Spot welding tips question

[4dabird]

Hello, long time since I've been on here. I am doing a rotisserie restoration on a 1969 Firebird convertible, and I recently purchased a spot welder from Telwin. It's digital and adjustable depending on metal thickness and has a nice feature to burn thru e-coat. It works very well and I like it alot.

The issue is the solid copper tips do not replicate the factory settings as I had hoped. It leaves a round spot which is smaller than what a factory setting would look like.

My question is I am thinking about grinding the tip points with a flat area to create a larger "dimple" perhaps 1/8" which is more tipical of a factory spot weld.

My concern is the weld amperage would be lower with a larger surface area and also if the integrity would be comprimised - I can adjust the settings for thicker metal, and also for longer duration to compensate, but I was wondering if anyone here has some experience with this?

Thanks,
Markq

 

[Robotstar5]

We normally ran about 5mm diameter tips (sorry not sure what that is in Imperial) for industrial automotive spot welders, you will need more current if you increase the tip diameter and may be limited by what a "hobby" welder (or your power supply) can provide.
A good weld will "pull a slug" which means when you peel the 2 layers apart (using a chisel) a circular piece should tear out of one panel and be left behind on the other.

 

[4dabird]

Ok, thank you for the info. 5mm = approx. 3/16" (0.1875"). That is the same size as a plug weld hole so it makes sense. My spot welder has 6.3kA and as mentioned, i can adjust the current up or down to have more or less "dwell" time. The welder is better than a "hobbyist" spot welder and made in Italy not China. I am familiar with the tests performed to insure a good weld and will be sure to test for what you mentioned. The copper electrode has a ball rounded tip that I can grind a 5mm flat tip to, and if this doesn't work to my satisfaction, the other side will be left as new. Here is the welder from their website.

Microprocessor controlled, spot welding machine. It implements a new Fuzzy logic control system that simplifies its use and increases the spot welding quality. Suitable for spot welding of sheets with maximum thickness 2+2mm. Characteristics: automatic regulation of the spot welding current and time according to the material thickness * choice between continuous and pulse operation (suitable for sheets with high yield points - high stress) * arms pressure adjustable from 40 kg to 120 kg (with arms L= 120 mm) * hand grip made out of thermic isolating material * thermal protection.

 

[Robotstar5]

Sorry, didn't mean to knock your welder I'm used to working with 50kA+ units

You may find some useful info/downloads here

 

[4dabird]

no worries, thanks for the info and those tips look like what I want to replicate on the ones I have.

 

[Jim Davey]

You may well struggle if you increase the surface area of your tips. The energy required to successfully weld with a larger surface area will increase exponentially as tip diameter increases. You may have to pull the trigger repeatedly in one spot to get the desired heat to weld which will locally add a lot more heat to the metal not to mention your spot welder's arms and tips! I wouldn't get too hung up about trying to replicate the look of welds produced with an industrial machine that can put an 8mm diameter spot on 2mm to 2mm sheet all day without getting warm with a 240 volt air cooled hobby spot welder. You will just end up wearing out your perfectly good welder and getting weaker spots into the bargain.