Teknetics customer service???

[screwynewy]

Well it appears that persistence has paid off and Fisher is going to replace my coil under warranty but they did state that this was a one time only arrangement. I will be sure to use some washers to fill the open space where the lower rod and coil connect so this doesn't happen again. I am surprised that more people have not had this same problem. I'm just happy that I won't have to shell out $180 for a new coil.

 

[Mega]

Well it appears that persistence has paid off and Fisher is going to replace my coil under warranty but they did state that this was a one time only arrangement. I will be sure to use some washers to fill the open space where the lower rod and coil connect so this doesn't happen again. I am surprised that more people have not had this same problem. I'm just happy that I won't have to shell out $180 for a new coil.

That is very good news and well done to Fisher

 

[GroundScanner]

No problem , glad they took care of you . GL HH GS

 

[Ed in SoDak]

I'm late to this thread and it's good to see FT treated you right. Looking at your coil pics, to my eye, it looks like they've been over-tightened and the coil was moved often without first loosening the bolt. The compression and friction actually wore a ring into the tabs and the bolt forced the tabs into a conical shape, further reducing the contact area. Of course they'd just become loose again as the thrust-bearing surface wore away, requiring further tightening. Rinse and repeat. Finally, the tabs were forced inwards enough compensating for the wear that they separated.

Maybe you have a habit of flipping the coil up or down to check targets with the heel or tip or for transport/storage. If so, keep the bolt's tension to where it holds position yet still moves easily, or loosen the bolt before making large swings of the coil's position.

I thrash my coils and frequently reposition them by pressing them against the ground or with my foot and haven't lost a tab yet. But, I've seen the same type of wear on our pivoted-arm shop lamps that are moved around a lot with very tight fasteners to hold them in position.

-Ed

 

[screwynewy]

I'm late to this thread and it's good to see FT treated you right. Looking at your coil pics, to my eye, it looks like they've been over-tightened and the coil was moved often without first loosening the bolt. The compression and friction actually wore a ring into the tabs and the bolt forced the tabs into a conical shape, further reducing the contact area. Of course they'd just become loose again as the thrust-bearing surface wore away, requiring further tightening. Rinse and repeat. Finally, the tabs were forced inwards enough compensating for the wear that they separated.

Maybe you have a habit of flipping the coil up or down to check targets with the heel or tip or for transport/storage. If so, keep the bolt's tension to where it holds position yet still moves easily, or loosen the bolt before making large swings of the coil's position.

I thrash my coils and frequently reposition them by pressing them against the ground or with my foot and haven't lost a tab yet. But, I've seen the same type of wear on our pivoted-arm shop lamps that are moved around a lot with very tight fasteners to hold them in position.

-Ed

I appreciate your thoughts on this. The wear on the coil tabs is definitely from the coil pivoting repeatedly on the lower shaft. I get what you are saying about the nut being very tight and increasing the wear in the area of contact but as you can imagine if I loosen the coil nut then the coil will not stay in position and constantly flip down. The design of how the coi and lower shaft is not ideal because of the limited contact area concentrates the wear in the area you see on my example. Also as a result of the smaller contact area the nut needs to be even tighter to keep the coil from pivoting during use which it still does even with the coil nut as tight as I can get it.

Once my new coil comes I will find 2 teflon washers to fit inside the recessed circle on the lower shaft so that they come flush with the outermost contact point. This will spread the contact area out and reduce the concentration of wear on the coil tabs.

 

[Ed in SoDak]

That might be a good plan if your propsed inner washers are thin enough to not cause you to have to force the stem into the space between the tabs. A stouter washer can be used on the outside of the tabs next to the bolt heads that would distribute the tension across the whole mating faces, instead of just where the bolt bottom's surface area covers it. But the inner hole must match the bolt size closely or it won't help much.

Once those friction clamp arrangements are over-tensioned, they are on the road to ruin. Running with them not as tight will help keep them from flopping so much later on. A good compromise that fixes it not like a brick, but allowing some movement will work best and not need a lot of attention.

I still say FT was very generous in your case. Broken tabs are pretty rare in the FT lines so it's not really a weak design flaw or we'd hear about it more often. We're talking decades of use on thousands of machines with identical setups. They're intended to be able to slip to allow stress or impacts to move the coil instead of breaking. Heavy use may equal heavy wear, whose fault is that?

-Ed