How I Design And Cut My Gears Without A CNC Machine: 045

when i started thinking about designing another clock i really wanted to tackle some of the engineering challenges or specifically manufacturing challenges that come along with building a clock by hand using woodworking tools now for those of you with cnc machines perhaps all you have to do is hit the go button and sip on your coffee while the machine does the woodworking but for me i have to do it by hand and so i design my gears accordingly to make them easier to make while still being attractive to look at and of course functioning like gears today i want to focus on uh the changes that i made to my gear design and also i'll show you how i make my gears for my clock later videos will show the whole build process and there will be plans available when this guy's done let's get started so before i show you the modifications that i've made i thought i'd talk to you a little bit about gears in general here i have a wooden gear set which i have cut with an involute style gear profile this is typically what you will find if you use say a gear generator that's the most common gear profile that's used in machines and that's why most gear generators use that as you can see this is that same type of profile now there are many different types of gear profiles but that's outside of the scope of this video what i want to talk to you about is first how do gears work well this guy the smaller gear will be the pinion is what it's usually called and if the motor is attached to this gear then this will be the driver and the larger gear is the driven gear with this setup you have what's called a torque multiplier the smaller gear actually has more leverage relative to the large gear so if you look at the center of rotation to where the gear is actually pushing and you think of this as a lever the small gear has a much longer lever than the large gear so while this gear is going to spin slower you're going to be able to move a much greater load you get a higher torque on this gear if you went the other way if you made the larger gear the driver and the small gear the driven there's no free lunch there's always a trade-off so what you're gonna get is this gear will spin much faster but it requires more force now on this side to get the same output torque so that's the basic principle behind gears you have spinning levers which allows you to produce a torque about another axis you could either multiply the speed by driving the large gear or you can multiply the torque by driving the small gear so again driving a small gear will get a slower output speed but more torque driving the larger gear will give you more speed but less torque so now that you know that gears are really just spinning levers all we need is a lever to push against and one that's got the proper length to give us the output speed that we want in the case of a clock i want to reduce the speed so that my hands move at the proper rate on the face of the clock to give us time so this this tooth could take any shape as long as it had something to push against if you look at my square gears for example these are not involute style gears it's just a triangle that i have patterned around the square now uh the process would take a little bit longer to explain in this video but basically what i have here is a varying pitch circle and as long as they change at the same time you can make any shape gear you want so here i have a much longer lever this lever has to be shorter to make sure i maintain this center distance and vice versa when this one is shorter this one is longer and as long as they vary at the same rate your gear can take any shape so we want a gear profile that's easier to make that's the goal now let's talk about that here we have a page from my plans which are in progress with the new geared profile design and then i went back and i made the same gears using a gear generator and you could get here from here so you could start with this profile and make these adjustments and that would be very easy to do this is not so custom that you couldn't copy it is what i'm getting at looking at a typical involute style gear profile over here you can see there are some notable changes number one my tooth is just ever so slightly thinner again the strength of the teeth is not super critical here because we're not pushing a very large load we only need to be able to rotate the hands of a clock i can make these gears just a hair thinner which gives me more slop also referred to as backlash that is backlash and this is good because it allows the gears to swell a little bit or even change their shape or even not be cut perfectly and still rotate because in the end what we want is a working clock right we don't necessarily want every tooth to be 100 perfect in fact i would say that should be the goal of every engineer right you want to design something that's got some forgiveness built in for the fabricator and in general is easy to fabricate looking at my gear profile you see these center marks which indicate a place where i can drill out the bottom of the tooth this is a five millimeter diameter circle that i have put at the bottom of every gear no matter what size it is they all use the same drill bit again that's for ease of fabrication even my larger gears like this one with 40 teeth and there's a 50 tooth one all of these have the same five millimeter diameter bottom on the gear but i took that one step further and i also did the same kind of change for the internal cuts these internal cuts have to be done on the scroll saw what i did is i put a center mark in all of these corners these rounded edges are designed to fit specific drill bits that i have so here we're looking at it's an eighth inch radius so it's actually a quarter inch drill bit that i will use right here in this corner so you're going to be drilling a hole no matter what to put your saw blade through so why not go ahead and drill three holes and have three perfect corners there and then you just have to focus on cutting the straight lines the same thing with the gear i mean with the face not the gear this half inch radius actually is a one inch drill bit one inch forcing a bit that i can use to make a nice perfect round corner here with my forstner bit and so when the plans are finished of course all of these diameters will be called out but the point is this makes it so much easier to fabricate a nice looking face because i can actually make these rounded corners with a drill bit which is designed to make a round shape as opposed to a straight saw blade where i have to try to go back and sand it smooth and round it off the drill bit will make it round from the beginning all right so let's take a look at how i cut the gears out okay we're going to start with a piece of baltic birch which i have somewhat unsuccessfully stained but we're going to keep going here and i will cover it with tape not only is this going to protect the face it gives me a removable surface i'm going to glue the pattern on top of the blue tape and then cut through both that way i can just peel this tape off and it comes off just like you would any painted surface it should leave the surface underneath just fine one other thing that i do is i use a one of the more aggressive glues so some people use the repositionable uh spray-on adhesive but i use the uh high-strength stuff that should help prevent some of the tear out because there's nothing worse than cutting through your gear and then having the gear profile start flapping up and tearing away while you're cutting it out so i'm thinking that using a better glue a stronger glue should help reduce that problem but still allowed me to remove it easily some people use like contact cement and then mineral spirits to clean it off prior to doing this what i did was no blue tape i would just use the repositionable glue and glue that directly to the wood and then i'd use a heat gun to try to warm the glue back up and peel it off that didn't always work i would still often have to use mineral spirits to clear it off [Music] all right let's do this all right it says let it dry for one to two minutes before you drill any holes go ahead and double check make absolutely certain that your table is square and we do not want crooked holes i have been drilling steel on this table and using fluid and so this table has a residue on it i want to make sure even after wiping it down that i don't rub any of that into my gear so i'm going to cover this table as an extra layer of protection now when i'm making stuff for the shop i don't really care but if you're going to make something really nice and take the time to protect the surface and cover everything in my touch helps to tighten the drill bit all right i'm most of the way through this gear and i just wanted to point out two things uh these gears number one i forgot to put my tape on the back i normally tape the front and the back and the dondo math i got most of the way through but here is why it prevents the tear out on the back or at least significantly reduces it and the other thing i wanted to point out is you can't tell in high speed but i will feed the drill and i kind of pause for a moment to make sure that the chips are coming out sometimes i will back off just a little bit and uh to allow the chips to go away the tendency when you're in a hurry especially after you've drilled a lot of holes is you just want to kind of shove it through to hurry up and finish but then you end up tearing off either the paper or clogging the hole it might grab the whole work piece and want to pull it up off the bench so make sure that as you're driving that drill bit that even when you get to the last one that you're not rushing you go slowly to make sure the chips are coming out and if it doesn't look like they are let your drill bit back off a little bit before you finish the hole this is about where i make the most mistakes generally i've only got a few holes left starting to get tired but i want to rush because i can see the light at the end of the tunnel and this is where you got to be the most careful the last few holes are most likely the ones you got to mess up so take your time if you're tired go take a break come back and finish all right took a little break came back now i'm ready to cut these gears out [Music] so i've tried to leave the line everywhere although there are like one or two places where i took the edge off of the line and lost it but the gear tooth still looks pretty good now we're going to sand it down to its final profile well hopefully you remember this guy here i've got some custom sandpaper that i purchased online this can be purchased at any length and width this is 120 grit sandpaper i'm going to use this to sand right up to the line i like 120 grit because it's just aggressive enough to shave the line off but it still leaves a nice smooth surface [Music] i almost forgot to say that i just pulled up a stool and sat down so that i'd get more comfortable when i was learning how to weld the guy who was teaching me kept saying a comfortable weld is going to be a good weld and he was basically just emphasizing that you need to be comfortable first and then you can lay down a solid weld and he was right i did much better when i was comfortable so anyway sit down relax make sure you're comfortable and you can do a good job we're at the last stage before we make these internal cuts and i need to sand this profile i want to use a circle sanding jig i haven't actually made one for my lathe just yet so i'm making a makeshift one really quick this is a scrap piece of wood where i was practicing my stencil the other day and i've got all this six millimeter shaft that i took out of a large industrial printer and yes there'll be a video on that i'm still looking up all the part numbers but i've got a whole bunch of this six and eight millimeter shaft now so i'm going to redesign the clock around that and that's part of the reason why i'm ready to build this thing and i will use this as an access to rotate about we are down to the last step and that is making these internal cuts i always save this for last because if i make a mistake here i can sort of modify the design and make it look okay but it doesn't affect the function of the gear if i mess up a tooth profile i might have to make a whole new gear and i would hate to invest all that time in cutting all the internal cuts and then ruin the first or second tooth on my clock so on my gear so i do all of the critical cuts first and then if it's still safe i can mess these up and it's not a big deal the clock will still work and i maybe can change the design a little bit to make it look okay this part is uh pretty easy i don't i don't have any special tricks here or anything i just feed it in take my time and try to get as close to the line as i can so that there's not much sanding left to do when you get done all right all right helps to plug it in two fails and one video [Music] well at this point i'll give it one more look over just to see if i've left too much of the line anywhere and other than maybe right there it's looking pretty good i might end up going back and doing a little bit of light sanding in between for those internal cuts but the best part is when you peel this off it all comes off not too bad that's totally raw first practice i didn't take multiple takes or anything like that that's really what it looks like each time i do it i'm pretty satisfied with this gear i think it's going to work well on the clock i need to get back to making the rest of these guys and uh hopefully you found that helpful if you want to design your own clock or if you want to build mine certainly you've got a lot of tips to make the fabrication a little easier thanks for watching

Channel: Jeremy Fielding

Views: 167,158

Keywords: Cutting Gears on the band saw, how to make wooden gears, how gears work, tips for making gears, tips for cutting accurate wooden parts, how to design gears

Id: QPY9cJS3eHo

Length: 18min 8sec (1088 seconds)

Published: Fri Oct 27 2017