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babelloyd
08-11-2010, 01:26 AM
Hi folks!

In the Kyoto Cruiser plans, it says to use a "fine grit" flap disc to finish welds. At Princess Auto (which seems to be ***** for many Edmontonian hackers), the finest 5" flap disc they have is 80 grit. Should I go finer? 120? 240? Where can I find such discs in Canada?

I'm just assembling the basic frame right now. I'm having a lot of trouble "finishing" the welds. Every time I do, I expose a hole that would not have been exposed if I hadn't applied the angle grinder. After many cycles of welding then grinding then flap-disc grinding, I'm afraid I'll wear through the unwelded tube and render the whole tube unusable, putting me back at square 1. I don't know if I'm welding poorly, or if I'm grinding poorly, or if the welder sucks. The welds come out in globules because the welder sputters. Thus the welds are a lunar landscape of globs, not a smooth river or "bead". I'm considering just leaving the welds unfinished in the interest of keeping the welds strong and intact.

PeterT
08-11-2010, 02:22 AM
Babelloyd,

The smaller the number the courser the grit eg 60 grit is extremely course, and 1200 grit is almost smooth in comparision. The number refers to the amount of grit per inch.

If you are welding with a faulty earth, then you will get bird poo welding. If you get Bird poo welding, it is actually better to clean all the weld off, and to start again.

With your welding check that you have a good earth circuit, your electrode isnt too far from the joint, and that the current setting isn't too low, and then start again and practise, practise, practise on some scraps of metal till you get welding runs every time you make a start.

PeterT

babelloyd
08-11-2010, 04:23 AM
Hi PeterT,

Thanks for your reply.

I know that 60 is coarser than 80 and so on. The guy at Princess Auto explained that to me too when I asked if they had anything finer than 80. I understand how "grit" works. My question is what does "fine" refer to in the Kyoto Cruiser plan? Does "fine" mean 80? Or 120? Or 240? Is 80 fine enough? Is 240 too fine? That is what I don't know.

I didn't know that one should just start over if one gets bird poo weeding. It's far too late for me to do that now. Anyway, I don't know if I have much choice, because with the welder that's available to me, bird poo may be all I get. It's a 120V flux-cored MIG welder with 0.03" wire.

However, I didn't know that it matters where I put the clamp. So I should put the clamp right near the joint I'm welding? I'll try that.

That reminds me of another question: When there are no open tube ends available, I have no where to put the clamp, because the 1.5" tubing is too big for the clamp. Even when there is an open end available, it's 68" away from the joint I'm welding. So I have to clamp a separate, larger clamp to the tube, then clamp the welder clamp to that clamp. That's the best I can come up with.

Thanks tons!

imamedik
08-11-2010, 07:05 AM
That reminds me of another question: When there are no open tube ends available, I have no where to put the clamp, because the 1.5" tubing is too big for the clamp. Even when there is an open end available, it's 68" away from the joint I'm welding. So I have to clamp a separate, larger clamp to the tube, then clamp the welder clamp to that clamp. That's the best I can come up with.

Thanks tons!

Babelloyd, you can use a C clamp attached close to the joint you are welding, then place the clamp from your welder to it, just make sure you clean some of the paint of of the clamp so you are on bare metal. :jester:

babelloyd
08-11-2010, 07:09 AM
Sweet! Thanks!

dementedDave
08-12-2010, 01:45 AM
check your wire feed rate if you are getting crap welding.

usually there is chart inside the welder cover to get you close, but you will need to dial it in

listen for a nice even sound, some say it sounds like bacon frying.

Early on I would have someone else weld while I monkeyed with the feed rate, and it was easier to hear when the feed was correct.

if the feed is too fast it tends to push the gun away, and when the wire gets long the voltage drops and so does the heat. Too slow of a feed and the wire is not making contact.

You should be able to keep the gun the same distance from the work all the time, but it takes a little practice to know what you are looking and listening for.

Dave

graucho
08-12-2010, 09:09 AM
My opinion only, flap the heck out of it with the 80 grit then finish it off with 240 grit wet
hand sanding. It's hard to even penetrate the steel with the 80 flapper wheels i've used.
Maybe i've used less quality flappers?

babelloyd
08-12-2010, 11:46 AM
Excellent feedback, folks! Thanks so much.

I met a professional welder through the club of which I am a member (and which hosts the space I'm welding in and the the welder itself). He said he'd help me on Sunday.

tree
08-12-2010, 11:48 AM
Maybe i've used less quality flappers?

There's probably something to that. The Harbor Freight consumables are CRAP. The cutoff wheels last 1/4 as long as the De Walt wheels I've used. Their flap disks last noticeably less time as well. Shop around and see what you can find.