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| Another new project... a QCTP (Quick Change Toolpost) |
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| AdeV:
It's finished!* *for certain values of "finished" Bit of a marathon session today; the first task was to figure out why the cam spindle was locking up when the central pin is tightened down. I figured it was probably due to the lack of concentricity (is that even a word?) between parts, and probably as the screw thread was tightening up, it was pulling the bottom of the pin out of centre. On that hunch, I whipped a few more thou off the bore of the cam unit (that being the easiest part to hold in the chuck while still cutting the bits I needed to cut). It took a couple of goes, but now the cam operates perfectly in "the zone" in which it's needed. So, next job, a slight modification to t'underside... X marks the spot, approximately: Milled 1/4" to within a smidge of the top of the base. Milled with a 6mm ball-end mill (the only type I have) just a smidge (that's an official SI unit, you know) into the base as well, then finally drilled 7mm & tapped M8 for a few turns: No prizes for guessing what happens next: Yep, there's a ball bearing stuck in there, with the tiniest fragment of a spring, all held in with an M8 bolt (in turn reinforced with Loctite), which was then cut off & filed flat. And that there is my "zero" position; the theory is, when the QCTP is set straight along the ways, the ball will drop into the dimple, so I don't need to think about it to return it to straight, it just goes straight in. In practice, I think the 6mm ball end mill was a bit too close to the 1/4" ball; so it locates OK, but there's quite a large amount of lateral movement with the ball in the hole. Shame, but never mind, it gets pretty close. If it annoys me too much, I'll just do it again somewhere else (and make a much smaller indent in the bottom of the tool holder. So, finally, we get to the end of this project; here's the QCTP successfully mounted on the lathe, no fettling required.: I'm pretty chuffed, even if I do say so myself. I have managed to wear/scratch the black surface off in a few places, just with general mishandling and - of course - the rust incident... so I may black it up again in the near future. And, of course, I have the proper handles to make, but they'll just be some 1/2" bar with an M10 thread on the end. The balls will have to wait until I've made a ball turner... but, of course, I now have a dandy base on which to mount any new stuff, like a ball turner. It only takes 10 seconds to whip the QCTP off, another 15 minutes to locate the bl**dy ball turner (or whatever tool is going on instead) from the deepest recesses of the workshop which have never been seen by human eyes (how does stuff end up there?), and another 10 seconds to pop it on & fix it down. MUCH better than all that messing with hold-down bolts, shims, etc. Goodbye 4-way toolpost, you won't be missed (not much, anyway). I'd like to thank everyone who's commented on this project along the way. :nrocks: Your comments have been inspiring, and have kept me at it more than once. Thanks in particular Lew for introducing me to a metal even more expensive than having a wife (weight-for-weight), although it did make a fine pair of pistons (the metal, the metal....). Hopefully, once Bogs has straightened my chuck jaws, I'll be able to make a staight one next time :lol: But.... wait...... what's this? Down in the deepest darkest recesses of the workshop...... A toolholder is calved! Yes, of COURSE this isn't the end of this project! There will be no actual end, 'cos I'll be making toolholders for the rest of my life. I'll do a bit of a photo writeup of the 1st one (the one that's even now being weaned in the basement), after that, no more... Until tomorrow, then.... :D |
| Ned Ludd:
Nice job there and soo much cheaper than buying lots of toolholders. Re. your 6mm ball, the dimple should be made by the next size smaller ball ended mill. For 6mm ball a 5mm mill is used, this allows the ball to sit on the periphery of the dimple and not fill it completely. If it fills it you just don't get a clean and positive location (too much of a cam action). I found this out the hard way after making a batch of indexable drilling jigs for woodturners. Oh well, you live and learn (hopefully) Ned |
| ibuildstuff4u:
Easy fix, all you need is bigger balls! |
| Divided he ad:
Looking good Ade :clap: I'd have thought a smaller dimple too... My old tool post had a one way affair on it. A spring loaded pin with a smoothed taper on one side (allowing the tool post to be turned to the left) and a flat filed across the back side, so the post could not be turned back to the right once in position.... Not bad but could get annoying if you turned it too far and had to do the full revolution again! Just another way of doing it. Tool holders ehh? Hope you're planning to make them in batches? Could prove tedious? I'm sure you'll have fun with the first few anyway :dremel: :thumbup: Keep us posted on the rest of the build.... Including the ball turner :whip: :) Ralph. |
| Ned Ludd:
My dear chap, if I had bigger balls that would make me a Politician on the make. :) Ned |
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