today's work

David

Amazing information in your photos.....
What is the black oil paint used for?

Peace,
Tom

salmon wrote:Amazing information in your photos.....
What is the black oil paint used for?

Peace,
Tom

To insure symmetry of channel form to each flange face of a rubber tool.

The sprue, riser, and vent channeling -- required to provide a path for both resin and displaced air -- is cut into one half of the RTV rubber tool. Then, to insure I get an impression of that channel geometry to the other half of the tool, I coat the edges of the channels with artist oil paint (very slow drying). I then temporarily press the two tool halves together and that imprints the other tool half. I pull the tool halves apart, and follow the paint outlines to cut the channeling into the second tool half.

Maybe this picture will better illustrate for you, Tom:



David

I learned something new.....thank you David!

SCRIBING   This is the process of scraping (abrading) engraved, often narrow, depressions into the work. Most suited to representing seams between plates in close proximity to each other, such as access panels, hatch or door outlines, safety-track, missile hatches, even cheat-lines (waterlines, centerlines, datum lines, etc.), and breaks between fixed structure and control surfaces. In sheet-metal work scribing lines onto the sheet (blued to highlight the shiny engraved line) is a part of the layout process.

Here I’m using commercially available, stainless steel and plastic sheet engraving stencils to guide my scribe along as I represent hand-holds and access panels on the sides and top of this submarine sail master.



I used to make my scribing tool by simply taking a rat-tail jeweler’s file and grinding its tip to the appropriately shaped point – a sharp tip for a starting tool, a blunt tip for a finishing tool. Today I make a scribe by starting with a blank, a rod of 1/16” diameter carbon steel (tool steel in some circles). This tough, brittle metal will dull slowly, keeping its shape and point longer than softer metals. An important consideration as some of the work involves dragging the tool through fiberglass laminate – and silica glass is a very tough customer.

I secure a length of the rod into the chuck of a mini-lath and turn it. While spinning I grind in the working end of the scribe with a Carbide cut-off wheel. I keep grinding till I’m within a few thousandths of the desired tip diameter and then finish the job with files and wet-stone.



Typical tip diameter of a scribe is .010-.015 inch. The shank is CA’ed to a handle and I’m good to go. It’s good practice to file, sand, and wet-stone and polish the sides near the tip to minimize ware on the stencil used to guide the scribe during the engraving operation.



Typically I’ll engrave using two types of scribing tools: the first passes are made with a pointed tip, this tool does the cutting to approximate depth. The finishing passes are done with a blunted tip, this tool only refining the sides of the engraved line. In some situations the finishing scribe will be outfitted with the depth-collar to insure uniform depth of cut.



Scribing stencils take many forms and materials. Most flat, but some stencils are made to adopt the compound curves of complex surfaces. Example here is the top of this sail; the plastic stencil blank was heat-formed over the master to assume the gentile compound curve, then appropriate opening were cut into the stencil, those holes would guide the scribing tool as I engraved in the periscope and mast outlines onto the sail.

I also acid-etch metal stencils for specific, unique scribing jobs. You see one to the extreme left.
And I never toss a stencil once a job is done – often an old stencil will find use on a future job. I’ve amazed quite a collection of stencils over the years. These stencils fabricated from acid-etched plate, heat formed plastic, sheet metal, to GRP glove-fit types.



For extreme compound curves, such as the bow of this 1/96 ALFA model, I’ll lay up a fiberglass stencil blank to make a glove fit, and cut out the engraving holes as required; then use that stencil to engrave the lines required. Here you see the elongated ovals representing the torpedo tube shutter doors.

To insure a no-slip matting of the stencil to the bow I drilled and taped holes into the model itself, and secured the stencil with little 2-56 machine screws. No way no matter how much pressure I applied to the edges of the holes within the stencil would that stencil shift out of place! Once the job was finished it was an easy task to fill and fair over those holes.



It’s good practice to first use a pencil, instead of the scribe, for the initial ‘check’ pass on the work. At this stage if you get the position wrong, or have chosen the wrong hole in the stencil, then no harm and no foul –you erase the pencil mark and try again. After validation of position and outline with pencil the process moves on to the engraving tools.

Many of the scribing stencils I employ are outfitted with pieces of sandpaper where they make contact with the models surface. This assures a no-slip tool when just using hand pressure to hold it in place as I maneuver the scribing tool with the other hand.

The scribe without the brass collar is sharp at the tip and makes the initial cuts. The ‘finishing scribe’, with the brass collar, is used to make the final passes and has a blunted tip – the adjustable collar insures a constant depth-of-cut.



A unique scribing tool is this two-point engraver, used to represent a submarines safety-track that runs the length of the deck.

Aluminum stencils are used to guide the scribing tool over the hull of this model. As considerable lateral pressure would be applied to the edge of the stencil I insured it against movement by literally bolting it to the model with machine screws. The two-point scribing tool is seen above two of these stencils along with the screws used to secure the stencils in place.



With the aluminum stencil bolted down tight I used a two-point scribing tool to engrave the two perfectly parallel lines that represent the safety-track atop the hull of this r/c submarine model. The long curved shank of the tool permitted me to rotate the head of the tool with great precision as I twisted it to conform to the curves of the stencil – failure to do so would produce lines of varying distance from one another.

After the engraving job was done the stencil was removed and the bolt holes filled and faired.



Another ‘special’ scribing tool used to under-cut an installed length of square section styrene rod to change its section to that of a ‘T’ is shown here. Careful grinding of a #11 X-Acto blade produced this tool.


What was once square in section is now T in section. This feat of magic accomplished by scribing the two sides of the square rod.



A similar scribing tool at work forming the safety track on another submarine model.



Once the engraved lines were cut into the models surface its good practice to free-hand the scribe within the established engraved lines in order to refine the shape, depth, and to correct errors like over-strikes, and tool marks. Inevitably, such localized repairs with filler or putty result in the goo getting into the engraved lines, which have to be re-established with the scribe to chase it out before the filler or putty dries/cures hard.

You see such tool-marks, datum lines, and over-strikes on the surface of this model. They will be filled with putty and the scribe then used to remove the putty from the previously engraved lines.



Sometimes I will augment the scribing operation with a low-torque drill and small bits. In this case I first pressed oblique holes into the body of this torpedo master and refined them with the shank end of a small drill bit. Note the brass tube used as a spacing-drilling jig.



The more exotic engraving tools are these punches/circle engravers. These tools are formed from brass tube with the working end sharpened. I serrate the ‘blade’ of the tube to give it the ability to function as a hand-held radial saw: I press the tool into the work and rotate it a few degrees, press hard again, and rotate, periodically removing the tool to determine the depth of the circle cut into the model. As you see, there are all sorts of diameters and metals used to fabricate this type tool.



However, for the larger circles that have to girdle a cylindrical body like this, it’s back to the stencil. Note how this thin stainless steel stencil easily bends to conform to the circumference of the torpedo body. The sandpaper I glued to the stencil serving me well here by preventing it slipping over the work as I press the scribing point tightly against the inside surfaces of the hole used to guide the tool.



BLADES   By blades I also include the sub-set of ‘cutting’ tool, the saw. The blade, or knife, is a cutting edge so shape that it forces the molecules that comprise a substance to break their bonds and to fracture along the draw of the blade. The knife induces a localized failure of the substrate. The blade leaves little kerf – material lost to the cutting process – but cannot be plunged too deeply into the work without encountering great resistance. However, the blade, pulled spanwise along the work will scrape material away and in this way works as an ablator.

A saw, on the other hand, imparts many localized impact fractures (the teeth of the saw blade, each working as a gouge) causing localized failure of the substrate, little bits of which are thrown clear of the saw blade. A saw, unlike the blade, oblates the substrate. And in so doing produces a substantial kerf -- material lost to the thickness of the sawing blade. One has to account for this lost material during the layout process. Unlike a knife blade, a saw blade has the ability to dig deep into the work without experiencing an increase of resistance. Unlike the knife blade, the saw blade, because of the wide channel it cuts, relieves binding stress between the work and the saw blade.

OK. Below are typical commercially available X-Acto knife blades – these are representative of the bigger handle and blade types they offer.

And here are modified X-Acto-blades, each to serve a specific purpose. They were ground and sometimes bent to suit the job at hand. Apparent here are the two sizes of handles and blades X-Acto offers. To the extreme right is their ‘swivel’ knife -- great for following tight radius stencils or free-handing some types of camouflage masks. These high carbon steel blades are easily bent once taken to a red-heat – once shaping is completed the blade is taken back to a red-heat and quickly quenched in water to restore its hardness.

Here we see tools that work to saw, scribe, and cut the work. At the top is a simple hack saw blade; beneath it a knife; second from the bottom a razor saw blade set into a heavy brass handle for some ‘special’ work; and at the bottom a scribing tool.

The four tools used to cut away the superstructure portion of this kits polystyrene hull. First, I scribe the separation line; then followed that engraved line with the knife to deepen the cut; followed by use of the razor saw which is steerable to large radius curves (those curves seen atop the bow of the model); and, finally, the hack saw to finish the job.

Why the heavy brass handle on the razor saw? To ‘tune’ the tool to the job, that’s why. If you can get a cutting tool to resonate just right you will increase its cutting action substantially. Play with a tools shank or handle length and weight and, if you’re lucky, you’ll achieve this little slice of model-builders nirvana. More art than science.



These circular cutting tools are of the gouging type and are ideal for cutting concave trenches in the work. They are used to form the concave nesting trench within the trailing edge of a stabilizer that accepts the rounded leading edge of its rotating control surface. These tools are quickly made from brass tube. Note the sheet brass ‘handle’ soldered to the tool – to make pushing and guiding the circular cutting tool a relatively easy task.



Special cutting tools, here several types of ‘gouges’ have been ground to shape using standard X-Acto blades as blanks. Each of these tools serves a specific job on these little louvers I’m cutting into the trailing edge of this submarine sail master.
The right tool for the right job!



Initial shaping of the blade is done on the bench mounted grinding wheel. Final shaping is done with a hand held Carbide cut-off wheel spun in the chuck of a Dremel moto-tool. The blade is brought to razor sharpness with a wet-stone.

I've completed most of the grunt-work on the masters of a motor bulkhead that will mount a brushless propulsion motor for one of our SubDriver r/c submarine systems. I use the raw masters to check fit and operation in mock-up form. Once everything is working as planned (best laid plans … and all that happy horse-shit), I refine the finish of the masters and turn them into rubber tooling from which production items will be cast.



















David

This version of the motor-bulkhead puts the motor in the water. Suspended aft of the motor is a gear splitter which outputs two counter-rotation shafts from the single motor input. This is still in the mock-up stage where I check fit and non-interference of the parts. I have yet to add the radial flange.

I'm just about ready to use these Modular SubDriver bulkhead masters to give form to the rubber tools from which cast resin production parts will be produced. Some last-minute machining, putty work, wet-sanding, primer, and things are now good to go. Fine with me, I'm sick of this grunt work, I want to get back to proper model-building, damnit! I use them to mock-up a practical demonstrator -- this is the stage where you want to find faults, not after you've committed to production tooling!









Last item on the MSD work list is this forward bulkhead used to give access to the forward dry space where the battery is stored. We wanted to provide the option of outfitting this bulkhead with two servos -- some customers would rather take the direct route with their linkages rather than run a long pushrod forward from the motor bulkhead mounted servos. Typical items needing r/c activation at the bow include bow plane, bow plane retract/deploy, anchor, and torpedo launching.

We’re familiar with the trick of bending a straight piece of plastic or soft metal rod, be it square, hexagonal, or other cross-section shape. You just pinch the rod between thumb and forefinger, and pull through with the other hand at an angle and so doing impart a constant radius curve to the rod; the more radical the angle, the tighter the radius. I wanted to fatten the flange on one of the masters and required a ‘circle’ of styrene strip that would be bonded to the existing flange.

To keep the wide strip from twisting away from the desired curl I pulled it through a circular channel cut into a big wooden dowel. Three passes of the plastic strip and I had the circle required, which was then super glued to the flange, building it up to the desired thickness.

Clamps held the circular piece of strip to the flange as I applied the glue. As the added strip was a bit bigger in diameter than needed, I trimmed it back on the lathe.









I spent the afternoon getting the modular SubDriver bulkheads, and gear-splitter masters ready for tool making. Some putty work, sanding, and setting each master in a clay backing.





The clay creating the separation plane between the eventual two halves of the rubber tool used to make the cast resin parts. The face of the masking clay dimpled to form a network of registration keys in the rubber that would insure proper alignment of the tool halves. Containments (flasks) of Lexan cylinder and masking tape would hold the catalyzed rubber as it cured from liquid to solid.

The last half of the two-part tools poured and cured, the masters were removed and placed into safe storage for possible future use. I then cut out the sprue and riser cavities, and the tools were ready for use.

My client directed me to denote this new product with a proprietary color (or, if you will, no color at all), gray. Breaking out the tint I doped a sample quantity of my production resin and made the first shot of the new tools with this … ugh! … color. I dub thee, 'puke gray'!







The tools were filled with catalyzed resin, pressurized, and once the castings were hard enough, they were extracted from their respective tools.

Time had come to find a model submarine to serve as a test-mule for this new type SubDriver.

I selected a nearly completed 1/72 scale THRESHER class model that has been sitting on the wall for a few years waiting for me to finish it. Now was the time.

Here I'm preparing the sail master by fitting it inside a flask. The job of the flask is to contain the rubber that forms the tool (mold) and give it rigidity during the eventual casting process. The trick is to make the flask stout, but of a geometry that will prevent excessive use of the expensive tool making rubber.

The best way I've found of determining how much rubber to prepare is to first pour rice into the flask, with master in place, to the desired level, then pour the rice into the rubber mixing pail and mark the level of the rice. That tells me how much rubber to use. Neat trick I got from a local chapter of the Nautical Research Guild. A rather stuffy group of old farts, but populated by some real sharp model-builders.











And this is when the wheels came off!

My over forty-year-old Vigor (they make machines and tools for the Jewelry trade) vacuum de-airing machine shit-the-bed! One use of this vital shop tools is to deair entrapped bubbles in the thick rubber mix before pouring it into a flask. Failure to do so will result in entrapped bubbles in the hardened rubber, which will evidence as positive dimples on the surface of a pressure cast resin piece. Can't have that! Must fix … must fix now!

I took the machine apart and found that the coupler between vacuum pump and motor had stripped out. I've ordered replacement parts, but can't wait. I've got jobs to get out of here! So, I ran over to Harbor Freight -- I LOVE HARBOR FREIGHT! -- bought a cheapy low CFM vacuum pump and pressed it into service using the old Vigor's table, plumbing, and bell-jar.

Back in business!











All fixy-poo, I went on to finish the THRESHER sail tooling by claying up the smaller sail masters. One sail top representing retracted masts, the other sail top representing extended masts; internal platforms; and masts. I'll pour the rubber to complete the sail tooling tomorrow, I'm dead tired and its getting late.

The test-mule for the new modular SubDriver will be this 1/72 THRESHER class model that has been sitting idle for a few years. I'm now working to complete it to the point where it will be water ready and outfitted with the MSD for a proper evaluation of the system. I've also included a shot of a previously completed model to show you what it will eventually look like.

My model is based on the HMK Creations kit produced by Joel Stadnick. Though it's not currently in production there is talk of it being re-introduced to the market with new features.





I spent the last two days finishing up the tooling for all the parts that make up the 'improved' sail structure. And from that I produced the cast resin parts, just a few hours ago. Tomorrow I assemble a sail unit and integrate it with the hull.

I took the cast resin sail parts and stuck them together. Assembly was straight forward: the three internal platforms were glued within the sail, the sail top piece (the one with the openings through which the raised mast fairings project) glued atop the main structure, and two holes drilled and tapped at the bottom platform to accept the screws that would pass up through the upper hull to secure the sail in place.



A simple poster-board alignment jig insured I sanded the base of the sail so it would sit level atop the upper hull. Any significant gaps between sail top and sail proper were filled with CA and flashed to hardness with either a sprinkling of baking soda or a good wetting with 'accelerator', followed by careful file work.







The engraved lines on the kits upper hull were not up to my standard: though an appreciated attempt the hull featured both non-skid and waterline cheat-lines -- these were way too deep and had to be filled to the point were once the model is painted, those cheat-lines will be barely perceptible. I spent the entire day using circular cutters and scratch awls to dress up the original work. Lots of putty to fill dings errors and overly aggressive cheat-lines. Once dry the excess putty was knocked down through some spot wet-sanding, followed by careful re-scribing.

Spent the better part of the weekend building duplicate tools so I could get into series production of the Modular SubDriver parts.







While waiting for the new rubber tools to cure I streamlined the methodology of reducing the diameter of my demonic metric brushless motor shafts to God's own Imperil standard of shaft size. In this case reducing the useless 5mm to a more rational 3/16" diameter. Gotta love tungsten tipped cutting tools! The masking tape keeps the metal chips away from the rotors internal magnets as I shaved down the stainless steel shaft. The object of the exercise was to match the motors shaft to my standard drive-shaft watertight seal.





Most of today was spent casting resin parts from the tools. I'll spend this week machining these bulkheads to fit Lexan cylinder and then integrate things into proper MSD's for my customer, Nautilus Drydocks. They wanted me to adopt a proprietary 'color' for this new product. We agreed on gray. you'll note that I played with various shades of gray to give my boss a choice.

Very interested to see you turning down stainless steel motor shafts. Not for the faint hearted!

Great work.

David