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    Default Building my first JGRO based on 2004 plan

    Hi everyone. Love the site. I've been wanting to make my own CNC router ever since seeing some examples (here or at buildyourcnc) of people fixing them up out of MDF and using skate bearings.

    I recently gained access to most of the significant machines I've needed by joining the local Tech Shop. It's been great. Primarily, I've been without a table saw, router, sliding compound miter saw, and drill press, but now they're available to me. I also have access to a laser cutter. And yes, the Tech Shop also provides a CNC Router, but I figure I have to make one without first, and then make a second using my own JGRO. That's the tradition, right?

    I chose to go with the good old JGRO router plans that have been online for so long. Unbelievably, the plans are almost 10 years old now -- dated 2/11/2004! -- so part of me feels like I'm 10 years behind but I also want to get one of these under my belt before attempting anything fancier.

    I also only have the plans. I've not seen any step-by-step instructions on how to build it. As such, it's been a great spatial learning experience, figuring out what goes where.

    I'm approaching the build from the inside out, starting with the Z axis, and eventually moving up to the Y axis, and then constructing the beds. Partly, I want to do this because the small parts exercise some of the "hard" parts of build for me -- routing grooves, precision drilling, etc. -- and partly because I'm undecided on how big I want to make the X and Y axes.

    The initial build steps are going well. As a starting point, I used the Tech Shop's laser cutter to create numerous jigs from 1/8" acrylic, thus getting precise pilot hole points everywhere. I also used the acrylic jigs for router distance placement, and then had more jigs set up to try to figure out router depth. The router depth jigs didn't work as well, but got pretty close, and I was always careful to cut test wood first and measure, rather than go for it all and cut too much. The pilot hole jigs were invaluable -- saved tons of time. (The drill press I'm using doesn't have laser guides.) For holes, I've been measuring drill bits with digital calipers to make sure they're the right diameter. All in all, it's been a great exercise in precision woodwork.

    I'm at the point where I've gotten most of the main, small pieces cut, and some of them drilled. I sourced the 1-1/4" aluminum angle online and am about to cut it up. I got bearings from freebie rollerblades (freecycle). A local restaurant supply shop had great 1/2" plastic cutting boards that will become my lead screw nuts. It won't be long before I get the 1" and 1/2" pipe.

    The things I'm wrestling with:
    - Strengthening the holes before screwing to them. From what I've seen, I'll probably do the soak-with-superglue thing.
    - Black pipe vs. galvanized steel? I'll probably do black pipe and sand it down.
    - Lead screw and tap. I'll probably get Acme 1/2"x10, single start. It appears to be the least pricey of the bunch. But to tap the holes, I'm not as sure what to do. It'd be great if this group could start some kind of tool lending program. I'm intrigued by those who have made their own taps, and might take a shot at doing that. But I have zero metal milling skills.
    - Adjustment blocks. I'm worried about these, as the original plans call for MDF, but most everything I've seen says that that's not going to work for the Y axis blocks.

    Things I just don't understand:
    - The plans call for 1/4x20 screws for connecting MDF to MDF with no bolting (e.g., connecting Z axis platform to Z axis bearing support). That doesn't make sense to me. Seems I'd be better off with either wood screws or machine screws with cross-dowels / barrel nuts.
    - The pipes that are connected through the X axis top and bottom plates, and thus allow travel of the Z axis bearings, appear to go through the holes and therefore they're not really supported from below. They're only held in place by the adjustment blocks. That seems, well, unsupported.

    Things I've given up wrestling with:
    - Shouldn't I just bite the bullet and make it out of extruded aluminum? Well, I got this far and like the woodworking aspect...
    - What about the first question they ask when building a DIY CNC Router: "What will you do with it?" Well, basically I don't have a plan for why I'm doing this, other than "It looks like a really fun project." I supposed once I've built it, I'll get on with building another one, using the one I'd made.

    Anyway, that's where it is right now. Lots of MDF dust flying around as I build all these little blocks and get ready to join them together. Any pointers would be appreciated, though now that I've found this forum, I think I have more reading to do...

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    I'd make the adjustment blocks out of plastic like Delrin.
    Acetal 3 " 3 00 x 6 inches Long Rod Bar Stock White Delrin | eBay Just cut off a slice and drill and tap. You might be able to find a similar size square piece, but I only spent a few seconds searching.
    - The plans call for 1/4x20 screws for connecting MDF to MDF with no bolting (e.g., connecting Z axis platform to Z axis bearing support). That doesn't make sense to me. Seems I'd be better off with either wood screws or machine screws with cross-dowels / barrel nuts.
    Yes, you would be better off with dowel nuts. You need to be really careful if using wood screws, as MDF splits incredibly easy when screwing into the edge.

    The 1/4-20 is just what was popular 10 years ago. If someone had thought of using dowel nuts back then, that's probably what would have been used.

    A lot of innovation occurred after the JGRO. Today, there are better ways of doing just about everything.


    - Black pipe vs. galvanized steel? I'll probably do black pipe and sand it down.
    My galvanized pipes have the coatings continuously flaking off, even after around 200 hours of use.

    Sanded black pipe is a better option. If you look through the old Joes 2006 threads, you should be able to find some home brew methods of making a lathe type sanding jig.


    - Lead screw and tap. I'll probably get Acme 1/2"x10, single start. It appears to be the least pricey of the bunch. But to tap the holes, I'm not as sure what to do. It'd be great if this group could start some kind of tool lending program. I'm intrigued by those who have made their own taps, and might take a shot at doing that. But I have zero metal milling skills.
    I made a tap for my 1/2-10 Z axis. Then I broke down and bought dumpster nuts for my X and Y axis. I used a dremel to cut/grind 1 or 2 slots, then a stationary disk sander or grinder to put a taper on it.

    Google "Making Acetal leadscrew nuts the easy way" to see a method that doesn't require a tap.


    - The pipes that are connected through the X axis top and bottom plates, and thus allow travel of the Z axis bearings, appear to go through the holes and therefore they're not really supported from below. They're only held in place by the adjustment blocks. That seems, well, unsupported.
    There's no vertical force on the Z axis pipes, so they don't need much support. The leadscrew carries all the weight.


    - Shouldn't I just bite the bullet and make it out of extruded aluminum? Well, I got this far and like the woodworking aspect...
    The gas pipe on the longer axis are the weak link ion the JGRO. Making aluminum parts won't help much, and may make things worse if they add additional weight.
    And if this is mainly a learning exercise, don't spend any more than you need to.

    Last edited by ger21; 02-06-2014 at 06:55 PM.
    Gerry

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    Just adding some pics as I go along. I can't tell the diff between a blog and a thread these days... Routing the X axis platform "H" shape was an interesting exercise. Adjusted router depth to my liking using jig, then cut bits and measured to make sure it was set properly. The router's fine depth adjustment doesn't appear to be working, though. Cut the "legs" of the H first, and then for the crossbar, I routed directly into the middle (laid the board down on the bit) and moved outward until it cut back to a leg. Then, gently bumped the guard this way or that until I got the cuts where I wanted them. Drilled holes into X bearing supports through the existing platform holes to avoid misalignment. I realize I should have done that in drilling the joining holes for the Z bearing supports, too, as they're ever so slightly off, making it tough to pin with dowels *and* fit into the slots. Ya learn.

    These are the jigs I laser cut for measuring router depth. The idea is that you unplug the router, then lift the router bit to the level so that it hits the "bridge".
    Building my first JGRO based on 2004 plan-router-depth-jigs-small-jpg

    A pic from a few days back - different parts getting into different states of readiness.
    Building my first JGRO based on 2004 plan-pieces-far-small-jpg

    Z axis assembly MDF (without clamp -- I don't have a motor spindle yet). Here you can see some of the other laser-cut jigs. For parts like the X axis top, where there are big holes, the jig just set me up for a 1/16" hole point. I'd place the jig atop the wood, and drill-press a 1/16" pilot through. Then, and I used a Forstner bit to cut the hole (half way through from each side, not all the way through from one side, so that I'd get a clean cut).
    Building my first JGRO based on 2004 plan-zplat-templates-small-jpg

    and X platform assembly MDF, pinned with wood dowels for the time being.
    Building my first JGRO based on 2004 plan-xplatpinned-small-jpg



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    Some slow progress. I cut my cutting board to fit the full depth of the Z axis slots. The band saw cut this quite neatly. Sanding yielded a bunch of fuzzy plastic hairs. Using a hand rasp to clean up the edges was much better. But, I did need to sand down the depth ever so slightly for it to fit into the slots.
    Building my first JGRO based on 2004 plan-img_0701sm-jpg
    I'm a little concerned that the tight tolerances on these will be messed up once I paint the MDF. And I have to paint the MDF to avoid swelling. We'll see...
    Building my first JGRO based on 2004 plan-img_0704sm-jpg

    I am glad that I cut it to a larger size than the JGRO design called for, though. The reason: I intend to use 1/2"x10 single start Acme for the lead screw, which will mean a bigger hole in the center, and will mean different offsets for the screws that hold this piece of plastic to its corresponding Nut Tensioner.

    I also got to use the horizontal band saw and chopped the aluminum angle down into the lengths required (6" x 2, 7.5" x 2, 8" x 2).
    Building my first JGRO based on 2004 plan-img_0706sm-jpg

    A test fit looks good for the grooves, but it rides a little high. I need to shave down the inner groove edges so that it can settle flat. I figure a Dremel + sanding drum should do the trick.
    Building my first JGRO based on 2004 plan-img_0708sm-jpg

    The next step is making a jig for the holes that will be used for mounting the skate bearings.

    I also have to carve out the center hole for bolting the angle to the Bearing Support. I've read other sites, and they suggest using a plain file to get that going. There may be a way to run a slow-speed Dremel with a sanding drum (not a grinding tool!) to start the process, and then finish with a file. I found a page on myheap that said they had advice on how to build this part, but then the update isn't there in that blog. As before, any advice would be appreciated.

    Attached Thumbnails Attached Thumbnails Building my first JGRO based on 2004 plan-img_0707sm-jpg  


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    Happily received Acme tap yesterday. "1/2" - 10 HIGH SPEED STEEL RH TANDEM STYLE ACME TAP" from B&B Supply via Amazon. Made in Serbia. Now I'm committed to that size lead screw. It was pricey, but my plan is to use it and then sell it some time later, lightly used, well cared for, to defray some of the cost.
    Building my first JGRO based on 2004 plan-img_0712small-jpg

    Also recently made jigs for pilot points on the gantry, and a little jig for the holes that go through the aluminum angle to hold the bolts that hold the skate bearings. In looking at the skate bearing assemblies, I couldn't understand why some have offset holes at .375" and 1.25", whereas another was .375 and 1", so I decided to just make them all the same. Really, what's important is that they stay level.

    I also would have preferred to have set up the jig such that I could drill from the inside, but there's a curved, structurally supporting corner on the interior of the angle, and that gets in the way of precision placement. That way, I could butt the jig up against the interior wall of the angle, and lay it flat when drilling. I may yet get that result by drilling initial holes through from the outside and keeping a piece of material on the inside to act as jig#2, and then use jig#2 to drill from the inside out.
    Building my first JGRO based on 2004 plan-img_0715small-jpg



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    Bearing assemblies are coming together now. Hand-filed areas for the K-size (OD 0.281) drill holes; drill bit caliper-measured at 0.279. Separately, I have a dozen decent skate bearings that were scavenged in various ways (freecycle, old kids' toys that went rusty). All bearings are clean and moving smoothly.
    Building my first JGRO based on 2004 plan-img_0887sm-jpg

    Also, happily got a big tube at the doorstep, containing both two lead screws -- both 1/2"-10, right hand, single start Acmes -- one 3' long, the other 6' long.
    Building my first JGRO based on 2004 plan-img_0888sm-jpg
    I'm planning to cut the 6' one into two pieces, one for Y, one for Z. The 3' section will be used for X.

    1/4"-1/2" couplers on order. I'm not sure if I'll use the ordered couplers or try to make some of my own or try some other approach. I did take a most excellent Jet metal lathe course at the Tech Shop, intending to turn the ends of these rods down to 1/4" OD, and use 1/4"-1/4" couplers. But then I saw the 1/4"-1/2" couplers and figured I'd give those a go instead. I just have to be sure to get steppers with the right shaft diameter.

    The question about couplers is: is it better to use a coupler that clamps onto the threading of my screw (the 1/4"-1/2" case, where the 1/4" side is to the motor shaft, and the 1/2" side is to the threaded lead screw end) or is it better to turn down the screw end to 1/4" OD, and have a cylindrical piece of metal to which I can clamp a 1/4"-1/4" coupler? The friction hold argument would be: there's twice as much surface on the diameter of a solid 1/2" vs. solid 1/4" cylinder. But the 1/2" side isn't really solid since it's threaded... so if you look at the actual thread contact surface, it's about 1/3 of the amount, so really a 1/2" thread in a 1/2" clamp hits about 2/3 the amount of surface compared to a 1/4" solid cylinder. Did I do that math right? Then again, trying to turn my lead screw's end in the lathe might cause me to mess up the threading at the point where the lathe holds the lead screw, so that's a risk I could avoid. Or maybe I'm just overthinking the whole thing.

    Now I'm trying to figure out motors and motor driver. After seeing all the reviews, I'm pretty sure I'll spend the extra $ and go for the Gecko G540. The DM542s look less expensive and they're nicely modular, but the Geckos have a really good rep.

    Once past that point, I think getting some 1/2" pipe is the last large material I need to get on with assembly of the Z.



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    Where did you order the acme thread from and how much did it cost?



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    Quote Originally Posted by hotdog21212 View Post
    Where did you order the acme thread from and how much did it cost?
    Got them on e-Bay from seller imsrv, located in New Hudson, Michigan. Price of 1/2"-10, single-start screws is pretty low everywhere. For me, $15 for 6'. I had to pay more for shipping than for the material! The seller says they *may* combine shipping costs if things can fit in one box, and if they do, they would provide an e-Bay rebate. The shipping cost reduction isn't reflected in your initial bill. Or so they say.



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    Good luck with your JGRO.

    I built the jgro many years back, it is a great learning experience and will help you understand what you'll need when you want to build your second machine.

    Enjoy the process!

    Rob.

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    Latest update: made good progress getting the Z axis aluminum angles bolted to the Z bearing supports. I superglued the holes and let them dry before attempting to bolt things together, and the threading appears to be holding well. The hardest part was getting the 0.125"-deep slots cut out before drilling holes. I tried hand-filing them, but only got down to about 0.05" to 0.07" deep. If they weren't cut down deep enough, the bolt heads would run into the 1/2" gas pipe.

    After some youtube browsing, I saw someone cutting aluminum with various types of saws (circular saw, jigsaw, Sawzall). So I tried something most shop teachers would cringe at: I used my variable-speed jigsaw, fit a fine-tooth blade to it. I clamped the angle to the edge of my work table. That allowed me to turn the saw mostly upside-down and at a 45-degree angle, and started cutting bits away. With a slower cut speed and some pressure into the metal, it did start removing material in small slots. Once enough material was gone, I cross-hatched more cuts, and then filed things down. It was loud and somewhat messy, but took far less manual effort than filing. But, it's arguably unusual, and usually "unusual" means "unsafe".

    I'm wondering if I could take another approach: take a 2x4, and cut a V slot in it using the table saw. Make it the right depth such that the angle fits into it, and the whole thing is flush to a table when turned upside-down (so the V of the angle forms a tent and is fully covered by the 2x4). Then, I could take a circular saw with the blade at an appropriate depth, and run it across the angle. But it seems I'd end up risking chatter, catching the blade, and flinging the whole thing across the room.

    Another thought: drill a pilot hole, and then go at it gradually with a Forstner bit?

    I think I'll stick with the jigsaw.

    Separately, I'm planning to use an old, unused desk as the main platform for the machine. That's now making me think of mounting the Y axis pipes directly to the desk (yet allowing for shim adjustments somehow). Then, I'd change the orientation of the Y axis slides so that the V points downward, not to the side. That might limit my X axis range too much, and would cause all sorts of other design changes. Still, I like the idea of reorienting the Y axis slides so that they put weight evenly on both pairs bearings.



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    Z axis is mostly assembled now! So many steps getting here...

    The aluminum slide slots (the grooves that you drill holes through so you can bolt them to the wood): I ended up figuring out how to use the jigsaw approach to cut these, and then filed them down with big files at the Tech Shop. Tools: handheld jigsaw with appropriate bit, large file, vise, digital calipers to measure depth.

    I cut all the 2" adjustment blocks. 3/4" MDF. Tools: Sawstop table saw, compound sliding mitre saw, various sanders.

    I drilled a ton of holes using the jigs I'd made earlier. Tools: drill press, 7/32" bit for holes that the 1/4"-20 bolts actual thread onto. Designated thread (per design) for the 1/4" through holes. 5/32" bit for the #10-24, if I recall. Original Super Glue to strengthen the holes. Note: I found that the spec saying to use OD 0.201" holes yielded holes that were too small, and I ended up cracking the first two test blocks that I'd made. Luckily, I'd made more than required. I looked at specs for 1/4-20 bolts, and found that 0.201" is just too small. It's smaller than the minimum minor diameter of the bolts. After bumping up a level higher and then higher again, I ended up with the 7/32 being the best choice for my needs.

    I bought 1/2" flange bearings online -- a pack of 4 or 5, I think, from MSI -- and those had a 1.125" outer diameter. I used a Forstner bit for cutting that hole after piloting the X bottom plate.

    My motors arrived along with the Gecko G540! (Bwahaha!) These are by far the biggest hobby motors I've ever gotten. I opted to go through Keling and got their 280 oz/in ones. The motor has a circular area that's 1.5" diameter, as called for in the spec, so I drilled that into the X top plate, and then marked the holes for mounting the #10-24 screws.

    The lead screw is a 1/2"-10 RH SS Acme. I got two lengths, and cut them at the Tech Shop on the horizontal band saw, and then used grinders to clean up the ends.

    I bought four 1/4"-1/2" couplers off of e-Bay, and they're beautiful. Aluminum, springy center, two clamp screws that bind around the circumference, and another on each end to bite down if there's a flat part to the shaft (which there is on my motor). BUT, the 1/2" end didn't fit over the lead screw! I measured it w/ calipers and came up with a bit less than the 0.495" OD of the lead screw. The company *immediately* gave me a full refund, leaving me to wonder about next steps. I ended up taking a JET metal lathe class as the Tech Shop and then got up the nerve and went to turn down the end of the Z axis screw. I ended up using the Samson lathe because it had a collet closer attachment, and after learning that and doing the lathing, the coupler fit! It was a most excellent moment.

    I cut my lead screw nut out of 1/2"-thick cutting board plastic such that it would fit in the right place. Here, I did not use the pattern specs. It's more important to see what you actually got from the cuts in case the routed channel depths weren't perfect. I then marked the center and drilled a hole for tapping. Per online specs, I chose to use a Y-size bit (measured at 0.402" whereas online it says it should be 0.404", so that's pretty darned close), and then tapped it. The result was mostly ok, but not perfectly vertical, so I may re-do that. When assembling it, I had to eyeball the placement such that the center of the hole aligned with the centerline across the slide V points.

    Then for full assembly, it was super glue, dowels, bolts, and then lots of finicky tightening and loosening.

    For the motor mounting, I also took some excess #10-24 1.5" screws, and just used a bolt cutter to chop them to about 3/4" length, then ground down the sharp tips with a Dremel. Worked like a charm.

    Picture!

    Building my first JGRO based on 2004 plan-img_0912-jpg



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    Default Re: Building my first JGRO based on 2004 plan

    Slow and not-so-steady progress. The Z axis now moves!

    I ordered a 36V 400W (12A, if I recall) power supply to drive it. Various scavenging done to assemble the power supply line (chopped computer power cable, circular spade things soldered on ends so they don't come loose).

    The motor is wired up in bipolar parallel. I wired the DB9 headers with 4200 ohm resistance across pins 1 and 5. The Keling motors I'm using state that when wired in parallel, they are rated at 4.2A, and the Gecko doc said to multiply that by 1000 to determine resistance. At some point, I'd bought a few resistor variety packs from Jameco, so I had a 2k and a 2200 (both 1/4 watt) laying around. So I just soldered those in series and trimmed them to fit into the DB9 header. The rest of the wires were just wired in as the doc specified (A, A/, B, and B/).

    To connect the Gecko to a computer, I needed a DB25 parallel cord. I didn't have one initially so I constructed on as a scavenge-solder job. I used spare bits from the Tech Shop bins -- an old DB25-Centronics printer cable wired to a DB25 D-cup male header. It was a bit tedious but fun checking connectivity on all points and rewiring it. But it only had 17 active wires, and that worked but it left the variable frequency wire and several ground wires floating, so eventually I went and found a real DB25 male-to-male at Weird Stuff.

    While at Weird Stuff, I also picked up several DB9 extension cords, so now all three motors are wired up and working.

    Driving it all is a scavenged old PC that's running Win XP -- which is out of service, thus vulnerable, so I'm only running Mach 3 on it and not letting it connect to the network. I did as Gecko said, making sure it was set up in the BIOS with EPP parallel mode, and then manually configured the flags for which pins do which things. It was amazingly easy and very satisfying to see the motors turn in Jog mode for the first time. (Coming from an Arduino world, having a full user interface where I can set acceleration and velocity and adjust jog percentage is a luxury.) I also got a set of ceramic adjustment screwdrivers from e-Bay so I could tune them, but it turned out they didn't need much tuning.

    I'm now working on the X axis box, and have found that I want a chart for what hole sizes to use where. This time I'm planning the hole drilling a little better, so I hope that works out. Basically, I'm not drilling the edge holes by measuring. Instead, I'm drilling pilots of the thru-holes, then lining the boards up and piloting through to hit holes on the edges of joined boards. But along the way, I still get confused by the plans, so here's my helper chart:

    If the plan says: OD 0.281, then use a K, 17/64, or 9/32.
    It's usually a: through-hole with slop so that a 1/4-20 hex bolt can slip through.
    A 1/4-20 hex bolt major diameter is 0.250
    So choices for OD 0.281 are K, 17/64 (0.265625), or 9/32 drill bits (0.28125).

    If the plan says: OD 0.201, then use a 7/32, which is quite a bit bigger than 0.201.
    It's usually a: hole that a 1/4-20 hex bolt will screw into.
    A 1/4-20 hex bolt major diameter is 0.250, minor diameter 0.1876. In practice, 0.201 is too tight and caused my adjustment blocks to split.
    So instead of 0.201, use 7/32 (0.21875")

    If the plan says: OD 0.150, then use a 5/32.
    It's usually a: hole that a #10-24 machine screw will screw into, either to hold an adjustment block (e.g., bolting an adjustment block to a gantry side), or to mount a Nema 23 stepper motor.
    A #10-24 screw's major diameteris 0.1900, minor diameter is 0.1379. Halfway point is around 0.164. Using an OD 0.150 hole may be too tight.
    I may use a #25 (very close to 0.150) but I think it's probably better to use a metric 19 or 20 bit, or 5/32 (0.15625").

    If the plan says OD 13/64" = 0.203125", then use a 13/64.
    It's usually a: hole that allows a #10-24 machine screw to slip through, like the ones on an adjustment block.
    0.203" is greater than the #10-24 screw's major diameter 0.1900, so that's fine.

    If the plan says OD 0.219, use 7/32, metric 3, metric 2, or as small as a 13/64.
    It's usually a: hole that allows a #10-24 machine screw to slip through for an anti-backlash nut assembly.
    0.219" is greater than the #10-24 screw's major diameter 0.1900, so that's fine, again, though it's not clear why I'd use 0.219 as opposed to 0.203.
    As such, 13/64 should still be ok here. An actual OD 0.219 spec on the diagram probably means "use a 7/32" bit (0.21875") with alternatives being a metric 3 (OD 0.213) or metric 2 (OD 0.221).

    I've been referring to Wikipedia by searching on "wikipedia drill bit sizes" to figure out what size will work for what, and also found this page to be useful in determining major and minor diameters of screws: ANSI External Screw Threads Size Tolerances Chart - Engineers Edge



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Building my first JGRO based on 2004 plan

Building my first JGRO based on 2004 plan