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My imagination was recently captured by an Instructable by a user named Seamster on how to build a wooden marble coaster. Since it looked like it was within range of my very limited woodworking abilities, I decided to attempt building one of my own. The only real sticking point was the spiral screw used to bring marbles to the top of the coaster.

Seamster used a Dremel to hand-carve the screw from a rounded piece of 2x4. I initially tried this with a store-bought wooden dowel, but quickly lost patience with the process (it turns out that I'm far lazier than I thought). I decided to see if I could figure out a faster way to carve out a wooden screw. I quickly hit upon a very simple method. This has probably been done before, but I'll document it here, just in case.

Step 1: Equipment and Material

The only woodworking equipment you will need to do this is:
- a table saw with a decent blade
- a miter gauge (pictured)
- a drill
- a suitable drill bit for your screws
- a clamp
- a screwdriver
- a pencil
...and that's it!

The materials list is equally simple:
- a scrap piece of board 1 to 2 feet long and a couple inches wide
- 3 screws (2 of these will need to fit the holes in your miter gauge)
- a wooden dowel to carve

Step 2: Make the Jig

The secret to making this process easy and accurate lies in this simple jig. It provides a guide for the dowel to keep it straight and to control how it moves during the carving process.

And, if the term "jig" calls to your mind the same nightmarish, complicated contraptions that it does to mine, then relax. I really do mean simple.

First, set your miter gauge to your desired angle. This will determine the angle of the spiral you cut. I found that setting my gauge to 60 degrees worked well.

Second, select or cut a piece of wood long enough to span from your miter gauge to about 6 inches past the table saw blade. It should be at least as wide as your miter gauge is tall and should be at least an inch taller than the tale saw blade setting you use (see the next step).

Third, attach this guide to your miter gauge. Your miter gauge should have holes in it specifically for attaching things like this to it. Just lay the wooden guide against the gauge where you want it and use a pencil to mark the location of the gauge holes. Drill matching holes and attach the guide to the gauge with suitable screws.

Step 3: Set the Blade Height

You'll need to set the blade height to get your desired thread depth. I didn't do any measuring and eyeballed a setting and went with it.

Different settings will produce different results. Specifically, setting the blade to reach higher than the middle of the dowel will produce more of a spiral than a screw. I haven't had luck with this yet, but, with patience it should be possible.

Step 4: Place the Guide Screw

I found it better to add a screw to the jig to keep the dowel moving evenly throughout the carving process. If you have a steady hand and nerves of steel, you could, potentially, skip this step.

Place the dowel against the jig and align it with the saw blade as shown in the first picture. Push the jig into position so that the dowel is over the middle of the blade. You will want to clamp it into place, if possible, to keep the miter gauge from sliding around.

This part is potentially tricky, but shouldn't be too hard and only needs to be done once.

Carefully and slowly turn the dowel toward you. You will find that the dowel will naturally slide to the right as it turns because the blade will continue to follow the groove it is making as it cuts (see picture 2). It should, theoretically, be possible to let this process continue as you carve the rest of the dowel, but it is difficult to keep it accurate.

Keep turning until the dowel has almost completed a full rotation and the starting point of the groove meets the jig (see picture 3).

To help guide the rest of the carving, you will need to put a screw here where it will fall into the groove created by the blade. make a pencil mark where the groove meets the jig (picture 4).

Select a screw that has a diameter slightly smaller than the kerf (width) of the blade, drill a hole for it at the pencil mark, and screw it in to the jig so that the tip extends into the groove in the dowel (picture 4). As you continue to carve the dowel, this screw will guide the movement of the dowel to keep the spiral cut even.

Step 5: Continue Cutting

Make sure to, again, clamp the miter gauge in place (picture 1), to keep it from sliding and changing the cut depth.

Continue rotating the dowel toward you, allowing it to move to the right, guided by the screw running through the groove. Go slowly and carefully and watch your fingers!

Step 6: Widen the Groove If Desired

The groove can be made as wide as you want by adjusting the placement of the dowel on the jig and repeating the carving. Take your time and go slowly.

Step 7: Cleanup and Enjoy

Cleanup the cuts with sandpaper and you're good to go.

This method is not very difficult, and produces some great results. Hopefully, this idea will be useful to someone and I would love to see what you do with it. Please include any photos of your end results in the comments below!

Cheers!
<p>People really into this kind of thing might like to search for &quot;wood threader&quot; or spend a bit of cash here: (BTW I have no connection to them)</p><p>http://www.bealltool.com/products/threading/threader.php</p>
Good instructions. Now, how do you make the nut to go with it?
Well done!
<p>One way to at least reduce the cross-grain chip out is to consolidate (impregnate) the fibers of the surface if the dowel with a heavy, saturating coat of thinned polyurethane before starting to cut the spiral. Wipe off the excess after it has time to be absorbed and allow to dry thoroughly. </p><p>Lacquer based sanding sealer, shellac, or even slow-set epoxy thinned with lacquer thinner will also help to solidify the wood fibers. add an oil based stain to the liquid will give a contrasting color to the surface wood too.</p>
<p>Bravo !</p>
<p>thanks for sharing this, great stuff! your freehand stick is awesome!</p>
<p>Forgot the most important part of my post: Great job. It worked very well.</p>
<p>My first attempt at this was done freehand using a Forstner bit in my drill press. I just set the drill bit depth stop, clamped a piece of wood for a guide, eye-balled the first hole, then started moving the dowel down and turning it. Turned out well, so would do in a pinch.</p>
<p>Now *that* is gorgeous!</p>
<p>Looks great! Do you think making a functional archimedes screw would be possible? or would the result be too rough? thanks in advance!! :):):):)</p>
<p>I don't see why not. I don't fancy my chances of making it accurately enough but, as long as you're patient and careful, you should be able to do it. Please let me know if you manage to do it!</p>
<p>Like it!</p>
<p>Thanks for this/</p>
You are very welcome!
<p>First off, this looks like it would be a great way to lose a finger, be careful. What happens if you tip the blade at an angle? I would think it would put a nice cove in that rather than a groove?</p>
<p>Lose a finger -- small price, and you would still have 9 left!! </p>
<p>Like it! (don't fully understand it yet -- but like it)</p>
<p>Ah now I've got it!! will try this later!!</p>
<p>This is very clever.</p>
<p>Who says it has to be useful? Just to make it would be fun. lol</p>
<p>So, I've been thinking about making a nut for your threaded rod. Before I go off and re-invent the 'nut', has anyone else done anything like that? </p><p>I envision an appropriate diameter hole through a block of wood with a nail driven part way into the hole to ride in the groove in the rod. (I'd probably round over the point of the nail, pre-drill the hole that the nail goes through to vary the depth as needed, then epoxy the nail in its proper location.)</p><p>As the rod is rotated, and the nut held from turning, the nut should advance along the rod. </p><p>Anyone done anything like this yet?</p><p>Thanks in advance for the help.</p>
<p>so simple I loved </p>
<p>This is a great wood/workshop hack. </p>
<p>I love it when something that looks really difficult (or impossible) is made so easy!</p><p>How brilliant is this? Very!</p>
<p>Great project, thanks for sharing!</p>
<p>That is so cool! I wonder.... could you cut the whole thing in one pass if you used a dado?</p>
<p>you might need to slow down the feed to a dead crawl with a dado to not stress that resulting thin shaft. dados hit too hard with only 2 teeth.</p><p>i'd also use a blade with more teeth. i really like the red diablo blades.</p>
I don't have a dado to try it out, but I don't see why it wouldn't work with some care.
<p>A dado blade was the first thought I had. Must be further proof that great minds think alike.</p>
<p>Very cool! I may have to go out to the wood shop tonight to try this out!</p>
<p>I've got a combo mini mill that can be converted to horizontal use, I think you just showed me how to mill my own screws, using this technique with the horizontal mill and some care I might be able to make some &quot;rough&quot; but serviceable lead screws and other similar items from round stock. With some OCD level of attention this could allow someone to even make custom bits and endmills.</p>
<p>If you have a dado blade, could you increase the width of the groove that way?</p>
<p>I don't have one, so I haven't tried, but I don't see any reason it wouldn't work.</p>
<p>Fantastic! I too have marvelled at the marble coasters and was always hung up on the lifting mechanism. Not any more! Thank you thank you thank you!</p><p>I grab rotisserie motors at any second hand shop I might stumble across them at for that day when I get to building - usually $2-$5. They have a good positive square connection point for square steel or wood and have pretty good torque so gearing for optimum RPM and/or running a few take-offs off of one motor will be no problem. The only thing I was missing was the lift but no more....thanks again. I'll be cutting a spiral tonight! Sorry - a helix.</p>
<p>You're welcome. I would love to see what you come up with!</p>
<p>So the drywall screw catches the first part/groove already cut and pulls it along through the rest of the cut?</p>
<p>Exactly! That's probably how I should have said it...</p><p>My original thought was to just turn the dowel and have the blade itself guide and pull the dowel along, but that proved to be pretty inaccurate, hence the screw.</p>
<p>I saw your main image and thought, "Hey, that looks like the one I made . . . only much better!" </p><p>Brilliant job, sir! Glad my project inspired you. Have you built a full coaster? I'd love to see how that looks!</p>
Thanks! No, I haven't finished yet. I'm still looking for the right motor to use. I'll certainly post a picture when/if I get it finished!<br><br>Thanks so much for the inspiration!
<p>might I suggest using a gear head motor? robot shop has a wide variety:</p><p><a href="http://www.robotshop.com/en/catalogsearch/result/index/?dir=asc&order=price&p=2&q=gear+head+motor" rel="nofollow">http://www.robotshop.com/en/catalogsearch/result/i...</a></p><p>Jaemco has quite a few too:</p><p><a href="http://www.jameco.com/1/3/gearhead-motors" rel="nofollow">http://www.jameco.com/1/3/gearhead-motors</a></p><p>I like gear heads for augers. you can pick one for a specific rpm or you can pick one a little faster than desired and pulse width modulate the voltage to slow it down to the right rpm, they are super torque-y and durable.</p><p>Also, I apologize if you were already aware of this option, and just looking for the right one. </p>
<p>Thanks for the sources. For the coaster, I would really love to repurpose a motor, like Seamster did. My budget (and wife) would be much happier that way.</p><p>However, I'm always interested in good sources for decent motors!</p>
<p>I would suggest looking into the Arduino world. You can get the UNO board, drivers, and USB cable for programing on the cheap, and eBay has tons of low end stepper motors that will run on it. You might also want to look into EFL (engineeringforless.com) for their CNC program that will run the motors for all kids of stuff for free. Love the wooden screw idea. Could be used for many different projects around my shop, including a bench type vise, providing, I can build a matching nut :)</p>
<p>What exactly do you mean by &quot;by adjusting the placement of the dowel on the jig&quot;?</p><p>Do you mean moving the jig in relation to the blade, or the screw that is the guide in the blade slot? Or am I missing something else, because the dowel you are cutting should only go onto the jig in one way, that is what a jig is for isn't it?</p>
<p>When starting the first cut, adjust your fence on the left side as a stop against the dowel. After one full spiral, adjust the fence a little close to start the next spiral.</p>
<p>More: The jig keeps the angle and piece stable as well as using the screw to keep it steady. Screw shouldn't need to be moved.</p>
<p>http://www.bealltool.com/products/threading/threader.php</p>
<p>A similar procedure could be used with a router table and a nose bit for a rounded groove/spiral. I've done one without a jig but it was pretty rustic-- still used it though. Nice tip</p>
<p>Well done! A very neat solution to a seemingly difficult problem.</p>
<p>This is very cool, I love to see when projects start building off each other! I loved seamster's coaster, and this is an awesome inspired project! <br><br>Also, never forget &lt;ahref=&quot;https://www.instructables.com/community/The-answer-is-almost-always-YES---AKA-Kitemans/&quot;&gt;Kiteman's Zeroth Law!&lt;/a&gt;</p>

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