Gallery, Projects and General > How to's
Making a flywheel
sbwhart:
That Brilliant John
:ddb: :ddb: :ddb: :ddb:
More please
Stew
Stilldrillin:
Only just found this post John...... ::)
But you`ve got me attention now!
Thank you! :thumbup:
David.
Darren:
I like the way you held those bit on the lathe John.... :thumbup:
bogstandard:
For those who have seen me make flywheels from plate will have seen these techniques used before. And they are legitimate ways to hold, it is classed as a safe method, and can be used to make plates almost as large as the swing of the lathe, as long of course you don't start to try to make 20" diameter by 1/32" thick. But you could make a dozen of them stacked together.
It was for the reason of people not seeing it being done before, was the final sway for me showing it.
I hope to show you a few more bits and bobs before it is finished.
I have got the next stage of disc preparation already in my camera, so I may make a post up about that, before showing the final spoke cutting bit when I get to it.
John
bogstandard:
This might look like a bit of a long winded post, but I am also trying to show a few things you don't normally see along the way, and explain what it is all about.
You must have read about me going on about soft jaws, and how I use them to achieve super accuracy.
I once read a post from a supposed 'expert' who stated that he used soft jaws because they didn't mark the metal he was holding in his three jaw, as they were softer than the metal he was gripping with the jaws.
How many people went away from that post thinking it was true, and didn't pursue them any further?
Maybe he was partially right, but I will tell you the correct reason for using soft jaws. They allow you to make jaws that are perfectly concentric, and because they are made for a specific part, they hold that part perfectly so machining can be carried out to high degrees of accuracy over and over again.
Soft jaws are one of the cheapest routes to go down to obtain super accuracy. I am such a believer in them, I won't buy a self centring chuck for my lathe or rotary table unless soft jaws are available for them. In fact I have a version that I use in my 5c collet chuck that allows me even more perfection than collets allow, and also I can easily skim say 2 thou off the face of a washer only 15 thou thick, and up to 4" in diameter. Try that in your normal 3 jaw.
So what are they?
They are a set of jaws made from soft iron to fit your 3 or 4 jaw self centring chuck. They can easily be bored using a normal boring bar to fit the circular part you want to hold.
Normally you would use your outside jaws for holding the blanks you have already made up from plate material, and hope that they don't have much built in runout. There is nothing worse on a show engine than a wobbly flywheel. But soft jaws can be used for many things where you want perfect concentricity, and also you can easily get repetitive quality on a batch production.
So away we go on how I use my soft jaws.
As you can see, the jaws are just a lump of iron with a scroll on the back and fit into the chuck like normal jaws, they are numbered as well, just like normal. BTW, what you think is rust on the chuck isn't, I haven't cleaned all the grease off it yet.
I have already rough bored these jaws for another job, but didn't finish the boring off, the job was done in a smaller chuck eventually.
Soft jaws should last the life of the chuck (I reckon on 5 years on the quantity of production work I do), and do need to be planned out so you don't waste the valuable material in the jaws. I start out by having the jaws as wide as possible to begin with, and over time, gradually bring the chuck jaws inwards. Once you get to a stage where the face is full of old bored holes, you skim the whole face back to flat and start again. I will also modify pre bored holes for new jobs. Once the jaws are removed from the chuck, even if used for the same job, they must be rebored, as they don't always go back in the same exact position.
Because of the surface area of the bored gripping surface, you will find that the jaws don't need to be bored very deep, as long as you are not taking massive cuts you can hold large jobs on a very shallow bored hole. For my 12mm thick job, I am boring only 4mm deep.
What I have done here is to get a billet of metal and put it at the back of the jaws and tightened the jaws down onto it. This isn't released until all boring and cleaning up is completed. The billet size is selected to allow the bored hole for your job to be bored without removing excess material, just enough to give a good back support for the part.
Soft jaws are not really for holding long bars, but if you want to waste jaw material, you can bore as deep as your setup billet.
Now onto doing the job, and here is a little tip on getting your boring bar to the correct height. My main boring bars use replaceable tips that angle downwards, and are a pig to set up by any other method.
What I do is put a bit of felt tip marker on one of the jaws, then using a tool of known correct height, scribe a line on the jaw.
Without moving the chuck, put your boring bar in the toolpost and bring it to line up with the previously scribed line. Your boring bar is now on centre.
Just a note here, you need a very robust boring bar because of the interrupted cuts. Flimsy ones are liable to get snapped off.
It is now just a matter of very careful boring until the part JUST fits into the hole. I then give the back face of the hole a skim over to smooth out any irregularities, and if you feel up to it, put a tiny undercut into the corner of the bore. Now it is a matter of very carefully deburring all areas of the bore.
You only need about 1/10th of a turn on the chuck key to release the spacer plug, and open and close enough to remount the part. The less you can move it, the better it will retain it's accuracy.
This is what the finished bore should look like, nice and clean, and totally burr free in the gripping areas.
So after all that, I mounted one of the discs into the chuck, put a cut on and sat back with a fag and a cup of well deserved coffee.
I skimmed up the front of all three blanks, then turned them over and put a single cut on to bring them all to thickness. No detectable thickness difference between all three.
I am not saying you should aim for this sort of tolerance, on a flywheel, near enough is usually good enough. I am just showing how good a cheap set of soft jaws takes you into the realms of super accuracy.
I rough marked up where the recess should end up, and mounted up my trepanning/recess tool.
The recess was quickly brought to the correct size and depth, then the other five sides were soon wacked out using the same settings.
After a bit of a deburr they are now ready to be set up on the RT for having the spokes cut.
I am not too worried about the rough finish, that will all be cleaned up and polished later.
So now you know how soft jaws work, I hope I haven't bored (pun) you too much.
Because of my interchangeable setup for the lathe and rotary table
http://madmodder.net/index.php?topic=422.0
I will be boring you again when I set my four jaw self centring up for doing these parts on the RT.
Bogs
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