Machining Dividing Head Index Plates: Drilling Hole Patterns

While the main holes for my the Dividing Head Index Plates were drilled on a CNC mill, I still needed to drill the mounting holes manually. In this video, I will show two methods of drilling hole patterns - one with a rotary table and another using the hole pattern function on my Digital Read Out (DRO).
Also check out Mike Wiggins (The Backyard Machine Shop) video on drilling the hole patterns on these index plates using a CNC Milling Machine: • Keith Ruckers Indexing...

[@barrishautomotive]

Hey, those extra holes are a story, a lesson and a video. Totally worth it.

[@fiorevitola880]

Everybody is human and It is refreshing to see that you admit your mistake and show us how to correct it. It is encouraging to know how to correct a mistake. Thank you for your videos as always.

[@luvstruck2733]

Hey Keith. Thanks for the lemonade. I think I learned more off of that than in any teaching video you might have made. Going back to all the old algebra, geometry and trigonometry, gave me a flashback made me very thankful, there are books and calculators, with all the calculations already written out for you.

[@roberthorner8494]

GREAT JOB. MISTAKES JUST PROVE YOUR SHOW IS REAL. FIXING THEM IS A LEARNING EXPERIENCE. I LOOK FORWARD TO YOUR VIDEOS.

[@VintageMachinery]

+ROBERT HORNER Thanks!

[@tardusmerula6102]

This is the tech , which took us to the Moon and farther, never forget. Beautiful mechanics!

[@StupidEarthlings]

Nice work, especially the math part. Kids shld learn this stuff for when the internet is gone someday.

[@cameronmccreary4758]

I would mill the bad holes on a rotary table and make them lightning cuts so the plates would be lighter than they normally are. Just stay about .500" away from your good holes. Then they would sit lighter on the dividing head while still being able to be screwed on. Nice work.

[@chennemeyer]

That is such a good video going into detail of every step, nothing left for imagination, and the multiple ways to do things was great. A real service to the community Thank you

[@dirtfarmer9161]

I'm one of those guys that told the teacher - This stinking math - through pre calc, and trig classes... I'll never use this stuff in real life. And boy was I wrong.... Use it every day. Nice Job Keith - Your Man Enough to Accept Mistakes and Fix Them.

[@VintageMachinery]

+Dirt Farmer I was guilty of singing that same phrase in math class as well. Many years ago, I ran into my old match teacher shortly after I got of college and started working. I could not thank her enough for what she taught me in school!

[@JulianMakes]

loving your videos Keith! i've just purchased my first lathe 2 weeks ago (a boxford AUD mk3) and your videos are super interesting and helpful. When i was at school we used to learn the phrase "Sohcahtoa" Sin=Op/Hyp. Cos=Adj/Hyp. Tan=Op/Adj. My rubbish channel is mostly about me trying to learn new things (i know who would want to watch that) so i'll be posting me attempting to machine things as i learn the lathe but i absolutely love watching experts like you make things! cheers and best wishes from the UK o/

[@johnbazaar8440]

Bozo is our friend. Right. Those extra holes would probably drive me nuts. I'd probably have to plug them. 😊 Nice video as always, Keith. Thanks, John

[@VintageMachinery]

+John Bazaar They will probably drive me nuts as well. A constant reminder of one of my many Bozo moments....

[@merrickray]

the universe is all about holes, and trying to fill them.. at the atomic level semiconductor are full of holes and the electrons jump from one to the next trying to fill them, getting hot and dying in the process.. At the other end is the black hole at the centre of the universe and planets and stars jump in, get hot and dying in the process.. Then in between is woman with a hole and man jumping from hole to hole trying to fill them, getting hot and dying. Yes the universe is all about holes.. :-)

[@ChrisB257]

Watched Mike's video - wow, that is some machine. So easy to make a small error - glad you managed a fix - enjoyable to watch. Very useful reminder about measuring an accurate diameter for a hole pattern.... brings home the usefulness of trig!

[@VintageMachinery]

+ChrisB257 Thanks - glad that you enjoyed!

[@Armedlegally]

My mathematics teacher always said "Show your work" famous last words I pretty much live by now. Thanks Keith for a great video!

[@royreynolds108]

My CE classes we showed our work so if by some chance we screwed the math part at least the method may be correct.

[@JunkMikesWorld]

Nice save Keith! I often share mistakes with my students so they can see that everyone if human and also to help them think through their problems. Thanks! Mike

[@VintageMachinery]

+Junk Mikes World Life is all about solving problems. Sometimes we have to solve for the problems we create!

[@STEVESL200]

Thanks so much for your KZbin video. I was going to buy a rotary table. but I have now decided to convert my milling machine to digita indexing for similar money which makes it a lot more versatile for other jobs. I have a dividing head and want to make some more plates this seems a great way to do it. thanks Steve

[@jerrycoleman2610]

Keith, I really enjoyed your video and your instruction on locating the holes for the index plates.!.!.!.

[@k5at]

Keith, Thanks for showing how to figure the bolt hole distance. Very helpful!

[@VintageMachinery]

+Herb Blair No problem - a good old geometry/trig word problem....

[@vicmiller7191]

I do love the custom feature you added for these parts. Thanks for sharing...Vic

[@shade38211]

Could see it almost immediately was different dia. . Glad it's a easy fix. Really like the dividing head vids. Thx.

[@VintageMachinery]

+shade38211 Thanks!

[@rogerdeane3608]

I am making some plates, you came along at the right time with Trig lesson. Thank you.

[@ianbutler1983]

Keith, I love the picture-in-picture action. Thanks, Ian

[@VintageMachinery]

+Ian Butler Thanks - now that I have a second camera that I can use, you will probably see that more often!

[@johnstrange6799]

Cool to see the various set ups, minor set back and all -Thank you.

[@VintageMachinery]

+John Strange Thanks John!

[@MikePalmer42]

Really enjoyed the video Keith and thanks for the trigonometry refresher

[@VintageMachinery]

+Mike Palmer (MP Custom Blades) My pleasure!

[@PaulTunnicliffeChannel]

For me it's not a matter of getting everything right first time every time that counts, it's how we deal with the mistakes we make that makes us who we are. Kudos to you Keith. PS I love the math, can you do more in your videos? If of course it's need as part of the project.

[@VintageMachinery]

+Paul Tunnicliffe I think I have showed some workshop math before and I will continue to do so when I can. Thanks!

[@martineastburn3679]

One of my prized books is the "Handbook of Mathematical Functions With Formulas, Graphs, and Mathematical Tables" National Bureau of Standards. The Circular Sine / Cosine s to Tenths of a Degree to 15 decimal places. And my "Table of Natural Logarithms for Arguments between Zero and Five to (in) 16 decimal places. These were used both in Engineering classes and Physics classes but in the design of Massive Radar electronics that calculated (plotted) orbits and paths. Dad, I and my brother were very high tech. My brother is still working. Dad and I were Home Shop Machinists while my brother and I also work in wood. A different age than now. I'm 72 running hard on 73.

[@marhue7026]

I watch all your videos, but never comment, just wanna tell you thank you so much, every new video is like a lil birthday present.

[@VintageMachinery]

+Mar Hue Thanks so much!

[@mrfrog3350]

Nice save Keith! I also bookmarked the trig lesson.Thanks!

[@VintageMachinery]

+Mr Frog My pleasure!

[@roncartwright8125]

Great instruction on the use of the DRO for doing bolt circles. It will help me with mine. Thanks very much from across the Pond.

[@garyc5483]

+Ron Cartwright For those without the bolt circle feature on their DRO's you can use an online calculator at :-littlemachineshop.com/mobile/bolt_circle.php I find it quite usefull at times.

[@VintageMachinery]

+Ron Cartwright Thanks - my DRO has a lot of nice features like that in it - many of which I have never even used....

[@mickdoherty8633]

Thanks Keith - another informative and entertaining video. Much appreciated. Cheers Mick

[@VintageMachinery]

+Mick Doherty My pleasure!

[@AmateurRedneckWorkshop]

Great video. I prefer the DRO bolt hole function, no heavy duty thinking required there. Thanks for the video.

[@cemx86]

Thanks for the video. at 3:18 - Who hasn't made a measurement error? Confession is good for the soul. But this was an easy fix and instructional. Note: The video mentions that the correct diameter is 1-3/8" which, I think, should be 2-3/8" correct diameter (drilled to the incorrect 2-1/2" diameter).

[@VintageMachinery]

+cemx86 Correct, the diameter was 2-3/8".

[@BlairBuildersllc]

Awesome Video Keith. Watched your video, followed along with the math, plugged my numbers in, got an answer, learned something new , solved my problem. Thanks

[@VintageMachinery]

+BlairBuildersllc Thanks!

[@kleinerbub84]

Well done Keith, thanks for sharing. Keep up that well-made stuff, work an videos

[@VintageMachinery]

+kleinerbub84 Thanks!

[@FredMiller]

Great segment Keith. You actually have me laughing out loud with the "special feature" comment. Great save and thanks for the trig review. We don't use it often but it is a nice "refresher". Fred

[@KeithDDowning]

+Fred Miller "It's not a bug, it's a feature"

[@VintageMachinery]

+Fred Miller Gotta make hay while the sun shines! "Yeah, we planned it that way...."

[@stuvs830]

+Keith Downing We say that a lot with new software releases. But darned if it doesn't end up being true.

[@tced2858]

Man Keith that there was some fancy double knot gazinda math...thanks for the lesson..!

[@PeterWMeek]

Good to see both methods. Thanks.

[@VintageMachinery]

+Peter W. Meek Thanks Peter!

[@david929190]

I use a drafting program to find a bolt circle radius. By taking the measurements between two points as you do and then sketching that in the program I can quickly and with no math get a radius, but this method is valuable to know!

[@sirlancer23]

Hey Keith Congrats on 50,000 Subs!

[@VintageMachinery]

+sirlancer23 Thank you! Quite a milestone!

[@buddylineman]

Great video! We all make mistakes, and when we share them with others, then the others like me can learn something. Thanks.

[@VintageMachinery]

+Buddy Lineman If you hang around me long enough, you will see lot of mistakes!

[@tolydukhovny682]

great salvage, keith! also, you've showed the way to derive an old geometry formula for the relation between the side and the radius of the circumscribed circle in an equilateral triangle. this alone is going to be very useful for many who did not do it at school. if you could, please post a ref to the actual man who does it on the cnc. thanks for the show!! -toly

[@VintageMachinery]

+Toly Dukhovny Toly - glad to hear that so many people are liking the math lesson in the video. I was not sure how that might go over! The person who did the CNC work was Mike Wiggins. There is a link to his video in the description for the video. Keith

[@submarinerresearch3233]

Keith Although I majored in math a long time ago, it looks like you could just put the plate in the milling machine, use the coax indicator to find the center of the bore hole, zero out the DRO and then use the coax to find the center of one of the mounting holes, and the DRO should directly show the radius of the bolt hole circle John

[@captainjerk]

Good work! That's really cool! And fits nice! Thanx Keith. :)

[@VintageMachinery]

+captainjerk Thank YOU for watching and commenting!

[@VintageMachinery]

+captainjerk Thank YOU for watching and commenting!

[@HolzMichel]

Hey Keith, that inset is a really nice addition to your videos. gives a really good overall view of the process. looks like i will have to start saving up some shekels to get into a DRO.. looks like it's inevitable... it was a little surprising to see you set up on the rotary table with the dial indicator on the outside perimeter of the table. mine is a 16" table so that method would be out for me. instead i cut a plug that fits in the center and i run the dial on that. cheers mike

[@VintageMachinery]

+HolzMichel I have not had that rotary table for very long and just have not made a plug to do that yet. Another project "on the list..."

[@HolzMichel]

Keith Rucker - VintageMachinery.org gotcha ;) looks like you're in dire need of "a round to-it" too... the backlog gets to be a little daunting

[@raincoast2396]

I like that! Custom plates with six mounting holes. Cheers.

[@VintageMachinery]

+Rain Coast Now I just need to make a custom dividing head that can use the other three holes!

[@charlescompton4495]

It's a shame the original didn't have six equally spaced holes then you'd have the radius. I learned that when I made a "stickler" wood splitter back many years ago. BUT, I learned that my old Algebra and Trigonometry functions can come in handy. Thanks for reminding me why we spent four years in high school back then. Greg

[@VintageMachinery]

+Charles Compton Like I tell my daughter who is taking high school geometry right now, it is not important that you remember every formula for the rest of your life, but it is important that you remember what you can solve for so that you can refresh your memory when the time comes to use it in real life.

[@paulputnam2305]

I remember telling my math teacher that I’m never gonna need to use this. Now, 50+ years later, I use math all day every day every day as a machinist for more than 40 years. Ha ha on me. At least it got much easier with calculators and computers. Great Job Keith. A great machiner can fix there own mistakes and nobody is the wiser.

[@binks166]

Thanks Keith, much enjoyed.

[@VintageMachinery]

+binks166 Thanks for watching!

[@rfcarlson1]

Nice recovery. I've found I can best keep myself out of trouble if I don't measure. Becomes truer as my eyes get older. Since I already had a plate with holes in the right place I would have used a transfer punch. I've had to drill holes that were slightly off of equally spaced on a bolt circle so that the plate only fit on one way and was therefore indexed to a specific position keeping the circumference of the plate synced to the driving element.

[@VintageMachinery]

+rfcarlson1 When I am woodworking, I often use a "story stick" to transfer measurements. Not so much in the machine shop. Transfer punches would probably work fine but I think it would be somewhat challenging to line the two plates up just right without making some kind of jig to hold them.

[@shawnmrfixitlee6478]

Bozo visits us all Keith .. Good fix man ! Thumbs up ..

[@VintageMachinery]

+ShawnMrFixitlee Thanks!

[@MattsMotorz]

Great video Keith. You da man!

[@VintageMachinery]

+MattsMotorz Thanks!

[@chemech]

Hi Keith, This is another one of those cases where 3 machinists can come up with at *least* seven ways to make a part... Personally, I'm a big fan of using transfer punches and transfer screws to copy hole patterns... especially at home, where I don't have a large enough rotary table or DROs on my mini-mill... Takes some careful work to set things up to hit the center of the dimple with the drill bit though... and, if I happen to have some suitable round stock (not a common situation!) I'm quite happy to turn a hub to rotate around. Most often, it's a matter of measure three times, cut once, rework the part, scrap that piece, and do it again to get it right... ;^) Cheers, Eric

[@VintageMachinery]

+chemech Transfer punches have their place but for this part, I think that work holding would be a challenge. You would probably have to custom make a jig to center the two parts on each other to get it done right. But, in the end, the results would be the same!

[@dinamboyz]

There's definitely more than one way to skin a cat. Nice techniques Keith.

[@VintageMachinery]

+dinamboyz For sure!

[@coffeemaddan]

Great video to show that even simple tasks can need reasonable math skills :) I'm sure there are a lot of people wishing they'd listened a little harder during maths lol

[@VintageMachinery]

+coffeemaddan No doubt about paying attention in math class. I keep telling my daughters that as they complain about what they are doing in math all the time....

[@tombellus8986]

If you were doing this as your full-time job, I'll bet you wouldn't have as many BOZO moments. I understand that you have a lot on your plate, what with your full time job and your job at the museum and getting your new shop built. Thanks for the bonus footage.

[@VintageMachinery]

+Tom Bellus Probably so. I get plenty of shop time but I am not as in practice as a full time machinist would be!

[@danfloyd695]

I know, and I appreciate everything you do. I routinely use my slide rule for computations like this because there seem to be fewer steps.

[@VintageMachinery]

+Dan Floyd The good old slide rule! When I was in school, they had just quit teaching how to use them as calculators were coming along and common enough for every day people to buy.

[@royreynolds108]

When I graduated from LaTech Unv. in 1969, the HP45 had not come out yet. I still have my K&E sliderule.

[@raysimon1368]

Keith always a good job and always explained very well but my shop teacher would be all over me for wearing gloves in a machine shop

[@skikang13]

Nice video. The old school approach reminded me that Oscar Had A Heap Of Apples :) Sin=O/H Cos=A/H Tan=O/A

[@VintageMachinery]

+Ski Kang Cool - I have not heard that one before.

[@stuarthardy4626]

Great vid Keith Those who don't make mistakes never make anything I am surprised you trust those calculators ( all of them are the same) just type in on one line 1+2/2 the answere is wrong , the reason is they follow the rule BMDAS but if you type in (1 + 2 ) / 2 it's correct , food for thought with the beasts Stuart

[@VintageMachinery]

+Stuart Hardy A calculator will will give you the right answer if you enter it in correctly. Garbage in, garbage out. I was taught "Please My Dear Aunt Sally" (Parenthesis, Multiply, Division, Addition, Subtraction). Now days, I tend to use Excel to calculate complicated formulas where I can see my formula properly expressed on the computer screen.

[@RichardHeadGaming]

Nice save, yeah spinning and drilling just gives you two sets of mounting holes for multi uses lol. And while laying out every hole is entirely possible having Mike cnc them was the way to go.

[@VintageMachinery]

+Richard Schmidtendorff Now all I need to do is build a custom dividing head that I can bolt that special bolt pattern to!

[@RichardHeadGaming]

lol shhhh.

[@hakunamatataadventurebus5944]

Nice save!

Hi Keith, As always I very much enjoyed your video. I am glad you could easily fix that mishap and combine it with yet another interesting video. You could however have made life much easier for yourself calculating the pattern diameter. As you say the angles in the triangle are 60° each, which makes it an equilateral triangle. The formula for its circumscribed circles radius equals its side length divided by the square root of 3. The diameter is of course twice this value. For each equally spaced hole pattern exists such a formula that has already been determined. Having those ready as a table could make your life much easier when having to deal with this kind of work on a regular basis. The general formula R=s/(2+sin(pi/n)) where s is the length of the side and n the number of holes you have.

[@VintageMachinery]

+Robert Köppl Thanks Robert - I was not familuar with that particular formula. However, part of the reason why I showed that particular method is that you can pretty easily adapt that approach for whatever number of holes you might be dealing with. But as with pretty much anything in the machine shop, there are many ways of getting to the same outcome!

[@RoelTyros]

Hello Keith, Interesting video as usual but that math piece in the beginning of the video was difficult for me because I am very bad with math. But when I can see it in real on the material than I mostly understand the math behind it. That's also why I couldn't go to a technical education because of the lack of math. Anyway again a good video and besides, I hope the rain is getting soon away because of the shop. Looking forwards to the next update of the shop and of course the next video. Greetings from Roel !

[@VintageMachinery]

+RoelTyros Thanks - math is important to know in this trade, or at least it makes it a lot easier. Still getting rain but we made some more progress on the shop this week - just slow. I will try and get another update out to you guys the first part of the week.

[@Smidge204]

Ah TI-35X - I've had one of those since 9th grade and it's a great little machine. :D Edit: It will also convert decimals to fractions which is particularly useful if you're doing inch measurements...

[@VintageMachinery]

+Smidge204 I have had that one since I was in college back in the early '90's. It is still going, and I think it still has the original batteries!

[@petefletcher]

For those of us without fancy stuff like dividing headed and DROs (or even a mill), it is possible to do bolt circles with just a rule and dividers. You wouldn't tackle dozens of holes but for 3 or 4, it's quite possible.

[@VintageMachinery]

+Peter Fletcher Very true, there are many ways to skin a cat. In the case of this project, the challenge would have been finding the center of the plate to put your dividers since that whole area was bored out and it has to be prefect to all of the other holes that were already drilled. Lots of ways to do that as well, but it is not as straight forward as starting from scratch on a blank piece of metal.

[@petefletcher]

+Keith Rucker - VintageMachinery.org Ah, but if you'd known you had to do it by hand, you would have set it out from the centre before boring out. I just love your videos, best on KZbin IMHO and I'm learning from every one. Keep em coming! Oh, and I'd kill for your new shop :-)

[@HaraldFinster]

Very enjoyable video, as always, Keith! Your explanation of the trigonometry used to find the radius of the bolt circle is excellent. However, I hope you don't mind a tiny little nitpicking-like comment here: at 13:17 you write x = 1.02825/cos(30°) = 0.86603 with a lowered equal sign to indicate that you mean that the sign refers to the cosine only, i.e. cos(30°) = 0.86603 This is clear and correct in conjunction with your explanation, but it might be misleading and incorrectly interpreted as x = ... = 0.86603 So, generally speaking one should take the small additional effort and repeat the complete term, i.e. x = .. = 1.02825/0.86603 Thanks you again for all your great videos! Kind regards Harald

[@jimhornicek1108]

Center original holeplate over the new and use a transfer punch. Drill first hole',pin plates together and punch for other two holes.

[@MikeGalusha]

Very nice Keith. I'd likely make some plugs for the extra holes, they would bug me too.

[@VintageMachinery]

+Mike Galusha They don't bother me at all!

[@douglasblacke9360]

Hi Keith. I "discovered" your channel a while back and have been enjoying learning a little about machining - a very interesting discipline. I found this video about dividing heads particularly intriguing since I'd never heard of dividing heads. Are that leads to my question: What are these used for? Thanks! PS: I figured out the "math problem" using trig, and was pleased to see that skill hasn't completely deserted me!

[@mrbluenun]

Hi Keith, I found this really interesting, though having had a terrible schooling I too learned Trig; but only to ref the code in the book, I was never told as far as I can recall it had anything to do with deg or any other function. I found Maths really great, but because I was not at school much because of illness I was in the bottom most class, and the three years I was in that class they taught exactly the same thing each year, so having learned the first year it was easy to do the following two years, but I learned nothing extra. Everything I learned I did myself the old fashioned way with Encyclopaedias. I would have liked a better cooling but that was the only choice. Anyway I won’t bore you with my history,. Take care mrbluenun

[@VintageMachinery]

+mrbluenun School is a great place to get the basics, but most real learning takes place in life!

[@garyc5483]

Nice save Keith. I hope you were able to correct the other plates in time. I would have to plug the extra holes I think. Thanks for sharing the Mr Bozo moment. regards from the UK

[@VintageMachinery]

+Gary C Everybody says to plug them up, but they are not hurting anything and sometimes I need a reminder to slow down and not be a Bozo....

[@mrbluenun]

Hi Keith, The mistake is a shame, though the time consuming stuff is surely the measurement? Still doing it on the cnc does mean the info is saved if it is a mistake on the three hole pattern that doesn’t take long to do. Really interesting hand worked video though, thank you so much. Take care mrbluenun

[@VintageMachinery]

+mrbluenun Thanks - if the extra holes really bothered me, I could always just make a new plate - it would be easy to alter the CNC file to fix that one problem.

[@outsidescrewball]

Great info!

[@VintageMachinery]

+outsidescrewball Thanks Chuck!

[@KeithDDowning]

Good video Keith. Thanks. Regarding the Co-Axial Indicator. I use one quite a bit. I have found it easier to unlock the spindle and turn it by hand. Really, all I'm looking for is the center between the two edges of a hole or boss in the X and Y direction. I have no control over what happens at any point between X and Y. I will manually turn the spindle, and move the table 1/2 the difference to find center in either X or Y. I think often times, the needle is jumping around because the feature is not perfectly round, but possibly elliptical a bit. If I first get a center reading in X, I can use that same mark on the indicator as a starting point for my location in Y, with the assumption it is perfectly round, then refine it from there. To verify my findings, I will then go in and check with an edge finder, to find I'm usually with .001" or so. If I have a diameter where I can't use a Co-Axial Indicator (diameter too large), I will use an edge finder and eyeball center of X direction to locate my center in Y. Then locate my center in X, then come back to Y and check to see if my eyeball was close.

[@VintageMachinery]

+Keith Downing Hand turning the spindle is a great idea with the co-ax indicator. I have done it that way a time or two and should probably use that method more than I do.

[@brianbutterfield9891]

Keith, Not to be a simpleton; but I would have probably measured the ID of the center bore, ID of the bolt holes, and then the thickness of the web between the two. Add half of both ID measurements to the web between them and then double the result.

[@PorchPotatoMike]

brian butterfield yep, quick and easy. At the very least, I would have done that to double check the trigonometric method.

[@johncrea9395]

Keith A little off topic, but since most of us really cann't justify both a rotary table AND an indexer, since many rotary tables have accessory indexing plates available, any down side to just getting good rotary table and the indexing plates/accessory? John

[@robertkutz]

keith nice work .

[@VintageMachinery]

+Robert Kutz Thanks!

[@walter2990]

Sorry, but you lost me at trigonometry..., I was "sick" that year in High School. I stopped at Geometry! I'm very sure that as I "tried" to listen & learn what you were teaching, my brain just got a blister!

[@user-yp9pc3rh6k]

Those extra holes are lightening holes... Yeah, that's it, lightening holes!

[@SharkysShop]

Fortunately, the extraneous holes will be easy to plug. A couple of easily machined pins, and a bit of Loctite 609 to keep it in place.

[@VintageMachinery]

+Sharky's I will probably just leave them as they are. They don't bother me....

[@gilbertodiazcastro8871]

That trig is used by machinists in a daily basis. The best way for me to do it is using my Machinist Calculator by Calculated Industry. All I need to do is input two of the measurements and it gives me the rest. In this case all I needed was to input the 30° angle and the adjacent and done.

[@VintageMachinery]

Cool!

[@shortribslongbow5312]

Thanks Keith, another very interesting video. :o)

[@VintageMachinery]

+Shortribs Longbow Thanks for watching.

[@jcs6347]

Great video Keith! Thank you for showing us 2 methods to do this, I learn a lot and have a question please. How would you set up the plate to cut the outer circle of holes using the rotary method and avoid drilling your table or any clamps? I just can't thank how you could get clearance, thanks again.

[@VintageMachinery]

+JC S Sometimes you just have to drill holes into something. If I were making an entire plate, I probably would have put a sacrificial piece of material under the plate (aluminum, plastic, even wood) and just drilled into it.

[@jcs6347]

+Keith Rucker - VintageMachinery.org Ok thank you!

[@scumbag373]

Those original holes could be called a "design feature" to lighten the plates lol Great video though Keith

[@VintageMachinery]

+Dave Sleaman Exactly!!!

[@OldeGuido1]

I never made that far in math. I would have had to consult my Olde Dad. Thx for sharing.

[@VintageMachinery]

+OldeGuido1 Thanks for watching!

[@richardhaisley1]

I always used an edge finder and the mid function on the dro to find the center. Go to the approximate center then crank to an edge, zero the dro, crank to the opposite edge and hit the mid function. Lock that axis and crank to zero, then do the other axis the same way. It takes less than a minute and is always within .001. btw I would make little t shaped plugs and press fit them into the bozo holes.

[@VintageMachinery]

+Richard Haisley I don't like using edge finders on an inside bore like that - they don't behave the same as on an outside diameter.

[@swarfrat311]

Keith, Maybe it's a good thing I don't have a shop and machines. Mr. Bozo's visit wouldn't do any good! Thanks for the information and for the video. Good luck with your dividing head project! Have a good one! Dave

[@VintageMachinery]

+Swarf Rat Mr. Bozo interferes with all parts of life, not just in the shop.... At least he does in my neck of the woods.....

[@rodwright225]

Stuff happens and who you going to call 😎👍👍

[@weldmachine]

With the Coaxial Indicator. I find it,s much easier to use this type of Indicator without the spindle running. Meaning : just rotate it by hand only. For Two reason it is easier to set your zero. And also you are not wearing out the the body of the Indicator. Thanks for the video Keith. Regards Peter.

[@yanwo2359]

Keith, I thought your explanation was very clear. Another approach is to solve the problem in general. That leads to CircleDiameter = DistanceBetweenHoleCenters * 1.15470, which is 1 / cos 30. Jon [edited to correct constant.]

[@VintageMachinery]

+Yan Wo Hummm, I will have to play with that. I would think that the constant would vary depending on the number of holes you are dealing with though.

[@yanwo2359]

+Keith Rucker - VintageMachinery.org Yes. The constant is only for three holes at 120 degrees.

[@busman2000]

Put a small center punch mark under the right holes to save time. (hint)

[@RobertKohut]

Nice!

[@salvatoremicale7746]

goes to show you. its not that easy. but you fixed it. very good .5 stars. sal

[@joetiller1031]

Great math lesson, everybody makes mistakes I know I have made my share of them.

[@VintageMachinery]

+Joe Tiller Oh yeah, I am not anywhere near immune from making mistakes...

[@roylucas1027]

Why didn't you transfer punch the holes from the original to the new plates? Thank you for the great video.

[@VintageMachinery]

+Roy Lucas Too much opportunity to not get the original plate properly aligned with the new plate.

[@richardhaisley1]

p.s. I'm still amazed at how you machined them.

[@VintageMachinery]

+Richard Haisley THanks!

[@ianmoone2359]

I have a suspicion I’m going to be making some of these dividing plates for my dividing head. I think mine might be double sided blind holes, so two plates in each disc. My chances of getting it right on both sides without making a mistake? ZERO 😜😂😂

[@MrPragmaticLee]

It might be beneficial to some to point out that if you use a scientific calculator to make such calculations to be sure the calculator is in the "degree" mode & not the "radian" mode. There'll be a button on the calculator to switch between Rad/Deg. You'll want to be sure the display area of the calculator is showing "Deg".

[@VintageMachinery]

+MrPragmaticLee Good point. I know that with my particular calculator that it automatically goes back to DEG each time it turns on so you have to put it in RAD mode.

[@AllodialTitle]

Keith, many thanks for taking the time to make this video. Do you know if all DRO systems have a bolt hole function. I'm just in the process of buying one. Thanks again. Phil

[@VintageMachinery]

Not sure about all of them but I would suspect that the modern ones will. Check out DroPro's - that is the kind of DRO I have and it is great. They are also a great company to work with - you can call them up and they will help you figure out what you need and will be there to help if you have a problem.

[@AllodialTitle]

Keith Rucker - VintageMachinery.org Many thanks

[@ronaldkearn3322]

This is all well and fine, however, how are these plates used? What do they do ???? :-)

[@427med]

they are same as my Ellis dividing head 5? in dia 1-125 bore three mounting holes 1/4 thick i want the last 4 plates can you make them for me

[@KnolltopFarms]

Thanks so much for the math lesson, I've got this bookmarked for future reference and will put that formula in my ring binder when I out to the shop, that will be very helpful! Sorry you had to host Mr. Bozo for lunch, but it's great you were able to salvage those plates and we got to learn that great math, so it wasn't a total bummer...except all that set up :( So just a random question here, nothing to do with a project I'm dreaming about or anything, cough, cough...But what plate would you need, if it's even possible, to make 125 divisions? My math tells me it's 2.88 degrees between scribe lines, but is there a plate you could use to "drive" to those coordinates? Thanks again and I hope the shop is getting water proofed ASAP, Aloha...Chuck

[@StraightThread]

+Knolltop Farms Yes, a plate with 25 holes would allow 125 divisions assuming the dividing head is geared 90:1, that is 90 turns of the crank moves the index head 1 complete rotation (360º). One turn of the crank would move the head 4º. 90 turns / 125 divisions = 18/25 turns. Therefore, if you use a plate with 25 holes and move 18 holes for each division, you would move the head 18/25 * 4º = 2.88º.

[@KnolltopFarms]

+Richard Freeze Thanks, I did figure all of that out and I'm sorry, I know should have replied that I looked into it. It was early for me and the old dusty cupboard atop my shoulders and between my ears wasn't working at full speed just yet ;) For some reason I just recall a video by Mr. Fenner saying that there weren't any plates with divisions of 5, but now I'm thinking that he was talking about masking plates or something? I still have to go back and look at his gear hobbing video to find out what he was talking about just to scratch that itch. But my solution to a little problem will likely be something a bit more crude and home-made. I've got a micrometer dial project for my 1919 SB lathe, and my dial is scribed at 125 divisions on the cross slide, and the compound doesn't even have one LOL! Thanks again for the feedback, and I'll put that info into my ring binder too, it's all useful to me...Aloha, Chuck

[@VintageMachinery]

+Knolltop Farms My dividing head has a 40:1 ratio - which means that you crank the handle on the dividing head 40 times to get one revolution. I just looked up 125 divisions in the book I have for the dividing head (vintagemachinery.org/pubs/detail.aspx?id=6525) and that is one of the few patterns that I cannot make with this dividing head with any of the five plates that K&T offered. I could do that job if I made a special plate with 25 divisions in it, but that is not a standard hole pattern. 40 turns / 125 divisions = moving the crank 8 holes on a 25 division plate.

[@KnolltopFarms]

Yeah, that's what I read yesterday too. Thanks so much for the reply and all of the extra homework. Sorry that I forgot to mention I found out the answer to my own question! I still was curious if you had the 25 hole pattern on any of those plates. I'll figure out how to index my dials, it's not like I don't have a stack of gears for both of my lathes to play with ;) Have a great weekend Keith, Aloha...Chuck