Truncating a round hole?

[whitmore]

Graphite rod with a flat filed on it, and EDM of the crudest sort. Maybe drill an undersized pilot hole, no
need to spend more sparks than bare necessity.

Or go to sendcutsend.com and get a laser-cut for the mount panel.

 

[RJSakowski]

The flat(s) on holes for electronic components are to prevent rotation of the component. . I make the D shaped holes for things like Heyco strain reliefs as they won't work with a round hole. Another is for components like rotary switches or cabinet locks. But in many cases, simply drilling the complete hole will be sufficient.

 

[jwmay]

I’d drill a hole and file a flat. If I wanted it right, I’d make a punch and die, and do it in a press. But I’ve drilled near a hundred holes for similar applications, and so far, the holes lasted longer than the components installed in them.

 

[WobblyHand]

I found old chassis punches on eBay when I needed to do that. Greenlee punches. They sure have gone up in price! On the other hand, just drill a hole for the bolt and tighten it up until the punch goes through. Otherwise, trace out the pattern on the sheet metal and do what needs to be done. Had to do that for a fused IEC socket in a Bud box. Lot of hand filing and fitting. At least there were straight lines.

 

[jbltwin1]

I've drilled the hole and then used the spot welder to stick another piece of metal across the hole. Also oxy-acetylene welded a few or brazed them. Just depends on whether the change in height will affect the work. Drilled and filed a few also. Like I said, depends on the use, thickeness and how freaking patient I feel that day!

 

[Frank O]

Thanks for all the suggestions. This is just a couple of holes, so I think drilling a 0.349" starter hole and filing out the sides would be the fastest way to get this done.

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

I agree, and I've had two or three of these over the years, but my most recent one is apparently on some unreachable stratum in the gear vault. If I wanted to get another, is there a better brand to look for than the knockoffs on Amazon?

 

[rwm]

Mine is an ancient tool from RadioShack so I cannot make a good recommendation.

 

[B2]

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?

Do you have a cnc mill? I did something similar so probably still have the gcode. If you have the cnc I can look tomorrow.

 

[B2]

https://www.hobby-machinist.com/attachments/pm1440gt-instr-panel-lc26-jpg.389882/

This shows the electronic cover plate I made . Note the switch holes.

 

[B2]

@Frank O

So I had written an Excel workbook which after you input some locations and hole type parameters will generate G-code to make various electronic device hole shapes at various locations. The project thread is linked below. It has been a long time ago that I made this spread sheet so I would have to read the README File to even understand it again. However, at this description you can see pictures of the cover plate I made for my PM1440GT lathe when I did the VFD conversion. The last posted version of the workbook generates the G-code and copies it to the clip board and you can use this to paste the results into a text editor to see the G-Code.

This is the second half of the post of the Excel Gcode generator. Perhaps you will find it useful.

To see the program in operation load the first spread sheet and then with Macros enabled simply press the keys Ctrl+Shift+M. It should generate Gcode and copy it to the Windows Clipboard. One can then paste it into a machine Gcode simulator or into ones CNC machine to see the tool path.

So I updated the zipped file for the panel spread sheet with the macros as well as the macro txt files. File names for attached files are:

If you have any questions or concerns about the workbook operation let me know. Or if you would like for me to go through this and generate the G-code for a the truncated hole for you just let me know. One of the photos is for the truncated hole, but it can also include other features. You choose them. It also can place it at your location and an any angle.