Points heel issue

[groily]

Does this act as an insulator?

Luckily no. The opening point is earthed on the brass cb units. The dimpled button just sits in the register and stops metal-to-metal contact as TT said. (It can help reduce wobble on the pivot if there is modest wear.)
If the clip blade is sloppy, it will slide out of position and the button will eventually fall out.
The clip is held by a simple pin. If it's loose, a fractionally bigger one - or for belt and braces, tap the hole say 6BA and use a small screw to retain it. It won't interfere with the secondary earth brush if there's one fitted up the rear face.
A button can be made from anything really, I use a bit of 'klingerite' or similar, a gasket hole-punch of appropriate size and then a pointy punch to create the dimple.

[jhg1958]

I have found that emailing the photo to myself works well. My email has an option for image size. I just choose small works every time. A bit of a faf but it works

[Black Sheep]

The tip of a syringe or the bit you cut off the end of a 3in1 oil tin or suchlike is a good substitute.

[BSA500]

I have sorted the photo sizing problem 

[BSA500]

Just to prove it

[BSA500]

I know could do better working on it

[BSA500]

Looks like  the plastic bit has gone walkabout.I will have to remove the points plate to make sure it's not wedged anywhere it shouldn't be

[BSA500]

So if the points are in fact opening and closing and the plugs/leads/pick ups and the mag had a full Andrew rebuild 500 miles ago why have I lost sparks??

[Triton Thrasher]

So if the points are in fact opening and closing and the plugs/leads/pick ups and the mag had a full Andrew rebuild 500 miles ago why have I lost sparks??

Is the insulator button now in place?

[BSA500]

Can't find it it has evapourated

[BSA500]

I suspect it escaped when I took the end cap off. I think the clip needs to be bent in a little as well to make better contact when I replace the button

[Rex]

So if the points are in fact opening and closing and the plugs/leads/pick ups and the mag had a full Andrew rebuild 500 miles ago why have I lost sparks??

Is the insulator button now in place?

So is it an insulator or just there to locate the arm on the dimple?

[JulianS]

Not an insulator, both the retaining spring and the moving contact are earthed to the mag body so just to hold the moving point in position.

With the original Lucas points the little nylon button is a tight press fit in the moving points and can be quite  hard to press it back in. The common pattern replacement points (which fit both anticlock and clock mags) with plastic heel  have a black button, larger diameter than the nylon one.

[Triton Thrasher]

Not an insulator, both the retaining spring and the moving contact are earthed to the mag body so just to hold the moving point in position.

I do get confused, especially with the steel plate being so different from the brass plate.

[BSA500]

Which adds to the confusion as to where have the sparks gone???