Thanks Bill
- took me a while to get over the 'flu, so nothing happened in the shop for a long time...
After spending the last two weeks sneezing, I was not about to get started on woodwork for a return shop-session; more sneezing from the wood dust would just be the pits.
I figured I might as well start on the flywheel, so I had a bit of a think about how to proceed with making it...
I checked some spacings on the lathe, and thought I might get away with making the flywheel rim without too much fuss. If I hacked off a suitable length from the parent stock shown in an earlier photo, I could actually mount it on the 4 jaw chuck and swing it in the lathe's head gap to turn - and end up with a flywheel that's just 2mm narrower than the plans show.
On to the "simple" shop session that became an entire saga, and a hidden "gotcha". There's not really a lot to see in today's update, though the tribulations might be amusing to some
A quick check on the bandsaw, and there was no easy way to mount the stock on it to start hacking at it. A 4"x6" bandsaw really isn't built to saw a slice off a 180mm (7") bit of round stock...
Next option - a slitting saw on the mill. I know my 1mm slitting saw cuts cast iron like butter, so I mounted the stock on the rotary table and 4-jaw chuck. No problem with headroom, even though the lot stands a bit tall:
I started the cut, and promptly ran into a problem... I forgot to check that the cut wouldn't make the chuck unscrew from its mounting on the rotary table - which it promptly did
. A new lesson was learned as well; my slitting saw arbor has a safety feature in it that I never knew of. If things suddenly gets too tight, the holding screw shears off
. It worked well to prevent damage to the slitting saw. Here's what remained of the holding screw - I'd already managed to get the rest of the screw removed from the arbor, replaced it and re-mounted the saw:
In the process of unscrewing the chuck, the slitting saw dug a nice trail of tooth marks
:
Something about the tooth marks looked wrong, but I didn't listen to my gut feel...
To prevent the chuck unscrewing again, I attacked things from the inside:
Soon after the last photo, the slitting saw arbor sacrificed another holding screw... The alarm bells were ringing, but Arnold wasn't listening
. Replaced the holding screw, started again, and not long before the screw popped again. The slitting saw still felt nice and sharp, but I was not about to push things any further; the saw blade itself cost me three times what the stock cost, and I wasn't going to push things any further and risk breaking the blade and have bits of high speed steel flying around. And I didn't hear the penny drop.
So, what next ?... I could just go for the hacksaw, but my energy levels are still a bit low after the flu. Tel mentioned a grinder... Hmmm... Got two of those; a 5" and a 12". The 12" takes quite a bit of effort to wield, and I was not feeling up to man-handling it yet. So, on to the 5" and the thinnest cutting disk I have. Securing the workpiece was a bit of a problem, but I eventually managed to clamp it in the big vise on the workbench. Things went OK until the blade started getting deeper into the slot, and then the blade started biting - a case of me not being steady enough. Rather than risk breaking it, I stopped and did some more thinking
. The penny didn't drop...
Back to the bandsaw... I removed all the add-ons I'd made for it, checked things out, and eventually figured out I could clamp the workpiece to the extended bit of the vise:
Then I started abusing the poor bandsaw:
Saw a bit until the "head end" blade guide stops against the workpiece, stop, rotate the workpiece a bit, clamp up again and repeat. The blade barely penetrated into the inner hole - it just left some short stringy burrs on the inside to show that it did go through. Stringy burrs, and still, the penny didn't drop
There were still some thin sections that were holding the bit I wanted to the parent stock. Seeing as this is cast iron, it's brittle, and a good whack with a hammer should just break it apart. Took more than a single whack though:
I had to basically tear apart one last section that held the bits together - where the band saw lines met, they were a bit out of alignment. Took a lot of wiggling around to break off that bit, AND STILL THE BLOODY PENNY DIDN'T DROP!
On to the lathe, and mounted on (or rather over the body of) the 4-jaw chuck in the head gap. I left just enough space for the chuck key, and the lot fits nicely in the head gap:
I had to set the top slide parallel to the lathe ways and crank it in to maximum to get enough clearance to be able to turn the workpiece without the carriage hitting up against it. This literally is pretty much my Myford's limits. There's some room left in the head gap, but even so, the cross-slide was just barely hanging on by a few threads on it's feedscrew.
With slowest speed back-gear engaged, I started turning the workpiece. It was only during this operation that THE PENNY FINALLY DROPPED:
I was looking forward to the smell, taste and black hands that come from the dust of turning cast iron. And fully prepared to duck the stream of tiny chips it makes. This material didn't do any of that; it came of in stringy swirls, didn't generate dust or give me any of those other (to me) feel-good cast iron experiences. In fact, I'm now pretty much convinced this isn't cast iron, but rather steel, and the bad experiences with the slitting saw, the stringy burrs on the bandsaw and all the rest adds up. That changes the ball-game a bit, and I have to re-think how I'm actually going to construct the flywheel.
I finished the shop session by rough-turning the outside of the workpiece to get rid of the crud:
So, now I have to sleep on what I'm going to do next. With the original intent of the material being cast iron, I was going to bore out the rim section I did today by about 50% on the ID, then cut off another shorter section from the parent stock to turn down to a press fit inside the rim and drill it on the periphery to fit the flywheel spokes. Right now, I'm not keen on the "extra" ring idea anymore; I might just bore out the rim to leave an internal "ring" in it, make a hub and spokes, make that fit inside the rim and solder the lot together. Choices... Choices...
Kind regards, Arnold