Drill a hole at the bottom of a V-notch...

[jmarkwolf]

... bisecting the 90 degree angle perfectly, in round stock (see the pic below)? I see it as two issues:

1. Rotating the round stock so the V-notch is perfectly symetrical about the vertical. Note the V-notch is offset from the center of the round stock.

2. Aligning the spindle of the milling machine exactly with the notch.

I can imagine using the 45 degree side of a machinist square for rotating the round stock, perhaps non-accurately, but aligning the spindle with the notch is a stumper. The milled flat spot is for starting the drill bit.

Any ideas?

 

[mmcmdl]

Lay a dowel pin in and indicate it for picking up c/l . If you didn't want to undercut the angle , you use a flat bottom end mill to spot your hole position . Center drill and drill .

 

[GL]

At any height above the bottom of the V, indicate the sides and bisect for center. Similar to the pin trick, but indicating "outward" instead of "inward". May give you some sweep room for the test indicator if the pin gets in the way.

 

[Martin W]

Could you make a piece of keystock . Not sure of the size of keyway? Maybe 1/4"x 1/8"? Make a piece 1/4" x 1\2"that fits tight, so you can indicate each side and find the centre from that. Rotating the round stock so its symetrical , I will have to think about.
Cheers
Martin

 

[higgite]

Do you have a lathe? If so, then how about this? Turn a piece of round stock, the larger the diameter the better, to a 90 degree point, but blunt on the tip, not sharp. Make sure their are no burrs. Mount it in the mill spindle and use it to position the workpiece. You can orient the V symmetrically while at the same time centering it to the spindle. You may have to use a backlight and sight down the length of the workpiece to make sure the two Vs are snugly aligned with each other. Then drill the hole like mmcmdl suggested.

Tom

 

[jmarkwolf]

Do you have a lathe? If so, then how about this? Turn a piece of round stock, the larger the diameter the better, to a 90 degree point, but blunt on the tip, not sharp. Make sure their are no burrs. Mount it in the mill spindle and use it to position the workpiece. You can orient the V symmetrically while at the same time centering it to the spindle. You may have to use a backlight and sight down the length of the workpiece to make sure the two Vs are snugly aligned with each other. Then drill the hole like mmcmdl suggested.

Tom

Hi Tom

I actually thought of something similar by using a "largish" 90 degree cutter but wasn't sure if "eyeballing for daylight" was very accurate.

 

[jmarkwolf]

Could you make a piece of keystock . Not sure of the size of keyway? Maybe 1/4"x 1/8"? Make a piece 1/4" x 1\2"that fits tight, so you can indicate each side and find the centre from that. Rotating the round stock so its symetrical , I will have to think about.
Cheers
Martin

Hi Martin
The flat doesn't exist yet, I don't know where to drill it yet. I only showed it because I intend to mill a flat before drilling the hole.

 

[jmarkwolf]

At any height above the bottom of the V, indicate the sides and bisect for center. Similar to the pin trick, but indicating "outward" instead of "inward". May give you some sweep room for the test indicator if the pin gets in the way.

I actually thought of something similar while lying in bed last night. Once the round stock were turned so that the v-notch were aligned vertical, I could touch off on the sides of the v-notch using the DRO center function.

Now for aligning the v-notch about the vertical axis, I'm thinking about laying a parallel flat against one side of the V-notch, then using the 45 degree side of a machinist square sitting on the bed of the mill, and "eyeballing daylight" between the scale and the parallel, while turning the round stock in the vise.

 

[jmarkwolf]

Excellent discussion everybody, thanks.

 

[38super]

Stick something under the part so you don't drill into your vice.