drill a 1/2 hole in 1" material

[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.

[krymis]

guy all of what lew stated is my problem is correct.  I have a Cummin's minilathe i believe it is a 7x14 not the 12" bed.  is there any way to search the net for setups like you guys are talking about with v blocks on a carriage. I was thinking i needed a special fixture for it. 

[Andrew_D]

I've held up to 8" long material (1 1/2" dia, I believe) in the chuck of my mini-lathe and drilled in the end, but 15" long as way too long for the mini lathe since it won't pass through the spindle. If you have no other machine tools at your disposal, then clamping it to the carriage is probably your best bet.

I once made a simple milling fixture once for the mini-lathe that was a flat piece of 1/2" steel. It had 3 holes into it to mount where the compound was - 1 through hole to line up with the center stud in the compound clamp and 2 through holes for threaded bolts to attach to the clamp. Then I drilled and tapped holes where I needed them for clamping.

Anyways, once you have a plate like that set up on top of the cross slide, you could attach your 1" x 15" shaft to it with whatever clamps, v-blocks, vise, etc. you have. Use the cross-slide to line up with the spindle. (You'll need to shim the stock shaft up when you clamp it, since you don't have an up/down adjustment.) Then do as you were thinking - mount the drill bits to the spindle using whatever lathe chuck, drill chuck, collet chuck, etc. you want. Use the carriage to move the shaft towards the drill bits.

Andrew

[krymis]

andrew,


thanks for the input.  all you guys have helped me come up with something i think will work. 

One more thing is can you guys help me find pictures of different setups. 

[krymis]

http://www.statecollegecentral.com/metallathe/MLA16C2.jpg

something like this only going parallel to the ways of my lathe

http://www.statecollegecentral.com/metallathe/MLA16C.html

[foozer]

andrew,


thanks for the input.  all you guys have helped me come up with something i think will work. 

One more thing is can you guys help me find pictures of different setups. 

Is not exactly what your looking for but might be close, at least a visual. I needed to drill a 0.125 X 2 inch deep hole so used this setup to see if I could drill it straight and not break the bit. Something similar should work for you. I'm running with stone axes and flint knives, your mileage may vary.

Robert

[krymis]

that is exactly what i need.  i was hoping to get pictures like this.  more if anyone has some.