I finished machining my first successful iron casting: it machined beautifully but did have a few internal bubbles in the bore that the machining revealed. The ferrosilicon did it's job with the scrap iron brake rotors, and gave a nice grey iron, even if it was a bit messy as there's iron/graphite dust all over the lathe that had to be cleaned up. The iron body was machined round on the outside at the same time as the first 6205 ball bearing bore, that let me end for end the casting and have reference surfaces to align the second bearing bore to be concentric to the first bearing bore. The spindle shaft has a left hand tapered thread on the left side and right hand tapered thread on the right hand side: this ensures the buff mops stay tight on the tapers as the buffing friction load keeps them tight on the tapers. Having a taper attachment for the lathe would have made the threading easy, as it was I had to hand feed the depth of cut as the leadscrew advanced the lathe carriage.
You did well. Must have had a good tunes playing in the background to keep time with hand guiding the depth of cut. All of my small buffs are thread mounted but my big buffs get clamp mounted on the shaft....Have a couple pictures of those big screw mounting buffs? Best, Kelly
Threading the left hand taper was easy, it runs downhill away from the chuck and you just keep a constant pressure on the compound screw, the right hand thread was a real pain as you back out going towards the chuck and I broke the brazed carbide tip a few times on each taper. If I mounted the rear tool holder on the cross slide, I could run the spindle in reverse and do a right hand thread unscrewing downhill to make it easier. I have a bunch of surplus triangle inserts with about a 1/8" radius corner that I braze onto 1/2" steel shanks and sharpen. I would have broken the tips off about 4-5 times on this job but can resharpen several times per tool. Those threads look a bit lumpy when viewed on axis but will do for the job. I've used up to an 8" cotton buff on bench grinder spindles with a 5/8" shaft with tapered adapter but that's about it so far. With 25mm steel shafts I hope to be able to mount a decent diameter buff, down to the small 3" wheels. I heard a description of an old Rolls Royce trained chrome plater who used large fabric buffs as the driving contact wheel for very long abrasive belts. The idler wheel was mounted high up in the workshop ceiling and belts would be changed with a long stick with a shaped hook on the end. The cloth wheel would expand with centrifugal force to provide belt tension and gave a contouring cushioning effect when preparing rounded bumper bars for plating. I guess with old abrasive belt technology and glues, such a long belt would allow cooling when really giving a bumper bar a good grind.
Thanks guys, I was thinking today that's it's a bit like a "By your bootstraps" process: you make castings to make the tools to make the castings. I showed someone the spindle today and got the usual reply: "why don't you use a bench grinder?", I said the average bench grinder is 3/4Hp when for serious buffing you'd prefer 2Hp up to 20Hp if you were polishing chrome plated bus bumper bars (done by industrial robots these days).
Looks great! You could have run your lathe in reverse and cut the right hand thread from the back side with a boring bar and still work downhill.
Over the last week or so, the spindle buffer unit has edged closer to completion: I spent this afternoon welding a pedestal to mount the spindle. The steel disc on the base helps the tipping point centre of gravity a lot: it has to get to 60 degrees off horizontal before it'll fall over. It remains to be seen if I'll bolt it to the floor permanently, it may not need it. I had a 2Hp 240 Volt motor lying around: it had a seized, rusty ball bearing so I replaced both of them, gave it a clean out, sanded the exterior and painted it in black acrylic and a tasteful shade of metallic charcoal for the sheet metalwork. The insulation resistance to earth was megger tested at 500 Volts and passed with flying colours. I'll use pulleys to slow the speed to 1800 RPM at the spindle and see how that goes with 10"+ diameter wheels. I'll mount the power switch just above the spindle and run the cable through the steel column out of sight. The motor will mount low on the column at the front to bring the centre of gravity forward a bit to make it harder to tip backwards.
Today I fabricated a motor mount out of 4mm / 3/16" mild steel sheet, it's easily the simplest motor mount I've ever made due the the motor being a flange mount instead of having mounting feet. On the column, the top mounting bolt lets you tighten the belt while the bottom bolt functions as a pivot for the motor mount....too easy!!. The spindle ran smooth with a bit of belt flap that some extra tension sorted out and the whole thing is pretty quiet, just the hum of the motor and the hiss of the buff cutting air. The motor runs a bit warm but current draw is only 5.7 Amps for a two horsepower motor which is less than the rated draw, so I'll have to see how it runs over an extended time. The 35uF capacitor measures fine so the only thing left to cause excess heating would be a partial short on the windings. About all that's left is a switch on the top and a coat of paint and it'll be done .
Bingo!: My almost identical 2Hp motor used on the air blower has a 16 microfarad capacitor, this one has a 35 uF capacitor and is running hot. The background on these motors is that they come off those electric home woodchippers, I can get them from the local recycle shop for $10 and these two came from identical branded units. Closer inspection shows one is from Taiwan and one (that runs hot) from China. I'll fit a 16 uF to it and see how hot it gets.
A wrong size run cap will definitely make it run hot. Next question... Do you have a MFD meter? Very few vom's will test mfd. I've got a handful of meters and only my field piece designed for hvac work will test it. Even the Flukes we use can't test mfd.
Yes I have a Lutron capacitance meter, I tested it and it does read 35 uF so it hasn't died. The cap was fitted with those dodgy twist on terminal cups instead of proper joins, which I thought was weird when I first pulled the motor apart....it's probably not original and someone fitted a new cap when the problem was actually seized bearings.
