The Home Machinist!

I am preparing to build a Von Broklin pump and it involves drilling a LOT of #50 holes to specific depths, more accurate than I trust the built-in depth stop for.

Is there and easy way to know the depth accurately (without installing a DRO) or is using a collar on the bit the best way?

I think a collar is your only choice.

If you can lock your quill, you could do a two-step process using a block whose thickness equals your hole depth (gage blocks or a milled to measure piece of stock). Lower the table/knee, extend the quill fully, then raise the table so that the drill bit is touching your hole location. Raise the quill enough to install the block, then lock it. Remove the block, then raise the table until it touches the bit again. Now you unlock the quill and drill your hole, and the quill will be at depth when fully extended.

This may be a little harder on a round-column drill press, because you'll have to also adjust horizontally to make sure your hole remains centered. Once you have that height set, you could drill all the holes of equal size and depth by moving the work around.

DianneB wrote:I am preparing to build a Von Broklin pump and it involves drilling a LOT of #50 holes to specific depths, more accurate than I trust the built-in depth stop for.

Is there and easy way to know the depth accurately (without installing a DRO) or is using a collar on the bit the best way?

What machine are you using to drill these holes, and are they all the same depth?

lg
no neat sig line

I agree with John by some ways. We don't know if the drill is being held by a collet or small Jacobs chuck. In most cases the drill will be retained when tightened up but there is repetitive downfeed pressure. If it were to slip, the shank rides up into the chuck or collet, so a quill feed depth gage becomes inaccurate. Even the smallest Jacobs chucks don't have an adjustable inside stop provision like a 5C collet. I have found that drills set deep inside a Jacobs style chuck, would grab the flutes but we don't want that. Either a spacer within the chuck or against the drawbar, if a collet, prevents the two forces from driving the shank inward.
When the pressure situation is resolved, there is only grip. The quill feed settings will be reliable.

WesHowe wrote:If you can lock your quill, you could do a two-step process using a block whose thickness equals your hole depth......

Geez. that's brilliant!

If I set the quill in the full-down position and raise the table until bit JUST touches the work, I can clamp my dial indicator on the table and set its height to give a zero indication on the head of the drill press, then release the quill and raise the table for the required depth in 1/1000ths. When the quill hits bottom, the hole will be the required depth!

I am using a round column floor model drill press and drilling bronze. There are about 20 #50 holes, all to different depths, and all off of 3 faces of a rectangle.

Another possibility is to bring the quill to the stop, raise the table to give zero clearance between the part and the drill bit, then put a spacer equal to the hole depth under the part to be drilled. Or a combination of the above and a spacer for the deeper holes.

lg
no neat sig line

A collar on a #50 drill?

tornitore45 wrote:A collar on a #50 drill?

http://www.wlfuller.com/html/drill_stops.html

I learn something every day.

Me too. I deleted some stuff about sleeves. How does the chip evacuation happen near the end, with collars or sleeves around the drill ?

spro wrote:How does the chip evacuation happen near the end?

It doesn't!