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Author Topic: Drilling and tapping platter tree Dan Chilton Expert Film Handler Posts: 191 From: Springfield, MO Registered: Mar 2004 posted 11-28-2008 09:44 PM                        I need to make some modifications to an old "big red" Speco platter, but I don't know what size bit I need to use so a 1/4 inch bolt will easily thread in without using a nut on the opposite side. Any suggestions? Any while I'm on the topic, what modifications have you made on older Speco platters (if any)?  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 11-28-2008 10:27 PM                     I always used thread-serts. You drill a hole in the tree and these pop into place with a small tool. They are what Christie uses in their platters. *Mount a film cleaning bracket. *Get longer roller bolts, such that the film is an extra 35mm away from the tree so when static electricity hits, the film isn't dragged up against the tree during payout. *Put keeper rollers on all rollers. *Depending on the model, upgrade the takeup roller chain.  |  IP: Logged Jeremy Weigel Phenomenal Film Handler Posts: 1062 From: Edmond, OK, USA Registered: Mar 2007 posted 11-28-2008 10:46 PM                     quote: Brad Miller *Put keeper rollers on all rollers. Did this a few months back on the payout side of our Strong platters.  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 11-29-2008 03:28 PM                     Hmm. At the risk of giving you enough rope to hang yourself: The standard tap drill for a 1/4-20" hole is a #7, which gives 70% thread engagement. It's also reasonable to use a #9, #8, or 13/64" drill, which give 77%, 73%, or 66%. You, of course, need to follow the drill with a tap, which will cut the threads. And use plenty of cutting fluid (oil). If you've never done this before (like it sounds), try to find someone who has, or at the least, practice on a piece of scrap metal (stick with aluminum, not steel, unless you're really going to be doing this in steel; aluminum is much easier to work with). --jhawk  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 11-30-2008 12:53 AM                     There is a problem with tapping the tree for 1/4" bolts - using the UNC standard 20 threads pre inch you only have a couple of threads in the metal, which (as I recall) is only about 1/8" thick. Strong uses UNF 1/4-28 bolts on just about everything in their platters, and it's a better choice for anything on the tree. The threaded inserts are the best approach though. Be really careful about wires inside the thing. Replacing any that are damaged by drilling is definitely a non-fun activity. Make sure there aren't any hanging right where you're drilling, and a drill stop to keep the bit from going much past the metal depth is a good idea.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 11-30-2008 11:02 AM                     Christie also is a user of 1/4-28 hardware. However, SPECO has traditionally just tapped the tree for their hardware. We have some platters in service for 3-decades or more of SPECO/DITMCO and never a problem with threads ripping out. Steve  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 11-30-2008 03:13 PM                     I've had more trouble with the alumnium inserts comming loose or competely out than with platter colum threads stripping out. The main thing is to have sufficient threads in any hole you tap. You can look that spec up in "Machinerys Handbook" Mark  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 11-30-2008 09:18 PM                     Umm, aren't pretty much all threaded inserts steel (or stainless steel)? --jhawk  |  IP: Logged

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