Spiral Milling in the Bridgeport

welcome back um just setting up here to do some spiral milling for the um cutter grinder project this is kind of loosely based on the corn design which has a helical slot milled in the um in the center spindle that the uh that the grinding head moves up and down on uh it's it's not critical it's purpose in life is really just to make sure that the um the work head when you try and adjust its height doesn't just slip way down to the bottom is usually manufactured on the lathe as a very coarse pitch screw but a the shaft doesn't fit in my lathe because it's too big and b that's a bonkers thing to do when you've got a um a set up here that will do spiral milling just noticed a little ding in there i don't remember doing that it's really annoying this is a piece of precision ground silver steel from coventry grinders um it's apart from that little ding it's really rather yeah i'm gutted about that but never mind it'll it'll buff out um a precision ground piece of um silver steel from coventry grinders and i've just set the milling machine up to do a spore milling operation now the reason you'd normally do spiral milling would be to produce helical gears and stuff like that um i will do some of that but for the moment all i'm going to do is actually use a little end mill to miller a little slot in here uh it'll be a four mil end mill we'll mill a nice little slot in there it's actually he's going to be left handed that's how my setup ended up and i can't be bothered to manufacture a spigot to reverse the uh the direction um let's not get into the gearing yet we'll cover that in a second this is set up i've got this squared up just with the dial indicator so if i move the table we're kind of within a few thou over the entire length [Applause] and that's the same in up and down uh that's achieved just by usual method of set it up indicate it bump it around a little knock it down and perfect little cap on the end here these are centerless ground rods and again it's too big to fit in my lathe so i couldn't just clock it in and set it up and do a marker center hole which would have been convenient i will get a bigger late at some point but you know it is difficult at the moment um this will do so this is just a little cap it's a snug press fit over there there's a um ball bearing in there and a little divot and that just butts up against provides a bit of um a bit of bearing surface because the the end of that wasn't um wasn't cut off in a precision fashion uh just makes it quite nice and easy so yeah it's it's it's quite a it's quite a rigid setup you can see i'm even on it quite quite a lot there and i'm only getting a few thousand deviation quite happy with that and it returns to where it should be so cutting forces nice sharp carbide end mill any four mil wide nice steady cut it's going to be easy no problem there with rigidity at all um the dividing head is carved out the solid it's a it's quite a lift um let's just set this back up i've configured this so i can actually still move the table around because as you can see it's quite [Applause] the table slightly knock the power feed off just so i can't do that accidentally it takes a bit more thought than just doing it right re-engage those this is the opposite of how you'd normally have these gears arranged for doing helical milling um because you'd not normally have a helical gear with a helix angle sort of 80 degrees is what we're going to end up with so i can't drive this with the table power feed that's a 13.3 recurring to one gear up there which it seems a bit crazy doesn't it i haven't actually got those meshed either just sort that out that looks better much better okay wonderful i've got a second collar to put in there that's why it's looking a little slidy that's okay we'll sort that out in a minute it will work and it is keyed so the fundals and fundamentals of this are that you rotate the work while you move the table which is achieved by i've got that unlocked i'm going to drive it from this end like i said because if i use the table power feed 13.33 to one increase yeah ain't gonna like that very much so inside there we're actually gonna turn the plate which has a set of helical transfer gears which turn this auxiliary shaft here you normally use this for um either sporometer or differential dividing with the attachment that fits in the end something like that and you can put another gear on there so you can rotate the auxiliary input as the head rotates and do differential dividing well i'll do a video on that at some point because it's pretty cool it's quite an interesting thing um but remove that for the moments we don't need that so basically it works like this i rotate the handle here and really helpful if we put a little mark or something on the uh all right let's put a little mark on there we go a bit easier to see now it rotates away moving the table feed and at some point in the not too distant future there's our mark cool huh so that's our lead it's um uh 16 mil sorry no 15 mil lead this gives with the gearing we've got i'll um i'll put the calculations somewhere because it's quite um quite interesting calculating this that's basically it uh the spindle's not in the right location yeah i need to indicate that in set my end mill up and uh i'll probably i'll show you in a minute i'll put the sharpie in and i'll run down the uh run down the length here just as a test cut without actually cutting anything we can draw a nice spiral on with the sharpie that would be pretty cool let me set that up and do that and you can see it in action what you never put a sharpie in an er32 collet touch off everything's locked up going the wrong way but cool huh that's going to be that's going to be interesting just managed to slip the okay well i'm going to have to rig up a motor for this and so on you get the idea there my arm is going to be naked that was a lot of rotating that handle and it's driving order this and the table it's um it seems a bit of power to drive as well so no wonder the uh the pearl power feed won't do it anyway in case you're wondering what the bits of paper in there are it's just to square this up in this old three drawer it's um it's seen better days need to arrange something better for it really but just it does work i guess i'd better take the car and i all right we're set up here to do the cuts i've got off camera i've just drawn a little hole in there just to start because i don't want to plunge with that tiny end mill it's a four flute three flute would have been quite nice here but i don't have one um it's not a ball nose it's just gonna slightly chamfered edges so it leaves quite a nice sort of corner on the bottom um apt i think that came from and choked up on it pretty well in there um as you can see i did the around the spiral down with the pen it all checks out perfect and just to check that i could get all the way down no interruptions no problems we've got the avoiding head set up all the gears there i was looking at setting a motor to drive this up that's why this extra gears here but i can't bother to fap about this one i just need the job done because until i get this off here i can't really use the middle i could use the corner here i suppose but yeah whatever anyway i think it is time [Music] [Music] [Music] so [Music] [Music] well that's how we got from a nice piece of ground silver steel bar to a piece of silver steel bar with helix milled in it to get there was actually a fair amount of uh set up i suppose the biggest job really is cutting the gears they had to be um fairly large because they needed um quite a decent um ratio and actually bridging the gap between the uh auxiliary input of the dividing head and the table lead screw is um quite a quite a way uh i couldn't do these on the um on the lathe it had to be done on the uh all the blanks had to be cut on the rotary table there another little job was making a bushing because the table lead screw is smaller than the uh the diameter that the dividing head takes um on its gear input so just had to make a little bushing there and do some broaching for woodruff keys and keyways and such like there's the results um just checking for fit and such like and eventually we end up with the compound train just like this so i made myself a little excel sheet to calculate the um the gear ratio here i'll just go through the calculations quickly we just got got a 42-1 dividing head which is pretty standard metric mill um five mil uh table movement per handle um rotation um so five mill lead there um a few important things here the [Music] uh it's a little different um the nomenclature for either helicals or um cutting a spiral um the helical would be cut on the pitch circle diameter not the outside diameter whereas we're just working uh the um the outside diameter of the bar here um this this calculation will work just as well for um a helical or a spiral of any kind so this there's two calculations here one you can actually calculate based on wanting a given helix angle it's not that useful as you'll see in a moment um the calculation over here actually is um based on the um uh the the lead you want to um you want to achieve um and then derives the helix angle from that so just to run through it here the the tan helix angle was just an intermediate calculation it was just easier to separate that out because it made the um excel formula formula a little bit uh easier to read so if we go through here um we've got 32 mil piece of bar and we want to derive everything from that outside diameter um here i've just chosen a helix angle of 81.5 because it arrives at about the the lead that i wanted to achieve um so this calculation here um excel obviously wants everything in radiance you've got to do the intermediate conversion here so you just take that the um the tangent of that helix angle there and then it gets plugged in down here so we've got um the pcd times pi over tan helix angle um which is already obviously been calculated there so there's the actual formula there um so with a helix angle of 81.5 degrees that's what we get as a lead which it's it's not it's not ideal it's close but it's it's not quite um down here this is where your meal specifications come into um come into play so we've just got a quick calculation here based on the um the desired lead that we want out of our helix and the um dividing head ratio and the mil lead screw and then we just take the reciprocal of that to get a you know a a kind of a sane looking gear ratio rather than something you're not looking um not used to looking at so that's 13.3 something something nothing to one we look over here similar kind of calculation here who's just derived from different things so here we've specified a 15 mil lead and we've got a the intermediate calculation there is kind of um is kind of kind of similar to over here um although slightly different um it'll explain just over here exactly what that's doing there and then we derive our helix angle from whatever the lead is so that's something off 81.5 degrees um here we use the uh i think it's the inverse tangent a tan um pops out with a calculation there so 13.3 recurring is actually relatively easy to achieve much as it's in a rational number as a there's a gear ratio at actually i've got a little thing here which um i used to calculate based on what gears i had available in a compound train i won't go through that though you can find that information somewhere else so there's the um there's the calculations um nothing terribly complicated there and this would work perfectly well for imperial measures as well just take the um take it in in thousand or inches whatever you want to do really it doesn't matter it will still work um so yeah there's the um there's the calculation um can be found in machinery's homework although i think i found that slightly obtuse and found it online from somewhere else but uh there you go any questions just pop them in the comments i'll try and get back to people i don't think this is a particularly well covered topic um on youtube um a couple of videos on um differential dividing and a few a few things you'll see people with setups like this but they don't i don't think i've seen anybody actually actually put the calculations down so hopefully somebody finds that helpful anyway like i said any questions just buy them in the comments um thanks for watching uh where this is some kind of a long video and it's been ages since i've actually uploaded anything um thanks to all the new subscribers that have been just randomly appearing over the last i don't know year or so um if uh if you're interested in more content like this i'm not going to post every little machining job i do but the things that are a little bit further out there and it's sort of not so well covered i'm kind of interested in doing so give me a thumbs up if you liked it and if you want to see more um thanks for watching hopefully see you again cheers

Channel: Designments

Views: 15,866

Keywords: machining, bridgeport, milling machine, milling, dividing head, spiral milling, helical milling, gearing, home machining, Quorn, Quorn quick start, course thread

Id: TU5iy4HQIKQ

Length: 19min 39sec (1179 seconds)

Published: Thu Dec 09 2021