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lehmann

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About lehmann

  • Birthday 07/21/1960

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    Surrey, BC, Canada
  • Interests
    USS Constitution: Scratch build solid hull 1:96 scale

    Member Nautical Research Society

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  1. In doing your tests, be aware that the blade may flex when you push against it during your measurements. If you want to verify this, put a dial indicator on the back side of the blade. Also, the fence will flex a little as well as it may not always register square each time. When you're trying to work in the range of 0.001" you need to watch for these things even when using large metal working machines. I do some work at 0.0001" and have to be hyper vigilant. If you want to just test the accuracy of the IGaging system, I suggest zeroing on a block of wood clamped solidly to the table right next to the rail that the fence runs on. I seriously doubt the iGaging system itself is not going to be repeatable within 0.001" as it's basically the same technology as your digital calipers. The 0.004" accuracy is probably over the length of the travel.
  2. The main concern here is whether the fence is parallel to the saw. If the back of the saw is closer to the fence than the front, then the saw will be pushed sideways, That's the only way I can imagine getting 0.090" thicker.
  3. I'll send you to the Wood Handbook. Wood Handbook CH 4 - Effect of Moisture See page 4.5 Figure 4.3 shows how wood from various places in the tree shrinks and warps Tangential - parallel to the grain rings Radial - 90 degrees to the grain rings or in a line from the center of the tree Flat grain (or flat sawn) - the grain rings are somewhat parallel the wide side of the board Edge grain - the grain rings are parallel to the narrow side of the board Another term you'll see for edge grain is quarter-sawn. I hope that helps
  4. Drazen, By the pictures of the deck planks it looks like you used flat grain boards (maple). The effect of moisture on wood shrinkage/expansion in the tangential direction is about twice that of the radial direction. In other words, edge grain boards will move only half as much. That is why wood floors and wide door sills are usually edge grain (that, and the wear resistance is higher). A few numbers: Relative humidity Equilibrium Moisture content 20% 5% 70% 13% Difference 8% Flat grain maple shrinks 11 % from green (28% to oven-dry (0%). So, your flat grain planks, over a width of 250 mm will want to shrink (250 mm) x (11%) x(8%)/(28%) = 7.9 mm The shrinkage for edge grain maple is only about 4.5%, which results in a width change of 3.2 mm. Either, way, since the plywood bulkheads/frames will have negligible shrinkage, a lot of stress will be generated. In looking at the shrinkage data for various species, I can see why pine was often used for decking. While is is much softer than oak, the edge grain shrinkage is Eastern White Pine (North America) is only 2.1%. As is teak, at the other end of the price scale. My second point, is that the cracks in the picture seem to be near transitions in how the deck is supported. In other words, near openings. The deck parallel to an opening can shrink with little constraint, but the deck at the ends of the opening is probably attached to a bulkhead and can not move. The difference in constraint creates the stresses and cracks you are seeing. I also suspect that since maple is so strong it does not crush like a softer wood, which would have relieved the stresses before a crack formed. So how to fix, or avoid in other large models? Edge grain decking is an obvious must do. Use a wood with a low radial shrinkage. Avoid gluing the edges of the boards together so that the shrinkage can occur at each join rather than finding one place to fail. Either no glue, or a glue that never hardens, so that it acts like tar - fills the gap, but does not restrain movement. Many narrow planks means the gaps that appear will be smaller, assuming the gaps are uniformly distribute across the width of the deck. Install the boards when they are bone dry (dry in an oven, or a small box with a light bulb inside (not LED light!)). That way, even at 20% humidity, the boards will swell. Full size ships rely on the planking swelling when the ship is put in the water to achieve water tight seams. However, I would firmly attach the water channels to ensure that railings are not pushed out when the deck expands. Last thought: I wonder if Admiralty models at 1:48 scale are often left half planked to avoid these issues.
  5. From what I can see they are still available from several sources. These are a few that I found quite quickly. https://mdiwoodcarvers.com/t/dockyard-micro-tools https://www.treelineusa.com/micro-gouge-carving-set.html http://www.chippingaway.com/cat/hand-woodcarving-tools-accessories/dockyard-micro-carving-tools/
  6. I have a set of micro-chisels made by DockYard tools that were, but no longer, sold by Lee Valley. However, I see that they are available from other suppliers. These are the smallest chisels and knives I have seen as the blanks are more of a wire than a bar or rod. Definitely, not tools for roughing. However, the steel is good in that I can get a razor edge on them. I also have a set of small chisels that Lee Valley sells (part 81D40.01 ). I thought they would be just good for scraping, but the steel is remarkably good so I got very sharp edges. The set included two fish-tails, which are difficult to find in such a small size. I've made a few small knives/chisels from broken (or sacrificed) drill bits. This is probably the cheapest source of tool steel available.
  7. Max, The answer, somewhat, depends on the species. If there is a marked difference between the early and late wood, then I would make edge grain planks, especially if they are to be bent. My reasoning is that if cut flat grain, assuming that the grain is not exactly parallel to the plank, the bending stiffness will vary along the length of the plank, resulting in kinks and flat spots in the hull, which will be very frustrating if the frames or bulkhead are far apart. There is also more chance of the plank splitting or "blowing out" as it is bent. I believe this in one of the reasons why woods with very fine grain or, as I call it, grain-less, are best for modelling. My other argument for edge grain is there is less shrinkage in the direction 90 degrees to the grain, so there is less shrinkage in the width of edge grain planks. As a result, there is less chance the gaps between planks will open up if the hull dries out. There is an argument for rift sawn boards (see woodenboat.com - Quartersawn discussion) in that it has most of the stability of edge grain, but is less likely to split if fasteners are used. However, this should only be a consideration when working at larger scales (1:48) where the planks are wide enough and it is possible to realistically reproduce plank fastening. My last comment: as a test take two slices off your 2x4 - one for edge grain and one for flat - and see which you like for you application. You don't need to commit the whole piece yet, and you'll eventually find a use for the "other" piece, so it won't be wasted.
  8. The medical community used to think that electro-shock and lobotomies were therapeutic. Each to their own...
  9. Generally, plane on bulkhead hulls are double planked for the reasons you give. With the bulkheads so far apart it is easy to get flat areas, especially if some planks stop at a bulkhead. The idea of double planking is to sand and fill the first layer so that it will provide a solid and fair foundation for the second layer. It also gives you an opportunity to hone you planking skills and discover potential planking difficulties for that hull, such as a need for stealers or a difficult garboard, before attempting the second layer.
  10. Here's where they ripped off the images of the real product: https://snapmaker.com/ Price is $799. I think this machine will do what it's claimed to do, but it's not rigid enough for anything beyond engraving or light duty milling of wood and plastic. Don't expect it to mill metals. The one advantage of this machine over other 3 in 1's is it appears that the printer, laser and engraver heads are easily changed. For other machines I've seen I get the impression that the change-over requires tools and a bit of re-wiring, which may deter some buyers.
  11. This principle of this knife is the "slicing effect". The most common example is cutting a tomato - if you push the knife straight in, it won't cut, but if you add a movement to the knife 90 degrees to the direction you want to go (add a slicing action), then the cutting forces are greatly reduced. The amount that the forces are reduced depends on the speed of the slicing movement relative to the pushing speed. The faster the knife moves, the lower the forces. The effect has nothing to do with the material properties, it's just geometry in that the slicing movement reduces the sharpness angle of the knife, as seen by the material being cut. There is a limit to how much the slicing speed will reduce the forces because there is friction and for an oscillating knife, which has to stop at both ends of the stroke so the full forces are needed to push the knife forward. The quoted 40,000 rpm is probably way more than needed. If you want to try a home-made version, attach a knife to the working end of a beard trimmer, electric hair clipper or an electric engraver. I suspect one of the main design problems with the Wonder-cutter is balancing it to avoid the fingers going numb and to provide better control. I've made a bigger version using a sharpened scraper on an oscillating multi-tool (Fein, for example). I was able to slice off 1/8 inch thick pieces with a roughly 80% reduction in cutting force.
  12. Does it look like this? https://en.wikipedia.org/wiki/File:Old_Northern_Rd_convict_workgang_carving.jpg. A bit of a discussion on this at https://en.wikipedia.org/wiki/Broad_arrow: scroll down to "Australia". On the page https://en.wikipedia.org/wiki/Benchmark_(surveying) there is this comment: The terms "height" and "elevation" are often used interchangeably, but in many jurisdictions they have specific meanings; "height" commonly refers to a local or relative difference in the vertical (such as the height of a building), whereas "elevation" refers to the difference from a nominated reference surface (such as sea-level.... So, the numbers may refer to some other elevation benchmark, not sea level. As another option: At: https://en.wikipedia.org/wiki/Survey_marker Geodetic survey markers were often set in groups. For example, in triangulation surveys, the primary point identified was called the triangulation station, or the "main station". It was often marked by a "station disk" (see upper photo at left), a brass disk with a triangle inscribed on its surface and an impressed mark that indicated the precise point over which a surveyor's plumb-bob should be dropped to assure a precise location over it. A triangulation station was often surrounded by several (usually three) reference marks (see second photo at left),[5] each of which bore an arrow that pointed back towards the main station. These reference marks made it easier for later visitors to "recover" (or re-find) the primary ("station") mark. Reference marks also made it possible to replace (or reset) a station mark that had been disturbed or destroyed.
  13. The above advice to use professional drafting compasses is the best option. Best compass I own: Made my living with it many years back and still use it. Made by Staedtler, but I don't see anything similar on their web page. A few on eBay though. The double start thread allows fast adjustments by just pulling on the arms, but the thread is fine enough for accurate setting. The ferule on the nut jams it tight, stopping any movement.
  14. These heat benders are nothing more than a standard 30 or 40 watt soldering iron with the tip cut off and a brass disk pressed on to the end. Actually, the soldering tip could be left on. Very simple to make and even simpler if the the soldering iron can hold different tips, as with the Weller models. I also have a wood burning iron that takes different screw-on tips: it wouldn't be difficult to make a large tip.
  15. Just for interest, on a scaled basis: $0.20 fitting at 1:96 scale -> 1:1 price would be $0.20 x 96 x 96 x 96 = $177,000.

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