Today's project got me into the shop for about 1/2 an hour, first time I've had anything to do in there for weeks. I was fitting the Triumph factory accessory "top box" to my Tiger 800, and that require drilling four 25mm holes through the rear top "parcel shelf" that the bike come fitted with. The hole locations are spotted on the underside as it's molded. The problem in drilling a 2.5mm (.098") thick piece of plastic like that it two-fold.
First, being somewhat thin and soft, the twist drills just want to grab and pull the part up the flutes. I did OK with an 8mm (.315") drill as a starter hole. The problems came with the 15/16" Silver & Deming drill I had to use, closest to 25mm I had that would fit in the Bridgeport. Two of the four holes end up being on an irregular surface, and nothing about the part is truly flat. I tried "freehanding" it, using the Bridgeport as a drill press. Since I had a little trouble with the starter holes, I quickly realized I'd have to strap it down for the big holes.
A very convoluted setup of wood underneath and the usual stepped block clamps and straps got the job done. It all went together as hoped, and I truly hope I never have to do that to another bike again! ;)
First, being somewhat thin and soft, the twist drills just want to grab and pull the part up the flutes. I did OK with an 8mm (.315") drill as a starter hole. The problems came with the 15/16" Silver & Deming drill I had to use, closest to 25mm I had that would fit in the Bridgeport. Two of the four holes end up being on an irregular surface, and nothing about the part is truly flat. I tried "freehanding" it, using the Bridgeport as a drill press. Since I had a little trouble with the starter holes, I quickly realized I'd have to strap it down for the big holes.
A very convoluted setup of wood underneath and the usual stepped block clamps and straps got the job done. It all went together as hoped, and I truly hope I never have to do that to another bike again! ;)