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Topic: Repairing stripped thread in plastic baffle (Read 3971 times) previous topic - next topic
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Repairing stripped thread in plastic baffle

Hi all. I have an issue where one of the holes for the 8 screws that hold the driver to the baffle is stripped very badly, not allowing the driver to form a good seal with the enclosure.

I've done some reading regarding the necessary repair and I haven't been able to reach a decision about how to go about it. The stripped thread is plastic and the screw is metal. I'm trying to avoid using a different screw because it would be too noticeable. I have no materials or tools, but all reasonable options are open to me.

Should I try using epoxy to repair the thread, or would it be too weak? Should I use a different adhesive? Zip ties? Superglue? Or should I take the speaker to a repair shop instead?

Thanks

Repairing stripped thread in plastic baffle

Reply #1 –
I will assume the plastic is ABS (most plastic speakers are).
Go a model hobbies shop (where they sell plastic model kits etc) and ask for a bottle of "plastic weld". It's a solvent that melts ABS and some other plastics. Find some more ABS, either off some scrap piece or by shaving off excess from the back of the baffle. Cut small shavings and stuff the hole with them. Drip a drop or two of plastic weld into the hole. Wait until the plastic softens, then carefully screw the screw into the hole (without the driver). Leave to set for a few hours, then carefully remove the screw. Leave another 24 hours, then reassemble.
Regards,
   Don Hills
"People hear what they see." - Doris Day

Repairing stripped thread in plastic baffle

Reply #2 –
Quote from: splice on
I will assume the plastic is ABS (most plastic speakers are).
Go a model hobbies shop (where they sell plastic model kits etc) and ask for a bottle of "plastic weld". It's a solvent that melts ABS and some other plastics. Find some more ABS, either off some scrap piece or by shaving off excess from the back of the baffle. Cut small shavings and stuff the hole with them. Drip a drop or two of plastic weld into the hole. Wait until the plastic softens, then carefully screw the screw into the hole (without the driver). Leave to set for a few hours, then carefully remove the screw. Leave another 24 hours, then reassemble.


Oh, that sounds sensible. I didn't even realize it was an option. I'll contact my speaker company on Monday and try and find out what kind of plastic it is. Do you think it'll be stronger than epoxy? Would this method work if I were to let the plastic set and use the screw to tap a thread?

Repairing stripped thread in plastic baffle

Reply #3 –
Quote from: lisbon on
Would this method work if I were to let the plastic set and use the screw to tap a thread?


ABS is not wood.  It will not compress.  You do not want to use a screw in an attempt to tap a thread through a solid block of ABS, rather one wants to form threads in the manner splice described since you don't have the equipment to cut them properly.
Creature of habit.

Repairing stripped thread in plastic baffle

Reply #4 –
Ok, thank you both.

Repairing stripped thread in plastic baffle

Reply #5 –
Quote from: lisbon on
Oh, that sounds sensible. I didn't even realize it was an option. I'll contact my speaker company on Monday and try and find out what kind of plastic it is. Do you think it'll be stronger than epoxy? Would this method work if I were to let the plastic set and use the screw to tap a thread?


I do repairs like this quite often.
If you fill the hole completely, with plastic or epoxy, you will need to make a new hole with the correct size drill bit before attempting to insert the screw. Many of the repairs I do are for the cases where the hole is in the end of a "pillar" of plastic. In many cases the screw is loose because it has split the pillar due to the hole being too small. I've had greater success by using the screw to mould the right size threads in the plastic before it hardens, as I described. It puts less strain on the repair.
As for the type of plastic, it's usually moulded into the plastic itself in some unseen place such as the back of the baffle. If you're not sure, put a drop of the plastic weld on the back of the baffle, wait a few seconds, then wipe it off. If it leaves a pitted surface, the plastic weld will work.
Regards,
   Don Hills
"People hear what they see." - Doris Day