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Member postings for Steve Pavey

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

Thread: Completing posts
18/02/2018 11:43:31

I think (and hope) I have always posted my thanks on here for help and advice I’ve received, but with one exception - a very helpful forum member loaned me an engine hoist to help with getting my mill from my van to standing vertically on terra firma. While I obviously thanked him in person both when I picked it up and when I returned it, I felt it may not be helpful to post my thanks publicly on here in case he was subsequently inundated with people asking for favours. I’m still not sure it was the correct thing to do! Not only did I get the loan of an engine crane, but also a guided tour of his workshop, an introduction to his friendly dog and an interesting chat.

Thread: Comments??
08/02/2018 19:27:33

She is clearly wearing some ppe. And she doesn’t look like a typical ‘model’, so while the picture may have been posed I don’t get the impression that it isn’t a typical working situation that has been photographed. To me it shows someone unplugging the test leads from some sort of engine test rig, so why would anyone need to worry about the long hair and necklace? There is a bloke in the background with a high viz jacket, so clearly he does a different job. The need for ppe is related to the job being done, which is probably why she isn’t wearing Kevlar chainsawing trousers and a life jacket.

Thread: What did you do Today 2018
05/02/2018 09:32:50

The change to SI units came when I was struggling with thermodynamics and structural engineering at university. It made life so much easier for me. But like Neil, I have struggled with the cross slide on the metric lathe, so I have a little scribble written down on the headstock - 1 div = 0.04, 10 div = 0.4mm - and now life is easy! I don’t know why this particular thing has been a mental block.

On a related note, I watched a Lawrence Krauss video the other day, which demonstrates how convenient it is to work with metric units and exponents to get good approximations - https://youtu.be/h9FurAf4C4g

https://youtu.be/h9FurAf4C4g Sorry, trying to embed a YouTube video on an iPad seems to be an impossible feat for some reason.

Edited By Steve Pavey on 05/02/2018 09:35:47

Thread: Bronze Alloy
30/01/2018 18:34:21

All the bronzes I’ve machined have been fine - some are surprisingly tough, all of them need very sharp cutters but rarely any problems (except sometimes when I’ve ignored my own advice and used a blunt twist drill on a very deep hole). I would say that 316 stainless is tougher to machine than any bronze I have experienced.

To be honest, since most of the machining I have done on marine work has been repairs and modifications to existing components, it is difficult to know exactly what type of bronzes that I’ve dealt with. I think silicone bronze is one of the tougher variants, and is used for machine screws, bolts and other fixings - I have machined lots of that with no problem. Some so-called bronzes are actually brass (copper/zinc alloy) - to be avoided at all costs because of dezincification (there are some exceptions to this, but not many).

30/01/2018 18:06:19

Duplex stainless steels have a different alloy structure,and have better corrosion resistance. Personally, I don’t think this is all that important for a marine application - the difference might be apparent in high temperature applications or with food or brewing equipment, but 316 is perfectly adequate for marine work.

One of the bronze alloys might work as well, maybe silicone bronze for example, but would be more expensive and more difficult to source. 316 is very close to bronze and brass alloys on the electrolytic scale, so electrolytic corrosion is no reason to avoid stainless.

The only real problem with stainless in marine applications is crevice corrosion - caused by a lack of oxygen. It won’t be a problem with something like your rope stripper which is surrounded by a free flow of water. It is sometimes a problem with prop shafts, particularly on the taper where the prop is fitted, and manifests as what appear to be burrows or worm-holes. But even this is not enough to persuade boat builders and engine installers to use anything other than 316 for prop shafts - yes, some older boats have bronze shafts, but I bet 95% of boats have stainless shafts fitted.

Thread: Meddings Driltrue blowing fuse?
30/01/2018 10:45:25

The Meddings Drilltru model shown on the lathes.co.uk site (a 15” capacity with a ½” chuck) has a 1/3hp motor, so in theory draws very little current when running, probably around 1-2 amps. I would have thought a 7 amp fuse would cope with even the starting current of such a small motor.

Since the fuse is blowing, rather than tripping an RCCD, that indicates there isn’t a fault to earth. That leaves either some sort of mechanical fault (seized or sticky bearings for example) or an electrical fault that is not due to earth leakage- faulty windings or a faulty capacitor or maybe a centrifugal switch that isn’t working correctly. Eliminate the mechanical faults by disconnecting the drive belt or removing the motor completely and running it on the bench - if it runs ok then check that the rest of the drive train spins freely. A bench test will also help to check the centrifugal switch (if there is one) as you should be able to hear it click off as the motor spins down to a stop. You could check the resistance of the start and run windings (the last 1 hp motor I checked had resistances of around 100 ohms on both the start and run windings). If you have a multimeter that can measure capacitance that would also be worth checking - they sometimes start to deteriorate and give strange symptoms before finally giving up the ghost.

A 13a fuse may work but if the problem is windings or a capacitor that are starting to fail it may just mask the real problem for a while. At the moment the 7a fuse is the weak link in the chain which is better than the start windings being that weak link.

Thread: Am I doing this correctly?
29/01/2018 17:46:59

It spent last season immersed in salt water - a magnet test is really not necessary

29/01/2018 17:29:38

As an alternative to Tufnol you could consider either acetal or Vesconite. I have made many cutless bearings and rudder bearings from Vesconite and it performs extremely well - a typical Vesconite cutless bearing for a 1”prop shaft will last for at least 5 years. **LINK**

Both acetal and Vesconite have very low moisture absorption and therefore little dimensional change, unlike just about every other engineering plastic.

Agree with what others have said re gauge plate in salt water - won’t last 5 minutes. 316 is ok to machine with low speeds and a decent feed rate, but will work harden if you let the cutter rub. I’m not sure the shape of the teeth are all that important - you could probably mill the overall shape out and then use an angle grinder to cut the teeth. If you make all the parts from 316 make sure that the blade which runs on the bush has a bit of clearance, as otherwise it will gall up and seize solid, which is not at all what you want to happen.

Thread: What to buy at Ikea?
25/01/2018 21:43:13

Another vote for the Helmer drawer units - I have two pop-riveted together as a mobile base for my 6x4 bandsaw. Also the Bekvam step stool **LINK** is dirt cheap and very useful if you store stuff in the roof joists of your workshop, or if you want to sit down at the bench.

I’m sure there are many other small items like waste bins, stainless roasting tins etc that can be used for washing parts in paraffin or for general storage, digital scales for measuring out epoxy resin, soap dispensers for swarfega- the list is endless.

Thread: Best way to do small production run?
25/01/2018 21:21:05

This might be a useful article **LINK**

Current thinking amongst the woodworking tool nuts is that plane irons and similar should be either A2 or O1 tool steel (with a lot of discussion over which is best). From what I can gather O1 is just the AISI designation for silver steel or gauge plate, and A2 is a more sophisticated CrMo alloy (according to my black book). Some suppliers of the more expensive edge tools, like Veritas and Lie Nielsen, specify which of these materials they use for their blades. It may be worth seeing if Clifton Tools are able to supply you with the correct material, or even if they would do a short run for you - the worst they will do is say no! Clifton Planes are manufactured by Thomas Flinn now, as they took the Clifton company over in 2014 **LINK**

Presumably, if you find someone to water jet some blanks for you, the machining and subsequent heat treatment is not a problem?

Edited By Steve Pavey on 25/01/2018 21:23:03

24/01/2018 23:32:51

For casting, a couple of companies spring to mind - for cast iron there is a casting company in Bridport that have some connections with Stuart Models - can’t remember their name but you may already know of them. If you want to have the part cast in bronze then Classic Marine may be able to help as they do small runs of bespoke items.

Thread: London model engineering exhibition
20/01/2018 20:10:35

I went today, first visit to many years. I would have thought that the venue organisers or the stallholders would have dreamt up a way of taking card payments - I think there were only about three of the larger traders that had card machines. I came away early, with my card intact and my shopping list unfulfilled. Sorry traders, but you missed out on my money because you couldn’t be bothered to sort yourselves out.

Edited By Steve Pavey on 20/01/2018 20:11:09

Thread: Stuart steam hammer
17/01/2018 21:04:29

I’ve made a start at long last, so far I’ve machined the base and the piston rod. At the moment I’m making a broach to cut the shaped holes in the cylinder base and the sealing gland necessary for the piston rod. The broach is from EN24T and I’m hoping that it will cut well enough in its as-bought machinable state without hardening - it obviously only has to cut two holes in gun-metal (comments welcome). One thing shown on the drawing is a groove in the piston, but no mention of a piston ring or seal of any sort. Is the groove intended for an O ring or a cast iron piston ring?

Thread: Bonding wood to steel
12/01/2018 23:04:32

One of the Sikaflex polyurethane adhesives would certainly work, but if I was doing it I would use a good quality plywood. For the sort of sizes you mention it will be more than strong enough, a lot easier to make, and in the unlikely event it is damaged it will be a lot easier to repair than a composite steel/wood construction. I would bond it with epoxy, and when finished I would also coat it with unthickened epoxy before painting (using something like West Systems 106 or Gurit SP106).

Thread: Grinding carbide inserts
09/01/2018 17:13:59

in an attempt to get my Banggood face milling cutter to achieve something other than clatter and bang I decided to have a go at grinding the inserts - the problem being that they didn’t all make contact with the work. And it seemed to work - with some trial and error I managed to get all four inserts to more or less touch the workpiece and this resulted in a much smoother cutting action.

I have since had a go with a couple of used lathe tool inserts, also successfully.

Does anyone else reground their inserts?

Thread: Recommendations for a quality milling vice?
31/12/2017 12:21:22

This Old Tony did a review of a Chinese made vice which is far more informative and unbiased than the one linked to above. Stefan Gotteswinter has a video on making his own machine vice, similar to the one Russel has linked to above. Both these YouTube contributors are experienced machinists, so worth watching (and TOT is hilarious!)

I recently bought a 125mm vice from Arc, which is pretty good. I stripped it down and cleaned it, and I also had to do a bit of fettling as it had no datum mark for the angle setting. In hindsight I should have bought a 100 mm version probably, but it’s worked well for all I have used it for so far.

Thread: New year offers
31/12/2017 12:07:14

I’ve just been sent a link from WNT **LINK**

Some useful offers in their downloadable catalogue, such as a countersink bit set, drill bit sets and ER32 collet set. I can’t remember the exact prices, except the countersink set is around £12 and the collet set is £70 reduced from something like £250.

The countersinks are good quality (I bought a set a little while ago, along with several other folks on the mig welding forum). No connection, just thought it might be useful.

Thread: Stuart steam hammer
29/12/2017 12:02:22

Thank you - I had no idea that Stuart would still be producing the castings for this model - my box of castings must be well over 30 years old! On seeing it would cost £11.40 for an A4 sheet I was encouraged to do a bit more searching, and found that I had made a scan of the drawings a couple of years ago which are just about readable. The ME article sounds promising though, and I will probably splash out on a couple of back issues in due course. Given the current price of the castings it will probably be worthwhile so I don’t make a mess of the machining!

28/12/2017 19:56:08

Some time ago I was given a set of castings for the Stuart steam hammer, which I would quite like to make a start on. Unfortunately the drawings have suffered from damp and mice over the many years in storage before it got to me. Does anyone have the drawings or know where I could get them from? Thanks.

Thread: A cantilevered bookcase.
23/12/2017 09:53:16

A timber frame for a heavy door would probably be machined from something like 100x75. In steel box section you could easily halve that and more - so 25x50 for example. It’s the fixings to the masonry that will fail before the frame, followed by the hinges.

I would go for resin anchor fixings - probably 4 or 5 on the hinge stile. I would also support the (presumably timber) bookcase in a steel frame, which is in turn hinged to the main frame. Make up some decent hinges (probably 3 or 4) with 10 or 12mm dia pins rather than just welding on some steel butts from B and Q. And a wheel or non-swivel castor on the latch stile as Baz suggests is a good idea.

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