Dividers were a mystery to me for a while, but they are a low-tech, elegant way to accomplish very accurate work. I love stuff like that. Here are some different scenarios.
The fundamental task is to divide a length into an arbitrary number of sub-lengths. Let's say you have a board about a foot wide that you want to make nine evenly spaced holes in for a coat rack or game or something. Draw a centerline, and set the dividers for about 1/10th of the distance across the board. Just eyeball it if you want. Then start at one end of the line and walk the dividers along. When you get to the far end, whatever error you made in the setting will mean over or undershooting the end of the board. Say you're about your thumb's width over. Narrow the dividers' setting by about 1/10 of your thumb's width, and step off the line again. It might take two or three tries, but it's pretty easy to get extremely close to perfect, at which point you step down the line again, but this time press as you go to make a clear pinhole mark at each center point. Note that at no point in this do you need to measure anything. The line you're dividing can be any length, and at any angle, although it does need to be a straight line.
Once you've done it a few times, adjusting the dividers to close in on your desired value isn't fiddly. It is trial and error, but you can home in on a very accurate measurement within three or four tries. So don't get stuck in the trap that dividers are some kind of old-school imprecision thing. Let go of your fear, Luke
A common use comes up in laying out dovetails. This can be used for pins or tails (whatever you do first) but here's my tails-first approach. Make a mark a half-pin width in from each end of the board Set you dividers to about what you want a pin plus a tail width to be, and step off down the joint line from one of the half pins. Do a few trials until the last step goes off the board and lands where the far half-pin would end if it were a full pin. It doesn't need to be super exact. Then step off that distance from both ends, pushing in the points to mark out the joint.
Another use is finding the center between two points on a line. This is the simplest case of division (into two). Set the dividers for what looks like the center by eye. Take one step from either end. The mid-point of those two new marks is the center. Widen or narrow the divider setting by half the distance between those points (by eye) and try again. When the points land in the same spot, you have the center.
Saturday, September 22, 2012
Wednesday, September 19, 2012
Dining Table Design and Top
Well, I got the top glued up, finally. I sliced the base of my thumb up pretty good while disassembling a handplane, so there was a week of nothing accomplished while that healed. This is by far the biggest panel glue-up I've ever attempted. Ten pieces were jointed by hand and glued up one at a time into a 7' x 3' panel. I used four Rockler 3/4" pipe clamps (with cauls) and a biscuit every 12" to help with alignment. The biscuits probably could have been further apart but I was cautious. One mistake I made was gluing the two halves together separately (into 7' x 18" sections) and then trying to glue that joint down the middle last of all. Hoisting one of the 50 lb halves up to test the joint while I planed it to match was no fun.
My wife thinks it looks good, but I think it looks like a bunch of 2x4's made into some kind of fancy picnic table. I'm planning on inlaying some dutchmen to hide a couple of knots and other ugly bits, and it will have breadboard ends, so I might be happier with it in that context.
There's around 3/16" of cup across one end, and 1/8" at the other. Cumulative errors of all the jointed surfaces show that I made a systematic error while jointing, since the whole top curves the same way. Or maybe it was the way I clamped it during glue up. I can flex it flat pretty easily with a couple of clamps and a piece of lumber, and I know a top this size will move some on it's own even if I planed it perfectly flat now in it's unrestrained state. I'm not entirely sure how to proceed though. How flat does it need to be before I put the breadboard ends on and screw stringers underneath to get it the rest of the way?
Here's the plan. I'm going to plane the bottom side with my #4 smoother and jack. That won't straighten it fully, just level the joints and smooth the surface. Then I'll install the breadboard ends and attach the stringers with figure-eight connectors, as it will be when the table is assembled. Thus, all the physical flattening devices will be on, and I can use my long planes to get the top properly flat so it looks good. As long as I don't feel like things are super stressed out when I assemble it, I think this will be ok. And like I keep telling myself - worst case, I blew $40 worth of framing lumber.
The rest of the table plan is still a little fluid, but will look something like the Sketchup rendering below. I picked up a 5/4 cherry board to make the breadboard ends and butterfly patches for a couple of spots on top, and I'm going to use walnut for a few small bits like the breadboard pins and the wedge that will hold the trestle together.
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| Top all glued up. This is the underside - the top has slightly fewer defects. |
There's around 3/16" of cup across one end, and 1/8" at the other. Cumulative errors of all the jointed surfaces show that I made a systematic error while jointing, since the whole top curves the same way. Or maybe it was the way I clamped it during glue up. I can flex it flat pretty easily with a couple of clamps and a piece of lumber, and I know a top this size will move some on it's own even if I planed it perfectly flat now in it's unrestrained state. I'm not entirely sure how to proceed though. How flat does it need to be before I put the breadboard ends on and screw stringers underneath to get it the rest of the way?
Here's the plan. I'm going to plane the bottom side with my #4 smoother and jack. That won't straighten it fully, just level the joints and smooth the surface. Then I'll install the breadboard ends and attach the stringers with figure-eight connectors, as it will be when the table is assembled. Thus, all the physical flattening devices will be on, and I can use my long planes to get the top properly flat so it looks good. As long as I don't feel like things are super stressed out when I assemble it, I think this will be ok. And like I keep telling myself - worst case, I blew $40 worth of framing lumber.
The rest of the table plan is still a little fluid, but will look something like the Sketchup rendering below. I picked up a 5/4 cherry board to make the breadboard ends and butterfly patches for a couple of spots on top, and I'm going to use walnut for a few small bits like the breadboard pins and the wedge that will hold the trestle together.
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| A fairly standard trestle table design |
El Cheapo Dining Table
I'm making us a new dining table, out of Douglas Fir. I started with 2 x 10 framing lumber from Home Depot... I found a couple in my outdoor wood pile that had been temporary supports during one of our remodeling projects. After two years outside and a trip through the planer they looked too nice to cut up for the fascia boards I had intended them for. So I went to the big orange store and picked out some more decent pieces of green, soaking wet framing lumber, and let them dry outside for awhile, then brought them to the basement for a couple of months. Then I ran them all through the planer, bringing them down to 1-1/8" thick. Today I ripped the pithy centers out of them, leaving strips of quartersawn grain ranging from 3" to 5" wide. Now I get to joint all the edges in preparation for glue-up. I don't have a powered jointer, so I'll use the tablesaw to even up the worst of it and then fine tune with my new Veritas jointer plane.
Design? I don't have a design yet. Well, it will be a trestle table, and the top will be about 7' x 3'.
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| Ten planks ready for jointing |
Design? I don't have a design yet. Well, it will be a trestle table, and the top will be about 7' x 3'.
Friday, August 24, 2012
Panoramic Head - prototype
A friend recently sent me a link to a panoramic photo of Mars, stitched together from a bunch of images from the Curiosity rover that landed last week. It was as close to I'm likely to get to the experience of really seeing the place, and that got me interested in making panoramic images of my own, of cool places that I have actually been to.
There is free software to stitch images together, but it works a little better if you take all the photos by pivoting the camera around a particular point in space, usually called the nodal point or entrance pupil. That point is generally near the center of the camera's lens, so a regular tripod doesn't quite cut it because it rotates around the tripod socket under the camera body. It's also typical to take photos with the camera in portrait orientation (sideways) to capture the vertical dimension as widely as possible.
Enter the panoramic head. Yeah, sure, you can buy them, but that's not how I roll. I made a bunch of sketches and here's the first iteration of a working design. The goal is to have two axes of rotation that intersect at the nodal point of the lens. This prototype is nothing fancy, just some scraps of plywood and some nuts and bolts from the hardware store. I tacked it together last night and took a quick set of pano shots of our living room. They stitched together nearly perfectly, much better than a similar set of shots I took with the tripod alone. So yay. Not so yay are some of the details. The base plate needs to be bigger, and the elevation arm can't swing down to 90˚ to take a shot straight up because of the way the camera is attached to it. I also didn't take time to rout the groove in the elevation arm that will allow adjustment for different nodal point positions.
Round two of the design will be a lot better.
There is free software to stitch images together, but it works a little better if you take all the photos by pivoting the camera around a particular point in space, usually called the nodal point or entrance pupil. That point is generally near the center of the camera's lens, so a regular tripod doesn't quite cut it because it rotates around the tripod socket under the camera body. It's also typical to take photos with the camera in portrait orientation (sideways) to capture the vertical dimension as widely as possible.
Enter the panoramic head. Yeah, sure, you can buy them, but that's not how I roll. I made a bunch of sketches and here's the first iteration of a working design. The goal is to have two axes of rotation that intersect at the nodal point of the lens. This prototype is nothing fancy, just some scraps of plywood and some nuts and bolts from the hardware store. I tacked it together last night and took a quick set of pano shots of our living room. They stitched together nearly perfectly, much better than a similar set of shots I took with the tripod alone. So yay. Not so yay are some of the details. The base plate needs to be bigger, and the elevation arm can't swing down to 90˚ to take a shot straight up because of the way the camera is attached to it. I also didn't take time to rout the groove in the elevation arm that will allow adjustment for different nodal point positions.
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| Canon 50D with 10-22 zoom on my plywood panoramic head. The idea is to allow pivoting about the nodal point (white) in two axes: azimuth in red, and elevation in blue. The green rotational axis is fixed. |
Round two of the design will be a lot better.
Tuesday, August 7, 2012
Why I Love Hand Tools
There seems to be a movement going over the past several years toward hand tools, at least for woodworking. So I'm definitely not the first to try to say this, but there really is a simplicity and elegance to taking care of a job with the simplest and most straightforward tool. And it's not more work. It's less. Less screwing around trying to get the height of your dado blade just right to cut the joint you're working on, and no time or materials wasted making test pieces to run across that dado blade. Less time is spent worrying about how precisely square your cabinet opening is. You can cut everything a little fat and shave parts down to perfection with a plane or chisel. You don't have to figure out how to set your miter saw to that weird acute angle, you just cut to the line with your hand saw. And on and on.
I wouldn't expect a production line environment to benefit from most hand tools. Jigs and big powerful machines are the way to go when you have to make lots of copies of anything. For the artisan or home craftsman, however, you gotta love hand tools.
My first personal example is fitting tenons. I make a lot of cabinet door frames with bridle or mortise and tenon joints. I don't worry too much about the width of the tenons. I cut them a little oversize on the tablesaw (with a tenon jig) or on the band saw, and shave them down to a nice fit in their particular mortise with a rabbetting block plane. Sort of a block plane / shoulder plane hybrid. It cuts right to the corner and shaves off a wide swath of the tenon cheek, which helps keep the surface flatter compared to a shoulder plane.
I'm currently working on a table top. At 7' x 3', very few of us can afford a drum sander or other power tool that would take on the job of flattening a slab this size. I've seen plans for a track system to run your router on, or I think there are baseplates for handheld belt sanders that help flatten large areas, or maybe you could rent a floor sander, but with a jointer plane it's a straightforward process to get it extremely, accurately flat. You may work up a sweat, but that's not a bad thing.
I wouldn't expect a production line environment to benefit from most hand tools. Jigs and big powerful machines are the way to go when you have to make lots of copies of anything. For the artisan or home craftsman, however, you gotta love hand tools.
My first personal example is fitting tenons. I make a lot of cabinet door frames with bridle or mortise and tenon joints. I don't worry too much about the width of the tenons. I cut them a little oversize on the tablesaw (with a tenon jig) or on the band saw, and shave them down to a nice fit in their particular mortise with a rabbetting block plane. Sort of a block plane / shoulder plane hybrid. It cuts right to the corner and shaves off a wide swath of the tenon cheek, which helps keep the surface flatter compared to a shoulder plane.
I'm currently working on a table top. At 7' x 3', very few of us can afford a drum sander or other power tool that would take on the job of flattening a slab this size. I've seen plans for a track system to run your router on, or I think there are baseplates for handheld belt sanders that help flatten large areas, or maybe you could rent a floor sander, but with a jointer plane it's a straightforward process to get it extremely, accurately flat. You may work up a sweat, but that's not a bad thing.
Monday, June 25, 2012
Bosch MX25E Quick Review
I just replaced my Dremel 6300 Multi-Max oscillating saw, which failed horribly after about an hour of runtime over several small projects. Home Depot was good enough to take it back (within the warranty period) and not make me deal with Dremel as directed on the warranty form. I took the credit and traded up to the Bosch MX25E. It's much heavier than the Dremel, which I take as a good sign. The tool was made in Malaysia, the blades were made in Europe, and the storage bag was made in China.
It came with several blades (what you get will depend on exactly which specific kit you buy) and an adapter plate that's supposed to let you use accessories from other manufacturers. The adapter plate just presents a bunch of hard, somewhat sharp points to a non-bosch blade, so you should be able to use it with anything that fits over the mounting screw regardless of the pattern of studs it was designed for. Unfortunately, you do have to completely remove the screw to change blades. Even the Dremel had a slightly faster option. It also came with a nice box to organize accessory blades in, and I prefer the heavy cloth storage bag over an inflexible plastic clamshell case.
I used it last weekend to cut the lath in the ceiling of our upstairs bathroom for a new ventilation fan. So far, so good. If you work with lath and plaster construction, these oscillating saws are great. Score and chip off the plaster with a knife, and cut the exposed lath with the saw. The high-speed oscillating action doesn't vibrate everything and damage the adjoining plaster like a sawzall or hand saw. It's house surgery with one of these things.
It came with several blades (what you get will depend on exactly which specific kit you buy) and an adapter plate that's supposed to let you use accessories from other manufacturers. The adapter plate just presents a bunch of hard, somewhat sharp points to a non-bosch blade, so you should be able to use it with anything that fits over the mounting screw regardless of the pattern of studs it was designed for. Unfortunately, you do have to completely remove the screw to change blades. Even the Dremel had a slightly faster option. It also came with a nice box to organize accessory blades in, and I prefer the heavy cloth storage bag over an inflexible plastic clamshell case.
I used it last weekend to cut the lath in the ceiling of our upstairs bathroom for a new ventilation fan. So far, so good. If you work with lath and plaster construction, these oscillating saws are great. Score and chip off the plaster with a knife, and cut the exposed lath with the saw. The high-speed oscillating action doesn't vibrate everything and damage the adjoining plaster like a sawzall or hand saw. It's house surgery with one of these things.
Bosch Rotary Hammer Angle Head Review
This here is a little writeup of the Bosch 1618580000 Angle Head for their line of rotary hammers. I bought one of these not too long ago, but had no luck even finding a decent photo of one on the web before I gave up and ordered it. Bottom line: it's solid. Made in Germany no screwing around solid piece of Bosch equipment. The body is some sort of reinforced resin casting, and what I can see of the guts is crisply-machined metal.
After removing the front handle, it slips right over the head of your Bosch rotohammer and a shaft inside engages with the chuck like a bit, except that doesn't lock in. You tighten a hex bolt to clamp it onto the body of the drill, and it can be rotated to any angle to help you reach in tight spots.
There are some caveats, one huge and the others worth knowing about. The big one is it doesn't fit all of their rotohammers. I wound up having to go buy a whole new drill to get my job done! The verbage is confusing, so either check your model number against the list of drills it says it fits, or measure the diameter of the collar behind the chuck. The inside diameter of the angle head is 42mm. My "Bulldog Xtreme" (model 11255VSR) is 50mm... So now I have two rotohammers, which makes me a tool badass, but I think I'd rather just have the extra money I had to spend.
Another issue is runtime. After ten minutes or so of continuous use, the head will get hot and you have to let it cool down. It also reduces the impact action, so don't expect to go as fast as you can with the drill itself. I think it took me about 30 minutes to drill a 5/8" diameter hole 13" deep in decent concrete, including breaks to let the head cool down.
So there you go.
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| Bosch Angle Head |
After removing the front handle, it slips right over the head of your Bosch rotohammer and a shaft inside engages with the chuck like a bit, except that doesn't lock in. You tighten a hex bolt to clamp it onto the body of the drill, and it can be rotated to any angle to help you reach in tight spots.
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| Angle Head Attached to My Rotary Hammer |
There are some caveats, one huge and the others worth knowing about. The big one is it doesn't fit all of their rotohammers. I wound up having to go buy a whole new drill to get my job done! The verbage is confusing, so either check your model number against the list of drills it says it fits, or measure the diameter of the collar behind the chuck. The inside diameter of the angle head is 42mm. My "Bulldog Xtreme" (model 11255VSR) is 50mm... So now I have two rotohammers, which makes me a tool badass, but I think I'd rather just have the extra money I had to spend.
Another issue is runtime. After ten minutes or so of continuous use, the head will get hot and you have to let it cool down. It also reduces the impact action, so don't expect to go as fast as you can with the drill itself. I think it took me about 30 minutes to drill a 5/8" diameter hole 13" deep in decent concrete, including breaks to let the head cool down.
So there you go.
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