Garolite grades for darkslides?

[Steve Goldstein]

I noticed two types of opaque black garolite at McMaster-Carr. These are called XX and G10/FR4. XX is about half the price, G10/FR4 is spiffier in that it appears to contain fiberglass. Is there any downside to the cheaper one for darkslides?

Thanks

steve

 

[Nicholas Lindan]

I noticed two types of opaque black garolite at McMaster-Carr. These are called XX and G10/FR4. XX is about half the price, G10/FR4 is spiffier in that it appears to contain fiberglass. Is there any downside to the cheaper one for darkslides?

FR4 fiberglass is the stuff the circuit boards in a personal computer are made of. Cutting fiberglass will dull your tools and put glass-fiber dust in the air. Use a face mask or work outside. A little bit of cutting and drilling won't be of any consequence but if you are planning an assembly line then take precautions.

GXX is a paper-phenolic and is the stuff the circuit boards in an AM radio are made from. It is easy to cut, but not as strong.

GXX is the standard material for DIY darkslides. The material in Lisco/Fidelity slides is also a paper-phenolic but it seems to be tougher than standard GXX.

 

[Dan Dozer]

Steve,

I used the cheaper material from McMaster Carr for my 8 x 20 slides. About the only thing I had any problems with was drilling large (1/4" diameter) holes through it. These were for the hand pull tabs on the ends of the dark slides (rather than a wood strip on the end). When drilling that size hole through the Garolite, it tended to split out a little as the drill bit came through the other side. Other than that, I found the material extremely simple to work with. Any sanding for final fit of the darkslides into the holders is very easy.

There was a very minor problem with McMaster Carr - they cut down the sheets to the size I ordered (12" x 24") from obviously larger sheets in the factory. The larger sheets in the factory weren't necessarily stored flat and they arrived at my house slightly warped. However, they have seemed to flatten out in time and are working just fine for my holders.

I used 1/16" thick material for my slides primarily because it's easy to get a slot cutting router bit that size. That thickness is a little more than what I was used to seeing in my commercially made 8 x 10 film holders, but it has seemed to work very will for the larger holders for my 8 x 20 camera.

Hope this helps.

 

[Colin Graham]

I used the XX grade as well- 1/32 for the slides and 1/16 for the septum.

 

[greybeard]

To drill clean holes in Garolite, look for either a "brad point bit" with spurs (such as # 120-269 at Woodworker's Supply) or a piloted bit like the DeWalt 1916 (these are both 1/4, but the same design is available in most sizes). This type of bit avoids the wedging action of a regular drill.

If you have access to a disc sander or a stationary belt machine, Garolite can also be scribed an broken a bit oversize, and then sanded back to precise dimension. That is also the best way to get rounded corners to prevent chipping. You do need either a very close-fitting table or a piece of scrap wood for backup, though.

 

[Steve Goldstein]

Thanks all for the feedback.

To Colin's point, I would consider using 1/32 for 7x11 darkslides but I'd be worried it's too flimsy for 7x17. Plus there's the challenge of cutting 1/32 slots. As Dan mentioned, I've been able to find router slotting bits available in 1/16, but not 1/32. Does 1/32 exist?

I have a Dremel table saw with a few blades. I'll have to try them out to see what kerfs I can get. I don't see that there's much difference using a small table saw versus a router, assuming I can get the kerf widths right. Adjusting the cut depth should be easier with the table saw. I guess I'll still need a router for some of the other aspects like cutting pockets for the light traps, shaping pieces that should fit together, etc.

 

[freygr]

I found at link: http://www.mcmaster.com/ on page 2460 of the catalog. Screw slotting cutter in 1/32 inch but you will need a 1/2" dai. arbor to use it.

 

[Steve Goldstein]

Thanks, these are very cool! I didn't look at McMaster because I usually think of them only in the context of working metal, but the solid carbide cutters might work just fine on cherry.

 

[Colin Graham]

Steve, I wouldn't worry about it sagging or being too flimsy, (there was a url link here which no longer exists) was someone who used 1/32 material on 8x20 holders. A little thin, but I think the weight savings might be worth it.

The slotting saws from McMaster are what I used. Be careful, not sure what the max RPM ratings are on them. I used them at relatively low speeds on a mill. The blades are high speed steel, but it's the arbors I worry about.

 

[Steve Goldstein]

I was just looking at Garolite on the McMaster-Carr site. It has a fairly large thickness tolerance, something like plus/minus 0.007" on a 0.0625" (1/16") sheet! This prompts me to wonder just how much clearance is I should allow for the darkslide and septum slots, something I hadn't though about before. Zero clearance would have too much friction to be useful and too-large a clearance wouldn't be light-tight. Or should I just choose a nominal cutter and sand the edges of the garolite if it comes in on the fat side?

 

[Colin Graham]

I adjusted the slot until I got the clearance just right. I erred a little on the loose side; didn't want the slides seizing up on some snowy pass. The stuff doesn't sand very well. Leave a little float room for the septum as well so it can expand and contract. You shouldn't have to worry about light tightness if the slots are deep enough and painted matte black- I just used a sharpie for the hard-to-paint areas like the slots. The main thing is to just make sure nothing can reflect the light around the 180 degree bend of the darkslide slots. The slots on plastic holders are pretty loose, and shallow as well.

I envy you with your project, makes me want to start on another. I had a great experience with mine, frustrations and all.

 

[Steve Goldstein]

I envy you with your project, makes me want to start on another. I had a great experience with mine, frustrations and all.

Thanks, I'm getting excited about it. On the other hand, with yours finished, you've got the time to go out and make photographs! This is time I'm already pretty short on now, and will have even less of once I start cutting wood. Ah, the insanity of it all...

 

[David A. Goldfarb]

Just out of curiosity, have you looked into carbon fiber for darkslides? Chamonix holders use CF darkslides. It's more expensive, but I'm thinking it might be possible to make the holders lighter that way. A darkslide isn't that heavy, but with larger formats, 10 of them for a kit of five holders could add up. If you're making your own holders from scratch, the septum could also be CF.

I found some of the technical details on robotics sites, which use all this stuff, and CF (depending on the type) is about 2/3 the density of Garolite, and is about 2-3 times stronger, so say you made them half the thickness, you would end up with 1/3 the weight per darkslide. The big questions would be--is 1/32" CF sufficiently rigid, and is it sufficiently opaque?

At least one of the robotics suppliers I saw will cut CF sheets to size, so if it made sense, I could be tempted to get a set of CF darkslides to lighten up my 8x10" or 11x14" kit.

 

[Steve Goldstein]

I've thought about CF but hadn't seriously looked into it, mainly because I didn't know where to get it (I didn't search very hard). You're right, though, the potential weight savings can't be ignored. I was planning to buy sheets of Garolite (1/32 and 1/16) just to play around, they're cheap enough - I should add a sheet of CF to the mix as well. Thanks for the tip about the robotics guys!

 

[David A. Goldfarb]

Here's the source that I found for CF sheets cut to size--

http://www.robotmarketplace.com/marketplace_carbonfiber.html

I didn't shop extensively to find the best price, but this looked like an easy way to order. Let us know how it turns out!

 

[Colin Graham]

What a great idea, and such a cool site! Thanks David.

 

[David A. Goldfarb]

They offer sample packs, and if you click on the FAQ, there are some good descriptions of the different thicknesses. I'm guessing .023" (.58mm) would do it, or .041" (1.0mm) at the most.