Repair stripped cylinder stud bore in cases. - Ducati.ms

gregsky · Feb 17th, 2011, 11:47 pm

A while back I was tearing down a friends 900SS and found a cylinder stud was pulled from the cases. As you can see by the pic the stud had pulled an installed Helicoil from the cases. I wasn't at all excited about the idea of replacement cases or welding and re machining the stud bore. As you can see there was not much meat to work with on what would be the cylinder side of the hole. I hoped I could find a thread insert with a 10x1.5 inside and a small enough outside to repair the cases. I found thread inserts Part # 0123150 at Fastenal. (I'm not sure if this is a Fastenal or EZLOK part #.) These are EZLOK M10-1.5M/F thread inserts. A machinist friend threaded the cases to match the outside of the inserts and sanded the face of one insert until one inserted on top of the other resulted in a strong continuous thread to receive the stud. Hope this helps someone else out of a similar jam.

yellow blur · Feb 26th, 2011, 7:33 pm

A bit hard to tell with the oil and aluminum bits, but it looks like the Helicoil wasn’t installed properly - skipped a thread or 2 (or 3) during installation - causing a cross-thread and probably what caused you to need your current fix. If Helicoils are installed correctly they work very well.

Thanks for posting what you did. Would like to see a pic of it.

gregsky · Mar 6th, 2011, 8:47 pm

Yellow Blur,
I agree. I have used Helicoils for years to repair stripped threads. I think whoever put this one in messed up the install.

RUNnDUC · Mar 6th, 2011, 8:55 pm

It looks as if the Heli-coil is proud of the case surface at least one turn. I use Heli-coils almost every day and they are installed between .75 and 1.5 turns below the surface. This is to prevent the first thread of the Heli-coil from deforming the first thread of the repair.

RUNnDUC · Mar 7th, 2011, 5:15 am

I have reread and found that I missed a very important point. Your are settintg yourself for failure by using two inserts in one hole. A ton of different problems can be caused by using multiple inserts with one of the worst being the fastener jamming against the two inserts. Inserts can be purchased in different lengths. The manufactures use the formula diameter times length or .5 times the diameter = 1/2D. Inserts come in lengths of 1/2 D, 1D,1 1/2D, 2D and 2 1/2D for the engagement length of thread on the fastener. In almost all applications a thread engagement of 1 ½ D will be near the maximum strength fastener will be able to provide. Inserts can be backed out or “pulled” from a threaded hole with an insert removal tool. Before installing a new insert, check what the full depth of useable thread is by using the insert tap and run it in to the hole counting the turns or measure the length. Note the amount of “lead” or partial threads there are on the tap and counting only the full thread will tell you how deep the insert can go in to the tapped hole; a bottoming tap has fewer lead threads and can be run closer to the bottom of the hole with full depth threads. If the hole is really jacked up and there is enough support material around the hole, a “Keensert” can be used to repair the threaded hole. That is another can of worms.

yellow blur · Mar 8th, 2011, 12:12 am

It also requires the special Heli-Coil tap that isn't good for much of anything else but Heli-Coils.

gregsky · Mar 8th, 2011, 10:33 pm

Quote:

Originally Posted by RUNnDUC

It looks as if the Heli-coil is proud of the case surface at least one turn. I use Heli-coils almost every day and they are installed between .75 and 1.5 turns below the surface. This is to prevent the first thread of the Heli-coil from deforming the first thread of the repair.

RUNnDUC,
I think this HeliCoil was probably well below the case gasket surface when installed. At the time of the picture it had pulled from the case having stripped the aluminum thread on the OD of the HeliCoil.

gregsky · Mar 8th, 2011, 10:36 pm

Oops. Sounds like I an indicating the outer side of the Helicoil is aluminum. I meant the steel Helicoil pulling from the stripped threads of the aluminum case.

yellow blur · Mar 10th, 2011, 12:41 am

I've actually had them skip the leading thread or 2 during installation. No way to fix that except remove it and install another.

rhubarbray · Mar 31st, 2011, 7:57 pm

I haven`t had to use them yet, but I can see these might be the anwer to your problems with coiled inserts. And from what I can read, they use the same taps as the Helicoils` tap. They`re called Timeserts. Anyone used them?

http://forums.pelicanparts.com/uploa...1083885650.jpg

Ray