Member postings for Bob Gitsham

Sorry I didn't see any instructionon how to do that, I hope this is correct. Thanks.

Edited By Bob Gitsham on 19/09/2017 08:17:10

How is this figure calculated? It would seem to me that as 63 is half of 126 that is 1 full tooth per revolution, short of 127, and given that the 63 tooth gear is run with a 60 T gear it is an attempt at approximating 127 x 120 gear setup which is, and has been, used on larger lathes for a very long time.

Therefore the error occurs to me to simply be 1/127th. Ok, not a lot, and particularly in short lengths of thread such as the average nut and bolt., where the thread engagement lengthy is typically about one diameter. But it would become a problem in any attempts to make a long running thread such as a lead screw. Sure the mating nut could be made to match, but the error would be significant in the total length travelled over many turns.

Bob.

Thanks Neil, Not sure what other recent thread you refer too. But yes it's all good now. I've just got to find the time to get into the workshop and actually make something. My head is full of ideas, but no time to do them.

Thanks Rod, I hadn't realised that the error was actually that small. I made sure that when I ordered my new lathe LD1216 last year that it came with the 127 x 120 compound gear, and although it is nominally an imperial lathe, Imperial leadscrew etc., all the handwheels are calibrated in both imp and metric, and the screw cutting chart gives both imp and metric threads straighrt from the norton style box., with only haveing to set the compound gear for Imp or metric.

A few months ago I did see a very nice spreadsheet on the internet that gave all the approximations that could be used, It actually listed them with thev actualerror as well. I had a look for it last night but couldn't find it. It had a built in calculator where could list the gears you had plus leadscrew pitch etc and it would calculate your options.

It is my uinderstanding that to cut a metric thread on an imperial lathe or vice versa, you need a127 x 120 tooth gear, as the gender bender gear in the train,

The other gears will then give you the pitch you require. there are other combinations that are used but they only give an approximation of the desired thread pitch.

I'm fairly certain that by level they actually mean that the bed is flat and straight, without any twist, also that the centerline of the head stock is parallell to the flat staright bed, inboth the horizontal and vertical plane.The tail stock should also be on the same centerline. I spent most of my adult working life as a Marine Engineer

Without exception the shi[ps I worked on all had a lathe in the engineroom workshop. Some also had other machines as well. The sizes varied from about 9 inch to about 14 inch swing with beds from about 3 ft to 6 ft longt, mainly depending on the size of the work that was anticipated.

These machines were usually bolted to a substantial steel sub frame that was made to be quite square. the sub frame as then resiliently mounted to the ships frame, so that as the ship flexed the lathe on its sub frame remained quite rigid, square and straight.

I always found tthat it was possible to do quite accurate and detailed work on those machines, except in extremely rough weather.

I can only recall one case where the lathe was pretty useless while the ship was at sea and in that case the above procedure had not been followed.

You can buy minature spark plugs, ignition coils and points sets from the specialty hobby shops that supply parts for RC internal combustion racing cars, I've not bought any, but I have seen them there when looking for other small stuff.

I'm fairly certain they cater for both 2 stroke and 4 stroke.engines.

Edited By Bob Gitsham on 29/08/2017 06:06:20

Hi, I have used a wide variety of epoxy adhesives and fillers over many years both as a hobbiest and as a professional marine engineer.

The cheap end products, from what are variously called dollar shops, pound shops or cheap as chips, etc. are usually fine for most non critical repairs around the home, and I usually keep some around.

At the other end of the scale, there is no substitute for the correctly formulated engineering products that are available, sure they are not cheap, but failure can be even more expensive. case in point, Many yeasr ago like about early 70's I used a Devcon product, don't remember which one, other than it was for high temperature, to repair a flame gouge out of a cylinder liner on a marine diesel engine.

The gouge was about 20mm wide and about 8mm deep in the top mating face of the liner where it mated with the cylinder head. The repair lasted about 3 weeks before we were able to get to a port where a more permanenet repair was available.

There are many specialist products out there, when it matters use them, they do work. when it's not important, cheap as chips is fine.

G'day, I originally posted this back last December 2016, but must have put it in the wrong place, so I'll try again.

G'day Bob Gitsham from Adelaide, South Australia. I have just joined this forum last night. I'm a retired marine engineer. My first qualification was fitter turner / toolmaker, I added Hydraulics fitter, specialist welder and finally marine engineer. I also took a job as a sales engineer for about 5 years '76 to '81. just for something different

After retiring I realised I missed the work of high quality machining and fitting so after much discussion with friends and arguments with "she who must be obeyed", I and against her wishes I bought a lath

My new lathe is a LD 1216 Still getting the hang of it, but so far so good. I also want a mill but do not have the room. So am thinking of building a vertical spindle milling attachment for the lathe. Interested if anyone has any info on such a project..

yep, I been thinking that for a while, I suspect this guy is just looking for someone to disagree with. It pisses me when people ask for help and get a heap of good advice, then go and stuff it up because of their own stupidity, ignorance and arrogance.

The moderators should pull him up, tell him, if he's not prepared to listen then at least do us all a favour and shut up.

Bob.

Yes I've tried a couple and for my money I would rather buy a real product from a known brand.

They both leaked gas from the solenoid valve. were hard to set current and feed in mig mode, which is what I use most. these machines were Mig, Tig and stick, no option for plasma cutting.

I finally bought a cigweld 175i, very happy with it, easy setup, no leaking valves quality accessories. And excellent instruction book.

Happy welding.

Bob

Item under Scribe a line in Autumn 2016 of Model Engineers Workshop showing a method of winding springs on a lathe using various sizes of screws as a pattern,

A few years ago, prior to acquiring a lathe of my own, I had a need to get some small springs made. having found a shop that made springs to order I was invited inside where the operator asked a few questions regarding the size and use of the springs. I had a sample of a broken spring

As the springs were required to operate in water he selected a coil of Stainless steel piano wire of the desired dia., and selected a plain steel mandrel to provide the I.D. of the spring. Setting the mandrel up in his lathe he then selected the spring pitch on the lathe gearbox.

Fitting the end of the wire into a slot at the chuck end the end of the mandrel he wound a couple of turns onto the mandrel by hand. Next he fitted a piece of hardwood to the tool post and wound it into press the wire firmly against the mandrel. The mandrel was supported at the tailstock end by a live center.

Running the lathe at fairly slow speed he produced a length of spring that he then cut into the desired lengths that I required. It was quick and simple. This method eliminates the need to find a screw thread of the right size as almost any pitch can be set on teh leadscrew.

The piece of hardwood was about the width of two turns of the spring and appeared to give the desired tension and wound a very even spring.

Edited By Bob Gitsham on 15/12/2016 14:05:11

G'day Chris, good to hear that you lathe is still going strong after 20 years, I hope mine does too but I doubt if I'll last that long.