How to Make a Large Plywood 'Cast Iron' Cog

in a recent video i made a large wooden gear there was a fair bit of work in that so in this video i'm going to make another but this time it'll be much easier to make i'll be using plywood which will cut down on time as i won't have to mill the timber and cut and joint the many pieces needed to make up the gear in this video i'll make this one cog but then i'll make another video i'll use these techniques to make a few more and hopefully connect them up to my propeller i started by making and printing off a template and from that i'll make a plywood template i'm cutting them as accurate as i can as i won't be doing anything else to the template other than sanding off any furry bits i'll be using it straight off the bandsaw the cog will have five spokes and the template covers the section between two of the spokes including both the teeth and the openings which i'll cut out with a jigsaw i should mention that the cog will be made up of four layers of plywood i should have marked the pivot point of the template which will be the center of the cog i got ahead of myself but i can still do that with a compass the template's ready to use so i'll grab a sheet of three quarter inch plywood that's been stored away in my lean to for about five years and we'll get started making it the pivot point needs to be very accurate and just the correct distance away from the teeth if the circumference isn't quite right the teeth won't line up when i get back around to where i started and when i did the small test cog it took me a couple of goes to get that right you can see that it's slightly off so i need to make an adjustment to the pin position the circumference is slightly too small so i need to move the pivot point further away to increase the diameter i screwed a piece of aluminium to the template and drilled oversized holes for the fixing screws and that's so i could move it around and make slight adjustments i'm not so confident this time so i marked just the first and the last tooth each time i moved the template and i ended up doing this three or four times making adjustments until it was just right it wasn't too difficult to do but another method would have been to make a full-sized paper template and then carefully cut it out doing it this way though will be a neater finish as i'll be using a router with the template to finish the final shape before i route it i'll cut away most of the waste with the jigsaw and i'm doing this pretty fast because i'm keeping well away from the markings i'm excited to announce that my new website has just gone live and because of that i wanted to give you a free set of my solid workbench plans it's an awesome workbench that's super sturdy and easy to make and i absolutely love mine whether you're a beginner or a weekend hobbyist these solid workbench plans were specifically designed to be extremely easy to follow for a limited time if you click the link in the description below you'll be able to access the workbench plans for free and hopefully they'll inspire you in your own workshop next i'll put the template back on line it up to the markings and fix it in place with a couple of screws i'm not worried about the screw holes at all as i'll be painting the finished piece so i can fill any screw holes afterwards i'll be using a pattern following bit on the router table but this could also be done with a handheld router there's 55 teeth on this cog so there's a fair few to do but i reckon this is much easier than joining the teeth individually like i did on my other wooden cog to route out the openings i'll swap out the quarter inch pattern following bit for a half inch one as it will cut easier and more efficiently although the quarter inch bit did do a great job that's the first layer done so next i'll make an identical layer but this time i don't need the template as i can use the first layer to do that job after rough cutting it i'll place it on top of the first layer and position it so all the teeth and openings have material overhanging and then i'll put a few screws in i then took the screws back out and glued the two layers together to line it back up i put the center pin in and the screws back into the original screw holes i did think about using just screws to hold it together while the glue dried but i would have needed to put a fair few in so i just clamped them instead when the glue had set i took it back to the router table and trimmed it flush and this time i used the half inch bit to remove most of the waste and it ripped through with ease i went back afterwards with a quarter inch bit to get right into the corners you can just see here where i need to get into and i may miss this step out on the next cogs i make and do the whole thing with a half inch bit as i reckon it gets into the corners just enough it's starting to feel a bit more substantial and more like a cog next i'll round over the openings with a three-quarter inch round over bit i'll do that on both sides and that will leave the spokes more rounded now on to the two outer layers which will give the cog more depth and even though there's still plenty of plywood left on the first sheet i can't get the pieces i need out of that but i'll be using them for the smaller cogs that i'll make later on again i'll use the first two layers as the template and i think you're probably getting the idea now i'll fix it down while i mark it ready for rough cutting away the waste that's the teeth cut on these two layers and these ones don't have openings like the first two did instead they have one big opening which basically makes it a ring i'll cut the inside of the ring with  a router and a circle cutting jig after making one pass about five millimeters  deep i'll cut it out with the jigsaw and finish it with a pattern following bit i left more material on there than i needed  to but it cut it easily enough anyway next i'll use a cove bit to add a fillet and add a bit more interest to the cog i reckon that's starting to look good but before i glue the two layers on i decided to do some more shaping to the spokes by removing the flat spots on the top and to make them more oval i did most of the work with an orbital sander and then i refined it with some hand sanding i'm much happier with the shape of those so i can get back to gluing on the outer rings i cut this stick to length with a pivot point on it to help center the ring while i glued it i screwed it on just like the other layers and then flipped it over glued the next layer and then clamped the whole thing while the glue set after flush trimming with a half inch bit i routed into the corners again with the quarter inch bit but this time i did it with the handheld router just for a change the last pieces are two circles and they'll be to make up a center hub if this was just to hang on the wall for display the center holes wouldn't need to be accurate but i'm hoping to mesh this with other gears so it needs to be fairly precise so i'm drilling it from both sides and the forstner a bit should hopefully follow the center hole that was there for the pivot pin i'm using a piece of 50 millimeter round bar to keep the pieces aligned while i glue it all together the plywood isn't the best and there's plenty of voids in there so i did quite a bit of filling before i could paint it i put a couple of coats of undercoat on sanding and filling between them to try and get a decent base for the final coats and to try and hide some of the wood grain i also meant to chamfer the center bore but i forgot to do that so i'll do that now that's the prep coach done so time for some  finish and on the outer rim with the teeth i'm using a rust effect paint so i'll get started on that the first part of the process is to apply two coats of base coat the next step is to put this solution on and that will turn the base coat to rust but i need to let that dry so while that's drying i'll start painting the spokes and with the spokes i'm going to paint those with a base colour and then put another colour on top and then distress it before i put the finished color on i'll put some dabs of furniture wax here and there and when the paint's dry i'll rub that off to expose the base colour i put two coats of the finished color on which is actually the same color as my bandsaw and i'm purposely loading it on and trying to get sags and runs to make it look more authentic the base coat for the rust paint is dry so now i can apply the rust solution and this gets two coats and i have to leave it 12 hours between them every now and then i'm spraying some water on and that's to speed up the rusting process i reckon that looks fantastic but the finish is pretty chalky and it will rub off easily so next i'm going to seal it even though it will completely change the look of it i've used this paint before so i knew what to expect but even though i'm pretty disappointed with the sealer and i may even re-rust it and take my chance with it rubbing off anyway it'll have to do for now so next i'll start distressing and aging the rest of the cog to age it i'm spraying water on and then from a distance i'm very very lightly spraying on black paint and then i wipe it off and it leaves a grimy layer anywhere where the water droplets weren't sitting it was awkward doing this on the floor so i put it back on the workbench and i carried on building up the grime i'm not sure if i went too far with the finish but overall i'm pretty happy with it let me know what you think and what you would have finished it with as i still have a few more cogs to make to make room for the new cog i need to change the position of the original one and put it a bit higher i need to add a cap to stop the cog from coming off and i also need a couple of washers to lessen the friction and allow the cog to turn freely and i'm making those out of a milk bottle here's the cap i made it off camera as it's pretty straightforward i think i'll make a steel cap with a larger nut but this only took a few minutes to make and it will do for now i made another support for the new cog and again i did that out of wood and i may remake them out of steel if this whole project works out and if i think that it's needed that's working pretty well considering the different style teeth on each cog to fix this cog on i made a plywood nut i did that off camera but before i fit it i'll give it the rust treatment i'm not sure how well they'd work under load but i'll get on and make the others and we'll find out and even if they don't work and turn the propeller it'll still be a pretty cool display it really was a fun project i'm looking forward to making the next ones hopefully you enjoyed the video if you did please like and subscribe thanks for watching and i'll see you on the next one

Channel: Pask Makes

Views: 223,152

Rating: 4.9538555 out of 5

Keywords: paskmakes, pask, pask makes

Id: v1k2oByis1Q

Length: 20min 36sec (1236 seconds)

Published: Sun Nov 07 2021