Theo Posted October 12, 2021 Report Share Posted October 12, 2021 (edited) I have a this here heater which has done valiant service for the past 15 years. I have occasionally cleaned the glow plug and once or twice cleaned the flame detector but now I have a problem. The two cross head machine screws that hold the glow plug boss in position have stripped the threads of the alloy casting into which they screw. Ditto a couple of the hex machine screws that hold the fresh air fan assembly to the alloy body. Is there a sensible way of sorting out this problem? Nick Edited October 12, 2021 by Theo Rubbish typing and not reading through before posting Link to comment Share on other sites More sharing options...
Tracy D'arth Posted October 12, 2021 Report Share Posted October 12, 2021 If the screws are out and not snapped off you are lucky. Either drill and tap to a larger size of new screws or the rough way use self tapping screws but be careful not to split the casting. Link to comment Share on other sites More sharing options...
Theo Posted October 12, 2021 Author Report Share Posted October 12, 2021 Thanks, Mr D'arth. Drilling and rethreading would seem the most satisfactory way. I had heard (read?) that you can insert a thing like a spring into the hole to produce a new thread but I suspenct that this would mean drilling out a larder hole and rethreading with a tap would be much more satisfactory. N Link to comment Share on other sites More sharing options...
nicknorman Posted October 12, 2021 Report Share Posted October 12, 2021 48 minutes ago, Theo said: Thanks, Mr D'arth. Drilling and rethreading would seem the most satisfactory way. I had heard (read?) that you can insert a thing like a spring into the hole to produce a new thread but I suspenct that this would mean drilling out a larder hole and rethreading with a tap would be much more satisfactory. N Helicoil. But not sure if you can get them that small. Link to comment Share on other sites More sharing options...
adrianh Posted October 13, 2021 Report Share Posted October 13, 2021 You could use helicoils or 'Cross thread inserts' but these are not good if you need to dismantle as they have a tendency to wind out on the threaded screw. A much better product to use in aluminium is called a 'Keensert. Look at Claredon fastener or WDS web site for details or pm me for help. I have used these a lot. They are screwed in and locked with small pegs but you do require enough material around the hole to do this, also the correct taps and drills. Ideally the heater needs to be removed so holes can be drilled and tapped in a machine. May be able to help you with this. PS I have the same heater. Alternatively look on eBay for old defunct heaters and build a good one up. Link to comment Share on other sites More sharing options...
Tracy D'arth Posted October 13, 2021 Report Share Posted October 13, 2021 Every Mukuni I have worked on had some stripped threads or sheared screws. They are very small to start with. Link to comment Share on other sites More sharing options...
Theo Posted October 13, 2021 Author Report Share Posted October 13, 2021 Confession time: Te threads have been stripped for some time. What I did for the last couple of services was to insert some bits of fine copper strands stripped out of scraps of wire that I had. They worked fine but I thought that there might be something a bit more refined. Thanks for all the suggestions. The problem with buying old jobbies to canibalise is that they might have just the same threads stripped!. N 1 Link to comment Share on other sites More sharing options...
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