Truncating a round hole?

[Frank O]

I'm making holes and other openings in an aluminum box to assemble an electronics project.

The maker of one of the components suggests making this hole for their part:



Obviously to keep the part from rotating when tightened or adjusted, etc.

I can drill a hole of the smaller diameter (0.349") and then use a file to remove material on the sides to approximate the stated width (0.382"). Any slicker ways to do this?

 

[rwm]

A hand sheet metal nibbler would do a nice job on this if the material is thin.


The hole won't be perfectly round, but you clean it up with a file.
This is also a good excuse to buy/build a die filer!!!!

 

[mcostello]

Any one ever made a custom punch for the nibbler above?

 

[ChazzC]

Make/buy a “D” punch.

Common type hole in electronic enclosures for switches, controls, etc.


Ouch! Make one, or find a shop that has one.

 

[rwm]

$383????!!!!

 

[ChazzC]

$383????!!!!

Thus the “Ouch;” also, McMaster.

They used to sell “D” shaped chassis punches, but that was in the days of Heathkit, Lafayette Radio, Elenco, Allied Electronics (before they went all industrial) and Radio Shack.

If I were making a control box, I’d select components that used tab-washers to clock them (double-D shaft with a matching washer that has a bent tab: large round hole for the shaft and a small adjacent hole for the tab; tab washer is on the inside, the tab doesn’t protrude through the sheet metal and a plain washer under the nut on the outside covers the small hole).

 

[MikeInOr]

What is the electronic project? Amplifier? How many of these holes does the chassis need?

If you have several of these holes to make I would consider a gasket hollow punch:

https://www.harborfreight.com/9-piece-hollow-punch-set-3838.html

and file off the part of the punch that needs to be flat so the punch only punches out a "C". Then use a chisel to cut the flat. Then clean everything up with needle files.

Or if you have just one or two of these holes then use a jewelers bow saw to cut the bulk out then clean it up with needle files.

 

[RJSakowski]

For one or two holes, I would do what you suggested. It only takes a few minutes to file the hole. Even though I have a CNC mill, I would still do it that way because it takes more time to create the G code than to manually make the hole. If I had a dozen or so, I might look at writing the code. If I had fifty, I would be tempted to buy the chassis punch.

 

[Flyinfool]

How many of this hole do you need?
You could drill the 0.349 starter hole.
Set it up on the rotary table with a 1/16 Dia end mill and mill the hole. The 1/32R left in the corners might not interfere with the part. or you could file just the corners.

 

[NegativeK]

Can you cheat? Cut the hole and put (weld? Maybe even glue?) a strip of metal on the inside of the enclosure?