To make a gear with 25 teeth I need a 20 holes indexing plate for the dividing head. And because I don't have one... let's make one. Milling and lathe work.
Hi Michel, I'm not sure as there was no close up of tool box section, but that grooving tool you liked so much may be an internal screw cutting tool 55 deg English or 60 deg metric , they are made so you grinder the top only to keep sharp. Steve
Nice job! We made some dividing plates on our SIP Jig Borer.... Love that machine to death.. RIP. Even though the machine was very accurate, I was questioning the accuracy of the center-drilled, drilled and reamed holes. I thought it would be a better practice to bore to finished size, and i'm sure it would have been, but due to the small diameter and lengthly setup & operation, we opted for the drill and ream approach. The plate alligned prefectly with the setor arms as did yours. Impressed with your material usage. Would have never even thought that to be an option. Aa always, appreciate your videos.
@@Rustinox I know what you mean. If I knew what I was doing, I'd be doing it better :) Around minute 05:00 you are turning on the lathe. The gear noise is quite uncomfortable on the ears. Try to lower the audio on machines running to about -12db for nice sounding machines like the belt drive drill press, to about -25db for angle grinders, or if you want to voice over it.
the new milling machine as opened up many new possibilities for you it was exciting to see how far your shop has progressed as far as your ability to do tooling. Bravo my friend rock on keep on keeping on and all that other jargon. Aside from that you're looking very well these days My friend all my family's best to your family. good days. Kemper
Nice job Michel. I always look forward to your "Friday Frolics" and I love a home made solution to the problem. Have a nice weekend and thanks for the video!
Always nice to watch a new video from You! Time 02:43, the find at the scrappy... I found one very similar when emptying the bludder around the corner of the train housing hall. I think I can pick it up..... Troubling You can't make 25, 19, 18, 17 holes. 25 is no problem. I can make 24,5, and 25.5 holes also if You would need it to be sure... Need to make a video about that setup.... Some rainy day when drone flying is unsuitable...
Nice! As you say, some day you can add more holes to the plate. I wonder if a 3d printed plate would work to get divisions enough to cut a metal plate? 🤔
Awesome outcome yet again 👍 With regard to that spring, I can just imagine the guy who designed it laughing to himself and thinking "I'd like to be a fly on the wall watching someone try to fit this"
Hi Rusty. Very well made for a quicky 😂😅 . Will egerly await you to cut the new gear as a demo & see the lathe do it's thing Well done, catch you soon.
Hi Michel. Does the Deckel dividing head do compound division (i.e. does it have a second indexing arm behind the disk). If it does, you should probably be able to get some pretty damn close approximations to your missing divisions. Otherwise, for the small numbers of holes you're dealing with, you could get by with "eyeballing it" from a printed paper template. It's an approach that works pretty well, and the inevitable errors are pretty much averaged out by the ratio of the dividing head itself - assuming you're out by, say, 0.2mm on a hole, which should be do-able, with a ratio of (I'm guessing) 40:1 you've got an error of about 5 microns on the division. Worst case, you could make a set of "throwaway" plates and use them to make a set of more-than-accceptably accurate "keeper" plates. As it happens, I'm busy working out a bug in my compound division calculating code, but it doesn't have the deckel head in its presets. Do you happen to know what the original plates for the deckel head were?
I once calculated that if all you had was a 40:1 dividing head and a disc with a single hole in it, you could make a plate with any arbitrary number of holes accurate to within 3 arc minutes in just three steps (two intermediate plates).
@@Rustinox Ah, right. That's what you get for assuming... So, I did a few calculations with the new version of my code. Assuming normal indexing only, and calculating up to 50 divisions, your original indexing plate is good for 1 2 3 4 5 6 7 8 10 11 12 13 14 15 16 19 20 21 22 23 24 26 28 30 33 35 38 39 40 42 44 46 48. Adding your new 20 hole plate into the mix, we get 25 32 50. I couldn't find any details on your dividing head on the 'net in order to find out what plates it originally came with. Given the plate you have, they don't seem to be clones of anything I have documentation for, though. The "typical" set of plates for a 40:1 head (as used by Browne & Sharpe, Emco, Kertney and do on), is 3 plates as follows : Plate 1 - 15, 16, 17, 18, 19, 20 , Plate 2 - 21, 23, 27, 29, 31, 33 and Plate 3 - 37, 39, 41, 43, 47, 49. That gets you every division up to 50 (and as a bonus, the division tables are in Machinery's Handbook). You should be able to make that set of disks pretty easily (although you'll probably have to eyeball at least 17, 27, 29, 31 and the whole of plate 3).
@@wibblywobblyidiotvision I think Rusti has a chinese clone of the Deckel dividing head, but missing 2 plates. I think he has the 33,38,39,42,46 plate & is missing the 27,31,34,41,43 plate and 36,37,40,58 plate.
Great job on the indexing plate Michel. You have received some nice tooling from your viewer. I like that spring parting tool. I have that on my list of projects to do in the future.
"this thing... so lets start cut-BRUZZZZZZZZT!!!" LOVED it! What a joy you must be to your friends and family, with such a kind heart, and brilliant sense of humor! Thanks for your videos! Please tell me your gantry is a repurposed kids swing-set!!! :)) you!
i love the way the dividing head made a part for itself!! lol. it gives a sense of satisfaction to have one machine in your shop making parts that another machine can use. keep up the good work..😊👍👍
When I am down on my luck, Ole Rusty brights my day by hanging around his shop turn scrap into useable stuff! Why to go once again for making this old fart fill good, and teaching me new tips & tricks. Bear
Thanks for sharing. My dad was a fitter/turner and he had a quirky friend with a funny accemt and a great sense of humor. You remind me of them messing around. I always look forward to listening in to your adventures. ❤
Such a lovely box of gifts. You have a wonderful community of viewers. 👏👏 I so enjoy how you make such useful tools out of what is no more than scrap metal. Thank you for yet another excellent video. 👏👏👍😀
I used a dro to make my dividing plates because im too lazy to scribe a circle on a lathe and step it off with a pair of dividers. Im curious to see your solution when you need to generate the next plate. I suppose you can use the dial scales with gret care. Good job captain
Well done Rusti, great result, and you now have some more steel stock for another project 👍. That clip certainly doesn't look well designed, is that a Deckel head or someone else's? Cheers, Jon
A free machinist app can tell the X and Y axis points to make circular divisions would probably be o.k on a non DRO Mill if no backlash mishaps. Great videos
I don’t know if it would work on your machine, but since I don’t have a quill stop either, sometimes I’ll use the bottom of the quill travel as the stop, and adjust the depth of the hole by raising the table. And yes, I was going to say you drill more hole patterns, but then I realized before you said it that you can’t drill the patterns you don’t already have (at least not that way).
I tried that before. But if I bottom out the quill, The bearings make very scary noises. So, that's not an option. But one day I will make a depth stop. For sure... well maybe... we'll see :)
So are we going to see some trepanning work ahead? but just be sure you don't suffer a mishap like what Brian of bcbloc02 did in his latest video. David Wilks' trepanning videos filled me with awe and are a little scary especially when he was tasked with another job on another machine nearby at the same time, wow.
I still need to try and make my own. I have so many things that is urgent and require all my attention that i dont always get to make and do what to. But this is a great video on your part and shows where there is a will, there is always a way(or 1000 more😂) to do it. The dividing head is a great tool to must have, but sadly, very costly in this country so i will attempt in near future the spin indexer(view Joe Pieszinski , from Texas channel in )to see this article or my version of it. I think it also uses the 40:1 ratio
Hi Michel, I love your English, like me also you do not know all the correct names of things, but try to tell them in your native languish and they will be in big problems. I suppose French is your native languish, mine is Danish, and i also have problems. Love your approach to problems and to solve them. I have a question, what is the make of your milling machine? i also work in a cellar with a low ceiling and your machine looks like it will fit, I do not have a milling machine yet, but want one. Have a nice winter in the cellar 🙂 Regards Steffen Denmark
As someone already pointed out, since the dividing head has a reduction of 40:1, even a cardboard plate would work since the error in the plate is reduced by 40. Also, you made the holes on the outer rim of the plate but it's probably wiser to always make the hole pattern as close as possible to the inner rim. This leaves the outer rim free for when you need a really high number of holes that only fit on the outer rim.
I guess you had another hole pattern on your original plate that divides by 10 to enable you to generate the 20 circle. Very nice job! To make the plate without a dividing head you need a DRO on your mill. Even the most basic ones will have a circle of holes function and I believe using XY coordinates results in a very accurate hole spacing if done correctly. The downside is drilling hundreds of holes... yawn!
That's where you need a CNC - lay out the holes in cad using whatever numbers of holes you need, mount the stock in the vise, and let the machine do the tedious work of drilling hundreds of holes
The internal gear in his dividing head (with 40 teeth) has one factor of 5. Any multiple of 5 would do for the new plate. He chose 4 x 5 = 20, based on the old plate. It looks like he had room for any multiplier from 1 to 13 (x 5). With his 20x plate he could make a 3rd plate w/ both 20 & 25 divisions (for sub-multiples of 800 or 1000 divisions, including 100, 125, 200, 250, etc.) to rule dials and the like. The real challenge would be to create new primes (of 79 or less?) which were not on the original disk.
If you use a digital spirit level with a 0.1 degree resolution, combined the dividing head ratio of 40:1 you would be more than accurate to make the 19 / 18 / 17 holes.
Hi Michel, I'm sure I missed something and Ive never used a dividing head before but if you need 25 divisions for the gear then how does the 20 divisions in the plate help you or is the gear 20 teeth. I'm confused!! Very generous gift from Tobias and congratulations to him and his new family as well A great video as always have a great weekend!!
Hi Michel, I've done a bit of investigating on dividing heads and understand the concept now. I can see how you get your 25 teeth from your 20 hole plate using a 90:1 head. Not sure what ratio your's is nor the range of plate holes that you have!! I look forward to your explanation in the next video. Sorry for asking a stupid question😅😅😅
Dividing heads usually have a ratio of 40:1 (rotary tables usually 90:1). 20 x 40 = 800. 800 is divisible by 25 so a 25 tooth gear is possible. 40/25 = 1 3/5 so 1 turn and 3/5 of a turn per tooth. 3/5 of 20 = 12 so 1 turn plus 12 holes per tooth
With a 40:1 dividing head, you can make any division that is a factor of 40 using only whole turns of the crank. For 40 divisions, one turn of the crank. For 20, two whole turns of the crank. The disk and ring of holes being used in this case is utterly irrelevant, as it's only being used to indicate a whole turn. Indeed, he could probably get away with no disc at all in this case, and simply eyeball it. More generally, though, for a division D and a dividing head ratio R, making the division requires moving the crank by R/D full turns. So for a division of 25, Michel needs to advance by 40/25 or 1+3/5 of a turn. per division. He can therefore use any ring of holes which has 5 as one of its factors - 5, 10, 15, 20, 25, (obviously), 30, 35 and so on. When choosing a set of disks for a dividing head, you try to cover the maximum number of factors in order to get coverage of the maximum number of divisions. I'm doing this at the moment, and it would probably be easier to cut a new worm wheel with a "reasonable" ratio than carrying on with my bloody 55:1 wheel (caused by buggering up cutting a 60:1 wheel and ending up with a blank that was too small)
Nice job Rusti. I like that you could see the part in the web of that I section. That's the mark of a good scrounger. Mart.
Thanks Mart.
Great job 👍 🇬🇧
Thanks.
eyup Michel
Problems are there to be solved, your the problem solver👍👍👍👍👍👍
atb
Kev
No problem, Kev. Thanks.
Hi Michel, I'm not sure as there was no close up of tool box section, but that grooving tool you liked so much may be an internal screw cutting tool 55 deg English or 60 deg metric , they are made so you grinder the top only to keep sharp.
Steve
This is indeed a square grooving tool.
Nice job!
We made some dividing plates on our SIP Jig Borer.... Love that machine to death.. RIP. Even though the machine was very accurate, I was questioning the accuracy of the center-drilled, drilled and reamed holes. I thought it would be a better practice to bore to finished size, and i'm sure it would have been, but due to the small diameter and lengthly setup & operation, we opted for the drill and ream approach. The plate alligned prefectly with the setor arms as did yours. Impressed with your material usage. Would have never even thought that to be an option.
Aa always, appreciate your videos.
Thanks. Well, I use what I can find.
Hi Rusty, I'm late to the party.. Enjoyed... that plate should be plenty strong since it was going to hold up a building in its first life 😁😁👍👍
Thanks Dean. I also think it will hold :)
Hi Maichael,
I liked the edit. You are making good progress and finding your voice.
Thanks Mark. Still working on it. It's not easy.
@@Rustinox I know what you mean. If I knew what I was doing, I'd be doing it better :)
Around minute 05:00 you are turning on the lathe. The gear noise is quite uncomfortable on the ears. Try to lower the audio on machines running to about -12db for nice sounding machines like the belt drive drill press, to about -25db for angle grinders, or if you want to voice over it.
the new milling machine as opened up many new possibilities for you it was exciting to see how far your shop has progressed as far as your ability to do tooling. Bravo my friend rock on keep on keeping on and all that other jargon.
Aside from that you're looking very well these days My friend all my family's best to your family. good days. Kemper
Thank you for your kind words, Kimber.
Nice job Michel. I always look forward to your "Friday Frolics" and I love a home made solution to the problem. Have a nice weekend and thanks for the video!
"Friday Frolics" ? Lol, that's a good one :)
Always nice to watch a new video from You!
Time 02:43, the find at the scrappy... I found one very similar when emptying the bludder around the corner of the train housing hall. I think I can pick it up.....
Troubling You can't make 25, 19, 18, 17 holes. 25 is no problem. I can make 24,5, and 25.5 holes also if You would need it to be sure...
Need to make a video about that setup.... Some rainy day when drone flying is unsuitable...
I don't think I will ever need 25,4 holes :)
@@Rustinox No, they are only for very special use....
Nice! As you say, some day you can add more holes to the plate. I wonder if a 3d printed plate would work to get divisions enough to cut a metal plate? 🤔
I think 3d printed plates could work. Well worth to give it a try.
Awesome outcome yet again 👍 With regard to that spring, I can just imagine the guy who designed it laughing to himself and thinking "I'd like to be a fly on the wall watching someone try to fit this"
Lol, he's making fun of me. For sure :)
Hello Michel, A delightful time watching your adventure today making a dividing head plate.
Thanks Allen.
Hi Rusty. Very well made for a quicky 😂😅 . Will egerly await you to cut the new gear as a demo & see the lathe do it's thing
Well done, catch you soon.
Next week... normally.
Hi Michel. Does the Deckel dividing head do compound division (i.e. does it have a second indexing arm behind the disk). If it does, you should probably be able to get some pretty damn close approximations to your missing divisions. Otherwise, for the small numbers of holes you're dealing with, you could get by with "eyeballing it" from a printed paper template. It's an approach that works pretty well, and the inevitable errors are pretty much averaged out by the ratio of the dividing head itself - assuming you're out by, say, 0.2mm on a hole, which should be do-able, with a ratio of (I'm guessing) 40:1 you've got an error of about 5 microns on the division. Worst case, you could make a set of "throwaway" plates and use them to make a set of more-than-accceptably accurate "keeper" plates.
As it happens, I'm busy working out a bug in my compound division calculating code, but it doesn't have the deckel head in its presets. Do you happen to know what the original plates for the deckel head were?
I once calculated that if all you had was a 40:1 dividing head and a disc with a single hole in it, you could make a plate with any arbitrary number of holes accurate to within 3 arc minutes in just three steps (two intermediate plates).
This dividing head is a "made in China" one, and doesn't fit the FP1. Maybe it is made for other Deckel machines. I don't know.
@@Rustinox Ah, right. That's what you get for assuming...
So, I did a few calculations with the new version of my code. Assuming normal indexing only, and calculating up to 50 divisions, your original indexing plate is good for 1 2 3 4 5 6 7 8 10 11 12 13 14 15 16 19 20 21 22 23 24 26 28 30 33 35 38 39 40 42 44 46 48. Adding your new 20 hole plate into the mix, we get 25 32 50.
I couldn't find any details on your dividing head on the 'net in order to find out what plates it originally came with. Given the plate you have, they don't seem to be clones of anything I have documentation for, though.
The "typical" set of plates for a 40:1 head (as used by Browne & Sharpe, Emco, Kertney and do on), is 3 plates as follows : Plate 1 - 15, 16, 17, 18, 19, 20 , Plate 2 - 21, 23, 27, 29, 31, 33 and Plate 3 - 37, 39, 41, 43, 47, 49. That gets you every division up to 50 (and as a bonus, the division tables are in Machinery's Handbook). You should be able to make that set of disks pretty easily (although you'll probably have to eyeball at least 17, 27, 29, 31 and the whole of plate 3).
@@wibblywobblyidiotvision I think Rusti has a chinese clone of the Deckel dividing head, but missing 2 plates. I think he has the 33,38,39,42,46 plate & is missing the 27,31,34,41,43 plate and 36,37,40,58 plate.
Very nice work. You always seem to turn chunks of scrap into treasure. Lovely work as always.
Don't know if it's a treasure, but it works.
@@Rustinox if it works then it's a treasure. The best kind of treasure, one that has a function besides looking good.
That's a fantastic scrap yard. They always have exactly the right piece of metal you need. Brilliant video Michel. Cheers Nobby
Thanks Nobby. Scrapyard is paradise :)
Great job on the indexing plate Michel. You have received some nice tooling from your viewer.
I like that spring parting tool. I have that on my list of projects to do in the future.
I never used one but I think they work very well.
Nice job
Thanks.
Thanks for sharing. Had to reclick on the video to like it.
Nice. Thank you.
Intrigued by the spring loaded parting tool. Interesting to see the dividing head mounted vertically. Cheers
I haven't used the parting tool yet. But if I do, I will put it in a video.
"this thing... so lets start cut-BRUZZZZZZZZT!!!" LOVED it! What a joy you must be to your friends and family, with such a kind heart, and brilliant sense of humor! Thanks for your videos!
Please tell me your gantry is a repurposed kids swing-set!!! :)) you!
It's indeed made with parts of an ols swing set.
i love the way the dividing head made a part for itself!! lol. it gives a sense of satisfaction to have one machine in your shop making parts that another machine can use. keep up the good work..😊👍👍
And it's fun to do.
Thanks
Welcome.
When I am down on my luck, Ole Rusty brights my day by hanging around his shop turn scrap into useable stuff! Why to go once again for making this old fart fill good, and teaching me new tips & tricks. Bear
Thanks Bear.
Thanks for sharing. My dad was a fitter/turner and he had a quirky friend with a funny accemt and a great sense of humor. You remind me of them messing around. I always look forward to listening in to your adventures. ❤
Nice. Thanks Max.
Such a lovely box of gifts. You have a wonderful community of viewers. 👏👏
I so enjoy how you make such useful tools out of what is no more than scrap metal. Thank you for yet another excellent video. 👏👏👍😀
Thanks Andrew. You're also part of this community.
Hi Michel, good to see that the tools get some use! Have fun with it. Looking forward to your next videos!
They will be useful. No doubt. Thanks.
I love your approach! Use what you have, figure it out! Problem= solution etc etc!!!
No problem, Don. Thanks :)
I used a dro to make my dividing plates because im too lazy to scribe a circle on a lathe and step it off with a pair of dividers. Im curious to see your solution when you need to generate the next plate. I suppose you can use the dial scales with gret care. Good job captain
I will figure something out the day I need it. For the moment I don't know yet.
Thanks Rusti! Entertaining episode, with a good result 👍
Thanks.
Well done Rusti, great result, and you now have some more steel stock for another project 👍. That clip certainly doesn't look well designed, is that a Deckel head or someone else's? Cheers, Jon
It's a Chinese clone. It doesen't even fit the table.
A free machinist app can tell the X and Y axis points to make circular divisions would probably be o.k on a non DRO Mill if no backlash mishaps. Great videos
I think it's doable. Thanks.
I don’t know if it would work on your machine, but since I don’t have a quill stop either, sometimes I’ll use the bottom of the quill travel as the stop, and adjust the depth of the hole by raising the table.
And yes, I was going to say you drill more hole patterns, but then I realized before you said it that you can’t drill the patterns you don’t already have (at least not that way).
I tried that before. But if I bottom out the quill, The bearings make very scary noises. So, that's not an option. But one day I will make a depth stop. For sure... well maybe... we'll see :)
I will check also my devider. i believe , i have many plates with a lot of holes on it and they should be different
Indeed, they should :)
So are we going to see some trepanning work ahead? but just be sure you don't suffer a mishap like what Brian of bcbloc02 did in his latest video. David Wilks' trepanning videos filled me with awe and are a little scary especially when he was tasked with another job on another machine nearby at the same time, wow.
It will be a very small geoove. That's all :)
I still need to try and make my own. I have so many things that is urgent and require all my attention that i dont always get to make and do what to. But this is a great video on your part and shows where there is a will, there is always a way(or 1000 more😂) to do it. The dividing head is a great tool to must have, but sadly, very costly in this country so i will attempt in near future the spin indexer(view Joe Pieszinski , from Texas channel in )to see this article or my version of it. I think it also uses the 40:1 ratio
With a spin indexer you can do a lot. Go for it.
Hi Michel, I love your English, like me also you do not know all the correct names of things, but try to tell them in your native languish and they will be in big problems. I suppose French is your native languish, mine is Danish, and i also have problems. Love your approach to problems and to solve them. I have a question, what is the make of your milling machine? i also work in a cellar with a low ceiling and your machine looks like it will fit, I do not have a milling machine yet, but want one. Have a nice winter in the cellar 🙂
Regards Steffen Denmark
It's a Deckel FP1. There is a video in the playlist.
@@Rustinox Hi Michel, now i have bought a milling machine, i found a Shaublin 13 in very good condition for good price. Have a nice day.
As someone already pointed out, since the dividing head has a reduction of 40:1, even a cardboard plate would work since the error in the plate is reduced by 40.
Also, you made the holes on the outer rim of the plate but it's probably wiser to always make the hole pattern as close as possible to the inner rim. This leaves the outer rim free for when you need a really high number of holes that only fit on the outer rim.
Thanks Erik. That makes sense.
Très bon travail …👌toujours intéressant de suivre vos projets bonne continuation 🍻
Thanks mayhem.
Well, I make all kinds of parts for something I don't have "YET" Talk about optimism. Or,,,,,, I need to re-access my goals, THANKS
Optimism is a very good mindset :)
I guess you had another hole pattern on your original plate that divides by 10 to enable you to generate the 20 circle. Very nice job!
To make the plate without a dividing head you need a DRO on your mill. Even the most basic ones will have a circle of holes function and I believe using XY coordinates results in a very accurate hole spacing if done correctly. The downside is drilling hundreds of holes... yawn!
That's where you need a CNC - lay out the holes in cad using whatever numbers of holes you need, mount the stock in the vise, and let the machine do the tedious work of drilling hundreds of holes
If needed, I will figure it out. I'm sure :)
In the being I thought the gear had 25 teeth and you needed a plate with 25 hole later you made 20 holes in a plate did you need 20 or 25 ?
To make a 25 teeth gear, I need a plate with 20 holes. One tooth is 1rotation plus 12 holes.
The internal gear in his dividing head (with 40 teeth) has one factor of 5. Any multiple of 5 would do for the new plate. He chose 4 x 5 = 20, based on the old plate. It looks like he had room for any multiplier from 1 to 13 (x 5). With his 20x plate he could make a 3rd plate w/ both 20 & 25 divisions (for sub-multiples of 800 or 1000 divisions, including 100, 125, 200, 250, etc.) to rule dials and the like. The real challenge would be to create new primes (of 79 or less?) which were not on the original disk.
Making a part for something you don't have ... yet !
You're absolutely right.
If you use a digital spirit level with a 0.1 degree resolution, combined the dividing head ratio of 40:1 you would be more than accurate to make the 19 / 18 / 17 holes.
Hi Michel, I'm sure I missed something and Ive never used a dividing head before but if you need 25 divisions for the gear then how does the 20 divisions in the plate help you or is the gear 20 teeth. I'm confused!!
Very generous gift from Tobias and congratulations to him and his new family as well
A great video as always have a great weekend!!
I don't have a dividing head but am fascinated by them. I was going to ask the same question 😁
Thanks David. Is it ok for you if I explane it in next video?
@@Rustinox Hi Michel, of course it is, I look forward to understanding the process better. Have a great weekend
Hi Michel, I've done a bit of investigating on dividing heads and understand the concept now. I can see how you get your 25 teeth from your 20 hole plate using a 90:1 head.
Not sure what ratio your's is nor the range of plate holes that you have!!
I look forward to your explanation in the next video. Sorry for asking a stupid question😅😅😅
Dividing heads usually have a ratio of 40:1 (rotary tables usually 90:1).
20 x 40 = 800. 800 is divisible by 25 so a 25 tooth gear is possible.
40/25 = 1 3/5 so 1 turn and 3/5 of a turn per tooth. 3/5 of 20 = 12 so
1 turn plus 12 holes per tooth
I got lost somewhere.
What did I miss ?
You needed 25 teeth but you made a 20 hole plate 🤔
Plus you already have a 20 division plate.
Is it ok for you if I explane it next weeks video?
With a 40:1 dividing head, you can make any division that is a factor of 40 using only whole turns of the crank. For 40 divisions, one turn of the crank. For 20, two whole turns of the crank. The disk and ring of holes being used in this case is utterly irrelevant, as it's only being used to indicate a whole turn. Indeed, he could probably get away with no disc at all in this case, and simply eyeball it.
More generally, though, for a division D and a dividing head ratio R, making the division requires moving the crank by R/D full turns. So for a division of 25, Michel needs to advance by 40/25 or 1+3/5 of a turn. per division. He can therefore use any ring of holes which has 5 as one of its factors - 5, 10, 15, 20, 25, (obviously), 30, 35 and so on.
When choosing a set of disks for a dividing head, you try to cover the maximum number of factors in order to get coverage of the maximum number of divisions. I'm doing this at the moment, and it would probably be easier to cut a new worm wheel with a "reasonable" ratio than carrying on with my bloody 55:1 wheel (caused by buggering up cutting a 60:1 wheel and ending up with a blank that was too small)
20 x 40 = 800. 800 is divisible by 25 so the 20 hole plate is good for making a 25 tooth gear.