Stripped!

[steveh]

A friend of mine is cruising in the Canaries and has contacted me with a problem. He has stripped the dipstick thread on his alloy Hurth gearbox. At the moment he has temporarily fixed it with PTFE tape but once removed it won't work again. Does anyone know if it is possible to re-tap the thread and what size it would need to be, or if there are any other solutions. In the mean time I will find out what model gearbox it is.
Thank you in advance.

 

[the_wanderer]

Yes. you can certainly fix it. I have had this sort of job done by an engineering firm (Burton Engineering at Eastern Avenue, Ilford.) You can get the hole re-tapped at a larger diameter and a sort of spring with a thread inside and outside inserted. They used to be called Helicoils but there is what I have been told is better called something like suresafe? Contact a good engineering firm and I am sure they can sort it out for a reasonable price.

Regards.

Alan

 

[pappaecho]

Re tapping the thread would result in swarf going into the gearbox , which is "not a good thing".
As the item is a dipstick, I would suggest making a slightly over size "plug" out of an engineering plastic such as Delrin, and then attaching a rod the same length as the old dipstick to achieve the correct fill level. What should result is an interference fit plug which will be oil proof, but which will be softer than the alloy case, and which should allow a good few inspections before needing to be renewed.

 

[dickh]

Yes, you can fit a Helicoil insert but it will mean g/box removal and complete stripdown, so no swarf gets in the box and then a rebuild. This method would rely on there being someone who has the special tap required and a suitable insert of the correct size. Pappaecho's method would be much cheaper, quicker & easier. No idea what size the thread is but from memory a coarse metric thread, probably 20mm Ø.
Better still, just use a cork or a modern 'plastic' cork would be even better. The chances are you will be able to 'screw' it in sufficiently to prevent leakage. Don't bother to fit a dipstick - if I remember you have to unscrew the dipstick and it only rests on the housing when you take the level. So you could continue to use the original dipstick for its intended purpose. (but make sure you tie it on close by).

 

[the_wanderer]

Yes. I thought it was obviuos that the gearbox would have to be removed. I just goes without saying.

Regards.


Alan.