Member postings for Martin Johnson 1

I had similar problems of insuffient clearance on carbide tip bars that came with the common 50 mm boring head.

Dont assume that just because you invested money in something that it will work out the box. That's engineering.

Martin

I know nothing of IOSS and live in Scotland (part of the UK so far), but hats off to Ketan for getting on with it.

Martin

+1 for keep the lot. It's all useful stuff and would cost a lot to re purchase later.

Martin

We all seem to have assumed the inverter is emitting unacceptable levels of EMC. It is quite possible you have a camera (and maybe my digi readout transformer as well) that has substandard protection from mains borne EMC.

Martin

I recently upgraded to a cheap ebay inverter package on my lathe and while I was on the job I installed a small power supply for my Arc Euro digi bar readout. Inverter works fine, digi bar works fine until the lathe is switched on. It seems interference wipes the settings on the digi bar readout. If I use a battery supply to the digi bar all is fine, so I infer the problem is mains borne.

Have operated for some months on batteries to the digi bar now. Must get that round tewit.

Martin

If you are asking "Will suppliers who have sweated the value of the same old drawings and patterns for far too many years already be prepared to invest in reams of G code and all the associated fixtures?" Then the answer is a flat no.

If you are asking "Does CNC have a place in model engineering?. The answer is yes.

Personally, I CAD my own designs, make wooden patterns, buy castings, laser cuts, bar stock and machine it on 60 year old machinery.

Martin

I have one from Chester which permanently resides in a drawer while an elderly Jacobs does all the work. Idont like the extra length or the reduced depth on the keyless. I also think the keyed provides beyyer grip.

For balance I also have keyed Chinese no name which is Ok bur the holes for the key are way oversize.

I would always go for quality name and a key by each machine.

Martin

Edited By JasonB on 31/12/2021 13:04:37

The standard Kerry goes from 1500 down to 35 rpm (I am not next to mine, so that is from memory). You really wont need much more range than that.

There is a Kerry owners group (small but select) on Io groups for specialist help on this rare breed.

Martin

I have a copy of "Installation and Maintenance of Electric Motors" by BCPM. The wiring diagram for the VS series motors shows terminal AZ as line, A as neutral and earth is the case as previously noted. The motor is a split phase type with starting windings controlled by a centrifugal switch. To reverse rotation, swap the internal yellow and blue wires between A and AZ. Internal wires red and black should stay where they are. It looks as though your motor has a thermal switch to prevent overload - that should be wired in series on the line input.

Not clear from the photos, but if you can get a proper cable gland into the housing to grip and take mechanical strain off the power cord, it would be a lot better. If you can't use the mouse hole as presently used, but anchor the cord nearby to the machine frame.

Martin

I regularly get similar marks on tough materials. By counting the cycles (number of starts and pitch) I inferred that it was due to the rather hummy single phase motor. Different motors improved things a bit, as did rubber motor mounts. I have just ordered an inverter and 3 phase motor.

It is no accident that Myfords used to come with resilint mount motors.....

HTH

Martin

I cosidered this type of design for my steam lorry - a large piston valve engine. I was cocerned that they would be rather poor at pressure relief because you would get the live steam line full of codensate. In the event of hydraulic lock on the engine, you have to shift a load of condensate in the actuation line - with it's own inertia. So I concluded it would not prevent damage to the engine. If someone has evidence to the contrary, I would be pleased to hear it.

Martin

As Jason says, it all rather depends. First step is always to knock the lumps off with a file. A good next step is to mark the castings out, with (say) the base underside surface and shaft centreline. Also mark out the base in relation to it's axial position with the bearings and spot where the holding down holes will come. You will soon see where there is not enough metal (happens on commercial castings too often) and too much metal, and can adjust your marking out accordingly to get the best shot at the casting.

I would then probably go for a preliminary cut on the under foot and the long side of the foot - not to size at first, just to give you square edges.

On complex stuff it can be like knitting with fog to get a start. A dodge then is to cut card templates to actual size and sight them against the casting to get the best shot.

Hope that helps,

Martin

On the Kerry, that damage does make a difference. It is a wedge type gib strip held endways by the mangled screw you can see in the photo and another at t'uther end. Someone has then drilled in a roll pin to hold it as a repair, but the gib strip cannot now be adjusted.

Three ways out as I see it:

• Get the base casting built up with weld and machine back to original. Could be tricky to machine the weld back and blend well enough for a machine slide.
• Shorten the base and re- drill for the gib strip screw. Will leave you with a little less support, but probably fine.
• Make a pattern up and get a new base cast. You might be very lucky and find a foundry that would work from the knackered base if you build it up with isopon or similar, but they are a rare thing these days.

The upper top slide casting is easy, you can hack that out of continuous cast bar - don't ask me how I know that.

I checked in my instruction book for metric screwcutting charts, but it refers to a different style of box. I think you will have to try it out and count input turns Vs. leadscrew turns and then work it out from scratch. You could try asking Tony Griffiths - you never know your luck.

As to cross slide screw - bite the bullet and put a digi readout on that and the long axis.

By the way, you got an absolute bargain when you bought the lathe.

Martin

I also have an 11 x 24 Kerry, imperial model with the angled tailstock handle - you'll know what I mean if you have one. I think you will be very lucky to find spares, but they will be worth the effort of making. You will end up with a very good lathe. If you need any photos taking I will be pleased to oblige, just P.M. me.

It sounds as though you have an unusual beast, the Kerry I have has 9 headstock speeds selected by 2 knobs with 3 positions.

My only quibble is that it doesn't cut 19 tpi (3/8 & 1/4" BSP)- but that won't bother you in metric! Changewheels on mine are 18 dp, but I don't know what the train would be on a metric model. My Tony Griffiths instruction book lists translation wheels for my imperial machine but nothing else. The book is worth getting anyway, as it has a lot of cross sectional drawings, which are useful if you need to make parts.

Martin

If the O.P. is working in industry trying to make a profit or bonus by turning things out as quickly as possible, then rake angles, clearances etc. all matter.

If as I suspect he is working in a home shop. They really don't. I turn just about any material with the same set of tools - all ground by eye with a bit of clearance on the front and whichever side face is cutting. Put a few degrees of rake on the top and that does the job. Only exception is some brass which is better without the rake on the top - even then, most of the time I can't be arsed to change the tool.

My qualifications for such a gung ho approach? 50 years model engineering, 40 years as a chartered mechanical engineer.

Martin

Another vote for adjusting the bore size to suit a commercial piston ring. My traction engine runs on a chain saw ring (High pressure) a Ural motorbike ring (low pressure) and I have just built a much modified Southworth steam pump that runs on a petrol strimmer ring.

Have a trawl round e-bay to see what you can find. If you go for non OEM parts, they can be dirt cheap - probably cheaper than the cast iron bar to make a ring.

For steam work, you can close a ring up slightly if you need to. Make a hollow ring to hold it in, cook the whole lot up to dull red and you will find the gap will close up nicely. A bit like the old trick of springing them open and heat treating, but in reverse!

Martin

If you have access to another lathe, the job is fairly simple. Some of the well known traders sell backplate and faceplate generic castings. It will help if the Holbrook spindle is available (i.e. dismantled) for fitting the threads and registers on your casting.

If you don't have access to another lathe, you really need to start with at least something that already fits on the nose - this can be a faceplate or a catchplate for between centres work. Have you tried the usual 2nd machinery dealers for something?

Assuming your Holbrook is now armed with a faceplate / catchplate the routine is drill, tap and screw your chuck backplate with boss pointing toward tailstock onto the facaplate. Now machine the thread and register - you will have to unscrew the whole lot to check thread fits and registers - a pain, but possible. Once you have a thread and register done, remove the backplate, screw it onto the spindle nose and machine the face and spigot for the chuck.

I hope that all makes sense.

Martin

Chris,

I know how much scrapping a boiler hurts, as I got myself into exactly the same situation with a Rob Roy boiler, more years ago than I care to remember. Just like you, the shell went quite well as did the tubes. But the stays.................

Well, I pickled, chased the leaks around using an oxy acetylene set at work to get inside the box. Created more leaks in diffferent placed, pickled, chased the leaks around a bit more ............. and so on ad infinitum. Until in the end, I was concerned about the safety of it all just like you.

I just hope knowing you are not alone will set things in perspective. You are not the first and I very much doubt you will be the last bulder to get into a similar situation.

The fact is, that commercial boilers represent a bargain when you look at cost of materials and the amount of fiddly work involved.

Best Wishes,

Martin

Forgot to mention - choosing a club:

For a larger scale model, you are probably going to have a steel boiler. At scales up to 4" or so, you can get that tested by a club. For 6" models and beyond you will be paying for a commercial inspector. If you are getting club inspections, be sure the club has experience of steel boiler inspection and know what to look for. Not all clubs have that experience, and you need that peace of mind.

Martin

Hello Karl,

Glad to hear you are hale and hearty! Also nice to know you have the room and facilities, so my advice would be to crack on with a big 'un - given the way things are going, it will be easier to sell when that day (hopefully far away) comes.

Aside from the Burrells (various including GMT, agricultural, SCC, showmans, road, crane in 2, 3, 4, 6 & 8" scales) I would have a look at the McLarens (3, 4 & 6" scale of a big engine), Garrett agricultural 4" scale, Garrett tractor in 6" scale, Foster 4" scale (available in compound and single guises - the single is an easy(ish!) build but not very close to scale), Fowler singles in 2, 3 & 4" scales - a nice close scale model, Fowler compound in 4 1/2" scale - a nice model, but Plastow drawings again.

Given your easy access to HGV vehicles etc., I would consider the 8" GMT - there is a build thread on Traction Talk, or a 4" McLaren - they have an excellent reputation. If you want to go silly, have you considered a 9" scale Foden lorry? or 6" Foden lorry if you want to fairly sensible - they go like the clappers.

As to casting purchase, I do not like to tie large sums of money up (nor does SWMBO) so I tend to buy castings in batches and split the build into phases accordingly.

Martin