[orthobiz]

So I have a giant tall dustcover on my highly modified HW-19 VPI. But the square aperture (hole?) in the back isn't big enough for the 10.5i tonearm and cable box.

What's the best way to enlarge the square hole? I figure a Dremel tool would work but am wondering about cutting bits, etc. as the heat generated could raise a furrow of melted plastic.

Ideas?

Thanks!

Paul

[Bob2]

Dremel has some sanding drums (tubes if you will) that go on a rubber mandrel. They are about .5 inches in diameter. Use a coarse grit. Finer grit will load up and stop removing material. If your dremel has a speed control run it at low speed. You can also run the dremel from a variac to lower the speed. Tape the area off so no accidental scratches! Finish off edges with a file. This will help bring back corner radius. For a more factory finish use progressively finer grit wet/dry sandpaper. 2000 grit should give a decent finish, much like original.
Good luck!

[Wayner]

Dust covers are usually made out of acrylic, and acrylic easily cracks.

[Bob2]

Wayner is correct. Acrylic does indeed crack very easily. When drilling holes the drill bit needs to be sharpened to a zero degree rake angle so as not to fracture the material.
Also any inside corner should have a radius so any stresses are not concentrated causing cracks.

[orthobiz]

Thanks. If I used a new drill bit, is it automatically sharpened to a zero degree rake angle? Or is that a special kind of drill bit? All I ever see are drill bits sold by the diameter, I have never paid attention to the rake angle??

Paul

[Wayner]

Paul,

I'd rather see you use a Dremel tool with a friction cutting disc. Using very light pressure, you use heat to melt away the acrylic rather then a mechanical means to cut it. Tape the area off (on both sides), including the cutting path, with masking tape, draw the pattern you want to cut-out on the tape, and fire up the Dremel. I think you will also be better off making several passes. Finish off the cut out with some sandpaper.

[orthobiz]

Paul,

I'd rather see you use a Dremel tool with a friction cutting disc. Using very light pressure, you use heat to melt away the acrylic rather then a mechanical means to cut it. Tape the area off (on both sides), including the cutting path, with masking tape, draw the pattern you want to cut-out on the tape, and fire up the Dremel. I think you will also be better off making several passes. Finish off the cut out with some sandpaper.

Will try the Dremel either way. And I'll post pictures IF I'm successful!

Paul

[Wayner]

Just remember to let the tool do the work. 

[Bob2]

Paul,
New drill bits have a positive rake angle.
If you have  a local machine shop stop by with the drill bit and ask them to grind it for you. Make sure you tell them you will be drilling acrylic. Takes about 20 seconds to do that against a grinding wheel.

I wouldn't use a friction disk! Those break very easy and the parts of the disc go flying. Make sure to wear safety glasses.
Bob2

[SCompRacer]

I had to trim my dust cover opening to fit a linear arm. This acrylic bit in a router will make a perfect cut. No way to do this free hand. I first applied masking tape to protect surface. Then I clamped a long straight edge to the acrylic to cut a straight line. First for horizontal cut, then for vertical cut. Some felt pads on the clamping surface prevents marring on the inside. 



http://www.amazon.com/Bosch-85611M-Diameter-Carbide-Acrylic/dp/B000GYE1LE

When I had my custom dust cover made they forgot to put a finger cutout on one side. I just cut it out myself. First pic is OEM cut, second my cut.

OEM cut.



My cut.