Removing flange from a Pentac 8 inch f2.9

[C. D. Keth]

Is the barrel also aluminum and will the glass come out of it easily?

[buzzski]

I had the exact same issue just a week ago. My lens is brass but was stuck solid to mounting flange. I applied a little touch of light oil to the thread, let it sit a bit then applied heat and loosened the flange over a period of about an hour. I only used a hair drier, not a heat gun and wore a pair of kitchen gloves to get a bit of extra purchase. Didn't think it was gonna loosen but it did!

Just fitted it on to a Jo Lommen board this evening and looking forward to a test tomorrow hopefully! Good luck with yours!

[adelorenzo]

Is the barrel also aluminum and will the glass come out of it easily?

I'm not certain but it's light enough to be aluminium and others on the thread have mentioned that it is. Front and rear elements came out no problemo.

I may try heat as my next effort as some have suggested.

[C. D. Keth]

If you try heat, use an icepack to keep the barrel cool and heat the flange up quickly with a torch before too much of the heat sinks to the barrel. It doesn't need to be crazy hot or glow or anything. The goal is to create a heat differential (expand the flange more than the barrel) between the pieces that will help them to come apart.

[adelorenzo]

Since there are screw holes in the flange, you can fasten it to a larger piece of wood and get a good grip with your strap wrench on just the barrel. I've found it helpful in the past to use brass or steel bristle brushes (hand powered or circular ones in a Dremel tool) to clean aluminum threads. Aluminum quickly forms a coating of aluminum oxide on any exposed part, and if it's been exposed to humidity this layer can be quite thick and thus bind threaded parts. I don't know of any solvent that would break this down without requiring a Haz-mat suit and respirator to use, so I generally limit myself to mechanical means.

Aha, this was the ticket. I screwed the flange down to the top of my work bench and was able to get more torque with the strap wrench and unthread it. The threads look pretty rough but definitely usable, I'll clean them up a bit and put the whole thing back together.

Anyone have thoughts on using a very light coating of grease or anti-seize on the threads? Or keep them dry?

[Jody_S]

Anyone have thoughts on using a very light coating of grease or anti-seize on the threads? Or keep them dry?

For aluminum, use toothpaste (with fluoride). There is also a petroleum-based paste with fluoride made especially for aluminum joints, sold by electrical materials distributors and some big box hardware stores. A common trade name is Noalox (No Aluminum Oxidation). But toothpaste is fine, in fact it's often used as a substitute by electricians. You could mix it 50-50 with white grease. Don't use too much, it can turn to goop.