Plastic Cases for Projects - Making the Holes

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1024MAK
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Joined: 24 Dec 2012 03:01
Location: Looking forward to summer, in Somerset, UK

Plastic Cases for Projects - Making the Holes

Post by 1024MAK »

So you have your lovely shiny new expansion device or gadget 8-) Your Memotech works great, but over time the PCB of your expansion device starts collecting dirt, dust and hairs and all of a sudden does not look so good :(

So how do you protect it? :?:

:idea: Well you may want to fit it in a nice plastic case. After all, there are many plastic project boxes to choose from, one of them is bound to be about the right size...

So you measure up the size of the PCB and then search for a suitable size case. Now some suppliers are nice enough to supply internal measurements. But some are less helpful and only quote the external box size. If this is the case (sorry!) add an extra amount. For the case walls, these are typically 3 to 4mm but you may have to add more if there are slots or plastic mounting posts.

Ahh, now comes the really fun part - making the holes in the plastic box... :lol:

Remember practice makes perfect (and a pile of scrap rejects... :lol: )

The results very much depend on how nice you want to make it vs. the amount of time, care and effort you want to put in to it.

For drilling use HSS metal drill bits. If you have a battery drill that can operate at a slow-ish speed (even better if it has a speed control), that is better than a full on mains powered drill. Plastic is soft and has a low melting point so you do not want to use a high speed.

At all times be careful. Only apply gentle pressure, you want the drill bit to do the work. If the drill bit is sharp, it may grab the plastic and get stuck forcing the plastic case to try to spin in your hand or trying to tear the plastic. So watch for this.

Also ensure that you do not slip and drill through your hand ImageImage

Small Round Holes (up to 10mm - 25/64")
Mark a small indent in the plastic where you want the centre of the hole to be using a sharp point. Then use a small 2, 2.5 or 3mm (5/64", 3/32", 7/64", 1/8") drill bit or similar to drill a pilot hole. Then you can use the correct size drill bit for the hole. If the hole will be visible, use a slightly smaller drill bit, then use a medium metal round file to finish off. This gives a neater result.

Medium Round Holes (10mm - 25/64" up to 13mm - 1/2")
Use the method described for Small Round Holes (up to 10mm - 25/64") and drill to 10mm - 25/64". Then use a hand tapered reamer to enlarge it.
Medium Round Holes (10mm - 25/64" upwards)
Do as per Medium Round Holes (10mm - 25/64" up to 13mm - 1/2") then use a new/sharp sheet metal punch.

Large Round Holes
Mark the outline of the circle on the case, then use the method for Square, Rectangular or Odd Sized Holes...

Square, Rectangular or Odd Sized Holes
Mark the outline of the cut-out on the case.
Carefully drill holes in the corners of the intended cut-out being sure not to drill outside the marked area.
Now either use a suitable saw to cut between the holes. For smaller holes you can slowly use a hacksaw blade.
Or drill a series of small holes in a lines between the existing holes. Then use a small file to merge the holes into slots. Soon you can press out the unwanted plastic.
Or use a drill-saw to merge the holes into slots.
Finish the hole using a larger medium metal file.

And then there is the smelly cowboy way...
Use a hot soldering iron or hot cutting knife. Leave a margin to file out if you want a neat-ish finish...

I hope these tips help :mrgreen:

Mark
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Looking forward to summer in Somerset later in the year :D

Not as many MTXs as Dave! :lol:
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