06 July 2012

Treadle Drill Press

  Treadle Machines
   My treadle machines are all built around the cast iron flywheel/ freewheel combination found on most exercise bikes. This piece is the heart of the machines it provides the means to input power into the system and stores energy to smooth out the intermittent power of a treadle drive.The freewheel is just like the one on the rear wheel of a bike so you don’t have to time your stroke as you would with a pitman or crank system, also the treadle is not moving on its own using energy better left in the system. The flywheel / freewheel greatly simplifies the construction of these machines as instead of having to build this piece it is just figuring out how to adapt it to the use you want.
   Exercise equipment is one of those things that people seem through away regularly (at least in Canada)  I have collected many pieces at our local dump as well as friends giving me equipment when they find out that I use it. There are bolts, bushings, tubing, foam, flat stock and many other bits to be used.
  Drill Press
    The drill press is ideally suited to treadle power because it doesn’t require much power or speed to work effectively. It will drill 1/2" hole in steel, a 1" forstner bit into hardwood and cut 1/2" plugs easily. With its low speed its not efficient when running a sanding drum or other high speed tools.
   This is my most used treadle machine. While the design is sound the tool needs a few tweaks.
   The drill is built of two vertical ways with a headstock of wood at the top that the metal parts are mounted on. The table slides between the ways and is clamped onto them. At the bottom the treadle pivots on a bolt between the ways. There are two mounting boards screwed onto the back that attach the machine to the wall.
   The headstock has a tube with two bronze bushings for the drill shaft to run through. The top of the tube has two ball bearings that the flywheel is attached to, these run on a concentric centre so the shaft can run through them while rotating.
 The feed is by a lever attached to the back of the headstock and through a linkage to a piece of tube with a ball bearing in it. The bearing is slipped onto the shaft up against a stop collar. A spring is trapped between the stop collar and the top of the flywheel to provide a return for the shaft.
   The drill shaft is a piece of 5/8" keyed shafting that I attached a 1/2" JT-33 (taper) chuck to one end. This was a labourious process of filling the shaft while rotating in two bearings, driving the chuck on, checking for it to be concentric and repeating the process until the chuck would lock on the shaft and run true.
   The shaft is driven through a key that is trapped in a 5/8" collar silver soldered to the top of the flywheel (visible above the freewheel in the photo above). So the shaft can move up and down while still having energy transferred to it from the spinning flywheel, a certain amount of slop must be in the system for the shaft to move and rotate at the same time.
   The treadle is connected to the freewheel by a piece of chain that runs between the ways and is guided by two inline skate wheels that I turned grooves in to accept the chain. The wheels guild the chain onto the freewheel. Chain only flexes in one direction so a link was made to change the direction of the chain to accommodate the freewheel.
The chain then wraps around the freewheel to a return spring attached to the wall. The chain length, treadle stroke and spring length had to be adjusted so the turning link didn’t run into the  freewheel. A crutch tip cushions the treadle impact on the floor.
   So now the operation. First a bit is put into the chuck and the piece to be drilled clamped to the table. Then the treading started , a full stroke and steady rhythm is best. The feed lever is pulled down and the object drilled. As you tread the spring at the top end of the chain is stretched and it pulls up the treadle when you lift your foot for the next tread. The freewheel ratchets and allows the chain to return around it. While this is happening the flywheel is still turning the bit in the work ( though losing energy )until you tread down and energize the system again. The flywheel is approximately 13" in diameter and weighs about 15 pounds. I had thought that this might be to small so made provisions to add another flywheel to it, this has never been needed. There is enough power to spin the bit in the chuck or rip a piece from your hands if the bit locks in the work.
   This tool was made with what was in the shop at the time and adapted to the materials at hand. The biggest expense was the chuck (a cheap import $20 I think) and the shafting. If I were to do it again I think I would adapt a commercial drill press to treadle drive and would certainly try it if one came along for the right price (free).
   Things to change, the table needs a simpler lockup and there is a tight spot in the rotation probably due to concentric problems but overall not a bad tool.

20 May 2012

Personal Knife-Sheath

    I start the sheath by cutting the kydex to size on the table saw. There has to be enough to cover the knife with an area for the rivets and the hanger tab. The kydex is heated to make it pliable, when its hot enough (about 375 degrees F) it gets flexible and limp. The hot kydex is pulled from the oven, quickly wrapped around the knife and clamped in the press. Once the kydex is cool the press is opened and the sheath inspected to check the mold, rarely does it go perfect on the first try. If its not right, back into the oven to heat up and try again I have had to remold some sheaths up to 5 times, the kydex will flatten out in the oven and remold with no apparent damage.

   The next thing is to drill the rivet holes.

  I make my own hollow rivets from the same brass tube as I used for the thong hole liner. The tube is cut to length with a hack saw. One side is flared with a punch against a plate with a hole in it for the punch to pass through. Then its inserted into one of the holes in the sheath and then the other side is flared, this locks the tube into the sheath and lets the die turn the brass down without crumpling.

   The dies, which I made from steel rod and a drill bit shaft, are slipped together through the rivet and squeezed in the bench vice. The rivet is half formed and the vice backed off, the die reversed in the rivet, put back in the vice and the vice tightened again. It may have to be switched a time or two more. Since both sides of the rivet are being formed at the same time this switching keeps them even. The last squeeze is quite tight to flatten the rivets against the kydex.

  The access kydex needs to be cut off, I trim it close to the finished size on the bandsaw, then finish it up on the belt sander. One thing to remember if the knife is snapped into the sheath before the trimming is done it will be very hard to remove usually resorting to tying a cord through either the bottom holes in the sheath or the thong hole of the knife. Securing the cord on something solid and pulling the sheath or knife to get a controlled release of the knife from the sheath. This is much safer than muscling it out. 

   Using a heat gun, aluminum foil to insulate the part I don’t want to heat, an awl and a piece of kydex off cut I bend the hanging tab,

 flare the thumb ramp,

   and open up a drain hole.

  The edges need to be rounded and everything made smooth. A few passes across the buffing wheel cleans this up.
   Hanger and belt clip
   The belt clip is formed of heavier kydex, around a mandrel the size and thickness of the belt I will use it on.

   Two holes are drilled for the cord in the tab and in the hanger. I use a drill bit about the same size as the cord.

   The cord ends are heated with a lighter until molten then pushed into a die, which is just a drill dimple in a piece of micarta. This flares the ends so they will not pull out of the hole.

When cool the end is inspected for symmetry and held close to the flame to just melt the surface, this sort of polishes it.
   This method eliminates the bulk of a knot on the sheath and the hanger.
   The cord is threaded through the sheath and hanger ,the length determined, the cord cut and the cut end flared. The sheath is done.

   This knife with the long cord is designed to be hung from the belt and dangled into the front pants pocket. This keeps it out of the way and easily accessible: also the sheath is attached to my belt so its there when I go to resheath the knife.

10 May 2012

Personal Knife II

  Construction always starts with material. For this knife I was going as thin as practical, a ten inch circular saw blade without carbide teeth provides the stock for the blade. Micarta scavenged from the dumpster of a local plastics shop, epoxy, brass machine screws and brass tube from a hobby store are used for the handle; two thicknesses of kydex, cord and more brass tube for the sheath.
     A pattern is clamped to the blade stock and the profile scribed onto it. After that the shape is cut out with an angle grinder fitted with a thin cut off blade. Next the blank is ground just to the scribed line on the belt sander. This has to be done carefully because when the line is passed the eye is fooled into thinking its just at the line and you will be removing material that should be left on the blank.
    The belt sander can grind everywhere but the curve in the handle where the blade drops. I clean up this area with a half round file. A smooth transition without a dip is what I aim for here. The choil notch is filed in with a 1/8" round file to half its depth.

   A simple two-brick furnace with a propane torch is used to anneal the blank. This is soft fire brick that I got by tearing apart an unwanted potters kiln. The knife is brought to a bright cherry colour and then buried in the ash of the wood stove that the furnace sits on. The top and bottom bricks are hard fire brick that hold the furnace together.
     The annealed blank is now soft so the pin and thong holes are drilled. Micarta handle slabs, brass hole liner and machine screws along with the matching tap are readied to fit the handles prior to finishing the blade.

   I used to use brass tube for pins and never had any problem with them but I was looking for a mechanical lock for the handle in addition to the epoxy. Not wanting to buy handle fasteners and finding them to be too much work to make (and not coming up with a serviceable fastener), I finally thought to use just screws driven through tapped holes in the tang and the handle slabs. Testing proved that the screws would hold the handles on without epoxy.
   The sides of the blade need to be sanded clean and flat. This is done by using a flat piece of stock with sandpaper stuck to it, I have made these sanding flats with 60 grit and up to 600 grit but rarely go beyond 220. A working knife is going to need to be cleaned and the blade will get scratched up anyway. The blade is clamped to the bench on top of a spacer to elevate it above the bench surface. Then the sanding flat is held in both hands and placing it flat on the blade moved back and forth along the blades length. 
   Great pressure can be exerted but care must be taken to keep the sander flat on the blade or the edges will be rounded. I am aiming for a flat surface.  I have found this to be faster (and safer) than a belt sander that always seems to round over edges.
   One handle slab is clamped to the blade and the holes are drilled, after the first hole is drilled a tight fitting pin is put through the hole so the pieces cannot shift, the next hole is drilled and pinned. This is repeated until all holes are drilled.
   With the handle still tightly clamped to the tang the tap is wound through the previously tapped hole in the tang and threads cut into the handle, as each of the holes are tapped a screw is threaded into it and the clamp moved close to the next hole and the tap run through until all are done. A pencil is run around the tang to mark the handle so the access can be cut off and the whole procedure repeated on the other handle slab. The knife is then dry assembled to ensure that everything fits.
   After the handles are trimmed one handle has its ends finished. The end facing  the butt is trimmed so that the point of the tang is exposed. Then the handles are attached together with screws through the tapped holes and the ends of the untrimmed handle brought to match the trimmed one. The ends are are finished now as it is much harder to do after glue up.
     Back to the belt sander to grind the bevels. Scandinavian bevels are quick to grind because the minimum amount of material is removed. I use a bevel gauge to check the progress as I grind. First one side and then the other, check with the gauge, adjust my hold and grind again. Eventually the angle is correct and I can concentrate on holding the bevel flat on the belt. Having the bevels centred on the blade is important so I keep checking by sighting down the edge and applying more pressure or the amount of time I favour one spot. The aim is to leave a thin line down the centre of the blade to be removed after heat treating.

   Heat Treat
   The knife goes back into the furnace and the torch fired up. I turn the blade over in the furnace a few times to heat it evenly then watch it heat up until it glows a bright red/ orange colour bring it out quickly, check it with a magnet if it dose not stick its quenched in previously heated oil, tip down and moved with a back and forth cutting motion through the oil, after about 30 seconds the excitement is over and I pull it out of the oil, it should be black and grey with scale flaking away on the hardened area.
   Heading to the vice I wipe it off and lock it into the vice spine up. Taking a file I attempt to file the spine, the file may take off some scale or decarbonised skin but then will skid over the spine without cutting if the blade has been hardened. I then flip it over and check the full length of the edge.If all is well it goes back into the hot oil for tempering.
   The oil is brought up to 190 degrees Celsius and held there for two hours with a propane torch or camp-stove.Temperature is monitored with a meat/candy thermometer I bought from a restaurant supply store. This is fairly boring and one has to keep there wits about them as hot oil is extremely dangerous if spilled. Outside is the best place for this.
   When the two hours is up I cool the blade by quenching it in water, polish it the same as I did before heat treatment and then soft draw the back and spine with a torch an a bucket of water or snow as the season dictates.

   Glue Up
   Before I can glue up the knife its back to the sanding flats to brighten up the blade. All the parts are cleaned with alcohol and readied for assembly, epoxy is mixed, screws coated holes wiped with a toothpick dipped in epoxy, screws wound into one handle. The tang and handle slab coated with epoxy. Carefully the one prepared handle slab is lined up and the screws started into the holes in the tang making sure that they are tight and an extra thread is not left between the handle and the tang. The other side is attached with the same care. After the handles are secured the thong tube is carefully driven into its hole and epoxy wiped out of it. Epoxy squeeze out is wiped off especially around the front end of the handle where it meets the blade An alcohol whetted rag works well here as this is a pain after it sets. The knife is left somewhere warm overnight (epoxy cures better in the heat).
     Handle Shaping
    I start by sawing the screw heads off then on a disk sander I grind the screws flush to the handle material. Now that the handles are flat I can bring them flush with the tang using the disk sander and files for the concave parts. Micarta burns very easily so fresh disks or belts are necessary. The heat generated during sanding needs to be dissipated either by quenching or letting the knife cool, it should never get to hot to hold in bare hands, the epoxy can let go if heated to high.
    I then taper the handle from thick at the butt to thinner at the handle. Once this taper is even and symmetrical I dome each side by rolling the handle against the disk sander. It is important to keep working from side to side and constantly check for symmetry.
    Moving to the vice the edges are rounded and blended into the flats top and bottom of the blade then the butt is rounded nicely and the exposed tangs edge is eased with files and sandpaper.  There will be no sharp or harsh edges left, the knife should slide through your hand. After the thong hole is slightly countersunk I sand the entire handle with 180 grit paper until all other marks are gone.
For a working knife like this that's all the handle needs.
   Finishing The Knife
   The knife has yet to be sharpened there is still that little flat along the blade that has to be removed. I belt sand the bevels again this time being very careful not to overheat the steel, bare hands are the way here. Much care is used to keep the bevels even and just come to a sharp edge. When I cannot see a flat any more and feel a bur along the edge I stop grinding and move to the sanding flats.
    Starting with 120 grit paper I set the bevel flat on the paper and move it back and forth along the bevel in a sort of sawing motion. I do this on both sides switching to finer grits when the bevels reach a consistent sheen. 600 grit paper usually leaves an edge I can shave hair off my arm with.
Putting a scraper on the back of the blade is something I find very useful. This  saves the edge from being used as one and utilizes the back of the blade without hindering your ability to push against it with your other hand when carving. If you have ever sharpened a cabinet scraper you know how this is done.
    With the knife held edge down in the vise and its tip just above the jaws the spine is polished with a 220 grit sanding flat. Then the back edge of a chisel (or any smooth object harder than the knife) is placed on the spine of the knife at about a 10 degree angle and with a fair amount of downward force pushed along and slightly across the back. This deforms the metal into a bur along the side of the blade. A number of passes may be needed to form the bur. It should catch a fingernail slid up the side of the blade. 
 Both sides are done. Being careful not to slip as I’m holding a sharp tool and working on one also.
   Testing the scraper on a piece of hard wood to make sure it is formed properly. It should produce curls of wood not dust.
   The scraper will have to be sharpened occasionally just like the knife and that involves sanding/polishing off the bur to a nice square edge and forming another one. This is another reason to not polish the blade.
    So now I have a knife but no way to carry it. 
    Next the sheath.

30 April 2012

Personal Knife


 - A fixed blade  "pocket " knife for use everyday
 - A minimal, light, unobtrusive, small knife
 - Simple, strong construction
 - Utility tool

   The size [6"x 1"x 1/2" ] was somewhat arbitrarily decided on. I thought this to be small enough to carry dropped into a jacket or pants pocket. Having experimented with smaller knives I kept returning to this size. This is a small knife four fingers barley fit on the handle, but powerful forehand grip is possible.
   The compromise is having something that is there and small or something that is left behind because its too large, obtrusive or aggressive looking.


   The knife went through four revisions.
   From left to right
   First idea. Classic double taper handle comfortable but hard to unsheathe, Half bevel, wood handle, tube pins.
   Second  Handle shaped with single taper from butt to blade, the angle at the butt should be reversed, Scandinavian bevel, wood handle , tube pins.
   Third  A skeletonised disaster with a fuller handle and a chisel grind awful.
   Fourth  The final shape. handle end is turned over for more finger purchase and a scraper is added to the back.
   Last  Optimized. Micarta handle, screw pins, thinner blade and exposed pommel.



   The sheath needs to be simple, safe, secure, easy to carry and the knife should come out and be returned with a minimum of fuss. The nature of the knife demands a sheath as small, flat and compact as possible.
   Kydex is the material of choice here, certainly the most compact sheath can be made by taking one piece folding and molding it to the knife and retention is achieved with the right shape. 

  Next post will be on construction