Gear Cutting on the Atlas Milling Machine

hey folks Vince here with the tinkerers workshop today we're going to do a little gear cutting I've got this Atlas craftsman power hacksaw and I'm in the midst of restoring it and it needs a new pinion gear so I thought that might be a nice project for the Atlas milling machine this will probably be a fairly long video I may break it into two parts or I may just keep it as one long video but anyhow let's get started this is a closer view of the gear in question this here is the pinion gear that I'll be making it's mounted to a shaft and the other end of the shaft has a pulley on it which is driven by the motor and as that pulley turns it the pinion gear drives this larger gear there's about a seven to one ratio between these two gears so for every revolution of this large gear the pinion gear is turning seven times so it's getting seven times the wear I'll pull this out so we can take a closer look at it and you can see what I'm talking about this is the gear assembly removed from the power hacksaw it's basically just a pinion gear and shaft and it's held in place by just a small taper pin which pushes out fairly easy the gear slides off I don't know if you can see the amount of wear on this but actually there were only takes place in on half of the gear so I guess in theory I could just turn this around and drill a new hole through the gear and the shaft and pin it to the shaft but part of the reason I want to replace this is because the end of the shaft is also really chewed up from the set screw on the pulley having worked loose and then I think the pulley must have spun on it and really chewed up this shaft plus there is somewhere where the shaft rides in bronze bearings you can see a little bit of wear on on the shaft there so I think it's probably a good idea just to make a new gear and a new shaft and I'm replacing all the other bushings and bearings on this power hacksaw so it'll be a good match to have new parts on everything just for fun I did check with Clausing because the original manufacturer of this power hacksaw was Atlas Clausing they made it for Sears craftsman and they actually still carry this whole assembly I think the price on it was $72 which honestly isn't that bad of a deal when you consider the amount of time that would go in to make something like this but you know you've got if you've got the machinery there's no fun in buying parts when you can make them yourself so let's get started on doing that first step in making this gear is going to be creating a blank I've got this little cut off piece of 1144 stress proof steel I thought that would be a good material for cutting a gear that's I've used this material before and it cuts nice and smooth it's already faced off on one end but I'll take it over to the lathe and part it off to length face off the other end and then create the bore for the shaft [Applause] [Music] I've got the blank cut to length and I drilled and reamed out a half inch diameter hole through the center that will be for the shaft that is added later next step is going to be turning it to diameter to match the diameter of the gear and in order to turn that I need a way to mount it in the lathe so I'm going to use a lathe mandrel like this one here this is machine on the ends for Center and it's slightly tapered in length so one end is about mm narrower than the other end and the idea is that you press the blank onto the mandrel and then you mount this between centers and you can turn it and machine it once it's mounted to this Arbor I'll actually leave it on there while I cut the teeth for the gear as well so I'm gonna head over to the Arbor press right now and press that into the blank well before I can do any more machining I need to do a little bit of calculations math work here so I've got the blank wall mounted on the mandrel is to set that aside this is the original gear and this is Machinery's handbook and there's a whole chapter in here on gear cutting with all kinds of formulas and tables that give you all sorts of dimensions pitch diameters clearance angles clearance depths but really there's three things that I'm concerned with and that those things are the diametral pitch of the gear the overall diameter and the depth of cut so because I have a sample gear in hand it's a little easier to calculate all these things but I'll kind of go through it real quick here starting with the diametral pitch and in order to get that we need to know the number of teeth and the overall diameter and I counted the teeth on this gear and there are 14 teeth and then I measured the diameter and it measures out at one inch and then the formula for figuring that diametral pitch is P that's equal to the diametral pitch P equals the number of teeth plus two divided by the overall diameter so when I plug in these numbers into the formula the pitch is equal to 14 plus 2 divided by 1 which turns into 16 over 1 or the pitch of 16 so 16 is the diametral pitch and with that information I will be able to now do all the other calculations as far as depth of cut and selecting my gear cutter and everything else which I'll go into that later but for right now I've got the diametral pitch and I know that the overall diameter is one inch and I'll double-check that in the tables and Machinery's handbook just to make sure I've measured that correctly but assuming that's correct then I'll start by turning the blank down to a 1 inch diameter I'm back over at the South Bend lathe and I've got the mandrel set up here between centers and it's a there's a lathe dog attached to the mandrel and it fits in the slot of the faceplate so we're ready to go this is just simple turning going to be turning this down to a final OD of one-inch so nothing nothing too exciting using our formula that we worked out earlier we know that the diametral pitch is 16 and the overall diameter we determined was one inch and then going by the chart in the Machinery's handbook the depth of cut works out to point one three four eight inches so these are the three factors that I I'm gonna need to know when I start cutting the gears next step really is to select a gear cutter that I'll be using Machinery's handbook has a lot of this information that you need for cutting gears but this is an old brown of sharp catalog and I'm not sure what the date is on this I'm guessing it's probably from the 20s or 30s but it has a lot of gear cutter information as well which is kind of handy if you're looking to select the gear cutter there's a little chart here that tells you what number of cutter you need because for each diametral pitch there are eight different cutters and the number the cutter you use depends on the number of teeth of the gear that you're cutting so for this particular gear we determined it was at 14 teeth so you look down here and the number 7 cutter will cut gears with between 14 and 16 teeth so that's the number we'll need at number seven in the sixteen diametral pitch one other thing to consider is the the pressure angle and I don't really want to go into that it's kind of a complicated discussion but this is an older gear two older tool so I've checked and it's a fourteen and a half degree pressure angle other gears are twenty degrees more modern gears but I I checked on this one and it is 14 and a half so that's what I'm going to be using well I took a look at the stash of gear cutters I have on hand and these are all this sixteen pitch cutters I have I don't have a complete set but fortunately for me I do have the number seven cutter which is the size that we need to cut this pinion gear and gear cutters are are what are known as form cutters in that the teeth of the cutter are formed into a specific shape and in the case of gear cutters that shape is designed to cut the space in between the gear teeth the reason you need eight different cutters for a given diametral pitch is that as the number of teeth on the gear increases the circumference also increases which means that the space in between the gears starts to get a little narrower as you go up in a number of teeth and that changes the overall shape of the profile of the teeth on the gear cutter so you need a set of eight to cover the range of teeth from you know the smallest number of teeth up to the largest this cutter also has all the information on it that you need to select it for for the specific gear you want it's a number seven cutter 16 pitch it will cut 14 to 16 teeth and it even has the depth of cut on there as 0.1 three five inches which is just rounded up from the 0.134 eight inches that we got out of Machinery's handbook so I'm gonna go ahead and get this set up on the atlas milling machine and then after a little more adjustment we'll finally be ready to actually start cutting some gear teeth here we are at the Atlas horizontal milling machine and I've got the mill set up with a pair of index centers this was an accessory that Atlas offered for their milling machine and they're used to make gears or to cut flutes or splines in a workpiece and the way these work it's sort of like a poor-man's dividing head you've got a headstock on one side and a tail stock on the other and I'll zoom in a little bit so you can see these a little closer because it's kind of a neat accessory and it functions very well for what it is here's the tail stock of the index Center it's got a ram with an internal number one more stapler to hold a center and you can advance their RAM using this hand wheel just like the tail stock on a lathe and then you can also lock it in place with a little clamp here the headstock of the index Center is similar to the headstock on a lathe it's got a hollow spindle running through the body and the end of the spindle is ground with an internal number two Morse taper to hold a Center the spindle is threaded to receive a dog driver and this allows you to turn work piece between centers using mandrel and a lathe dog just like we did on the lathe or alternatively you can unscrew this dog driver and mount a three draw Chuck to the end so you can hold items in a chuck there's a lock to hold the spindle to lock the spindle in place when you're making a cut and then at this end of the spindle the end is machined to accept a gear and these index centers actually came with a set of nine different gears of different teeth counts and the idea is that you mount a gear on the end of the spindle and then there's a little indexing plunger here that you can release and it will lock into the tooth of the gear so this is what's known as a direct indexing center in other words let's say you wanted to cut a gear with 48 teeth well you would take a 48 to change gear and mount it on the end of this spindle and then simply move the gear one tooth for every cut and then the plunger locks it in place so you don't lose track so you can make it a direct one-to-one cut for every tooth you make a cut now the nice feature is that say you have a 48 tooth gear on here well if you do every other tooth you're gonna end up with a 24 tooth that you're cutting and if you do every third tooth you'll end up with a 16 to 4 tooth you'll end up with a 12 tooth so with with this set of nine gears you can actually cut quite a few different tooth counts so it's it's very useful for for cutting gears and the nice thing about it is because it's direct indexing unlike dividing heads where there's a system of gears and index plates and you have to turn it a number of turns and and quarter turns and partial turns this is a lot simpler so basically all you have to do is be able to count off the teeth when you're cutting a gear and it's it's kind of hard to go wrong so for the gear that will be cutting we decided it was we determined it was a 14 - that is a multiple of 14 so the closest or the the lowest tooth gear that I had that was a multiple of 14 was this 56 tooth year and 14 times 4 is 56 so what I'll do is count off every fourth tooth when I'm making my cuts so I'll start make a cut and then simply release the plunger or count out four teeth let the plunger in and make the second cut to mount the blank in between the index centers I've got it on the mandrel still and I've got the lathe attached to it and just place it between centers and advance the tailstock you don't want to make it too tight so at this point I'm just to have it be a little bit loose the lazy dog fits in the in the drive plate here and there's a little set screw here that I'm going to Snug up just to take up the play here you don't want this rattling around so it doesn't have to be real type it has to be snug down so that that doesn't move and then you want to be able to turn this freely but you don't want any play here so kind of have to play around a little bit here tightening this tail stock just to get it so it's snug no play in it but can still turn freely that looks about right so I'm going to lock this clamp down on the tail stock this clamp you leave loosened when you are turning and then when you're ready to make your cut just to keep it roofing rigid go ahead and lock that down so that you don't have any chance of anything moving on you so our workpiece is ready to go now I'm gonna go ahead and mount the arbor in the mill and start stacking on the cutter I forgot to mention this earlier but before installing this this gear cutter I went ahead and measured the thickness of it and it mics out at 247 thousandths so I wrote that down and I'll kind of explain why later but basically you need to know the thickness of the gear to make it easier to help Center this gear over this cutter over the workpiece and I'll run through that later but it's easier to measure that now before you've mounted it on the Arbor this this gear cutter has a 7/8 inch diameter bore so obviously I'm going to use the 7/8 inch Arbor that comes with the mill just go ahead and clean out the inside of the taper there get any swarf out of there and then wipe off the end of the Arbor so that there's nothing on that that just slips in here this is a number 2 Morse taper and the Arbor is held in place with a drawbar that's inserted through the back of the mill yeah that's just tightened in place there there's a crank handle that is used to cinch that up when we set this cutter in place you want the cutter to be as close to the headstock as you can get it just for rigidities sake if you mount it away out here there's more chance of it flexing so you want to get it as close to the headstock as you can but you also have to take into consideration that we've got these kind of bulky index centers here that are gonna have to pass back and forth in front of this headstock so I've moved this table out far enough that there's enough clearance for these to pass through without interfering with anything on the headstock and I've got the workpiece in place so if I can use a combination of spacers that will get this cutter more or less centered over the workpiece where it sits now all should be good so I'm gonna use these three there's a key way in this Arbor so I'm gonna put a little key in there and then there's a key way in the cutter lined up a couple more spacers gonna put the nut on but I'm only gonna tighten it finger tight you don't want to put a wrench on this and reef it down yet because if you do without any kind of a support on the end here you can end up twisting your Arbor and turning it into a corkscrew so finger tight for now and then we'll go ahead and put the arbor support on and then cinch that up a little bit later so this is the Barber support it mounts on to this over arm and then there's a bronze bushing here that fits over the end of the Arbor and supports that I'm going to go ahead and just mount this onto the over arm first you want to mount this so it's just flush with the end of the over arm it shouldn't be sticking out any further because you're going to come back later we'll have a support arm that mounts to the front of this and if this bar is sticking past if it's standing proud of the surface of the arbor support it'll interfere with that arm so that feels like it's just flesh go ahead and tighten that down I'm gonna slide this out and slide it over the end of the Arbor I'll put a little oil in here that should be good I'll lock these clamps down and now I can go ahead and tighten up the nut on the end of the Arbor even with this heavy overarm the harbor support there's still a tendency for this whole assembly to flex a little bit when it's under load so I'm going to go ahead and add the support bar and what this does is ties the over arm into the knee and adds a little more rigidity so this simply fits on to the end of the harbor support and it's held in place with a couple of bolts and then there's a clamp piece that fits underneath here and clamps it to the cross feed all right the next step is going to be to Center the gear cutter directly over the workpiece and I'm gonna try a method here see if this works I've got just a machinist square and I've set this up against the face of the cutter and resting flat on the on the bed and then I've moved the table in until the workpiece is just also touching that square so there the outside edge of the work piece and the outer face of the gear cutter are lined up and then I've zeroed out my y-axis cross feed and what I'll do is advance this so that the cutter is over the center now this is why I measure the thickness of this gear cutter because we know that the workpiece is half is one inch so half of that is in half an inch but that would take it that would if I moved it half an inch this way it would take it so that the center of the workpiece is underneath the far edge of the cutter so then I've got to subtract out half the thickness of the gear cutter so what we're looking at then is half an inch 500 thousands minus half the thickness of the gear cutter we said that was two hundred and forty seven thousand so half of that is one two three five do the math there and that comes out to 0.3 765 so I've got to move the workpiece this way 376 and 1/2 thousands so I've zeroed out my cross speed there's 100 200 300 seventy-five six and half those numbers are hard to see on these little cross speed dials but that should be centered now and once you have this centered you can lock this y-axis in place there's a little lever underneath the table here to lock that in place because you won't be moving the table in or out at all you want to keep it in this spot as you cut all the teeth so we've got the workpiece centered under the gear cutter and now just need to to touch off on the top of the workpiece just to know where to zero out our dial so I'm gonna turn the mill on just slowly raise the table up until the cutter just starts to dig into the workpiece okay so that's our top dead center all zero that out and that'll be our baseline I've got the spindle of the mill set up in back year mode and I've got it set at the lowest speed I believe it's around 60 rpm as far as the table feed I'm going to adjust that to 0.01 to 5 I'll start there if if that seems too slow I can I have one step up from there I can go but we'll start from there and see how it goes well believe it or not I think we're finally set up to start cutting we had determined that the the depth of cut was going to be 135 thousandths but there's no way that this little mill can handle that deep of a cut so I'm gonna have to do this in multiple passes and I'm gonna start just by taking a 20,000th depth of cut just to see how that does and if the mill handles it okay l might might speed it up from there but I'll put a little cutting oil on there I've already raised the table 20,000th got everything set up locked down all the locks the overarm support everything's fairly rigid setup so I'm going to go ahead and turn the metal on start [Music] all right that's the first cut so I am now going to advance this four teeth on this gear so one two three four and I'll lock the spindle down give it a little oil here I did increase the feed rate and I raised the table a little bit so it's cutting 30 thousandths of an inch now so let's see how that does [Applause] [Applause] [Music] [Applause] okay that's looking good so now it's just a matter of step and repeat for every every two that I every pass that I have to make I just advanced this four notches on the gear one two three four lock it in place and make a cut it's pretty repetitive but I'll go all the way around and then I'll raise the table to take a deeper cut and go around again and keep working my way around till I get close to the full depth [Applause] [Applause] [Applause] [Applause] [Applause] [Applause] [Applause] well I've done all the way around first pass and everything looks good so I raised the knee up another 30 thousandths and I'm going to go around now start making the second pass it's just continuing to do the same thing one one cut at the time so a little oil on there [Applause] I've now taken five complete passes increasing the depth of cut by about 25 thousands on each pass and it's finally starting to look like a year I'm about ten thousandths away from the final depth of cut so I'm gonna take this over to the bench and take some measurements and see how close we are one of the nice things about working between centers as opposed to having your work clamped up in a chuck is that you can easily remove the workpiece I simply backing out the tailstock and as long as you don't remove the lathe dog you can take it over to your bench take some measurements come back pop it back in place and you won't lose your position it'll stay indexed to the cutter so that's one feature that one benefit of working between centers is nice one method to measure the thickness of gear teeth or the depth of cut is a technique called measuring over wires or measuring over pins and this technique is covered in depth and Machinery's handbook essentially what you do is take a pair of gauge pins of a specific diameter and you place them in opposing teeth of the gear and then you use your micrometer to measure over the pins and there are a couple pages of tables on what those measurements should be for a given diametral pitch gear of a certain number of teeth and then you also have other calculations for backlash and clearance and it's it's somewhat complicated if it's a method that you're interested in though I would highly suggest a video from another youtuber the name of Keith Rucker he's got an excellent video on gear cutting basics and he covers this measuring over pins method and and does a great job of explaining it to check the gear that I'm cutting I'm going to use a method similar to the measuring over pins technique but with a slight twist earlier we determined that the original gear was only worn on one half of its length so this this half of the gear is basically unused so what I'm going to do is use this gear as a comparison for the final depth that we want on the gear we're making so I've already taken the measurements but what I did is simply take a couple of gauge wires and for this instance the diameter of the wires doesn't really matter so I just dropped those in place in opposing teeth and then measure across that distance with the micrometer and I did that on the new gear and on the old gear just to make a comparison to see how far away I am and what I ended up with is the new gear measured an inch and ninety thousand so cross the old gear measured an inch and 60 mm so there's a difference of twenty eight thousandths and because that's measured across the diameter and we'll be taking a cut on on each side you have to divide that in half so I need to take another fourteen thousandths of an inch cut all around the gear so I'm gonna take this gear back to the milling machine and put it back between centers and make that final cut and I'll do that off camera alright I got my gear and my to test pins here and when I measure across the pins we are right at 1 inch and 60 mm right on the money well here's the finished gear I made a shaft for it milled multiplet for the set screw for the pulley this is just some turned in ground shaft material that I cut to length and then I pinned the gear to the shaft to hold it in place the gear turned out pretty nice I'm pretty happy with it here's the gear installed in the hacksaw and it turns smoothly no binding so I'm happy with the way this turned out I hope you enjoyed this video and if you're interested in other machining and woodworking videos please subscribe to my channel or click on the bell below the screen and you'll be notified every time I upload a new video thanks for watching

Channel: The Tinkerer's Workshop

Views: 89,715

Keywords: gear cutting, Atlas milling machine, machining, horizontal milling machine, lathe

Id: fdSaK-6HocU

Length: 42min 16sec (2536 seconds)

Published: Sun Mar 10 2019