Metal Planer Restoration 40: Making a Bevel Gear on the Horizontal Milling Machine

[Music] hello keith trucker here at vince machinery.org guys today we're going to be doing a little project out here in the shop i'm going to be cutting some bevel gears and i'm going to be honest with you guys when i realized a month or two ago that i had a need to cut some bevel gears to fix a gear broken gear on a metal planer that i'm restoring i started doing some research and looking into what i was involved in cutting bevel gears i've never done it before i've cut tons of spur gears just regular gears with straight teeth across them using the milling machine with a an involute cutter and a dividing head i'm very proficient at that but i had never attempted to do a bevel gear before and i started doing some research and delving into it and realized real quickly hey there's a lot to this there's a whole lot to it not impossible by any means but there is a lot to it and i want to go over just a few of the basics and things you need to know if before you get ready to start cutting bevel gears and then we're going to go do it but i'm going to start off by just saying that cutting bevel gears on a milling machine with an envelope cutter is really not the ideal way of cutting a bevel gear the best way to do it is to use dedicated gear cutting machinery such as a gear hob or a gear shaper i think your shaper is probably the best way to do it because when you use those tools you develop a 100 true involute cut in these in these gear teeth it's true really for any gear including spur gears but i think it's even more so true with the bevel gears but with that said it still can be done on a regular milling machine and that is what we're going to be doing today because that is the machine that i have i don't have a a gear cutting machine that i can go use without sending it out and having someone else do it let me zoom in here i'm going to go over a few little things you need to know before you start cutting bevel gears and then we'll go get it done so to start off with do your homework and i have two really good books here the first one is machinery's handbook if you've got anybody that has a machine shop even a hobby machine shop you need to get a copy of machinery's handbook they're easy to find you can buy them on ebay you can buy them brand new but these things are full of information for just about anything that you do in a machine shop and there's a whole chapter in this book on bevel gears and all the math all the formulas everything you need to calculate it will tell you how to do it in here another good book that i've got is this one here a treatise on milling machines our milling and milling machines this is by the cincinnati milling machine company it also has a very good chapter in it on cutting uh the uh bevel gears on a horizontal milling machine which is exactly what we're going to be doing so uh i would definitely by all means you've got to have this book again if you've got a machine shop you've got to have this book this one here big help i will say that some of the formulas between the two books aren't exactly the same they kind of come up with the same answers or something real close i would pick one or the other and just make sure you're running all your math using not be mixing the formulas back and forth either one of them will get you to the same same place now as far as the math is concerned i created a spreadsheet and i actually use that to do a lot of my my math for me rather than trying to do it on a calculator and guys i'm gonna get somebody asked hey can you send me your spreadsheet as a starting point and i'll be honest with you guys this spreadsheet is not really something that i'm willing to send out mainly because there's a lot of gotchas in it uh it's not just where you put some numbers in and it calculates everything there is some uh numbers that have to come out of tables in these books and i don't have all that programmed into the spreadsheet to automatically calculate it and i kind of know what has to be done but it'd be difficult for me to tell someone how to do that and come up with all the right numbers but i've calculated the main things i need to know so as far as you know really the important things you really need to know i need to know the angle to cut my face so the face angle calculates here in this case it was 40.684 degrees there's really three different angles you've got to know in here there's the the face angle there is the pitch angle which is kind of where the center of that is really i don't guess i need to know that but that's really kind of the angle that the gear is calculated on and then there's the cutting angle there's another angle that's down in the bottom of that and that's the angle that the cutter is going to go through here because with the bevel gear the tooth is bigger in the back than it is the front if you look here see the front see the back that's because it's running you got a change in angles the angle that the face and angle in the bottom are different so it's cutting more out of the back than it is the front another thing that you need to know is the outside diameter of the gear we calculated that right here outside diameter in this case it was 1.633 inches based on all the measurements that i have here and another very important one here is the whole depth of the cutting depth so off of the big end so you touch your cutter off up here and tell you how far you need to feed down to cut that out and there's lots of other things in here and some of these you have to calculate one thing to get something else but all the math is right here you also have to know your uh offset distance and roll angles we're going to talk about that in just a minute i've got you zoomed in here on just a diagram showing a pair of uh bevel gears and again i just wanted to make sure we understand a few things so the outside diameter is going to be from the tip to the tip out there and again we've got some different angles here going on so that pitch angle is the kind of this line in between that is kind of uh where the the cutter really kind of starts bending over in that arc it's kind of center of that arc but again you've got an angle of the of the face and then there's also a cutting angle which is different because if you look that's not parallel lines those lines kind of come in it's bigger on the outside than it is on the inside another thing i want to just real quickly mention is the actual envelope cutter that you use to cut bevel gears so there's a standard set of envelope cutters that are used for making spur gears i've got a pretty good collection of them and for comparison this one here happens to be a six pitch number four so if you know anything about cutting gears you have different pitches and there's a dif there's uh there's eight different cutters within a pitch depending on the number of teeth as to which one you use so this is a six pitch number four for regular spur gears this is a bevel gear involute cutter it is also a six pitch number four and i want you to look at the difference in the tooth down here can you see that the bevel gear envelope cutter is thinner than a regular spur gear cutter and that is because uh that that front of that the small end is narrower and as it gets to the back it widens out down in that bottom and it really makes it difficult to use a regular gear cutter to do this it can be done if you look in the machinery's handbook it actually talks about you actually have to use a different pitch cutter i believe it is i haven't studied it real hard because i happen to have a bevel gear cutter but you just can't go use a regular cutter another thing you have to look at is on the number of teeth you have to mathematically calculate the number of teeth so another thing you have to watch out for is on your number of teeth like i said you pick the involute cutter based on the number of teeth that you have with a regular spur gear we're doing 18 teeth but there's a formula you have to convert that for bevel gears and you actually select a cutter as if you were picking one for 22 teeth instead of 18 teeth so again do your homework that's one main thing i'm trying to tell you here all this information is in machinery's handbook but in in new note 2 that i have found that finding these bevel gear envelope cutters is extremely difficult at least to find new ones you can find old ones and and i'm fortunate i've got a pretty good set of these through a lot of my pitches but i don't have all of them and but i had the fortunately the one i needed for this particular job but regular cutter is is different for a bevel gear in preparation of cutting the gear i'm going to cut today instead of just going and doing my first attempt out of my my metal blank that i cut i decided i was going to do a practice run and just make sure i had everything down so i actually just turned the gear this is a piece of plastic is what it is it's just some delrin i think is what it is and that's a piece of scrap i had laying around shop i cut all the tapers and all the angles face angles and all that on it and went over and just quickly did it uh just to make sure i have my process down and it came out perfect i probably would have been fine had i just gone straight to the metal gear but i wanted to test everything but here's something else you got to really look at is that see how this gear gets thinner down here in the bottom but when you just run it through straight what it ends up happening is is you don't get it thin enough down in the bottom so it actually you have to make three passes on the milling machine to get an approximate gear tooth and the first one is just a regular one straight through the second one you actually move the part towards you and then turn it back just a little bit and you can almost see it on here but you've actually got on each side there's there's like two angles so it comes in and there's another one that comes in a little bit different angle it makes it a little bit wider down here in the bottom or thinner on the top and on the small end so there's you have to actually go around in three different times that's another thing you have to calculate is your offset distance so how far do i have to move the part either to me or away from me and then how far do i have to rotate the part and again i did the math for the gear that i'm cutting and those numbers are here so i had to do 15 000 of an offset and a roll angle of 1.317 degrees and uh basically i just used my index plate i figured up how much one hole on my index plate was i had to basically go four holes either side of that first cut to get something really close to that degree it wasn't exact but it was pretty close and when you cut bevel gears on a horizontal milling machine one of the things that you often have to do is you have to go in here after it's all said and done with the file and kind of blend in that little center section where those two angles come together and here's a diagram in one of my books and you can kind of see what we're talking about so the dashed line here on the outside that was the original cut that we had and you have to go in here and kind of take that dashed area out and that's what that offset and roll does is when you do that it's just kind of taking a little bit out so again when you end up you have really two angles across the top of this it's not a smooth arc like it really should be which what you would get if you were doing this on a gear shaper but we can get something really close to that profile over here gears cut bevel gears cut on the horizontal milling machine work okay in slow turning applications when you get into high-speed applications that's when you can really run into some problems with these angles not being just right with this particular gear that i'm cutting uh it's basically going to be an elevation screw uh on a machine it's it's going to be turned by hand probably very slow rpms probably three or four rotations per minute is all it's going to ever turn and not very many revolutions at any given time so i think that this is going to work out just fine so guys that was a really quick and really pretty tame introduction to some of the technology and science behind a bevel gear and i will be the first one to tell you i am by far from being an expert on this but i have done a considerable amount of studying on it the last couple of weeks getting ready for this job and i have a good understanding of it i'm not sure how well i conveyed that but i'm going to just be honest there's a lot to this uh it's something you can do but do your homework first study it make sure you understand what's going on and you should be able to produce a successful bevel gear let's go over to the mill machine now we're going to get set up and we're going to do some cutting i'm over on the milling machine now and i've got my dividing head set up on the middle machine this happens to be a kearney tracker model h dividing head it's a 40 to 1 ratio so when you turn the handle on the front 40 revolutions of this handle here will result in one revolution of the chuck up here on the front and you have different index plates these plates have different sets of numbers holes in them and there's charts and mathematically you can calculate and figure out which plates you need to get the number of divisions so our gear has 18 teeth so to get to 18 teeth i'm using in this case a 27 hole pattern so there's i'm in one of these circles of holes that has 27 holes around there and to get that division that i need 18 divisions you go two two full revolutions plus six holes and there's a little sector in here you put that over there on this hole and then you just pull it around and it will tell you right when you get to the six hole you can adjust that little uh scepter in there uh to to help you find that so i've got all that set up already and then the other thing i had to do because we're doing a an angle on our cutter i've got this set and my cutting angle is 32.459 degrees well now my scale in here is just it's incremented in one degrees so i just kind of uh eyeballed it and this is about 32 and a half degrees is what i'm at it's probably not the exact cutting angle but uh it's going to be close enough and there are ways you can set this thing up and get it exactly right but uh guys i'm gonna be honest with you we're splitting hairs when you get down to you know a tenth of a degree uh over such a small area it's just not going to matter so anyway i tilted it back i read my angle right there everything's tightened down and we are ready to put our part in here in this case it just goes into the chuck and let me tighten that up i need to make a proper chuck key for this chuck but that quarter inch drive fits it pretty close all right that is firmly uh in place and again uh the angle that i'm doing is my cutting angle or the angle that's in the bottom of this gear if you look the angle on the top is not flat that's because it is two different angles the the face angle is 40.68 degrees and the cutting angle is 32.45 degrees so again as it goes through it's going to be making a heavier cut as it gets to the back it's cutting more material out of the back because that top is at an angle as you go through there it's getting thicker and thicker as you go through we are set up here i've already got my cutter set up on the center of this uh and we're ready i think to start making some some cuts so let's get in here first thing we need to do is we're going to touch the cutter off on the large end and i've mathematically calculated the cutting depth which is a 180 degree or 180 thousandths so after we touch off there we will raise the table up 180 thousandths and then we should have our full cutting depth and i think i can cut this all in in one pass without any problems we'll give it a try if we have to we'll back off and do it in two passes but i think if i slow my feed right now we'll be fine all right i've got my cutter running right over the center of this thing at the at the highest point there and what i'm going to do is uh just raise this up until i just touch off right there i'm actually touched off that should give me a starting point on my depth i'm going to move out now i've got a dial indicator set on the top of the machine going down to the dividing head and we're just going to raise the table up 180 thousandths of an inch so i'm gonna release my lock there's a little bit of wear in this machine so i have to be careful when i lock it that's 150 60 70 80 right there and there we go right there my table is locked in place zoom 33. all right i think we're ready to make our first cut here i've got my rpm and my cutter set up at about 150 rpms i think it's 153 and i've got my feed rate set real slow to start with according to the calculations i can go like up to 15 20 inches per minute but i'm i don't know that i'm brave enough to do that so uh anyway i got it set on something real slow right now we'll just feed it in there i think it's one inch per minute and we'll see how this goes and then speed it up if we feel like it's cutting good i can hear it cutting pretty good now and of course as it gets into that cut it's going to be taking a deeper cut as we get toward the back since we're uh cutting such a the full depth all in one pass i'm slowing my feed rate down to kind of compensate for that i always get comments from folks about my my arbors not running true or my cutter is not running true and guys that's just the reality of working on a horizontal milling machine particularly when you got an old one that's wore out like this one is it tends to have a little bit of a wobble in it and it cuts more on on a couple of teeth in there but slow down your feed rate and everything will be fine you'll kind of average it out over there it's going nice and slow through there so that looks like it's cutting just fine i'll probably uh on the next one we're going to speed our feed up there a little bit so i think we can go a little bit faster let's let it get all the way through cutting though all right number one we will uh one turn two turns and six teeth right there should be ready for our second cut and i'm gonna go up to about an inch and three quarter per minute on that so let's feed that in there now so the first pass again was one inch per minute was my feed rate i'm up at an inch and three quarters per minute so we're feeding a good bit faster this time all right come out unlock the dividing head and again one turn two turn and six teeth right there we'll lock our dividing head and we'll feed in again all right i've sped my feed right up another notch so we're at two and one-eighth inches per minute now on the feed rate it'd be a lot better if it was uh cutting on all the teeth but it's pretty much just cutting on a couple of teeth in there so i'm probably not gonna speed it up much more than this right here if we like said if we were cutting on all the teeth i think we could go a good bit faster all right we'll turn our head again make another cut just kind of rinse and repeat after this you just keep doing this until you get all the way around [Music] so last one here on the first operation split the difference love to see them when they line up perfect like that so first thing i want to do is i want to move the table i'm going to come toward me and my offset distance is 15 000 so i'm going to unlock my table here and we're going to bring this toward me making sure we're nice and free make sure i got a good zero there and that's ten fifteen thou right there we'll lock our table back in place so if i was coming here right now and do this it would just come right down this back tooth here and it would more or less just go straight across what i'm really want to do is kind of trim up this front edge again it's going to be angled and to do that i need to roll it over now what was it 1.3 degrees and that equals four holes in my dividing head i'm going to roll it over four holes we're just going to go in here and do manually count them that's one two three four i move my scepter over and we'll just go around again starting in this hole go all the way around and do each one of them and then we'll have to go back and roll it the other direction all right here we go and we're just going to be cutting off this little corner right over here about halfway up it's gonna be a light cut i can barely hear it cutting it's not taking much off it's just fuzzing it but it's getting that geometry of that gear too is just right and put a mark on here so i know which one i started on we'll go all the way around and cut each one of them and like i said when we get through we'll come back and we'll cut the other side we'll offset and roll it in the other direction the last cut here and i like to go back to my starting tooth and now we're going to do our offsets again i've set my indicator back to the fifteen thousands because we need to go fifteen thousandths in the other direction so we'll go back to zero and count back out fifteen so uh let's bring our table in we're back to 0 10 and 15 and now i need to go back to four holes and then four more so we go one two three four that's back to where we started from one two three four i'm gonna move my sector down there to that one i actually want to go past it and because i'm turning in this direction i want to come back to it that just takes out any backlash we will start on that hole now and go around and do everything again one more pass and we should have this thing trimmed up and away we go i'm not going to make you guys watch this whole thing we'll bring you back at the end well now for the moment of truth i believe it's going to work i need to get that shaft in there and make sure my alignment and everything is just right but that looks and feels good i think it's a success well there we go guys my first bevel gear um i hope i did it right we will uh know for sure when i get it installed back on the machine i can really test it out but it appears that i got a good part here at least based on just meshing it up on that other gear so i think it's going to be fine for what it's going to be used for and hopefully coming up soon in another video we will get this installed back on the metal planer and really make sure everything exactly like it needs to be and with that guys that is going to be a wrap i hope you enjoyed some hope you learned something along the way uh i sure did like i said i had to do a lot of studying on this and i will again tell you guys up front i'm no expert just figuring this stuff out as i go but sharing what i have learned so far and i'm sure i've still got more to learn on this and it's more we do the better we'll get but uh one successful part at a time that's what we do guys uh that's gonna be a wrap as always thanks for watching please subscribe the channel if you haven't already and thumbs up appreciate as are those comments and we will catch you on the next video [Music] you

Channel: Keith Rucker - VintageMachinery.org

Views: 153,386

Rating: 4.9477196 out of 5

Keywords: Machine Shop, Machinist, Milling Machine, Restoration, Vintage Machinery, Metalworking, how to run a mill, Keith Rucker, VintageMachinery.org, bevel gear, dividing head milling machine, dividing head gear cutting, dividing head, horizontal milling machine, gear cutting, gear making, bevel gear making, bevel gear cutting, bevel gear design

Id: RBco7PVuPDI

Length: 32min 27sec (1947 seconds)

Published: Fri Aug 07 2020