Drilling/Tapping Long Part

devils4ever

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I need to drill and tap (3/8-16) the end of a 1" X 1.5" X 18" 1018 steel bar. I'm trying to think which is the best way to do this. My PM25 mill would be preferred, but I would need to rotate the head 90 degree until horizontal and clamp the steel bar appropriately. I guess this is doable, but the head has protrusions on both side making clamping the bar challenging.

I do have a floor drill press, but it's not as precision as the mill would be. I could use an angle plate and get it perfectly vertical, but getting the holes in the exact position would be tricky.

I would like the position of the tapped hole to be within +/- 10 thou, but 5 thou would be better.
 
How about holding the part on an angle block at 45 degrees and tilting the head to match? That might give you the clearance you need and allow you to use the mill to position the holes. On my Bridgeport I'm not even sure I could get an 18" part and the tooling in there. That's also a lot of stickout. I think I'd try 45 or hanging it off the side of the table and moving the head around to match. But I'm not sure if the PM25 has that option.
 
Sorry, I am not familiar the PM25 so I don't know if this is possible. On my Bridgeport, I would mount the part on an angle plate off of the back of the table offset to one side, then I would just pivot the turret to the side, line up and drill as usual.

Richard
 
I had to machine off and the tap the ends of the fuel rails on my boat engines. The parts were kinda gnarly with bumps all over the place. I took a piece of black iron pipe and tapped 2 rows of 4 holes each to act like a double spider of sorts. It was cheap, worked great, and I've used it a number of times since then. One piece I tapped was a tractor axle 4 feet long so I let it protrude right thru the headstock on the back end.

DSC_1077.JPGDSC_1139.JPG
 
The easiest way to do this is with a lathe but, based on your question, I'm assuming you don't have access to one. I've never had to try it on a mill, but a machinist I know told me exactly what Jim F and Mini Cooper S said: Hang it off the back the mill and rotate the head.

If you know anyone up there with a lathe, I would think that would be easier. Any guys near Long Valley, NJ?

Regards,
Terry
 
I don't think it's possible to hang off the table with the stand and pan underneath.

45 degrees might be possible, but would also be tricky.

20200405_082042.jpg
 
P.S.: Because of the rectangular shape, you'd need to use a 4-jaw independent chuck.
 
I have a lathe, but it's a mini-lathe and wouldn't be long enough.
 
Hopefully, somebody with a lathe will be able to help you out.
 
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