How do you drill or bore a part with a center one end?

[pdentrem]

Can you place the threaded end on a threaded mandrel? Therefore turning it around to drill etc from the other end?

 

[Tony Wells]

Diameter of part? Desired bore diameter? Tolerance? Knurled length and linear limits? Type of material?

Just full of questions, ain't I?

 

[Tony Wells]

I failed to ask about a steady rest, but that would be a possibility on the area at the very end, or secondary choice, just left (in this photo) of the top of the taper.

An aside, I appreciate you teaching the old methods of workholding to your students. It makes for good thought process development.

If the OD is finished and no marks are permissible, a cathead would need to be built for use in a steady rest.

Since the OD is finished, one way would be to bore a relatively thick walled aluminum sleeve about the length of the knurl. Split the sleeve (one side only) and chuck directly on it, grabbing the OD. There is no guarantee of good concentricity, but for the drilling, it should be sufficient. Boring for the thread, maybe another issue. Unless the cap would be finish turned "in situ". Then of course, a similar situation presents, usually no center hole is allowed on the cap.

If concentricity is a concern, the sleeve must be split, set up with a few screws to collapse it onto the part OD, then chuck and center the part. Turn the OD of the sleeve true with the centers. Then everything done while the sleeve is installed will be pretty close to concentric with the OD, knurled or not.

If I were making the part from scratch, with what I have, I'd just chuck the OD and finish the ID, then come back and knurl. A scissor knurl would probably still collapse the tube, so I'd stuff a close fitting bar in it for the duration.

This might be a case for deliberately sharpening a twist drill off center a few thousandths. No way for it to get pinched up when drilling that deep. Hole size being not really critical.

If none of this makes sense, ignore it....I just awoke from a sofa nap.

 

[Zigeuner]

Hind site is 20-20, the deep hole should have been the first operation. I do this on crankshafts that have oil holes drilled in them. Drilling them in the blank saves this major headache.

That said here goes. Make a sleeve to a push fit for the threaded end. Leave enough room for a nut. This sleeve will hold it in the chuck. Now the hard part. Make a split bushing from soft material to fit over the knurled end and big enough to fit your steady rest. It should be about 2 inches long. Add the steady rest and drill away. Have fun.

"Bill Gruby"

Hi,

You are right Bill, he should have done the hole first. This is why order of operations is so important. And should based off of what equipment and tooling is available to you at hand. Following exact steps of how someone else did it with different tools and different skills can sometimes lead to difficulties.

I would also lean to simply gripping the part with a soft material like aluminum or copper. 1045 is fairly stout stuff and can take some abuse without damage. Though I have used everything from wood to cardboard when needed.

One thing I might do differently is not to drill it out with a 1" drill. I would lean towards drilling only so large, (size depends on how secure my grip was for that job), and then switch to a boring bar. I can easily control the depth of cut and the amount of torque required to cut better that way. Though step drilling can also work if you have enough drill sizes to make for small steps.

It does look like your student is doing a fine job that he can be proud of when finished. I hope he allows you to post photos of the finished project.

dalee

You beat me to it. Drilling with a 1" drill is OK of you want a hole that is somewhere near 1". They nearly always drill someting O.S., say 1.002, 1.003, especially if you are going to drill 5" deep. I think that drills do have a tendency to wander somewhat leading to O.S. holes, especially in steel and with large diameter drills.

What Bill says here is the best way - drill undersize in rough (before doing finish features like a taper) to remove most of the material and then finish with a boring bar for a nice 1.00" hole. I learned this the hard way and now I will almost always drill undersize in rough and then finish with a boring bar. This has been made much easier since I added a DRO to my lathe late last year.

JMO.

 

[pdentrem]

Everybody beat me to it!
Yes use a steady rest for the far end. As stated a split pipe that fits well as the running surface. In a pinch I did use body filler on an octagon rifle barrel to make a bushing. If the spindle bore had allowed the handle could be been inserted to allow chucking up.
I would never start drilling with a 1" bit. Although the hole does not have to be exactly 1" in this case, I would work up to the finish size.
I never took shop in high school. The teacher there would never let anyone use the equipment. IT WAS HIS or so he thought. The new guys coming out have better access to the equipment today. I feel left out, I never got to make my hammer.