Using a Myford Dividing head to graduate a Quorn.

Hello everyone, I will soon need to graduate the various scales on the Quorn. I have a Radford style graduating tool and a Myford dividing head. How do I use the Myford dividing head to graduate dials in degrees?

Looking at the various methods of indexing and dividing, it seems that GHT's method of putting a dividing head, meshing with the Bull wheel seems the neatest way to do the job. However this seems to require other bits of GHT's dividing and graduating tool, for example the plates with appropriate holes etc.

Now when it comes to rigging up a Myford dividing head to do a similar job on the Bull wheel. I simply do not have a clue, indeed I don't know if it is even possible. I have only used the dividing head once to cut a rack. So I am really clueless on this aspect of dividing apart from reading GHT's book on the subject.

Any help or advice will be greatly appreciated,

Andrew.

Edited By Andrew Tinsley on 03/07/2017 19:03:45

I have the Myford dividing head, and have an adaptor with a No2 morse taper on one end to fit the dividing head, and an expanding parallel the other to plug into the rear end of the lathe mandrel. I originally intended to fit some sort of stay to secure the body from rotating, but in practice it just sits on the change wheel cover. This allows me to divide stuff held in the chuck or whatever, and have done numerous graduating jobs with it, with the engaging tool held in the tool post.

Maurice

I've not seen his method but it sounds as if he sets the dividing head up for something like 72 divisions and then arranges a gear on the head to drive the bull gear with a 5:1 ratio as it is easier than trying to get 360 out of teh dividing head ( 5x72 = 360 divisions)

Any combination of divisions and gear ratios will work so long as they add upto 360

EDIT 4:1 gear may be better if it is a 90:1 dividing head then you just need one turn of the handle to give 1 degree. and could do it without plates in that case

Edited By JasonB on 03/07/2017 19:29:15

Now that makes a lot of sense, too busy trying to ape GHT's design and not thinking laterally. Thanks Maurice for showing me the way! Now how do you make an expanding parallel? You cant use a bar pulling on tapers to force out the parallels, because the Morse taper is on one end of the adapter and the chuck carrying the cylinder to be indexed on the other end. Ah, one can remove the chuck and cylinder and tighten up the bar from the chuck end of the mandrel. Then screw the chuck back on and the register of the cylinder will be undisturbed. Simple if you think first and write afterwards!

Thank you ,

Andrew.

Have a look at the Myford site, they show the parts needed to use the dividing head as Maurice described.

Mike

Thanks Mike,

I will do that and then perhaps make them.

Andrew.

Sorry if my description of my dividing head on the mandrel was inadequate. The adaptor plugs into the morse taper in the dividing head, then the parallel part plugs into the rear of the lathe mandrel and is expanded by a tapered plug, pulled in with a drawbar from the extreme left of the dividing head. The chuck carrying the work to be divided is screw onto the lathe mandrel. I will post a picture tomorrow if it helps.

Maurice

NO need to use a dividing head. You can make a simple plunger, or even a piece of hacksaw blade used as a flat spring ratchet pawl, and use the standard change gears for indexing. For example, to make 100 graduations on a handwheel collar, it is mounted in the chuck and the changegears are set up so you have a 60T gear on the lathe spindle, meshing with a 30T on the first stud on the quadrant. This gives a 2 to 1 reduction. Now we mount a 50T gear on the same stud as the 30T and engage the plunger with the 50T gear. So every tooth on the 50T gear moves the spindle around by 1/100th of a revolution.

To do 360 graduations, you could use a 60T gear with the plunger engaged with it, set with a compound gear train to give a 6:1 reduction to turn 60 graduations into 360 over 6 turns of the plunger gear.

Dividing head is mostly only necessary for gear cutting where teeth numbers do not divide neatly into 360 degrees, just about everything else can be done by direct indexing with change gears etc.

A good book on the topic is Harold Hall's "Dividing" in the Workshop Practice Series. From memory, he includes charts of gear trains for different numbers of graduations to be indexed, which saves a bit of calculation.

I agree with Hopper, but in his original post, Andrew says that he already has a Myford dividing head; so why not use it with the aid of a simple adaptor. Once made its very quick to set up and gives a very wide range of divisions, even with only the two basic division plates.

Maurice

Because you can set up the change wheels and make a spring-loaded detente plunger or even a piece of hacksaw blade ratchet pawl in less time than it takes to make a dividing head adaptor. And because the use of the change gears is much simpler. Instead of having to wind the dividing head handle around so many turns plus so many holes in between each and every single division, you just move the spindle one tooth on the gear. By using a spring loaded hacksaw blade set up like a ratchet pawl, you just move the spindle one click at a time. If you are doing 360 divisions, you will really appreciate this efficiency by the time you get to about the 20th division.

One gear train that will work for 360 divisions is: 75T on the lathe spindle (or tumbler output on ML7 etc), meshing with 25T on the first stud which is keyed to a 70T on the same stud. Which meshes with 35T on the second stud, which is keyed to a 60T which is engaged with the spring loaded detente plunger or hacksaw blade.

Six of one and half a dozen of the other I suppose. But having made a few graduated handwheels on the lathe recently I really appreciated the speed of the single click change gear method. And the almost impossibility of making a mistake in the indexing as it is all one click by one click.

Hello from "down south" Andrew. Maybe I look at things a bit simpler! You have a Myford dividing head which (correct me if I'm wrong) has a 60:1 ratio. One turn of crank = 6 degrees spindle rotation. formula is Turns = degrees required/6.  Mount the dividing head as normal on the vert slide/cross slide arrangement and hold a cutter in collet/chuck on spindle.

For your 1 degree T=1/6 , All you need is a plate with a hole circle to give you 1/6 turn. If you want 0.5 degrees, it is 1/12 of a crank turn. The formula for that is T = minutes required/360.... T= 30/360 is 1/12 turn. Use a bit of say 1/4" round tool steel ground to about a 30 deg point and halved like a D bit held in your 3 jaw chuck and off you go scribing the lines in degrees on your dials. You'll be back inside having an ale in no time!!

DH

Edited By D Hanna on 04/07/2017 07:32:31

Thanks Maurice, Hopper and my fold made Mr Hanna,

Now it looks as if I am spoiled for choice! I like your method Maurice as making the necessary 2mt to expanding rod device is pretty easy to do and I can also use my Radford style tool for scribing the lines, it is good to have the 3 stops to give degrees, five degrees and 10 degrees different scribed lengths.

Hopper, your method will give me similar results for the cost of making up a detent system to fit on the lathe. So it all comes down to which of the two "adapters" do I want to make? the detent lever is probably simpler. However the 2mt taper and expanding tube will allow further adaptive use of the Myford dividing head.

Dallas, your method has got a lot of merit. If I can devise some variable saddle stops to do the different lengths, then I am home and dry. I do have the Myford 6 position stop, so I could use that (it came with the lathe and has never been used as yet).

Talk about spoiled for choice! I think I will make the dividing head adapter anyway as well as the detent system. I like making goodies for the lathe. I will give it a thought or two over a glass of Australian red this evening! Thanks everybody for so many helpful suggestions. I need to machine the circular T slot in the rotating Quorn body before I can finish off the degree scales so I will have time to mull it all over. I am now down to small doses of morphine, so I am probably OK to start machining safely, once more.

Thanks again everyone,

Andrew.