Three Ways To Cut Keyways! No special tools!

hello internet my name is quentin and this is what what's the name of my channel oh it's been a long day hello internet my name is quinn and this is blondie hacks keyways splines and other interior radial features on a bore seem like very difficult things to make but i'm going to show you three ways you can make them in your home hobby machine shop with things you probably already have lying around so let's go what is a keyway and why should you care well if you've got something big and heavy like this flywheel it's just going to spin on the shaft so what we do is we cut a keyway half in the shaft like this that's easy just do that with an end mill but then we need to continue that gap there up into the hub of the spinning thing that is considerably more difficult because that feature has to be cut inside of a bore so how do you do that the quickest easiest and therefore most expensive way to do it is with one of these this is a keyway broaching kit this is used on the press comes with these little bushings here that go in the bore one for each pair of key and bore size then there's the broaches themselves one for each keyway size it cuts the keyway in a series of increasing bytes and in fact for larger keys there's going to be multiple passes you put a shim behind it after the first pass and do a second pass and even larger keyways may have multiple shims let's do a little demo of this i've got a piece of scrap here with a bore in it i've got one of the bushings from the kit i'll slide the bushing in there before you begin make sure you've got room underneath for the brooch to pass all the way through the part at least the teeth anyway and make sure the broach isn't going to fall on a concrete floor or something like that you don't want the brooch to be damaged broaches are very hard they're like taps so they can shatter next of course lots and lots of cutting fluid for an operation like this then we just remove any cat hair that might be present slide the broach down in there to get it started and then line it up under the ram on the press then just start pressing at home i periodically release the ram to let the broach straighten up if something isn't perfectly straight and you keep pushing the broach is going to bend until it shatters so you don't want that and i should say that this is an eighth inch keyway broach and this is about the limit of a small two-ton hobbyist press like you see me using here anything larger than this and you're definitely going to need a lot more press this takes a surprising amount of force for how small these tools look like they are if you need to you can add a little spacer underneath to get a little more height to finish pushing that through sometimes even though the teeth are clear you might need a little help to just push the rest of the shank of the tool through make sure to clean all the chips off the brooch between each pass if there's chips between those teeth the second pass will get very difficult indeed there's the result of the first pass you can see it's basically half the depth of the keyway just getting started so i'll put the bushing back in and we'll do the second pass normally just leave the bushing in place but i wanted to show you what it looks like so far then the shim goes in the back and now we do pass number two the same way once again don't underestimate how much force this takes i'm using all of the two tons on this two-tone press i've got the handle at full extension i've got it clamped firmly to the bench and i'm leaning on it with my body weight to get this down through here it really does take quite a lot of force even for a tiny little model scale sized keyway broach like this and there we have one tidy little keyway that was very quick very easy and very expensive if you look at the brooch now you can see these lovely flat spiral chips that it makes we'll be seeing more of these later aside from cost are there any other downsides to this method there sure are the big one is that you need a custom bushing there for the center of the bore for every bore diameter and keyway size combination that you ever want to do and the bushing has to be at least as long as the bore or longer otherwise the bottom of the brooch is not supported as it goes through and chaos will ensue so what that means is when you use a keyway broach you pretty much are going to have to start by doing what i'm doing here which is making a custom bushing for the center of your bore in this case i'm going to demonstrate putting an eighth inch keyway as before but in a 5 8 bore and the kit of course didn't come with that combination because it only comes with three or four of those bushings and it's never the one that you need i grabbed a chunk of garbage steel here off the junk pile and i turned down the od to be a nice sliding fit in the bore and i'm also just cleaning up the wider shoulder at the top there there needs to be a bit of a shoulder as you saw on the commercial bushings and then you want to undercut the shoulder here a little bit so that it'll sit down cleanly on the outside surface of the bore without getting wedged in there because of a fillet or a slight chamfer that you might have in there jam for the end of course because chamfers are what separate us from the animals and the finish on this garbage steel was making me sad so i took a little bit of emery paper to it and yeah now i'm 18 less sad i guess then we can part it off as you can see it doesn't take too long to make one of these but you know you do have to make it so factor that in if you're going to use keyway broaches a lot and yeah next i have to set it up in the mill i'm using this little tool maker's vise because it's got a nice v-groove jaw that makes it easy to hold a part like this in a way that gives me access to the full length of the part if you don't have something like this another way to do this would be to leave the stock long in the lathe that gives you something to hold on to and then you could hold this in a collet block or something like that in order to cut this groove down the entire length of the part for the width and depth of this groove you can just take measurements off of one of the commercial bushings that came in the kit the depth will be dependent on the size of the brooch that came in your particular kit and then the width is going to be a few thousands wider than the brooch in this case i used gauge block to determine the commercial brooch had 129 thou gap there so my single pass with the eighth inch end mill wasn't quite enough so i just moved over a couple bow did a side mill pass down one side moved over the other way a couple thousand another side mill pass and now that gauge block is a perfect fit and we can test fit with the brooch itself as well make sure that's a nice easy sliding fit there to demonstrate this custom bushing in action here's the flywheel i showed at the top that slides right in there and then once again here's that brooch lots and lots of cutting oil for the vitamins and then we just push that down through first one pass by itself and then we put the shim in there and do a second pass that's all well and good that clearly works fine but is there another more perhaps hobby friendly way to do this without all the expensive tools yes there is we can start with this scrap of high speed steel here with a cutting shaped ground on it by some grizzled old machinist i have no idea this was in a box of high-speed steel scraps that i acquired from somewhere and we are going to grind our own keyway cutting tool here this is a very low budget and very flexible way to cut keyways as well as internal splines slits and collets and all sorts of similar longitudinal bore features if you don't have scraps of high speed steel you can also use an old end mill or an old drill something like that just make sure that it is high speed steel if you're going to use a regular grinder like this if you've got an old carbide end mill for example you need a carbide grinder for that this is the shape i'm aiming for here there's a groove cutting profile here at the end with clearances around the back and the front just like you would use for a groove cutting tool on the lathe there's what i ground up it's far from perfect but it goes to show that as long as the width of the nose is correct and you've got some kind of half-baked clearances behind it in this case it's a combination of what i ground and what was already there from the previous tool grind it'll still work great you can get very beautiful features from unbeautiful tools in the machine shop i didn't put much of a top brake on that which maybe i should have because it's steel but as you'll see it's fine because of the light cuts that we're taking i like to give a fresh ground tool a hone here as well i want to make sure that the cutting edge there is nice and sharp to the touch in the direction that the tool will be cutting so i'm looking for a nice sharp front edge there next up we need a mandrel to hold this little cutter so i've got another piece of scrap steel here from the junk bin and i'm going to chuck this up and we're going to quickly turn down a little mandrel here to hold this the critical dimension here is the diameter of this mandrel it has to be less than the diameter of the bore plus the depth of the keyway that you want to cut we need to be able to fit the mandrel plus the full extension of the cutter required to reach final depth inside the bore so that means your mandrel is going to be quite a bit smaller than the bore and of course the length has to be sufficient to cover more than the full length of the board that you're going to cut a keyway in jam for the end separate from the animals and i'm going to drill and tap a little set screw in the end here that's going to hold the little piece of high speed steel in place hopefully the form of this tool is starting to make sense now we're done with the lathe so over to the mill and we're going to drill a cross hole you could also do this step in a drill press of course if you don't have a milling machine the nice thing about the technique i'm going to show you is that it does not require a mill at all you can cut key ways on a lathe with this technique final step on this tool is to cut the little chunk of high speed steel to length it needs to fit entirely within the cross hole of the mandrel that we just made so we're going to need to cut it to length i do this with a grinding disc on a rotary tool along with some coolant to keep anything from getting too hot don't try to cut high speed steel blanks on any form of bandsaw or hacksaw high speed steel is harder than all your saws so you definitely have to use some sort of grinding tool to cut these a little test fit now and you can see how the pieces go together so i've got the cutting edge facing up because that's going to be down when the tool is in use and then get the little set screw in there and clamp it together now at this point you may need to make some adjustments to your grind in my case you can see that the cutting edge has kind of a negative top rake on it because the top of it is not very flat so i did some adjustments to the grind there once again verifying the tool dimensions here the mandrel needs to slide through there with the cutter at full extension and the cutter needs to be extended enough that it can reach the full depth of the key slot as you see there just sort of test fitting on the one that i did with the broach with this tool made we'll go to the second way to do a keyway and that's here on the mill so i've got the bore tappy tap tapped down nice and flat and square there to align that bore on the spindle which is important i'm just using a pin but you could use any of the common methods for doing this then we take that cutter that we just made and we put it up in the spindle i'm using a collet here i suppose you could use a jacob's chuck as long as the cutter was bottomed out in the top of the jacob's chuck so the jaws are not experiencing too much downward force there is going to be a fair amount of force in what we're about to do so i like to use a collet for this then you want to rotate the spindle so that the cutter is going to be tangent to the surface in there and honestly you can just do this by eye if you wanted to be really fussy you could put a gauge pin through that cross bore there and indicate that in to get it parallel to the x-axis of the mill but honestly eyeballing this is close enough then apply lots of lots o cutting fluid for the vitamins then i'm going to touch off the cutter by moving the x-axis over a little bit at a time until i feel that cutter dragging on the inside of the bore and away we go so all we're doing is pushing it down through the work with the quill and then after each pass advance the cutter a little bit on x now a little bit is the operative word there a one thou cut is the absolute most you wanna do i'm aiming for between five tenths and one thou on each pass for even a small keyway like this you're looking at more than a 100 passes probably but it really doesn't take that much time you get into kind of a rhythm and if you accidentally try to take too much of a bite you'll know pretty quickly because you won't be able to push the cutter through with the quill you don't have a whole lot of leverage there with the quill so the process is fairly self-limiting in that way in this wider shot you can see that i'm really not using very much force like that's pretty casual arm motion you're seeing there and that's really all you should be using like i can feel the tool cutting but i'm not having to lean on it with my body weight or anything if you're needing to do that if you're taking cuts that heavy you're definitely abusing the little rack and pinion in your quill and you don't want to be doing that again it's not designed for high forces so just take your time and be patient now what's really great about this method is that of course you can cut any depth of keyway as you can imagine but we can also easily widen this keyway if we need to after you reach full depth you can do more passes by moving the y a little bit and widen out the keyway so with a single tool we can cut any size or shape of keyway that you might need which is a lot more flexible than those broaches are for final depth if you don't have a keyway broach to compare to like i'm doing you can check in machinery's handbook and for a given bore and keyway size it will tell you how deep it should be or if you have the key stock on hand you can test fit with that as you can see that's indistinguishable from the fancy expensive broach method that we just used it works very very well with very little equipment but wait i don't have a mill you say you can still do this you can do it on the lathe don't ever try to tell a lathe what it can't do yeah you can cut this keyway on a lathe as well and it's really the same process i'm going to start once again with this tool that we just made and in this case i'm going to put it in the tool post you could use a boring bar holder for this or i'm using a v-groove tool holder as you see here you want to get that tool horizontal parallel to the bed of the lathe but again you can honestly do that by eye if you wanted to be fussy again you could put a gauge pin through that bore on the tool and indicate it in but honestly i think doing it by eye is good enough for most keyways then to get the tool height set right once again you could get all fancy about this or just do it by eye by feeding the tool into the bore and then what i'm doing is comparing the gap above and below center line between the tool and the bore there and i'm just adjusting the height until those gaps are even and honestly again doing that by eye is good enough just like on the mill now i touch off by moving the cross slide out towards the near side of the bore there until i feel it's starting to drag and then lots and lots of cutting fluid for the vitamins and i feed in a little bit on the cross slide and away we go so it's really the same process that we used on the mill except now i'm feeding the depth with the cross slide and i'm feeding the tool through with the carriage hand wheel now you have a little bit less leverage here than you do on the mill i mean unless your carriage hand wheel is a lot bigger than mine maybe but again between half a thou and one thou depth of cut is no problem if you're doing more than that and it's hard work then you're probably stressing the feed gear on your carriage a lot more than you want to so if it's hard work then take lighter cuts and just be patient i don't have a dro in my lathe so i'm measuring the depth of each pass with my cross slide hand wheel there each tick mark there is two thousand diameter reduction or one vowel depth of cut so i just go between half and one tick mark each pass that's quite easy to do and if you wanted to measure a really accurate depth you could also put an indicator on the cross slide there which would also tell you when you've reached your final depth in my case i'm just eyeballing it for this demonstration but once again it's just in and out in and out oh behave you might be wondering how i'm keeping the spindle from rotating while doing this both on the mill and the lathe and the answer is i'm doing a big fat nothing at all because all the force is towards the bearings there's really nothing that's causing it to try and rotate so as long as you're careful not to touch the spindle or the chuck while you do this it honestly doesn't rotate and once you've got a bit of a cut started it's going to self-align on each pass now in this case i'm using a dc lathe which has permanent magnets in it so i start with the motor in one of its natural magnetic kind of notches that it has and that holds it pretty reasonably still but if you wanted to you could also rig up some sort of spindle lock on the mill or the lathe for doing this just to be certain here's those beautiful spiral chips again the tool that we made makes chips just as nice as the fancy expensive tool and that little shaper style tool only took about 45 minutes to make well there you go that's three easy ways to make keyways in a hobby shop and if you're looking at that finished piece and thinking hey that kind of looks like the beginnings of a spline you are not wrong you can absolutely make splines and other more complex internal bore features the same way you just have to add the additional component of some way to index either an indexing tooth on your lathe chuck or an indexing head on your mill something along those lines i hope you enjoyed this little demonstration of how to cut keyways and i hope you learned something useful thanks to my patrons who make all this content possible and i will see you next time you

Channel: Blondihacks

Views: 696,651

Keywords: blondihacks, machining, machinist, abom79, this old tony, vintage machinery, steam, electronics, making, maker, lathe, mill, woodworking, workshop, shop, model engineering, engineer, engineering, live steam, machine shop, metal lathe, vertical mill, metalworking, metal shop, diy, how to, do it yourself, do it yourself (hobby), mini mill, mini lathe, tutorial, model engineer, steam engine, key way, keyways, pulley mount, pulley keys, keys, key cutting, keyway cutting, cutting keyways

Id: B3ZIiCIOA4c

Length: 18min 48sec (1128 seconds)

Published: Sat Jun 25 2022