tkay11

I've seen the recommendations for dusting the mould cavity with powder, but, being totally ignorant, am wondering why the powder would not interfere with the surface of the mould. Is it just absorbed into the liquid as it is poured? And what is the function of the powder? Thanks for any tidbits of illumination! Tony

Thanks, Mark, David and Joe. Mark and David: It's ok, I did understand. I just also thought it useful to reflect, as always, that there are often simpler ways to approach a problem, and that having a lovely toy such as a wood lathe can lead me to lose that search for simple solutions. I have much appreciated this thread of discussion as it really has shown lots of ways to approach the problem. In order to practise working with this kind of detail on the lathe, though, I've already started with the cannon barrels by turning boxwood from an old ruler that I have. You can see the efforts if you want on my log at http://modelshipworld.com/index.php?/topic/335-hmc-sherbourne-by-tkay11-–-caldercraft-–-scale-164-1763-a-novice’s-caldercraft-sherbourne/?p=173630. It's headed 'Wheels/Trucks', but the barrels come at the bottom of the post. I will also be trying with files when the 4mm brass rod arrives. Joe: Your thoughts about balsa and basswood are really ingenious and useful. So now I have heard of perspex, balsa, basswood, ebony, brass and boxwood as substrate for the barrels, and I might well try each one of them just to learn. My next stage is to learn to make molds and replicate. This is all enormous fun. Thanks again, guys! Tony

Many thanks, Jay, Bugra, B.E., Gregor and Geoff for the lovely comments and the 'likes'. As you all know from your own experience, such appreciation contributes enormously to the motivation -- as well as tickling that eensy bit of pride in achievement. However, more than that, it also serves to remind me of your own contributions to my learning from the builds of you and others in this forum. Tony

Very impressive, Mark! That makes me feel very lazy indeed. Tony

Thanks, Dirk. You'll just have to keep on being one of my inspirations for me to continue making these efforts. Tony

Wheels/Trucks I haven’t been satisfied with the gun carriages I made, so I set about thinking how to do them more accurately. First off was the problem of how to make wheels. Making the rods that were to become the wheels was fairly straightforward. I used a tip from Hubert Sicard’s site ‘Wooden Ship Modeling for Dummies’ at http://www.shipmodeling.ca/, where he suggested using an adjustable spanner with wet&dry paper glued to its faces. That gives a rod of the diameter you want. You can see how this is done in the picture below. I used a stick of pear wood cut from a pen blank (you can buy these cheaply at eBay). But how to drill the holes for the axles? For a long time I couldn’t think how to drill holes in the centre of the wheels to take the axles. However, once I had the wood lathe in place, I thought it would be simple to shape a rod and then drill a hole in the end using a Jacob’s chuck. At first my attempts at centring the hole were not good – until I found that I could put some shims into the tailstock end. You can see the details in my posting at http://modelshipworld.com/index.php?/topic/2765-proxxon-mini-lathe-db-250-opinionsassessmentsrecommendations/?p=154323. With that sorted, I found I could drill the holes quite centrally, but found three further problems: 1. Because of the length of the drill bit, I could only drill a hole to its depth, which was the equivalent of about 5 or 6 wheels. That meant I had to drill the hole each time again after cutting off 5-6 wheels. 2. I also found that despite a good initial centre, the drill had a slight tendency to go off centre the deeper it went. It was slightly reassuring to read in Frolich’s book ‘The Art of Ship Modelling’ that even he had the same problem with his Unimat lathe when making his wheels. 3. My skill with the adjustable spanner probably not being perfect, I could not make perfectly circular rods. I found that there could be up to 0.2mm discrepancy in the diameters. Whilst thinking about these problems, I made a simple jig for my saw to cut the wheels to 1mm thickness, as you can see in the following photos. The spacer block is there to act as a stop. Once the wheels are cut from the rod, they go back on to the drill bit to be filed of any burr. You might think I was satisfied with this result, but because of the three problems listed earlier, I thought I’d have a bash at other ways of achieving perfectly circular trucks with perfectly centred holes for the axles. My solution was to use concentric brass tubing. Starting with the central hole, it was important to have exactly the right diameter. So I took a 2mm diameter rod and, using the wood lathe again, widened its 1mm internal diameter to 1.2mm for the axles. This is to allow for the same drill bit to be pushed into the central tube once the jig has been made. I then added the higher diameter tubes. One thing I noticed was that the tubes had a wall thickness of 0.45mm, thus leaving a 0.1mm gap to the next tube. I reckoned that if I were to put a layer of PVA glue round the tubes that would spread evenly and fill the gap. It seemed to work. Finally the inner tubes were filed smooth at the ends, ready for the outer tube to be slid over to hold the wheel. Clearly this method will only really work for wheel diameters that increase in 0.5mm amounts since the tubing can only provide 0.5mm steps. I had chosen to have wheels at 4 and 4.5mm diameters, so that worked for me. In reality, there was not much difference between the two methods (drilling with the lathe versus drilling through a jig made of concentric brass tubes). The brass tube method allowed for consistency and speed, although its limitation is that of the 0.5mm steps. It also means I am left with a jig that will work for future wheels of the same size. The lathe method works fine too, but takes longer and is more fiddly. The gun carriages Having sorted out the wheels/trucks, the next stage was the carriages. I decided I’d use my modified Proxxon stand, [which you can see at http://modelshipworld.com/index.php?/topic/4539-how-to-modify-proxxon-mb-140-drill-stand-to-act-as-mill/?p=130660, together with the x-y table] to mill a block from which the carriage sides would be cut. This method is the one used by Frolich, along with countless other modellers on this forum and elsewhere. The second iteration of the carriages had been based on CAD drawings I had made of the carriages scaled down to 3 pounder carriages. This proved awkward, because the barrels provided by the kit are in effect 3.5 pounders, but I thought that few would notice their over-size if I placed them in 3 pounder carriages. This time round, for the third iteration, I thought that in order to make everything match up, and because I couldn’t imagine making barrels myself, then the carriages ought to be 3.5 pounder carriages as well. So I rescaled the drawings to make 3.5 pounders. As before, I cut pear wood to size with my table saw and used CAD drawings glued to the wood sheets to cut out the beds, quoins, axles and bolsters. The handles for the quoins were made from rods of pear that were passed through a drawplate. The next stage was to prepare a jig on which to assemble the carriages. I had seen several jigs made of wood, but I was lazy and decided to use double-sided sticky tape. It’s transparent, so can be laid over a print out of the CAD drawing. With this, it was easy to hold the two axles in place in order to put the sides on to them. It should be noted that the transverse bolt was used to link the two sides before placing on the jig. This helped in accurate placement. You’ll also note that I have drilled holes for all the bolts that will be going into the carriages. Before painting, they will have brass wire placed in them to make sure I can find them again after painting! The gun barrels Having done all this, I once again looked at complete guns with carriages and thought that the barrels looked distinctly ropey. But I couldn’t make the barrels myself. Or could I? I decided to give it a bash with the Proxxon wood lathe. I first tried with some of the same pear wood I had used for the carriages. This didn’t turn out too well as the wood just looked too grainy (probably my ineptitude, and I hadn’t thought of using filler), but it gave me the courage to try again. I thought I’d investigate how to make them in brass, and so posted a question on the forum (you can see the discussion at http://modelshipworld.com/index.php?/topic/5975-using-chisels-for-turning-brass/). It turned out that I didn’t really have the right tools to do this, so I thought I’d have a go with boxwood. I still have plenty of the wood from the boxwood ruler I had bought on eBay to make the gratings, and lo and behold the thickness was 4.5mm – just the right size to make 3.9mm barrels with. The barrel rings were left over-sized until the last. This allowed me to use them as markers for the different barrel diameters as they decreased. At the same time I made constant reference to the CAD drawing held by forceps (shown in the picture). This was all quite interesting as, until I had actually made the new barrel at the proper size for a 3pdr, I had thought that the difference in size with that of the kit would not be really noticeable. In fact the difference is size is very noticeable. I can now see that should I make all the cannon at this size, they would fit the gunports perfectly. The barrel hasn’t turned out as beautifully as those made by other modellers, but I now have the courage to improve the skill. Although I had thought making barrels would be incredibly difficult, in fact it just required patience and care, shaving very small amounts off at a time with the turning chisels. The Proxxon turning chisels proved to be wonderful, and I now understand why boxwood is so admired for this kind of thing – it allows for very precise cutting indeed. The big decision now is whether to make a THIRD set of carriages to fit the new barrel, and therefore to make a complete set of barrels. I am still thinking on that one! I have just ordered some ebony at the suggestion made by Nigel in the discussion referred to above about cutting brass and will try turning a cannon in that wood before I make any final decision. Oh, decisions, decisions! But all this experimenting with techniques is definitely going to put me in good stead for future builds. Spending time on getting techniques right at this stage is, in my view, a very good investment for the future. Tony

We probably need to start another thread to document such lovely stories. Thanks for the info about grinding, Per. I'm just writing up my log to document my experience with rebuilding the cannon carriages and making the barrels. Tony

Thanks, Per. The Clerkenwell story reminds me of some local car mechanics I once knew at Lake Manyara in Tanzania. The road by them was often flooded (if you know the area the river was Mto wa Mbu, or Mosquito River), and cars regularly died as a result of foolish attempts at getting through -- sucking water into the engine. They could dismantle a car and knock a crankshaft back to straight using hammers and iron blocks, checking alignment by eye. I use the Scary Sharp method for my wood chisels, but I have been a bit hesitant after reading about the variety of angles needed for graver bits. I'd probably need to practise quite a lot. At the moment I've been turning some boxwood and have been very impressed with the result (not with my technique or the appearance, more the beauty of the wood and the way a sharp blade can be used so accurately for fine detail with this wood). So once I've learnt the skills with the wood lathe, I'll definitely consider moving to brass, using proper gravers and sharpening by hand. Thanks again for the input. By the way, I didn't understand your commment "there is really very little steel to remove afterwards to get the right shape". Is that a good or a bad thing? What is the implication? Tony

Yes, thanks, Walt. I was in fact grateful for your explanation about the different needs in tooling and should have made that clear. Before, I had just known that they were different -- you provided the very helpful explanation. And you're right. I'm doing the best I can to know as many of the ins and outs as possible to any new skill before I try it out. Tony

Thanks very much, Per. Very useful. Just out of interest, and sorry for what must seem endless questions, what do you use to keep the graver dead sharp? Tony

Thanks very much, Walt, Brian and David. I had understood that metal turning was quite different, but had been interested by the video of the guy turning brass by hand. So I wanted to find out more about that and the tools required. As usual with this modelling business, the moment I start looking at a new question I find there's a whole new world of experience, expertise and tooling. So I now hear about gravers, length of gravers, lathe speeds, grinding, grinding tools, use of files, sharpening methods (by hand or with tools), heels, faces, dangers, and a variety of possibilities in addition to some fascinating stuff about the world of engravers. All wonderful. What I can see is that there is plenty of room for experimentation with suitable cautions. Just a couple more questions (for the moment!). Brian (or anyone), could you let me know what 'slow' speed you use that is suitable for turning brass with a graver (in rpm)? It sounds like 200-500rpm would be good. Is that right? And what kind of gravers do you use? I have seen some hand gravers on eBay (see http://www.ebay.co.uk/itm/291056537288?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT) but suspect that the handles are too short and are designed not for turning but for engraving sheet metal. Would that be right? Thanks so much for all the help I have had so far in answering what must have seemed to you pros a daft question! Tony

Thanks, David. That's reassuring to know. I've ordered some 4mm brass rod that I can experiment with, alongside the ebony and boxwood that I've ordered. I have some very nice needle files (Klein, Swiss style). Tony

Those are interesting and nice ideas, Mark. I've already been using files with the wood, but hadn't thought of using them exclusively. I'll look into grinding stones and mandrels, but if the files work, then so much the better. In fact I have very small grinding wheels with my Proxxon drill which I used for tiny chisels (until I found the Scary Sharp method), but I should imagine they are far too small and underpowered for gravers. Thank you very much! Tony

Thanks for the tips, Trailguy. Yes, pen turning blanks are useful -- I've been using pear and apple blanks from eBay to learn how to work with these woods. I hadn't known about Volcanic Ash Black Lava, so I'll have a look for suppliers here in the UK. I like the idea about the polish. Tony

Yes, indeed, David. Good advice re practice and safety. I've been using mask and safety glasses, and I'll continue the carefulness once I get to metal. Thanks Tony

Thanks, David. Takes a bit of the mystery out of grinding the tools. I'd seen exactly that second video about turning a cannon and that was what gave me the idea to try it on my lathe. Do you have any idea of the speed he was using on the lathe? It seemed quite fast to me. I was also thinking that the hand-held watchmakers gravers I've seen on eBay might be already sharpened and so give me an idea of how to use them. Would that be right? Tony

Makes sense, Jud. Thanks. I suppose you'd need long arms as well. My arms are only about 60cm long and I need to keep my eyes fairly near the workpiece to make sure i can see what's happening down there. But I suppose the hands wouldn't have to go all the way to the end of the handle. Joking aside, I get the message. Mechanical advantage and control! Tony

Yes, thanks, David. The Sherline sounds like a great machine from all that I have heard on the forum. I had been thinking of casting them once I'd managed to make a good master (even though there are only 8 on the Sherbourne). That's yet another on the long list of skills I am eager to learn. Tony

Very interesting comment, Jud. I note that watchmakers lathes can be powered in a number of different ways -- which would allow for the very slow turning speeds. My Proxxon turns at 1,000 rpm at its slowest speed, so that looks as though it would be far too fast. As a matter of interest, why the long handles (3ft)? Tony

Thanks for the advice and suggestions, David and Nigel. I've ordered ebony along with the boxwood and will be interested to see how it all turns out. I'll keep the ideas about brass turning until a future date when I can treat myself to a bench grinder. In any case, it's always good to improve basic skills at the wood lathe to the point at which I can be satisfied with the skill. Tony

Hmm. Thanks, Nigel. I've been looking at Workshop Heaven for the boxwood. I've also been thinking of Castello Boxwood. I hadn't considered ebony, but it's another good idea for me to consider. Isn't ebony dust rather poisonous? Or am I being over-cautious? I could easily order boxwood and ebony to see how I got on with them. Tony

Thanks, David. They look like the tools suggested at the Sherline site for making by hand. Do you use a bench grinder to sharpen them, or do you use something like Wet & Dry paper glued to a smooth surface (as in the Scary Sharp method)? Tony

Thanks, Bill. That's a good idea about the paste filler. and primer. I think I'll do that. After a bit of web searching, I found a nice link on the Sherline site about making and using watchmaker's gravers. It's at http://www.sherline.com/gravers.htm. It links to a page that shows how to use the Sherline T-rest with a graver. Unfortunately, though, it looks as though the business of buying a bench grinder and a stone to do all the sharpening and shaping required seems to put this idea out of my reach. I think I'll be sticking to the boxwood. Tony

Thanks, David. I'd be very interested in the photos if you can get round to it once you're back in Chicago. I had a feeling that I'd have to end up grinding my own, so if you have any links on how to do that I'd be grateful. I found that even with the wood very light cuts give the best results -- and it was so satisfying I am rather hooked on the idea of doing more lathe work. (I had bought the lathe mainly for yards and masts, but was delighted to find I could do quite fine work on it). Tony

Ok, Antony. I think I'll keep my head. Nice idea about the gilding, though. I had seen it, and that was what made me think of the boxwood. My guns are going to be black, so a coat of paint is all I really need. My problem was with the pear wood that I had -- the finish was just too grainy. It's possible that the wood I am using is not quite the right type of pear wood (it was from pen turning blanks sold on eBay), so that's why I'm looking around. Of course it's equally possible that it's my technique that is at fault. I've seen a video of someone using a watchmaker's lathe with a graving tool to turn cannon from brass, so that's what gave me the idea of using my own lathe. I presume it's just the type of cutter that's important -- rather than the lathe itself. But I'm all ears to any advice! Thanks for the very prompt reply! Tony