Repairing cracked Bakelite.

[stevehertz]

The black Bakelite component in the photos is the base of Philips 930a 1931 radio. It had an open crack from one side across a corner over to an adjacent side without actually separating it into two parts. I thoroughly washed and rinsed the base to ensure that there was no contamination or dust within the crack, applied thin superglue to the inside of the crack and clamped it up. After an hour or so I used lengths of threaded rod (bolts with heads cut off) and Araldite to reinforce across the cracks in selected corners of the base having first keyed and degreased the areas. This was done in three places, each being done separately time-wise to enable the base to be appropriately tilted such that the reinforcing rod and Araldite lay tight in the corners during the curing process. Whenever I effect a repair using Araldite I use this metal reinforcement procedure if the application allows it. I recently repaired some freezer draws using it.

[The Philpott]

Where the crack hasn't caused the material to split into two, I also use conventional (thin!) superglue as the wick effect is very useful. White stains come off with acetone. Where the parts have separated I revert to the slow cure of A66raldite. All is good as long as the bakelite has snapped cleanly rather than tearing like cheese.
I can see the benefit of threaded rod- large surface area and good 'grippage'.

Dave

[stevehertz]

Originally Posted by The Philpott

Where the crack hasn't caused the material to split into two, i also use conventional (thin!) superglue as the wick effect is very useful. White stains come off with acetone. Where the parts have separated i revert to the slow cure of araldite. All is good as long as the bakelite has snapped cleanly rather than tearing like cheese.
I can see the benefit of threaded rod- large surface area and good 'grippage'.

Dave

In this instance the superglue was only used to hold the two pieces together tightly prior to using the Araldite and pins. Saying that, a good superglue joint can be quite effective by itself, it just depends on the application. In this case the Bakelite base is carrying the weight of the whole chassis etc, and is being 'pulled' and potentially contorted by four strong mounting bolts. Which is probably how/why it cracked originally.

[The Philpott]

-I have just had one of those awkward bakelite issues where a piece hadn't completely parted company...i couldn't just wick superglue into the crack as the piece had shifted out from the main body but the crack had a 'dead end'.
Forcibly snapping it off in order to reinstall went as well as could be expected. The 'cheese' effect I referred to earlier had happened to a small degree so it was a job for slow araldite, to get a reasonable alignment.

Dave

[McMurdo]

When I worked for a company that took in test equipment for repair, one of the common jobs was gluing AVO 7s and 8's that had been dropped. We used to drill tiny holes and use veropins glued in as reinforcements, and mate the broken edges with Araldite, which worked well on the coarse Bakelite.

[Philips210]

Originally Posted by McMurdo

When i worked for a company that took in test equipment for repair, one of the common jobs was glueing AVO 7s and 8's that had been dropped. We used to drill tiny holes and use veropins glued in as reinforcements, and mate the broken edges with araldite, which worked well on the coarse bakelite.

I've used a similar method with ribbed steel wire. It certainly gives the repair significantly better strength. The greatest problem is ensuring good alignment when drilling the holes to accept the pin or wire. Pencil lines on the two pieces can be a help.

Regards,
Symon