nigel Bennett on 12/05/2016 12:40:23

Hello Ron

I presume you mean that effectively you have a simple blanking plug as a "blowdown". Obviously this cannot be used as a means of blowing the boiler down when it is still in steam. It is desirable that this can be done as it will enable the debris and accumulated sediments to be blown out of the boiler under pressure. With a plug, if I understand your situation correctly, you will have to wait until the pressure has entirely disappeared before removing it. The boiler water will then dribble out, leaving a lot of sediment behind. Undoing a plug fitting with the boiler in steam is not to be recommended. You would need a good supply of replacement plugs and it would damage the threads in the boiler when it blew out!

Over time, sediments would accumulate in the bottom of the firebox and could lead to premature boiler failure due to overheating.

It should not be too difficult to fit a proper blowdown - there are lots of them described in ME and other magazines, and they're available from suppliers like Blackgates. You may need to provide a bigger hole in the frames to clear it, however.

The "Green Book" does not insist on blowdown valves to be fitted. However, a Boiler Inspector is quite within his rights to refuse to issue a certificate if in his opinion the boiler is inadequate in some way, or if it contravenes Club Rules. The Boiler Inspectors have your own interests at heart in this case - so don't despair, just fit a proper blowdown and everybody wins.

I think (in this instance) I may well have issued a certificate with the proviso that a proper blowdown valve be fitted within a fairly short time scale.

Superb!! Many thanks for that very speedy response, Nick, it's much appreciated.

Does anybody have a Metric Boxford 280 or similar with the screwcutting gearbox? I've got one, but the screwcutting chart affixed is for an Imperial leadscrew. Can some kind soul please send me a photo of the chart so that I can sort things out? I'd get one from Boxfords, but a) it's rather expensive and b) the new colour scheme on the new ones won't match the other fascia labels on mine and I don't want to fork out for all of them!

Nigel9172 at talktalk.net would find me.

Many thanks.

If you're thinking of having spoked wheels, you should consider castings for those. If you keep your eyes open on the second-hand market, they sometimes come up; that might dictate your choice of prototype.

My current loco has everything fabricated except the wheels; I made my own patterns for those and Blackgates cast them for me at a reasonable cost. The cylinders were made from brass because I happened to have some, and it silver-solders very well. Cast iron liners were fitted for piston valves and main bores.

Going back to the spoked wheels, John Heslop described how he chewed his wheels out of solid for one of his creations, a 5"G rebuilt Royal Scot if memory serves. I can't now recall if it was in ME or in Another Place.

Was that the one on eBay from South Wales? I rather fancied it, too, and if it had been nearer home I'd have bought it. As luck would have it, a Boxford 280 came my way instead. Not run it yet but it smells rather of new paint...lot of wiring-up to do as well. And as Steven Vine has said, it's costing me a fortune...

Another was Nile Perch cooked over an open fire and served in a rich stew/juice. Then another was to catch a 2lb Brown Trout and cook it on a sick over the fire for a midday snack.

Clive

Bloooargghhh!