Robbo beat me to it, but I'll post this anyway - it's the table I use: Thanks Neil, I am in no major hurry as I don't need it right now, I am just experimenting with different things for when I do need them. John's away for the weekend so he may not be able to get back to you for a day or two. Thanks for that, I have just looked at his site, but it looks as if everything is at ?0.00 so looks as if it's closed, have sent him a PM and will see if he gets back to me. Hope he doesn't object to it being reproduced. (Hope I remember it right John)īelow is the gear chart he supplied with the 33/34T pair. John Stevenson used to sell a pair of 33 & 34 T gears from his online shop but had to close the shop, then sadly his wife passed away don't know if he re-opened it. Sorry if I am sounding thick on this, once I can get it all working and can play it will all become clear, but until then and it is all theory my brain dosnt like it too much. So I need to get the 33 and 34 tooth gears which are about £10 each which is better than the £250 for the conversion kit, the next thing is without me going hunting through the net for something that I don't exactly know what I am looking at, where about's would I find a chart for the settings, using the 33 or 34 tooth gears, and what pitches the QC gearbox will cut. There dosnt seem much movement to drop the gears down, but if it is only another 10 teeth it might just do it, So just getting this into my head, to alter that 24 tooth gear, I need to adjust this bit The clamp slot at the bottom of the banjo limits the movement I'm sorry to contradict RichardN, the restriction on banjo movements comes with fitting gears of 35 teeth or more, NOT the smaller gears. You will have found tables that include gears with 33 and 34 teeth to put in place of that, which together with gearbox changes, will give metric ratios in more than sufficient accuracy. The 24 tooth gear, which is coupled to the second 30 tooth gear is what Myford term the mandrel gear and that is the main drive gear down the chain to the gearbox.
So far the gearing ratio from spindle to the second 30 tooth gear on the tumbler shaft is unchanged. So that you can follow the logic from the spindle down, the spindle gear will be 30 teeth, the fibre gears are those that do the reversing which in turn mesh into the next gear down, also 30 teeth on the tumbler shaft. You do need to rotate the banjo to get the correct mesh, and if you use a small gear on that stud some lathes don't have quite enough adjustment. Yes that's the one- you don't get a 'perfect' thread pitch for every thread, but with a couple of other gears (to swap into that same place) you can do all the metric threads with more than sufficient accuracy for most needs. So am i somewhere in the ball park, or have I got this whole thing twisted in my mind and I am going off on a random tangent? So my first question is, is this the gear that is being discussed?Īs by my understanding the input gear would be the one at the top, not the one with the arrow, but the only gear I can find with 24 teeth is that gear. The nut tightens to hold the cutter between some spacers, far enough out from the lathe spindle to get the cutter to engage the blank gear and not run foul of anything else.Ok this started to be talked about in another thread, so to stop me from taking it off topic too much I thought I would start a new thread, now me being dislexic and dyspraxic learning from books and written bits is not my strong point so you might need to bare with me while I try and get my head around this.įrom reading other threads I have worked out that it is possible to cut metric threads, with a quick change gear box on a Myford super 7, by just changing one gear, this gear being the 24 tooth input gear on the tumbler shaft. You can buy nice hardened steel arbor spacers with 7/8" or 1" bores in any thickness you could want. The end by the tailstock gets threaded smaller than the 7/8" or 1" for a big nut.
That saves you from centering the bar in a chuck. If you are into turning between centers, do that with your blank bar. It is a simple thing to hold a 1.25" steel bar in your lathe chuck and turn it down to 7/8" or 1" to fit a standard gear cutter. Use a 4-jaw and get it running dead true. An R8 shank arbor to fit a Bridgeport milling machine right angle attachment has enough straight shank to let you hold it in a lathe chuck and is pretty long. You can find a 1" straight shank stub arbor in catalogs, but they might be too short for your purpose. Such arbors were made to fit certain small horizontal milling machines (Atlas, Barker?), but it would take the luck of the Irish to find one these days.
It will be very hard to find an old 3MT arbor for a horizontal mill to hold your gear cutter.
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