I retrieved my camera from the workshop last night, and have found enough pics on it to make another instalment of this epic saga.
All this to make one flywheel. But as I said, I will be doing it from the roots up, and showing how I do other things as well, complete with the reasons I do it that way.
Sorry to be showing a lot of people how to suck eggs, you should just filter out the bits you need.
I have skinned the plans down, to show you all the dimensions that you need to make this flywheel are already provided on the plans.
1 - 6 spokes. So 360 degrees divided by 6 = 60. So if you were doing 5 spokes, 360/5 = 72 degrees.
2 - The radius required for each corner. So you would double that figure to give you your drill size. 2x4mm = 8mm.
3 - The internal diameter of the flywheel rim where you will be cutting to. This will require dividing in half, then have the radius of your drill subracted as well to put you in the correct position for drilling. 84/2 = 42. Then 42-4 = 38mm. That is the centre point for your drill, measured from the centre point of your RT.
4 - This is the PCD (Pitch Circle Diameter) for the position of the drill centre point near the central hub. You need to half that figure to give you the distance from the RT centre point, 26/2 = 13mm.
5 - The width of the spokes. You need to half the width of the spokes and add the radius of the curve (half the drill size). This will give you the offset from the RT centre point to end up with the spokes of the correct width. 5/2 = 2.5mm, add the radius, 2.5+4 = 6.5mm.
I always work in the Y axis for the main hole centres, and in the X axis for spoke width offset.
This all sounds very complicated at the moment, and sometimes it can be. But later on in this post I hope that the way I will be showing it done will clarify everything.
I will just add now, cutting flywheels is a job where total concentration is required. One mistake and you will be modifying the design slightly. There are natural stop points during the process, so if you need to take a break, it should be done then. Never stop half way thru a machining cycle, in this case, if say you were cutting the side face of the spokes, you would complete all six sides before having a break. A big sign on the workshop door of DO NOT DISTURB will help.
I would suggest you go thru this article from front to back, and watch all the short vids as well. It gives you a basic insight into how a rotary table works and some pointers on how to set it up.
http://www.jjjtrain.com/vms/mill_rotary/mill_rotary_01.htmlSo now onto the rotary table itself.
There are basically two bits of attachable machinery that allow you to do jobs on a mill. The straight line attachment is your vice. The RT allows you to do all the curvy bits (with a few straight bits if needed).
When buying an RT for your mill, it can turn into a bit of a minefield, and you can end up with one that will only do half of what you require.
It is all to easy to run out of depth. That is the distance from the bottom of your quill to the table. By the time you have added say the height of the chuck and jaws plus component. Put a collet chuck in the quill and added the cutter, things will start to get tight, to such an extent, you can't even change cutters or drills without moving way off centre, then coming back to centre again. The distance between the two on my machine is 14", and I wish I had a couple of inches more. A lot of people get around it by not using a chuck, and set everything up on the RT face, but chucks do make life a lot easier.
RT's come in all shapes, sizes and even ratios of the worm gear. So really I can only concentrate on what I use, you will have to work out how to do the same thing with yours. The main difference is the ratio, so you will have to find out how the vernier system works on your one to get the minutes and seconds of a degree. But in the case of this flywheel, only full numbers are used.
You can buy fairly low profile RT's, that address the height problem, but they are usually limited to horizontal use only, they don't have the built in castings to go to vertical operation. This can usually be solved by using an angle plate to put them in the vertical position. So if you are tight for height, maybe that would be the way to go.
For most small mill users, they have 3" & 4" RT's, that will do an admirable job, and if you get say an 3" or 4" chuck on there, will cope with most jobs you come across, and by taking the chuck off, even though you only have a small table, if you can get the job clamped down to it, will allow you to go to extraordinary radii for cutting and drilling if a little care is taken. Size isn't everything when it comes to RT's. Big is nice, but not compulsary.
So I had better stop beating my gums and get on with the job, but I will also be giving a bit more info in these first few pics.
I centred up my RT using a gizmo my mate brought back from the States for me. They are available in the UK if you search them out. It is called a coaxial indicator, and he got it for me from LMS.
http://littlemachineshop.com/products/product_view.php?ProductID=2060&category=And boy, does it make the job easy, but it does have a down side, it eats into those precious height inches. By the time you get the chuck and part on there, it becomes a bit of a tight squeeze, but well worth it if you have the facilities and need. Otherwise, you will have to use your normal DTI system.
I suppose this could also be used on the lathe for say centring up your tailstock to the chuck, or for setting up in the four jaw. I haven't tried that yet, but will do in the future.
This is the RT I have used for a long while. It is a Vertex 6" horizontal/vertical one, that also by changing the handle for a disc set, can be used as a dividing head as well. Normally on these sizes of RT they have a 2MT centre to the table. Smaller tables can sometimes have just a plain hole, and it is the central hole that you use for centring the table up.
I have modified my table to take a Myford nose adapter, so that I can use a range of chucks and plates on it, and on my lathe as well, so I can swap between the two at will. It just speeds up the way I personally do things, and for normal users isn't necessary.
This is the normal method for mounting a backplate. This is one to fit an 80mm 3 jaw onto my RT, and was turned up on the lathe. Four t-nuts secure it to the table faceplate. To assist on the centring up onto the RT it has a hole bored thru the centre of it, done at the same time the spigot was cut for mounting the chuck.
A back view, showing the chuck retaining bolt holes and the t-nuts and bolts.
This is the other bit of the puzzle, a MT blank arbor turned down on the end to be a very snug fit into the hole in the backplate.
This is how it fits together. First the arbor is put into the RT central hole, and tapped down into position. Then the backplate with fitted chuck is put onto the sticky up bit. The backplate is then bolted down onto the RT table.
The chuck is automatically centred up onto the table, with the added advantage of not having to stuff paper down the middle hole to stop your chucked up bits dropping down the well, usually necessitating the removal of the RT table from the mill table to retrieve them.
If any visitors to me have the same sort of setup and would like this backplate and bits for their RT, remind me and it will be yours. I have no further use for it.
Sorry about all this drolling stuff, but we are starting to come to the bit where I get to cut some metal.
So the RT is now onto the table, centred up at 0,0, the chuck has been fitted, with your outside jaws in the chuck and the part to be machined in the jaws.
Unfortunately, in my case, I am not quite ready. What do I spy on the end of the table to the right.
You guessed it.
In my case, I fit a set of soft jaws and machine them up to fit the part. I have a definite fetish for accuracy, I just hope you don't catch it, and use your outside jaws, just like normal people.
So the job is held tight in the chuck jaws, and I have the angle set to zero on the RT.
The main table was set to zero both in the X & Y axis.
We start to set up to drill. I will be doing the inside set first, because this is the easiest to do to begin with. An 8mm drill is in the chuck.
The drill points around the circle will be 30, 90, 150, 210, 270 & 330 degrees. These are the centre points between the main spokes.
So I set the first one to 30 degrees.
The Y offset was set to 13mm.
It was at this point I started to lose it and forgot to take pictures.
I drilled each hole just over 9mm deep at the above angles and offset, this depth was because I don't want the drill tip to hit any part of the chuck jaws. This pic was after I had finished the full circle.
The RT angle was then set to zero. The placement of the holes on the outside circle is 0, 60, 120, 180, 240 & 300 degrees.
The Y offset was then moved to 38mm (remember the workings out on the drawing), the position of the outside holes.
Then the table was moved to a positive reading in the X axis of 6.5mm. This is to give us our spoke widths.
This pic shows the drill at the outside and offset position.
Again, no drilling pictures. I drilled the series of six holes at 60 degree spacing.
The only adjustment done on this manouvre was to move the X axis to -6.5mm, then the repeat drilling of the set of six holes at 60 degree spacing, the same setting angles as the previous set.
If you managed to follow my instructions, you should have ended up with a set of holes looking like the pic below, except for the blue marking, I put that on to show when the blue bit was removed, you would be left with the makings of your flywheel.
It was at this point I gave up.
I know most of you don't have the equipment I have, and will have to rely on using your X & Y handles to give the offsets. I showed the DRO's display because it was the easiest way of showing what was required at each operation.
Once you can get the basic understanding of what is required to make a flywheel cutout on the RT, you will soon be doing what I do, plan it out on a bit of paper and just cut away. Believe me, once you have got the first one under your belt, you will kick yourself for not doing it before. It really is a reasonably easy operation to do. But time consuming at times.
This bit is now open to questions if anything at all is wrong in your eyes, or more than likely, not undertood. I would like to get them out of the way before proceeding any further.
When I get back to it, there is very little to do except cut the centres out. But again that is done using offsets, so you end up with a flywheel that just requires a bit of hand dressing before use.
John
