Shaft Set Up in Mill

[mcman56]

I have a short 10 mm shaft that needs a threaded hole through the shaft near one end and a through hole near the other end. These holes should be aligned with each other. It will go into a carburetor that seems to have close tolerances on everything so the holes should be precisely located. I would like to do this in a single setup but if I set it up with a standard V block, the block is longer than the distance between the holes so there is no access. I can set it up using an adjustable angle device as a V block but the block is so tall that it will interfere with the drill chuck. I have a 6” center drill but it wobbles quite a bit. The best I can come up with is to drill one hole, slide the shaft down, use a pin through the first hole to make sure it is square and drill the second. I just have one standard V block that if far from pristine so I'm also tempted to saw it in 1/2. Is there a better way?

shaft in mill1_rotated.JPG (338.74 KiB) Viewed 202 times

shaft in mill2_rotated.JPG (488.16 KiB) Viewed 202 times

[rmac]

Here's what I would do -> Make a sacrificial parallel slightly thinner than the diameter of the shaft from some soft material like aluminum or hardwood. Set the shaft on the parallel in the vise, squeeze 'er down and drill away. No V block needed.

[jcfx]

You could hold the shaft perpendicular with the jaws rather than parallel, support the shaft with
vise parallels for drilling and tapping.

[Bill Shields]

Would a U clamp on the v block provide alignment as you reorient?

[ChipMaker4130]

Doesn't even need to be a sacrificial parallel. Just set it on top of one, tighten the vise and tap the parallel out. If your vise is in good shape and the shaft is of uniform diameter there will be no problem holding the work for such minimal machining.

[GlennW]

...and if your vise is indicated parallel to the table travel and set up properly using a stop, you will already have 0,0 to reference from.

[earlgo]

When I had a similar situation where I needed to add 2 parallel flats to a cylinder, I made a new set of vise jaws. One jaw had a V-groove in it that was cut parallel with the vise base. Both had the tops cut away to make clearance for the parallel cut. In your case you could just cut the V groove and not the clearance cuts. These vise jaws were made from just soft steel that I had in the scrap box, but you could make them from anything that could be hardened or not.

v-groove vise jaw.jpg (35.08 KiB) Viewed 118 times

v-groove vise jaw end.jpg (15.86 KiB) Viewed 118 times

(I didn't take the time to install them in the vise for the picture, but it conveys the idea ok.)
--earlgo

[Harold_V]

Doesn't even need to be a sacrificial parallel. Just set it on top of one, tighten the vise and tap the parallel out. If your vise is in good shape and the shaft is of uniform diameter there will be no problem holding the work for such minimal machining.

BINGO!
No need to complicate the setup. A parallel thinner than the part is all that is required. It should be short enough in height for the part to be below the top surface of the jaws, so once the part is installed a DTI can be swept between the jaws to establish dead center (if necessary). With the shaft extended slightly beyond the left side of the vise, an edge finder can be used to locate the end of the part for proper orientation of the drilled holes along the shaft.

H

Edit: Assuming the shaft is shorter than half the width of the vise jaws, a like sized thickness piece of material would be placed at the opposite end of the vise to prevent the movable jaw from tilting when the jaw was tightened. It need not be a long piece.

[Charles T. McCullough]

Two parallel spacers against each vise jaw, of appropriate height to keep the work piece below the vise jaws upper edge but not too low for the drill to reach depth, and thin enough to be away from where the drill will come out the other side. Center it all in the vise jaws, so the jaws do not get torqued out of square. Position the vise on the drill table (even something non-moveable) with one end of the work piece centered under the drill bit. Drill... move the vise to center the other end of the work piece under the drill and drill away. As long as the work piece is perpendicular to the drill bit in both directions, and the bit starts the hole at the peak of the curved work piece, the holes should come out at the peak of the curve on the other side (a true diameter hole), and the same distance from the end of the work piece. If I were using a mill, I'd mill a flat where the hole is to start, to keep the drill bit from skipping off the curve... especially if it is a small diameter hole.

[mcman56]

Thanks for all of the ideas. My vise is not great so I ended up machining a sacrificial parallel and putting the shaft on top for support. I did not realize a vise without v block would hold it adequately. It was a good idea to verify vise was square to table. I had it stick out the end of the vise to find center but see how using an indicator for centering would have been better. It fit and worked OK. However, the shaft is 303 stainless and was very difficult to thread with M5 x .8 and it created distortion at the drill/ tap start point that took time to file out. I don't remember 303 being that difficult to machine. It seemed like the material preferred to move away from the tap rather than cut. I seemed close to breaking the tap but I used a lot of back and fourth motion to get it through.

[Harold_V]

I don't remember 303 being that difficult to machine.

It isn't. It and 416 each machine very nicely. If you have problems with them it's due to speed or dull tools.

It seemed like the material preferred to move away from the tap rather than cut. I seemed close to breaking the tap but I used a lot of back and fourth motion to get it through.

Most likely a dull tap. Also, while drilling speed can be too fast and toughen the perimeter of a drilled hole, that's usually not a problem. If you experienced any squealing while drilling, though, it most likely was the reason you had trouble.

You can avoid issues with a drill skating away from a rounded surface simply by using a center drill to start the hole. I like to drill near the finish diameter with the center drill to gain maximum starting surface. I also prefer a center drill over a starter drill as the center drill provides a pilot hole that is deeper than the starter drill and helps keep the drill on center. I also generally double drill holes when size is critical. Yields holes that are typically a lot straighter and round, and also usually on size, unlike drilling with a single target size drill.

H

[mcman56]

The shaft turned and drilled OK but I may have gotten a little squealing with the drill. I did double drill. I do remember using large drills in stainless and if you went too slow you could create hard areas. I also remember some raw stainless coming with hard sport but that was 45 years ago. I tried 2 different taps and they felt about the same so maybe it was my drill speed. It was a 3mm drill at around 1135 rpm. The finish drill came from Amazon so had unknown quality.

I used a center drill of maybe 3/16 diameter and it did make some noise as the larger diameter hit the stainless. In fact, I think I could see a visible bulge just outside. It was at the same speed so what could I have done differently?

I have never heard of a starter drill. How is it different from a center drill?