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Member postings for Paul Kemp

Here is a list of all the postings Paul Kemp has made in our forums. Click on a thread name to jump to the thread.

Thread: Gipsy manifold material
21/01/2020 00:45:41
Posted by Tim Stevens on 20/01/2020 18:19:24:

Brass has an expansion coefficient very close to that for Al alloys. The value for Steel is rather less. I suspect this might have been one factor in the mind of the bloke what made it.

Cheers, Tim

Not sure I follow your thinking there? Steel top, brass bottom, sounds like a recipe for a banana to me? As it's the inlet manifold would it actually get hot enough over its length to make any appreciable difference? If it were the exhaust a different story maybe. If you are suggesting coef of ex to match the aluminium crankcase then that only holds good if the whole thing is brass?

Paul.

Thread: Compressors
20/01/2020 22:43:43

Not sure what pressure they attain? That have a reasonable volume but pressure would drop off quickly so personally I doubt it but prepared to be proved wrong!

Paul.

Thread: Can we have a really clear distinction between Silver Soldering and Brazing
20/01/2020 22:22:40

Silver solder contains a proportion of, wait for it, silver? Brazing filler rod is mainly brass. Silver solder has a low viscosity when fluid and flows easily into small gaps - essential property that is always laboured. Braze has a higher viscosity when fluid and likes bigger gaps. Main differential between basically the same process is the temperature it becomes fluid at. Silver solder more suited to smaller sections and potentially lower melting temp parent metal and whilst fillets can be formed they are relatively small. Braze better suited to bigger sections and higher melting temp parent metal and capable of forming larger fillets.

Paul.

Thread: Centec 2a Gear Box Oil
20/01/2020 22:13:19

Smith and Allan will have something suitable.

Paul.

Thread: Silver Soldering Brass
20/01/2020 22:08:46

Bexley Heath, Hempstead Heath, too large?

Paul.

Thread: How to soften steel
19/01/2020 14:22:57

Good spot Jason. Revolving centre that revolves should have still gone round though despite being up against a hard edge? Maybe excessive pressure from the tailstock too? Maybe as Journeyman suggested it wasn't the revolving centre in the picture he was using, that would do it. No sign of grease or tallow though if it was.

Paul.

19/01/2020 12:56:00

Picture looks to show a rotating centre if that is the one being referred too. Appears to have a couple of round holes in a retaining ring holding bearings for a peg spanner? You need to be doing something wrong to screw the point on a rotating centre if the bearings are ok!

Given we now have a catch plate on the back of a chuck, reduced thickness slide to take a monster tool post, desire to use oversized tools and a knackered centre, this journey isn't going particularly well. I think the OP would do well to take SOD advice and slow down a bit.

Paul.

Thread: Compressors
19/01/2020 12:42:30

David,

Good advice from Paul. It's a bit of a minefield as compressor sellers often exaggerate their claims! Short answer is get one as big as you have room for and with a motor that can be supported by the power supply you have available, pretty well all hobby machines start on load so starting current is the limiting factor.

I think if you want to try to calculate it, work out the displacement of your engine cylinder (bore X stroke), double it (because it's double acting) and multiply by the maximum speed (rpm) you want to run the engine at (say 30?). That will give you a volume per minute at atmospheric pressure. Your compressor then needs to deliver more than this to maintain any pressure in the reservoir. A larger tank will give you a greater buffer.

Paul.

Thread: Why is my silver steel undersize
18/01/2020 18:21:11

That's a little more than a thou. What are you measuring it with? I have just measured a piece of 3/8" with a Starret 0-1 mic and its bob on 0.375. As you say all the bits you have you have measured are undersize maybe it's your instrument?

Paul.

Thread: Silver Soldering Brass
18/01/2020 18:03:57

Not sure about 'dials' with a 3.5 bar range if you are looking for less than 5 psi. 3.5 bar is around 50 psi so using a gauge to measure 1/10th of its range is not going to be terribly accurate? I know nothing of the Smiths torch or the bottles it will be combined with but usually oxygen and acetylene regulators have a gauge on either side, inlet will be high reading showing cylinder pressure and giving an idea of contents, outlet will be line pressure to the torch. Also be sure to understand you generally screw regulator control in to increase pressure and out to reduce.

Paul.

Thread: Myford super 7
18/01/2020 00:45:50

0.004" is in finishing cut territory, it's a mere kiss. In fact a cut that small is not great generally with anything carbide unless using one of the polished aluminium style tips. If you have taken a cut of that size and the tool is sharp it shouldn't cut anything bar maybe rubbing moving back. With everything set right you should be able to take a 0.050" cut without too much stress for roughing if you have a bit of free cutting stuff. When roughing out I generally take as big a cut as the job / machine will stand and approaching size decrease the size of cut to end up with a finishing pass between say 5 and 10 thou dependant on tool and material. On the myford the lead screw is generally left set up at 0.004" per rev (because I don't have a quick change box on it and I am lazy swapping change wheels!). Depends on the material and tool but usually roughing I just wind the saddle back to the start and put on the next cut, final pass I note the reading and back it off before winding the saddle back. Hope that helps. You will develop a feel for what's right and what works in time.

Too fine a wheel will load easilly and require regular dressing, I have a "medium"' standard wheel one end of my grinder and a green grit the other which covers all my off hand grinding needs for HSS lathe tools and drills and brazed carbide lathe tools.

Paul.

Thread: Ally Pally Exhibition
17/01/2020 23:41:31

Well I went today. I wouldn't say it was any better or any worse than last year, it wasn't bad but it wasn't great!

There were a lot of good models to look at, the detail on some of the motorcycles on the stand along the back wall was very impressive. Some nice boats too. I would say the balance in model types generally continues to move away from the 'engineering' base towards boats, planes and trucks. Not necessarily a critiscm as I appreciate the different fields and skills involved even if they don't really totally grab my interest. I find the radio control trucks and diggers fascinating to watch but it's not something I ever see myself getting into. Was impressed by the large planes. Was also nice to see some of the 'ordinary' models that obviously have done and still do a days work on the track. Loco's that are not polished to perfection, have the odd brush mark in the paint, file marks on the rods etc. These are more likely to inspire people to have a go I think than the traditional gold medal winning, flawless exhibits. Not decrying perfection before anybody rips my throat out, I just observe it as perhaps intimidating to the ordinary bloke in his shed just starting in the hobby! Full marks to the two bigger club stands, Chelmsford? (Sorry not good with names and places) where I watched a couple of people have a go at firing on the simulator, water on, pressure dropping and the wheels slowing down, coal on to try and bring it back, what a great way to demonstrate boiler management! Also the repair shed, well deserving of their prize. The fellow on the mini lathe on the SMEE stand facing a bit of aluminium worried me when he adjusted the tool post with the chuck spinning. Ornamental turners were amazing, again not something I could see myself doing but very clever stuff!

Traders; well done RDG, with Warco gone they obviously had the edge on engineering tooling, also good to see Tracey tools still supporting the event. Home and Workshop machinery still I see maintaining their gold standard pricing, indicative maybe of the costs that have to be covered by the traders? Metal prices seemed to vary widely, I bought a lump of bronze from Polly Models which College seemed to be selling for twice the price?

I usually travel up with 4 or 5 other club members, this year I was on my own, one having just had an operation, one dog sitting, one not wanting to make the journey, not sure on the others. Usually I meet at least half a dozen people I know, today only one. When I arrived about 11.00 there was a healthy queue still for tickets but inside it didn't seem terribly busy. Buying a coffee at the pizza outlet just inside the door about 14.00 I was the only customer and with the price less than £2 that couldn't have been the reason! I spent about £80 between various traders, a rake of tips from JB Tools, a length of stainless bar, aforementioned bit of bronze, an ER 25 ball bearing nut from RDG and a few other knick knacks to stock up so I didn't make anyone rich! Other than RDG I didn't have to wait to get to the stock for the crowds in front to disperse it was a case of walking straight up to the stands and making the purchase.

Will I go again next year? Probably but because it's what I usually do (and as another said because that's what I did with my dad going back to the Seymour Hall days, then Wembley) rather than because it was a great inspiration and uplifting experience! However if the traders dwindle further I think I will seriously question if the 2 odd hours each way and the cost of travel plus the entrance fee is really worth it! I can't put my finger on why I wasn't feeling it was a really great day out on the way home, I just didn't think it was! It wasn't a bad day out it was just OK.

Paul.

Thread: Myford super 7
15/01/2020 23:32:59

When I did my apprenticeship all the lathes had 3 jaw chucks, somewhere, mostly unused. 3 jaw chucks were considered poor on holding power and little if ever fitted, even frowned on unless you were holding hex bar. 4 jaw was the order of the day. 4 jaw is so much more versatile for odd shapes, off centre work, no problem with special reverse jaws, you just turn em round, you can even have some one way and some t'other. In terms of running true, they can be bang on, every time. It's hardly a problem to dial a job in and if it takes 5 mins in a hobby setting no real problem. If you want true in a production setting collets are the answer. I can't see 2 1/2 thou runout on a 3 jaw as a problem.

Paul.

Thread: VFD Question
15/01/2020 23:08:03

You might find 12rpm quite a comfortable speed for cutting say a 4tpi square thread or even a multi start thread

Paul.

Thread: Silver Soldering Brass
15/01/2020 21:19:19

A propane torch with a range of burner sizes is all you need. I have a caravan size propane cylinder and a Micky Mouse Clarke propane torch kit with an adjustable reg, no idea of the Kw sizes of the burners but they range in diameter from about 3/8" to probably 3" it also has a gas soldering iron for soft solder comprising a copper bit with integral torch which I used quite succesfully to soft solder 1/2 round brass beading to my 4" traction engine steel tender. Last weekend I silver soldered a steel bush for the oiler 5/8" diameter onto a steel fabrication comprising a 2" length of 1 1/4 round bar previously welded to legs of 2" wide 1/4" thick steel flat bar so a fair old lump of steel. All done in what is essentially a CuP brazing hearth with HP5 flux using the 1 1/2" burner. No problem at all. I don't profess to apply any science to the choice of burner for any given job outside "that looks big enough"! For small jobs I use a self contained plumbers style torch with a propane aerosol size cylinder and the small nozzle of the pair it came with. As others have said if you can contain / reflect back the heat loss with some decent insulating bricks or mineral blanket, Charlies your aunt! I very much doubt you will find any clock bits barring one from the cathedral that sort of rig won't manage. I doubt the whole set up over the years has cost me more than £70 and I even used it in conjunction with a wood burning basket to harden and temper the front spring for my 6" TE. You can spend a fortune on kit but if you haven't developed the technique the job will be no better!

Paul.

Thread: Hello from North Hampshire!
13/01/2020 13:21:15

Nat,

Great to see someone from your generation on here with an enthusiasm for practical skills. They will stand you in good stead in the future! Welcome.

Paul.

Thread: What Did You Do Today 2020
13/01/2020 00:42:29
Posted by Steviegtr on 12/01/2020 23:02:22:
Posted by Paul Kemp on 12/01/2020 22:29:50:

Andrew,

Many thanks for the pictures. I have seen a similar effect previously on some questionable grade material so my guess would be an inconsistent material, several of your comments would support that particularly I think where you referred to the roughing cuts and a similar change in performance with the 'torn' finish. I doubt it is anything to do with your machine given you have not noticed a similar effect previously, I am sure I have read accounts of instances where you have used the hydraulic copy attachment for other components previously on TT? The fact that it appears visually regular but when measured confirms it is more random would tend to support that. I don't remember if you have a hardness tester but it might be interesting to take some comparative hardness readings between the more pronounced areas of the finish? I can't really think through how impurities may be unevenly distributed through the bar from melt to final rolling but I suspect it could be to do with the composition and the action of the working to produce the bar.

I have a friend who has a business running several automatics and he has commented in the past of having batches of bar, supposedly of a standardised quality that gave this kind of finish on the components which caused them to be rejected which was fixed by nothing other than changing the source of supply without any resetting of the machines (this was all bright bar). On tracing back the material the poor finish batch was from an Asian source, the good replacement from Germany. There is often comment re steel from Asia being poor due to its recycled origins, I do find that difficult to understand sometimes as a solid with the supposed same chemical composition from different sources (according to the material certs) but there does seem to be something in it - behaviour of boiler tubes in service with unexplained rapid and localised pitting being another example.

Just my thoughts.

Paul.

You have just quoted something that I said on another thread. Yes the steel from other countries can be rubbish. It has all sorts of crap mixed in with it. China buy every bit of scrap they can & recycle it & so do India & others. We buy things made there & get along with it , but at the end of the day it is substandard.

I think that is a generalisation, I also said I find it difficult to understand why that should be so! I don't believe that all steel produced outside of Europe is "crap". As to car bodies, is it that all bodies made today that don't rust are made from 'new' European steel? I find that hard to believe. I think that is more to do with improvements in paint technology and probably assembly standards. It's many years since I studied metallurgy and it's not an avenue I persued in my career so most of what I learnt I have forgotton! I do believe standards can vary between batches even from the same mill but I don't believe that every piece of steel originating outside Europe and the America's is substandard. There were operations in the UK (Sheerness Steel being one) that operated entirely on recycling scrap granted though they produced mainly low grade materials such as rebar and not bright products destined for machining operations. I do believe however there are variations in standards (and that can be form whatever origin) but only a full analysis would provide any evidence to support Andrew's experience and my hypothesis and the source of origin would need to be determined. Who knows where it was really manufactured!

Paul.

12/01/2020 22:29:50

Andrew,

Many thanks for the pictures. I have seen a similar effect previously on some questionable grade material so my guess would be an inconsistent material, several of your comments would support that particularly I think where you referred to the roughing cuts and a similar change in performance with the 'torn' finish. I doubt it is anything to do with your machine given you have not noticed a similar effect previously, I am sure I have read accounts of instances where you have used the hydraulic copy attachment for other components previously on TT? The fact that it appears visually regular but when measured confirms it is more random would tend to support that. I don't remember if you have a hardness tester but it might be interesting to take some comparative hardness readings between the more pronounced areas of the finish? I can't really think through how impurities may be unevenly distributed through the bar from melt to final rolling but I suspect it could be to do with the composition and the action of the working to produce the bar.

I have a friend who has a business running several automatics and he has commented in the past of having batches of bar, supposedly of a standardised quality that gave this kind of finish on the components which caused them to be rejected which was fixed by nothing other than changing the source of supply without any resetting of the machines (this was all bright bar). On tracing back the material the poor finish batch was from an Asian source, the good replacement from Germany. There is often comment re steel from Asia being poor due to its recycled origins, I do find that difficult to understand sometimes as a solid with the supposed same chemical composition from different sources (according to the material certs) but there does seem to be something in it - behaviour of boiler tubes in service with unexplained rapid and localised pitting being another example.

Just my thoughts.

Paul.

Thread: Hi from Sleaford
11/01/2020 10:11:12

Martin,

Welcome. There is quite a bit of stuff on Centecs on here and a few people with them so you should be in good company.

Paul.

Thread: 4ft Model Steam Boat Project *need help*
11/01/2020 10:04:11

Works with my iPad, just got to albums at the top of the page, click new and away you go.

Paul.

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