Weird Fresnel Question

[playpunk]

What do you guys use for the fancy Fresnel lenses? I have used them in my last two builds, and in one it is very, very tight, and in the other, it is almost too loose and fits absolutely flush. Is there a metric drill bit size I should be using? I have been using a cheapo unibit, but it seems like the size is in between two of the steps.

Thanks.

[davent]

For those in between sizes I fine tune with a tapered reamer, drill it small then creep it up to size with the reamer.

dave

[playpunk]

Thanks. I should probably get a reamer, but I don't have one currently. I was also thinking about just getting a 6.5mm drill bit, as the VCC lens has a 6.35mm OD, and the lip is 7.1mm.

[Leevibe]

If I remember right, the data sheet on the ones I bought from mouser said 1/4" but the 1/4" step on my Irwin bit is ever so slightly too big. It could be that I'm drilling too fast and getting some wobble. I do like the reamer idea. I recently saw an un-stepped bit. It's cone shaped just like my unibit but there are no steps. That might be a good way to fine tune the hole size.

[peAk]

Any reason you guys prefer the Fresnel over...say....the metal bevels?

just curious

[jkokura]

Different look. No real preference here.

Jacob

[GermanCdn]

If I remember right, the data sheet on the ones I bought from mouser said 1/4" but the 1/4" step on my Irwin bit is ever so slightly too big. It could be that I'm drilling too fast and getting some wobble. I do like the reamer idea. I recently saw an un-stepped bit. It's cone shaped just like my unibit but there are no steps. That might be a good way to fine tune the hole size.

The unstepped bits are nice to have, but you have to be careful with them, as when the ratio of length to width gets smaller, they are hard to control and it's really easy to overdrill or end up with an inadvertent dimple.

Aluminum is relatively easy to ream with a hand reamer, and you can pick them up for under $4 on ebay.

[davent]

Guys, Is Princess Auto in Western Canada, i picked up a couple reamers from them including a monster for tube sockets and they were a pretty decent price.

For fine tuning and creeping up on perfection slow is best, even by hand it's easy to over-ream in the relatively soft aluminum.

[GermanCdn]

Guys, Is Princess Auto in Western Canada, i picked up a couple reamers from them including a monster for tube sockets and they were a pretty decent price.

For fine tuning and creeping up on perfection slow is best, even by hand it's easy to over-ream in the relatively soft aluminum.

PA's are all over Western Canada (same idea as Harbor Freight for our American friends), I just referenced the ebay thing as a universal source.

[muddyfox]

Even though I'm of the metric folk, my step bits are imperial. I just drilled a hole for a Fresnel and it's a nice 1/4in fit. If 1/4in is too loose then it's either not 1/4 or you have more wobble/play in your drill than usual.

[Hangingmonkey]

I've just used a fresnel for the first time and had the same problem of inbetween sizes. I ended up over drilling and figured id hot glue it in from behind. By the time I painted and cleared the enclosure the extra coverage of the layers of clear made it fit real snug

[Strategy]

I love fresnels and have never found the right bit size, I use a dremel with one of the smaller rough filing/scraping/sanding ends, use a tapered one for that as well. Beware aluminum dust - nasty wear a mask.

[Stomptown]

On mouser there is a data sheet that also has retainer rings that help if you over-drill the hole. I still add a touch of apoxy around the base of the retainer ring to make sure the bezel doesn't pop up. They are nice to have on hand...

You can find the retainers here:

Datasheet:
http://vcclite.com/_pdf/CLB-300-5mm-round-lens-drawing.pdf         
Mouser Catalog:
http://www.mouser.com/catalog/catalogusd/646/178.pdf