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| drill a 1/2 hole in 1" material |
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| krymis:
well as it says i have to drill a 1" x 15" solid stock with a 1/2-13 threaded hole 1.5-2" deep in one end. Here is my thought: remove the compund slide from the carriage and replace that with a 5-C collet block on the carriage. mount the 1" stock in this. Then mount an er collet in the er collet chuck. Then mount a center drill, drill, endmill, and starter tap and bottom tap to do the drilling and tapping. then use the carriage movement to make it the depth i need. does this sound like a plan or am i flawed in my thought and design? |
| Lew_Merrick_PE:
Krymis, I assume that your stock is actually ø1 X 15 inch stock. You need to drill and tap 1/2-13 (UNC) holes in the end threaded to a depth of 1.5 to 2 inches. You need to do this on your lathe. Is that a proper summary of your problem? 1) I assume that the headstock of your lathe has a pass-through less than ø1 inch. Otherwise, the problem would be trivial. 2) The only "issue" I see with mounting the bar on your cross-slide is supporting it over length to maintain whatever alignment is required for your tapped holes. Mounting it in a 5C collet should be fine -- as would mounting it in a v-block -- so long as you have enough clamping area and force to maintain alignment. 3) I assume that this is some kind of adjusting mechanism. A standard hex nut for a 1/2 bolt is .345 nominal thickness. A heavy hex nut for a Grade 8 1/2 bolt is .480 nominal thickness. If I need to project alignment using a 1/2 thread, I need 1-1/2 to 2 diameters (i.e. .750 to 1.000) of engagement to assure such an alignment. A hole 3-4 diameters of engagement should only be used to provide adjustment. If this is not the case, you can save yourself some pain in manufacture. There is a document on Pilot Hole Considerations posted at http://www.scribd.com/Lew%20Merrick that may be of interest to you. |
| mike os:
3 jaw, fixed steady & use the tailstock to drill/tap |
| kvom:
If your lathe doesn't have a spindle lock (or someway to lock it), tapping 1/2-13 with only one hand to turn the tap wrench needs a lot of strength, even in aluminum. If you can get the tap started straight, it will be easier to tap with a bench vise where you can use 2 hands. |
| No1_sonuk:
If the stock will pass through the lathe spindle, the thread could be done single-point. I have an indexable threading tool which I know will do M13 x 1mm. It was a bit tight, but it did it. 1/2 13 isn't far off that major dia, but the depth would be deeper. A "normal" ground internal threading tool could probably manage. However, as the OP is discussing mounting on the carriage, I would assume he has something like a 7 x 12 which has 20mm pass-through, and a relativley short bed. |
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