Not sure if the title is exactly right. I have a quantity of plastic tubes that I need to modify. I've attached a sketch of what I have and where I need to go. In the attached sketch, the part on the left is the starting point. The one on the right is the finished product. I am cutting the end off first, then enlarging the bore.
I'm not exactly sure what type of plastic these parts are. I'm a steel guy. It is a hard plastic, though, that was probably injection molded originally. They are similar to the bottom end of a ball-point pen in shape.
I originally thought this would be super simple - just drill, using the existing bore as a pilot. Turns out the existing hole is not centered, so of course, the enlarged hole is also not centered. Ideally, there would be a flat surface at the end approximately 0.015"-0.020" wide. But with it off center, the samples I have drilled were off center by about 0.004"-0.008". After the first and second parts, I thought I needed to do a better job of keeping the drill centered on the pilot hole, but on the third, I confirmed that the existing hole was off center to begin with, so the drill really was just following it.
The part has a rubbery surface, so while I can put it in a collet, it isn't consistently centered. So, I was registering on the tapered end and just gripping the body to keep it from spinning.
If I can make this a somewhat quick process, there are about 2000 more to be done, but I've got to get the time per part down to a reasonable number of seconds. If it was just a couple, I could fixture them in the mill and use a 3/16" EM to bore a hole concentric with the outside. That's not practical for a large number, though. The I.D. of the existing hole is approximately 0.090" and the finished I.D. is 0.219".
Is there a good way to do this quickly that you can think of? If I use a very short drill, could I "persuade" the drill to drill where I want? (I think probably not well.) Or, if I use a guide of some sort that bottoms on the end and guides the drill to where I want the hole, would that work? I'm open to suggestions.
All that said, the customer may accept them slightly off center, since that is what he's giving me to work with. In fact, the finished sample he gave me that he had done was off center. But, me being me, I would like to do the job right if I can.
http://i97.photobucket.com/albums/l220/whateg01/pen.jpg
I'm not exactly sure what type of plastic these parts are. I'm a steel guy. It is a hard plastic, though, that was probably injection molded originally. They are similar to the bottom end of a ball-point pen in shape.
I originally thought this would be super simple - just drill, using the existing bore as a pilot. Turns out the existing hole is not centered, so of course, the enlarged hole is also not centered. Ideally, there would be a flat surface at the end approximately 0.015"-0.020" wide. But with it off center, the samples I have drilled were off center by about 0.004"-0.008". After the first and second parts, I thought I needed to do a better job of keeping the drill centered on the pilot hole, but on the third, I confirmed that the existing hole was off center to begin with, so the drill really was just following it.
The part has a rubbery surface, so while I can put it in a collet, it isn't consistently centered. So, I was registering on the tapered end and just gripping the body to keep it from spinning.
If I can make this a somewhat quick process, there are about 2000 more to be done, but I've got to get the time per part down to a reasonable number of seconds. If it was just a couple, I could fixture them in the mill and use a 3/16" EM to bore a hole concentric with the outside. That's not practical for a large number, though. The I.D. of the existing hole is approximately 0.090" and the finished I.D. is 0.219".
Is there a good way to do this quickly that you can think of? If I use a very short drill, could I "persuade" the drill to drill where I want? (I think probably not well.) Or, if I use a guide of some sort that bottoms on the end and guides the drill to where I want the hole, would that work? I'm open to suggestions.
All that said, the customer may accept them slightly off center, since that is what he's giving me to work with. In fact, the finished sample he gave me that he had done was off center. But, me being me, I would like to do the job right if I can.
http://i97.photobucket.com/albums/l220/whateg01/pen.jpg