Technique? Final finish on Aperture Plates.

[Ryan Gallagher]

So you've filed fresh plates, what methods do ya'll prefer to "clean up" and remove any burrs or rolled edges without removing additional meat at the opening.

I've had to file 3 sets of plates so far here, and for a clean up pass I've just been using emery cloth (a fairly course electricians grit) to knock down everything, but curious if there are better recommended methods? Perhaps ones that reduce risk of plate scratches should you have film start to curl in the gate?

Also I've read that filing a bevel can increase the sharpness of the masked line on screen. I assume this is beveled open towards the lamp, with a sharper peak towards the film? I have not tried this method yet, doesn't seem needed for 70mm but 35mm might benefit. Would you add the bevel at the end (feels risky), or take care to use that angle the entire time you are filing?

Edit to share my most recent, 70mm 2.39 filed from BLANKS. I've grown fond of a diamond wire saw to do an undersized rough opening when starting from a true blank.

IMG_6670.jpg

[Randy Stankey]

I always used an emery board like the kind that ladies use to file their nails.

I made a couple of light passes, along the length of the edge (not a sawing motion) to smooth things out then, holding the emery board flat, against the face of the plate, make a couple more passes to knock off any burrs.

In my experience, I have never felt the need to bevel the edges of the opening as long as they are straight and square.

After that, I wipe the plate down with 90% alcohol to get off any remaining dust.

[Ryan Gallagher]

I always used an emery board like the kind that ladies use to file their nails.

I made a couple of light passes, along the length of the edge (not a sawing motion) to smooth things out then, holding the emery board flat, against the face of the plate, make a couple more passes to knock off any burrs.

In my experience, I have never felt the need to bevel the edges of the opening as long as they are straight and square.

After that, I wipe the plate down with 90% alcohol to get off any remaining dust.

Noted... so basically my technique but with the benefit of the "board" form factor to do a parallel to the face debur.

I also need some better technique in my corners, I've improved but still it is the crux for me. I have a couple files with no grit on the edges that help, but can still over-file using them if not careful. The triangle file is pretty akward, I have not yet resorted to just putting circles of over-filing in the corners yet using a small round file. On these plates I used an unfiled undersized 2.20 and a fat paint pen to draw my "rough" line to follow leaving room for keystone later... that was a mistake, one of my rough cut edges was nearly touching the 2.39 vertical on one side already, and led to a slight over-file in the bottom left trying to get my corner happy. I'd have been better off drawing my rough vertical line using my 1.85 plates as reference, or just avoid starting from blanks next time!

[Jeremy Weigel]

I always beveled the back side of my Simplex plates and used an extremely fine jeweler's file to get rid of any burrs.

[Randy Stankey]

... One of my rough cut edges was nearly touching the 2.39 vertical on one side already, and led to a slight over-file in the bottom left trying to get my corner happy. ...!

Solder a bead of silver solder over the place you over filed to fill it back in. Scrape off the excess solder and sand the faces of the plate smooth. Now, just file the edge back until it is right.

Use silver jewelry solder it has a high melting point and won't be affected by heat from the lamp. Electronics grade will certainly do just as well, although it has a somewhat lower melting point. Lead-free electronics solder can be used just as well. It melts at a lower melting point but still above traditional tin/lead solder which has the lowest melting point.

But the lowest melting point of any of the solders is about 180º C. If your plate gets hotter than that, which is almost twice the temperature number of boiling water, you've got a problem! Especially these days when we have better lamps and optics that don't overheat the projector. There are ways to keep aperture plates cool...water circulators and such. You shouldn't have to worry about it, much. If your projector is getting hot enough to melt solder, I'd say that you've got bigger fish to fry.

Anyhow, just fill in the gap with solder and file it smooth. Gooder than grits!

[Tj Hopland]

All I ever used was files from Lavezzi and a for roughing out a blank a hand nibbling tool usually from Radio Shack. Too bad neither one of those still exist in the forms they once were. One of the things you are looking for in a file is one that doesn't have teeth on the narrow edges. I seem to recall that maybe that no teeth feature was sometimes called a safety file? Looks like McMaster just calls the edge tooth "none". I don't recall what finish the Lavezzi were, maybe a no 1 fine?

https://www.mcmaster.com/products/fi...angular-files/

https://www.mcmaster.com/products/hand-nibblers/

[Ryan Gallagher]

All I ever used was files from Lavezzi and a for roughing out a blank a hand nibbling tool usually from Radio Shack. Too bad neither one of those still exist in the forms they once were. One of the things you are looking for in a file is one that doesn't have teeth on the narrow edges. I seem to recall that maybe that no teeth feature was sometimes called a safety file? Looks like McMaster just calls the edge tooth "none". I don't recall what finish the Lavezzi were, maybe a no 1 fine?

https://www.mcmaster.com/products/fi...angular-files/

https://www.mcmaster.com/products/hand-nibblers/

I did pick up a diamond nail file based on recs in other threads... it is effectively a "safety" file too.

https://www.amazon.com/dp/B007242LWC...d_asin_title_1

But how "ideal" of a safety file it is depends quite a bit on manufacturing tolerances when applying the diamond abrasive it seems.

I do have a traditional nibbler, as does the booth, but the wire saw is great starting from blanks and pilot hole if you have a undersized reference to aim for.

What's funny is there has been a two stone knife sharpener souvenir type thing kicking around in the anti-booth for who knows how long. I always assumed prior projectionists liked to keep their blades sharp, but just maybe it had a dual purpose of doing a surface finish on app plates too.

[Randy Stankey]

I don't think it out of the ordinary for there to be a stone kept in a projection booth. It might not be common in recent days but I can imagine a time when a good projectionist also had to have a bit of machinist experience, too. He didn't have to be an expert but he would benefit from knowing his way around a machine shop, as the saying goes.

After smoothing aperture plates, the next thing I think of is polishing and smoothing gate runners and such things. It might not be ideal but, sometimes, you gotta' do what you gotta' do. Right? A stone would be a good thing to have on hand in case you need it.

In a booth that's been around since the old days, I don't think that finding a stone is all that much out of place.

[Ryan Gallagher]

I don't think it out of the ordinary for there to be a stone kept in a projection booth. It might not be common in recent days but I can imagine a time when a good projectionist also had to have a bit of machinist experience, too. He didn't have to be an expert but he would benefit from knowing his way around a machine shop, as the saying goes.

After smoothing aperture plates, the next thing I think of is polishing and smoothing gate runners and such things. It might not be ideal but, sometimes, you gotta' do what you gotta' do. Right? A stone would be a good thing to have on hand in case you need it.

In a booth that's been around since the old days, I don't think that finding a stone is all that much out of place.

If you were good you could probably put an edge back on a worn out splicer blade too.

[Randy Stankey]

I imagine that anybody who worked in a projection room, back in those days, would have known how to sharpen blades of all sorts. They didn't have things like disposable blades. Sharpening would have been a common skill. Anybody who called himself a man would have, at least, known the basics of sharpening.

As an intuitive example, how many times do you remember reading ads, magazine articles and books that say things like "A dull knife can be more dangerous than a sharp one!"

[Jim Cassedy]

< Edited > I've read that filing a bevel can increase the sharpness of the
asked line on screen. I assume this is beveled open towards the lamp,
with a sharper peak towards the film? I have not tried this method yet,
doesn't seem needed for 70mm but 35mm might benefit.

A 1960's projection manual I have, as well as some of the JJ manuals gave this advice when filing plates:

'"after the plates have been filed to the proper requirements it is suggested that a 30° bevel be filed around
the aperture opening with the sharp edge towards the film. . .After filing it may also be desirable to paint
the bright surfaces with a dull black enamel to stop all reflections. "

Both of those sources only seem to mention painting around the aperture opening in relation to 70mm, but
I've worked in several 35mm screening rooms & theaters that had the aperture opening trimmed with flat black
paint. I think I actually have several 35mm plates in my collection that are made from some sort of black metal.

[Gordon McLeod]

Haveing in the last 55 years filed 1000's of plate i still use the same file called an Auger bit file exclusively and a small needle triangle file a nibbler and dremel tool sometimes

https://orka.ca/products/racaufile?variant=41249076969577&country=CA&currency=CAD&utm_source=google&utm_medium=organic&utm_campaign=shopping&utm_content=Rack-A-Tiers+Auger+File,+Model+Aufile*&utm_source=google&utm_medium=cpc&utm_campaign=ASUC+-+Performance_Max+-+Category+-+Hybrid+-+All&gad_source=1

[Ryan Gallagher]

Haveing in the last 55 years filed 1000's of plate i still use the same file called an Auger bit file exclusively and a small needle triangle file a nibbler and dremel tool sometimes

https://orka.ca/products/racaufile?v...l&gad_source=1

I don't have any that taper to a point, I snagged one of those. Thanks.

[Tim Reed]

Made lots of bloody fingers here from filing plates. I could never see a difference by filing an angle on the aperture. Even on the side closest to the film, the plate still isn't in the focal plane and will cast a shadow. I seem to think the lens speed had more to do with the reduction of aperture shadowing... slower lenses having a greater depth of focus.

[Ryan Gallagher]

Made lots of bloody fingers here from filing plates. I could never see a difference by filing an angle on the aperture. Even on the side closest to the film, the plate still isn't in the focal plane and will cast a shadow. I seem to think the lens speed had more to do with the reduction of aperture shadowing... slower lenses having a greater depth of focus.

That makes sense. It is probably not something I’ll ever try here, we have masking to overlap the slightly fuzzy edges. But maybe in a fixed masking room it would matter more, but if you don’t have masking why bother with still running film, lensing is rarely perfect these days it seems… unless you got deep pockets for those perfect lenses.