Drilling and milling large panels on my Bridgeport

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jmarkwolf

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I have a "one-off" job whereby I need to drill a lot of holes, including some large ones at nearly 2in diameter for MS type military style bayonet connectors, and mill some DB-9 connector openings in a 23in x 23in x 1/8in thick aluminum front panel for a big hoffman nema type box.

I have a Bridgeport with a DRO and 12in Y-travel (minus 1in for DRO scale), and my dovetail ram has nearly full travel. But it seems it would be a very clumsy job with such a large panel.

At the very least, I think I'd have to fabricate some sort of platform to support the panel that is significantly large than the width of my bed. And even with my dovetail ram I'd have to "flip" the work at least once to be able to reach everything.

The large holes are kinda problematic too. Hole saws make jagged holes, and 2inchers might be asking a lot of my old Bridgeport. I suppose I could use my boring head, but that will be tedious.

Any pearls of wisdom, or should I just find a shop that can bang it out with one setup?
 
Ideally this is done on a sheet or half sheet size CNC router, but I have done pieces larger than my KMB1 can handle. Yes, You have to support the work. Except for the fact that it will absorb coolant I like MDF for this. I price jobs like this to include being able to buy enough MDF to do the job. Then the first thing I do after building my platform is clamp the stock to it, and drill (or spiral mill) flip pin keying holes through the stock into the spoil board.

Not sure how you will mill the DB-9 holes on a manual mill, but I suppose you can drill the corners, make the major cuts inside your layout lines, and finish by hand files. I recently did that with a 25+ inch long control panel for a boat. It had a lot of compound curves so I use the original as a template, penciled it out, and cut the whole thing by hand. It was faster than doing the CAD to CNC mill a piece that was an inch to long to fit on my mill anyway. The out side was cut on the bandsaw and finished the line on the belt sander. The inside was cut out with a nibbler and cleaned up to the line on an oscillating drum sander.

I've got 4 CNC mills and a CNC Router, and I did the whole thing manually free hand. LOL.
 
Use an annular cutter for the 2 inch holes, nice clean edges and very fast, might be a little pricey buy check flea bay
 
jmarkwolf said:
I have a "one-off" job whereby I need to drill a lot of holes, including some large ones at nearly 2in diameter for MS type military style bayonet connectors, and mill some DB-9 connector openings in a 23in x 23in x 1/8in thick aluminum front panel for a big hoffman nema type box.

I have a Bridgeport with a DRO and 12in Y-travel (minus 1in for DRO scale), and my dovetail ram has nearly full travel. But it seems it would be a very clumsy job with such a large panel.

At the very least, I think I'd have to fabricate some sort of platform to support the panel that is significantly large than the width of my bed. And even with my dovetail ram I'd have to "flip" the work at least once to be able to reach everything.

The large holes are kinda problematic too. Hole saws make jagged holes, and 2inchers might be asking a lot of my old Bridgeport. I suppose I could use my boring head, but that will be tedious.

Any pearls of wisdom, or should I just find a shop that can bang it out with one setup?
Click to expand...


I've had good results using hole saws on 1/8 inch aluminum sheet. I usually provide a 1/2 inch pilot hole and make a slip fit pilot to adapt the hole saw. This provides a generous bearing size for the pilot and avoids "side milling" that often happens when using the standard drill pilot. Stp or a similar EP lubricant helps with the pilot. For better results a near under size hole saw and boring bar approach would produce better accuracy and finish.
 
I've used the Greenlee DB9 punches and they are sweet, but terribly expensive (nearly $500).

I think I'll look into having the whole panel water jetted or CNC'ed.

Otherwise, I drew up a mechanical study of what a DB9 connector opening could look like with just three tool paths on my manual mill, and some minimal dremel "retouching".

The lower pic shows the tool paths and the upper shows the opening after some minimal dremel work.

I only need to do 2, maybe 4 of these so I think it's doable.

The 7 big round holes I may have to bore.

DB9_milled_panel_cutout.jpg
 
I'd be tempted to cut them out with a router by using templates and a rub collar. Rough the holes out first for minimal cutting with the router.
 
Update:
I've nearly completed the panel and it was a pain.
My Bridgeport table travel is only 11in by 22in, so I couldn't get to all the nearly 200 points on the panel without several setups.
The DB9 connector openings were particularly onerous.
There may be a CNC router in my future.
 
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