Drilling plunging holes in acrylic

[hunggaur]

Hi folks I have to punch about 800 12.5/12.7mm holes in some 6mm acrylic

(200 holes in 4 peices each so want to stack all 4 up and cut all at one time)

I have tried some drill bits but I seem to get break out and it is a slow process

I have also tried plunge cutting with a standard 12.7mm wood bit but it seems to melt and clog before it get though.

Any suggestions I did see this but it the goes on to state at the bottom not for plunge cutting

https://www.trenddirectuk.com/56-3x1-2h ... gKG4vD_BwE

Cheers Jon

 

[CHJ]

The restriction on plunge cutting is because of the central web, if you can devise a method of pilot drilling and accurately lining up the end mill afterwards the end mill you linked too will work.

I've achieved the alignment problem in the past but it's a bit of a fiddle for so many holes.
Start the plunge cut with the end mill to the depth of the nose flutes, pilot drill the rest of the way through, then use the initial counter bore to re-align the cutter.

I do the same with large diameter Forstener bits in wood to reduce the drilling loads and heat generation.

 

[Myfordman]

Get them CNC'd by experts in plastics. They will need to be flooded with coolant to manage the heat and use a cutter smaller than the finished holes, stepped round under cnc control.

 

[hunggaur]

Allinement won't be a problem as I will be using a jig with collar so if this bit will cut its a great option

The only other option I have was to get them laser cut which would be expensive.

Cheers Jon

 

[Rorschach]

You need coolant, water and washing up liquid works great but it is messy and you need 3 hands.

Best method for application I have found is a laboratory rinse bottle.

 

[AndyT]

Good luck with this.

When I was a nipper I had a Saturday job in a factory where they made small plastic parts.
One job was hooks for a display of fishing tackle. Ok, no problems, but then they got the job of making the display stands as well. A foot square piece of perspex with a grid of over a hundred holes, at inch centres. The toolmaker made a board of steel bushings that fitted over the perspex. I just had to stand at the drill press, slowly drilling one hole at a time. If I went too fast, the heat welded the swarf to the drill bit. If I went slow, it was even more boring! If I got it right, I could start on the next one.

If you sub the job out, spare a thought for the 16 year old at the other end of it!

I feel better now.

 

[sunnybob]

Andy, that lad would have to be 18 before he could touch a machine even under supervision. 20 by the time he's passed his NVQ and H&S courses and is let loose on his own.
Tempus fugit and all that.

 

[hunggaur]

:!:

Andy nice to see you are offering to help come and drill them for me based on your extensive experience

 

[AndyT]

Supervision? What was that?
I had my own key, so I could open up, get the moulding machines warmed up and the kettle on, then give the boss his early morning alarm call to wake him up to come in!

And I'd gladly help, but I have had to put my hourly rate up to more than you can afford... :wink:

 

[hunggaur]

i normally pay in cups of coffee or tea anyway

 

[RobinBHM]

I machined some perspex with solid carbide spiral router bits.

It cut very cleanly and no over heating.

Maybe a router with guide bush and a 6mm dia bit?

You would have to do them in singles though.

 

[Lons]

Hi Jon

Just trying to remember my days in the plastics industry though it was a long time ago.
We were distributors not fabricators but did do a lot of cutting and drilling for specific orders.

You can buy drills for plastic somewhere but can easily modify normal dormer metal drills which as supplied have too shallow an angle for plastic, from memory we ground to about 80deg angle but not certain as we had a jig. We also relieved the cutting edges a little so they scraped rather than cut the acrylic and didn't dig in. I don't think we had a single failure.

A router is far too fast unless you can get the speed down to no more than 1000 rpm which I would think about max for a 1/2" drill.

If I was stacking sheets to drill I would sandwich them between ply or mdf and drill slowly through the lot though I would also take 2 passes using a 6mm drill first as pilot hole.

If you drilled a practice hole with a standard drill even if it looks perfect it will have micro cracks around the hole when examined under a magnifying glass.
Cheers
Bob