Grounding lug connection in Painted Chassis

[Platefire]

On a chassis that I've painted before adding all the components, I've been sanding/scraping the paint off to the bare metal around the hole where a grounding bolt goes through the chassis. Somehow I feel better about that but does that really help or necessary? Plate

[toomanyslurpees]

We do it to grounds on aircraft, so it can't be a bad idea...

[stingray_65]

I drill and tap the hole and thread a brass screw through it. (from the outside of the chassis)

The screw then always has good electrical contact with the chassis and its handy to have a lug that doesn't need tools on both sides of the chassis.

I also use a star washer under my first terminal just to bite into the chassis a bit.

This is on an aluminum chassis. steel chassis aren't thick enough usually to even get a single threat to bite, but the brass screw could be soldered to a steel chassis.

Ray

[LooseChange]

I use a Dremel grinder around every chassis ground  connection. I'll use it around the pots too. Just to make sure they are shielded with the chassis.

[Fresh_Start]

I also use a star washer under my first terminal just to bite into the chassis a bit.

+1 on this practice. 

My order from bottom to top is bolthead/lockwasher/chassis/lockwasher/ring terminal or solder tab/Keps nut.  That way you have lockwashers biting into the chassis on both sides and biting into the ring terminal on both sides.  Overkill?  Sure, but how much do 2 extra lockwashers cost?

Cheers,

Chip

[rzenc]

I use a Dremel grinder around every chassis ground  connection. I'll use it around the pots too. Just to make sure they are shielded with the chassis.

+1. I use powder coating on aluminum chassis and grind both side around ground lugs.

My order from bottom to top is bolthead/lockwasher/chassis/lockwasher/ring terminal or solder tab/Keps nut.  That way you have lockwashers biting into the chassis on both sides and biting into the ring terminal on both sides.  Overkill?  Sure, but how much do 2 extra lockwashers cost?

Cheers,

Chip

I read about it on a Philips DYI hifi book. It makes a really solid ground connection. Althought I add a second nut to ensure it won't become loose due to vibration. I had a 5E3 making a bit of hum and it turned out to be H.T.C.T. loose ground. Fixed it and installed a second nut just to be sure..

Best Regards

Rzenc

[Platefire]

  Thanks for sharing your ground lug methodology! I have been doing a main star ground kind of thing with a 1/4" steel bolt and single grount term. The head of the bolt goes on outside of chassis with a locknut. On inside of chassis star washer against chassis, then ground terminal and lastly the nut. I also use a dremel to get down to bare metal right in the washer contact area.
  On this type of ground one problem I've been having is with all the different gounds coming into this main ground terminal is getting it hot enough to melt the solder. I've been thinking it might be a good idea to try to solder it without the bolt  attached to chassis? Plate 

[LooseChange]

    On this type of ground one problem I've been having is with all the different gounds coming into this main ground terminal is getting it hot enough to melt the solder. I've been thinking it might be a good idea to try to solder it without the bolt  attached to chassis? Plate 

It gets hot??? Never noticed any heat at a ground point.

[Merlin]

On this type of ground one problem I've been having is with all the different gounds coming into this main ground terminal is getting it hot enough to melt the solder.

Holy crap, that is NOT normal!

[RicharD]

I think what Plate is saying is:

The 1/4" ground post is acting like a heat sink and he can't get his iron hot enough to land all the grounds to a common point.   Sounds like he is doing a star to a singular point and there is too much mass for a poor little old Weller to keep up with.  I don't think he's turning the amp on and the ground point is melting.

Personally, I grind every chassis ground point regardless of paint or not.  I've built a quiet amp using only the chassis as the ground path.  I soldered every bolt too.

-Richard

[Fresh_Start]

Plate, if you're trying to solder to a ring terminal, you have to do it unattached to any bolt, etc.  Just heating up the ring terminal enough takes a little while.  One of those things to hold parts in place with alligator clamps comes in handy (or foreceps).

These "lockwasher terminal lugs" from Keystone work well.  You can solder to them when they're already bolted to the chassis if you want to, but it's still easier to get a good solder joint by doing it before bolting to the chassis.
http://www.keyelco.com/pdfs/M55p50.pdf

However, IME when you start trying to solder multiple leads (3 or more) to a single point it's better to use multiple lugs (whether you're using ring terminals or these solder lugs).  

Ring terminals do give you a much better mechanical connection for the ground point because you can crush the sleeve onto the wire(s) inside the sleeve.  A good reason to always use a ring terminal for the safety ground.

HTH

Chip

[Platefire]

Yes I have been using a ring terminal and I was talking about getting the heat up hot enough with the bolt tightened up in chassis. I crush the ring terminal after all the grounds are inserted in the ring to make the best mechanical connection and then solder using my Weller gun 8200N 100/140 watts. At the hardest I finally get it to melt down. Pretty tedious chore. Looks like the answer is simple, just solder it before I bold it down! The chassis and bolt has been absorbing to much of the heat. I'll have to come up with some kind of holder to hold it in pace when I solder it. Plate

[Tiny_Daddy]

I leave the nut loose until all the grounds have been soldered to the terminal or lug.