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Edgwick spindle taper adapter |
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AdeV:
Anyone following my sump build will have seen that I've just bought a nice new ER32 collet holder (with MT3 arbor) for the lathe. Unfortunately, the spindle taper adapter, as well as being very short, also suffers from some runout. Sounds like a good excuse to make a replacement :proj: While I'm at it, I'll make it a bit longer, so I don't need to take the 4-jaw chuck off the lathe when I want to use the collet chuck. Once I've made the spindle adapter, I'll have to knock up a drawbar, handwheel and collar for the other end of the lathe - as pretty much everyone said, I will need one to keep the collet chuck from wandering out of the taper & flying across the room. :zap: :nrocks: So; here we are with an 8" length of 2" leaded mild steel, all dialed in to as near as buggrit zero runout (maybe 1 or 2 tenths - it took a good hour just to set that up). I've set the top slide over about 3 degrees, but for the final checks I'm using the dial gauge and a known distance (1"). I've calculated the taper at 605 thou/foot - which works out pretty close to 50.4 thou per inch. The dial gauge only does thou divisions (eejit that I am, I've got a perfectly good Mercer dial in the cupboard which does tenths, should have got that out): The only place I could get the dial gauge mounted up was on the side of the toolpost. I got it all as straight & level at the dial end as I could... Anyway, quite a considerable time later, start cutting the taper: Whilst it was in the chuck, and before I moved it, I decided to drill the centre hole; that way, it's definitely concentric with the taper. I'd already centre drilled for the live centre, so now I just drilled a 6.5mm pilot hole as deep as the drill bit, then a 10mm (same again), then: That's my third longest drill, an 8.5" 1/2" beastie. A couple of weeks ago, I'd have been nervous as hell of putting that amount of drillbit through a hunk of steel. But now? Pfff. 8" is so small :lol: Thus, a short time later: Time to hit it with the Dastardly Drillbit of Demonic Length! That's not the longest drillbit.... that one is the £5 from eBay drillbit. It proceeded to munch through the steel like it was some kind of marshmallow, or something. So, less than 10 minutes later: You can clearly see the length difference (at least, I hope you can!). So, time to slip the 4-jaw off, blue up the spindle & pop it in there with a light battering from the Plastic Hammer of Destiny: Arse. The taper is too steep. Just for reference, I popped the other one in & had a look at where that one blued up; it seems to do most of its gripping in the central portion, with less contact front & back... so, maybe the taper's actually 0.600"/ft - that would certainly make more sense than 0.605"/ft... Hey ho, tomorrow's a bank holiday at least, which means I get all day at it. |
Andrew_D:
--- Quote from: AdeV on April 01, 2010, 06:04:25 PM ---Just for reference, I popped the other one in & had a look at where that one blued up; it seems to do most of its gripping in the central portion, with less contact front & back... so, maybe the taper's actually 0.600"/ft - that would certainly make more sense than 0.605"/ft... Hey ho, tomorrow's a bank holiday at least, which means I get all day at it. --- End quote --- Do you know what the taper in the spindle is??? If it is 0.600"/ft, that would make it a Jarno taper I believe. Less than 0.600" could be Morse or B&S. Of course it could be something proprietary! :doh: Andrew |
Jasonb:
Did you have the DTI spot on ctr height, anything else will give a false reading. Also take a DTI reading on the taper after machining to make sure it reads zero all the way, the cutting force will move the topslide a fraction if there is any movement in the ways. When you recut the taper leave it in the chuck and take the whole lot off to test fit, though if your 4jaw does not go back on spot on then not much point. You also need to get a consistant hand feed on the topslide as you can see by the blue there are steps in the taper. Are you sure you will be able to improve the existing runout, something like this is best done with a toolpost grinder that can take fractional amounts off. You will also have to get the extension back in the same spot each time you mount it Jason Edit just a thought why not put a taper to take an ER collet in the end and thread for a nut , rather than an MT taper. |
AdeV:
Andrew - No, I don't know what the taper is (nor does t'Internet, it seems). The sleeve I have was made for a Mk1 Edgwick, but doesn't appear to be original equipment, i.e. it's not ground to a smooth finish. But it does fit quite well into the taper, it just has that damn runout. Jason - yep, I had the DTI right on the centre height, albeit measured with a dead centre in the tailstock which - as Ralph pointed out when he visited - might not be 100% spot on. I've not checked to see how well the 4J repositions itself when re-mounted. It seems to go back straight enough, and there's an "A" stamped on the spindle which allows me to put the same bolt of the chuck through the same hole each time. I'll maybe try it, if my back is up to manoeuvring that lump for any length of time. As for the steps in the taper - if you mean the ones near the very end, they are deliberate. I cut the taper a smidgeon too long, and had to make a piece which goes into the main spindle bore. The step near the top of the taper (where there's a thin line of blue) is a genuine accidental step, which needs resolving... I don't have a toolpost grinder, unfortunately, so I'm stuck with turning tools. I may cheat & do what I've seen done on some morse tapers; and cut a recess in the middle, leaving say 1/2" either end to actually mate up to the internal taper; but I need my main taper to be about right first... Your final thought; it's a good one; but as I say my main desire has been to allow me to run the ER32 chuck without removing the 4J. If I make the end of the sleeve take an ER32 collet, then it'll be inside the 4J jaws, and I'm back to square one. |
Divided he ad:
Looks and sounds like your having fun Ade!? :bang: You'll get it sooner or later, anyone who's willing to attack that sump is going to get this done :thumbup: Nice to see a return of the "Plastic Hammer of Destiny" :lol: Have fun :dremel: Ralph. |
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