parts for an old time genny.

[steamer]

1/8" plus or minus what?

If your just blasting a slot through, a two flute endmill and a indexer would be my choice for the slots

You could also use a 1/8" wide saw, but they can be expensive

Bore the ID
Mount part on temporary mandrel
Turn OD to size.
Mount mandrel/part on indexer
Mill slots..Whats the material? Bakelite?...or G10/G11?

G10 is nasty...and can be hazardous to your health to say nothing of the abrasive nature of the dust to machines and cutters.....hope it's bakelite ;D

Dave

 

[Kermit]

I have the 1/8 endmill, two flute, solid carbide.

I will have an 1/8 inch slitting saw and arbor by end of the work day as well.

Yes, it is Garolite. Not the G10/11 variety but the LE version which is paper versus cotton cloth as the base. Hopefully not as toxic but it smells just like printed circuit board material when it gets hot.

The part is already bored, as I bought it as a piece of tubing

The ends for it have already been done, with your most helpful suggestions.

Another machinist here at work suggested the end mill as well. He says because the saw blade will load up fairly quickly and might ruin the dimensions of the side walls. Which I don't have alot of play with dimensions. The side walls for the slots will be about .083 inches at their thickest and taper to about .067 at the base. They'll be pretty easy to muck up.

The slots tolerance can be anything close or under .0126 but not over it.

Thanks for the attempts at help,
Kermit

 

[Alan J. Richer]

Re: Endmill vs. slotting saw:

What about (instead) a horizontal milling cutter? Seems to me that that is a LOT less likely to load up and ruin your day, as the teeth/gullets are much larger. They're not at all expensive and I've used them in plastics work before to good effect.

Alan

 

[Kermit]

This is my mill.

 

[arnoldb]

Kermit, I don't see how you have any option except the milling cutter - unless you can mount the workpiece in the vertical slide and have enough space on it in front or at the back, as well as enough vertical clearance movement on the vertical slide to cut the slots using the slitting saw... - if you clamp the workpiece in the vice, you cannot cut through the center at top or bottom, as the center line will be in the jaws, unless you have something else in mind for holding the workpiece... OK, you could, depending on dimensions needed, clamp the piece vertically - and use up/down to cut the slots on the front or back - but everything depends on the size of the workpiece and whether you have enough travel. A lot also depends on the size of the saw you ordered.

For using the milling cutter, Id venture a rough "guess" that you'd need at least 3000 RPM for the cutter speed - does your lathe go up that high ?

Very intriguing problem you have here....

Regards, Arnold

 

[steamer]

Hi Kermit,

You'll get by with running the cutter slow, if you feed slow. What you need is an indexer for your rig.....Do you have a 25 or 50 tooth gear?

You can do it with what you have, but your going to have to rig up an indexer of some kind really....especially with the tolerances you talking about.


Dave

 

[Kermit]

2.02 inches long. Supposed to be 2.00 inches. Close enough for me as its not a critical dimension.

1 7/8 inches OD. 1 1/2 inches ID. 3/16 wall thickness.

MY choice of setups this time out. The saw center line is at the top of the cylinder and the mill vise is at the bottom of its travel. I got lucky with that. one more 1/16th and it would be to tall to do in one pass this way.

OR should I try to make them in multiple passes? I'll have all the gibs on the lathe tightened up real good, and I'll be feeding with the milling attachment thread. Which is set pretty tight after I lapped it smooth. All things I found were needed in order to cut without vibration. I do plan on cutting a piece of sacrifical scrap from the tube for educational/destructive purposes. So I ask; Multiple passes with the saw doing 30 or 40 thou or one slow pass at full 1/8 depth?

indexing can come after I have 4 slots at 90 deg. I can do that simply. Then I just need a jig that will index me 15 deg from a slot; use it in all four slots, reset jig to one of the newly made slots, then repeat till done. At least that is my vision at this point in time. It is apt to change depending on the direction and consensus from all you; my inspirational engine building leaders and teachers. (blatant attempt at brown-nosing)

Kermit

 

[steamer]

Kermit,

Mighty brave way to index 24 slots

Your logic is perfect, but for one thing...stack tolerance.

I am afraid that after you do successive indexing, you accumulated error will be pretty big. My guess is far too big.

Try it on a round of maple or some other hard wood first and see how far you get......I'll do some digging on my end.

....as we drift into uncharted territory! ;D I love it when I do that ;D


Dave



OOOPS 24 slots ......miscounted....

 

[Kermit]

Assuming I can put slots perfectly opposite each other I should be able to get a slot every 45 deg around the tube. That just leaves two 15 deg offsets from the 45 degree slots. So whatever error I have on my offset is only doubled, being reset to zero when I reposition to another 45 degree slot.

I made a quick sketch

 

[steamer]

Sent you a PM......

Dave

 

[Kermit]

Lots of new angles to work out yet...

So. Sew. Needle pulling thread and whatnot. I went ahead an cut off a matching piece for experimental purposes and got it mounted up. Played with my dial indicator for what seemed like ages befor I finally got the top and bottom of the tube reading the same. Perfect vertical alignment achieved, I repostioned the belt on the head stock and cranked 'er up to about 2000 RPM. Never had the chuck spin that fast before. I have lots of little grease spots in an arc about the room now. ;D.

Moved in for a slice and it acted and sounded like cutting hard butter. Not even a bad smell of overheating to be detected. So I dialed in the full .125 inches and started my cut.

So far I'm very happy with this set up. Now for the head scratching and eventual jig making for doing 15 degree offsets ???


Good progress for a lazy Friday afternoon. Time for bacon lettuce and tomato sandwich,
Kermit

 

[Kermit]

I was thinking about my two fairly accurate triangles. a 30-60-90 and a 45-90-45.

The difference (or sum) leaves me 15 degrees.
which brings me to my jig idea. Somebody pipe in if they see a better way to set this up without a rotary anything...

Looking down from above I have drawn my idea for the jig with offsets for 30 and 45 deg. That should let me cover every angle needed on this rotor.

 

[steamer]

Well ...without a "rotary anything", I can't think of one...

The best way to learn how is to do...so have at it, Give it a whirl and see where you get.....Your not violating any laws of physics, and its not illegal or fattening.....give her a shot.

I'll sketch up a indexer concept for you if it don't....if it does I'll have a beer with ya instead! ;D

Dave

 

[Kermit]

whoa, I'm still not used to running the lathe at this highspeed! It seems to take forever to whind up to its whistling sound. Leaving me many seconds to wonder about my tightening job on that chuck.



I've gotten a bit more done. 4 slots now on the test piece. Enough to let me test out the jig idea.

I need a refill on this little bottle of elbow grease, or access to the nurse. "Honey" 8)

Goodnight Austin Texas; wherever you are!!!
(Kermit blows kisses to the audience and smashes his guitar on the stage)

 

[Noitoen]

Hi.

I've picked up this thread just recently and haven't had a chance to go through all the posts. My small workshop deals with electric motor and generator repair so I like the theme. Back to the part, you could make it a little longer so that you can have a little "un-machined" area to part off later and clamp the part to a 24 or 48 tooth gear to use as index. scratch.gif

 

[Kermit]

Update: 4 slots in the test piece. Max. Deviation between slots. .012 To small to see with the eye on a 2 inch circle. My method for doing 90 deg slots proved successful. If I use a better surface than the bottom of the vise currently provides me, I'm sure I could improve those deviation measures.

Welcome to my mess Noitoen.

The two inches length is just barely short enough for my vise to carry the part evenly across the blade. Any more length and I'd not be able to cut the slot end to end.

The idea for using a gear is a very good one though. I'm just very unclear on how I would fit anything else in the vise with the tube and still make the cut all the way through.

I don't think things very far ahead in this hobby because I don't have the experience to see any further ahead than the part right in front of me. ;D

Please stick around and enjoy the circus. Clowns should show up soon ;D

Kermit

 

[Kermit]

Soaking up the coffee. While I do, I thought it might be good to revisit some design images

I haven't updated the drawing with the new slot size yet.


Glorious day,
Kermit

 

[bearcar1]

Hiya Kermit. I have a 'solution' of sorts that may be of use to you in accurately making the slots you are wanting to achieve. I hope that this explanation will be easy enough to follow along and better yet understand :big: What I propose is this: turn a small spigot, the inside diameter of your future armature on the long side of a flat metal bar that will be clamped in the mill vise. The bar or plate should be larger than the OD of your armature. At this same time drill and tap central hole to be used by a capture bolt. Are you with me so far? Now, use a protractor or a set of dividers to accurately lay out datum lines at 90* and also at 15*. Measure out from the center point of the spigot far enough that a locator pin would engage the slot when the slot was cut to depth, and drill and press in a small peg the width of the slot at the 15* mark. Man I hope this makes some sense. Now, after the first slot has been cut in the part, this plate with the locator peg is placed in the vise, the armature is placed onto the spigot with the slot engaging the peg and the piece is the held down by the previously mentioned clamp bolt. The next slot is cut and the armature is unbolted, rotated until the next slot is engaged on the pin, the clamp bolt tightened up again, the next slot cut and the whole process repeated until all of the slots have been cut. If the initial location of the peg has been accurately carried out all of the slots should wind up (no pun intended there) ;D exactly the same. Quick and easy indexing at its finest. If everyone understands any/all of this than I am sure that there are modifications that can be done but the basic concept is there. Good Luck Kermit, this project is starting to take on a life of its own. Thanks.

BC1
Jim

 

[Noitoen]

Hi.

I've gone through the posts (drawings and pictures) and have a question. Is it a three phase AC generator (alternator) or a DC one? Since you have a 2 pole field system, which is separated 180º from each other, the rotors coils should have the same amount of poles. The output frequency of a AC generator is directly related to the RPM's and number of poles. In Europe we have 50Hz so on a 4 pole machine, the engine must run at a fixed 1500 rpm (1800rpm for 60Hz), generating 2 frequency cycles at each revolution. Those ancient generators on the initial posts, achieve the same frequency at a much lower speed. The 8 pole one, must run on 750 rpm.

 

[steamer]

Hi Kermit,

Here's what I was thinking......

The orange block mounts in your tool post.

The yellow disk is 7.639" in diameter and is made of plywood......you then take a peel and stick measuring tap from one of the woodworking supply stores and put a 24" long piece all around the OD of the wood index disk

The arm with the tool makers clamp looking thing is just that, and arm with a tool makers clamp on the outboard end. Attached to the side of the clamp and not shown is a little bent piece of plastic with a small colored groove in it. If you index every inch, you will have 24 divisions. Every half inch 48 divisions, every quarter inch, 96 divisions...ect.

These tape markings are good to +/- .002" Your eye and the plastic reticle I described above will probably on be as good as 1/64...though perhaps with experience you will get better...in any case, 1/64" at that radius is 0.20 degrees error....plenty good enough for your project.

The arbor is located in a V block you make with a single flute countersink bit. I've done it and it works just fine. It's good to mill a slot first to give the cutter some end relief. Doing it this way puts the V directly in line with the lathe spindle. EXACTLY.

Now the block on the other side of the arbor is a clamp that locks the arbor before a cut is put on. It is held on with two threaded studs and nuts. Tio index the arbor, loosen one nut and then the index arm clamp. Move the index to the next cut, lock the index arm clamp and then the arbor clamp

The other end of the arbor is turned to fit the ID of your part to be cut just like the arbor we made before..

Very Importanat, turn your wooden disk while mounted on the arbor. Then it is concentric.

You could build this in a weekend or less.....when you done making the part, put a metal disk on the arbor and make up an index plate.

Solved a problem and made some useful tooling to boot!

Just a thought.

Dave