Counterboring

One more detail. If your drill press does not have a depth stop, lower the table until full extension of the quill will cut the depth you want. How hard you're pulling on the quill extension handle may matter also (small DPs are not usually very stiff) so be consistent for consistent counterbore depth.
 
You guys have been awesome! I think I’ll proceed with using the piloted counterbore (RJ sent one that works, a .406 smooth pilot for the .410 hole, with an 11/16ths counterbore). I’ll use it on a drill press, and the pieces are quite large, so per you guys, let the pilot locate and I don’t so much need to clamp, as just prevent part rotation. As you guys suggest, wd40 oil and off we go. Thank you all again!
Also, this solidifies purchase of a new tool— a drill press!... so if you guys have favorites, let me know! I've got decent budget for this project and would like one that would last a long time of good quality. Thanks again!
Just fyi, the other main operation I will be immediately doing with the new drill press will be boring some holes in the shaft of bolts for accepting cotter pins.
 
Just how large are the parts you will be working on? A picture or a rough sketch are great to help us get you the best information. Obviously the drill press needs to be big enough to fit the part. Not always but often bigger is better with machines.

When you place the part on the table to do the C'bore you want to place it so that if the c'bore grabs and tries to spin the part the part will already be against the column of the drill press preventing rotation. A spinning part can do a lot of damage to your body way faster than you can react to it happening.

As mentioned above, most end mills do not cut a flat bottom hole, they have the tips just a bit lower than the center and will leave a slight center high cone shape to the bottom of the hole. A c'bore will cut a flat bottom.

You will want to get the parts from the water jet people so that you can measure how big the hole actually is to get the best size of pilot. Water jets (and Lasers) often leave tapered edges so the hole will be cone shaped. You want your pilot to just fit the small end of the cone.
 
Think flat donuts, cut in half to be semicircular. All the counterbores will be near the edges of the donut. The outer diameter of the donut can be anywhere from radius of 10ish" to 25ish". The inner radius sort of correlates to the outers, so widths of the half donuts are roughly 4-10"s.
 
Flyinfool is speaking the gospel, I know more people that have lost fingers to drill presses than table saws!

Use a piece of plywood or MDF and make a table top large enough to support the largest part. I drill 3/16" holes in the corners of ALL my factory tables so I can use drywall screws to attach sacrificial tops, use clamps if you can't bring yourself to drill holes in your equipment. Once the part is located, screw down a block of wood to stop the part from rotating.

While you're at it, you can add toggle clamps to firmly hold the part down/in place, this will also keep the depth consistent.

When this round of parts is finished, unscrew the wood top and save it for the next round of parts.
 
For cross drilling your bolts get a square chunk of scrap and scribe a line around it in center.

Thickness should be less than length of bolt.

Scribe another line around the metal the other way, crossing the first line on all sides, this line is placed from one side the distance from end of bolt tye cotter pin goes.

From one end drill small hole then again on a side hoping the holes cross.

Smaller holes have better indication of proper alignment.

Holes need to be smaller than final size.

Once this is done enlarge to final size, one hole drill and tap to bolt size and other hole to cotter pin size.

Not thread in bolt to desired position, until end is flush with face of block, and cross drill hole using smaller hole as drill guide.

Sent from my SM-G781V using Tapatalk
 
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