Best bit for rosette weld holes

Lizer

Lizer

Mad Scientist
I read that a step bit is best for making holes for plug welds because it doesn’t leave a bur. I am making 1/4” holes and went out and bought a set of Irwin titanium US-made step bits. Only to find they leave an ENORMOUS bur. Much larger than a standard bit.

So what do you use ?
 
A punch type tool is the only thing that doesn't leave a burr. I have a Dent-Fix 1/4" punch that I like. I have resigned myself though to just cleaning any burrs before welding if I'm using a bit.
 
If you can access the backside easily, using a Unibit like you have works well if after you drill the hole flip the part and use the unibit on the backside where the burr is. It will deburr the hole nicely. A small amount of burr is acceptable as it will melt when you plug weld.
 
I have a Whitney punch that makes very clean holes, and as an added bonus it also makes filler plugs for welding up holes.
I don't get much of a bur with my step bits if any, what gauge material are you drilling?
 
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This is 18 gauge metal. It’s to a new bed floor For a truck I am working on. The bed floor is on stands so I have complete access to everything on it. It is just the floor and no sides.

I have a metal hole punch from Harbor freight which makes fast clean holes, but my problem is they are too small and I cannot get good plug welds with them.
 
Burrs happen on drilled metal for several reasons, dull drill bit, drilling at too high or low of a rpm, not drilling perfectly vertical or horizontal. Though I can't recommend a good drill bit, I can however recommend a de-burring tool that makes short work of de-burring.

I have this de-burring tool by AFA Tooling.
20220917_083508.jpg


Here's a link to purchase one.

Here's a video on how to use a de-burring tool.
 
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The good old Roper Whitney set has a 9/32, which is usually enough for 18ga. if the welder is set a bit on the hot side. Typically the welder should be set hotter for a plug weld than for a continuous bead, maybe that is common knowledge but I thought I'd throw it out there.

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Vintage Roper Whitney No. 5 Jr. Hand Punch Set Complete w/ Dies Case Made in USA | eBay

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I'm all for a bargain, but I wouldn't buy a used Whitney punch unless I could hold it in my hands prior to purchase. The list price of the kit with the full range of punches and dies is $95. If you buy used and unseen, and it happens to need new dies, those are $67 for the set, or 20 bucks each.

I spent a good portion of my adult life in a sheet metal shop, and the average person can't even imagine all the creative ways some guys can dream up to abuse a Whitney. Other men would have one they'd used for 20 years or more, and it would still work just like a new one.
 
@metlmunchr that's great advice. I do not have a lot of experience with the way other guys treat tools, other than I've had more than a few "grow legs" over the years.
 
Lizer said:
This is 18 gauge metal. It’s to a new bed floor For a truck I am working on. The bed floor is on stands so I have complete access to everything on it. It is just the floor and no sides.

I have a metal hole punch from Harbor freight which makes fast clean holes, but my problem is they are too small and I cannot get good plug welds with them.
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What size hole does your HF punch make?
 
Oh, 3/16" is definitely too small. A decent punch like the Roper Whitney is a worthwhile investment, imo. Big time saver and it makes a very clean, minimal distortion hole. The max size in the #5 set is 9/64", just barely shy of the 5/16" or 8mm that is usually recommended for 18ga.
 
You know Don, that is probably a good option, I guess I got turned against the air punchers because I used the you-know-what out of them and I wore a couple of them out. Just ended up deciding to go old school and avoid the breakage. I guess that isn't a problem for a hobbyist, though...
 
crashtech said:
You know Don, that is probably a good option, I guess I got turned against the air punchers because I used the you-know-what out of them and I wore a couple of them out. Just ended up deciding to go old school and avoid the breakage. I guess that isn't a problem for a hobbyist, though...
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When you only build a couple of cars a year one of those punches can last a backyard hack many years. :D

Don
 
@crashtech @dhutton01 that punch is the same thing I have from HF...combination punch and flanger and it works well (and will last me a long time too because I hardly use it) except the hole is just so small and not sure why they'd put such a small hole on it; smaller than the 5/16" on that Astro. One of the things I've not liked about the punch, and I see the Astro suffers from the same affliction is it doesn't have a very deep neck, meaning the hole is punched close to the edge of the panel, maybe within 1/8-3/16". If I have a half inch flange that needs to be plug welded I've always tried to put the hole right in the middle, but perhaps closer to the edge is actually better?

I also was not aware that 5/16" is what I needed to be using for 18g. I've got all my holes reamed out to 1/4" but apparently I need to step up another size.
 
If it's structural 5/16 would be the minimum. Unibody frame rails, hinge pillars, stuff like that. Quarte panel skin you can use smaller.
A good rule of thumb is to replace a spot weld with a plug weld of equal or greater size. It gets harder to do a nice plug the larger the hole gets. So it's good to keep the hole no larger than necessary.
 
Chris_Hamilton said:
If it's structural 5/16 would be the minimum. Unibody frame rails, hinge pillars, stuff like that. Quarte panel skin you can use smaller.
A good rule of thumb is to replace a spot weld with a plug weld of equal or greater size. It gets harder to do a nice plug the larger the hole gets. So it's good to keep the hole no larger than necessary.
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This would be welding a truck bed floor onto the bed sides (1970 F250), and the bed front to both the bed floor and bed sides. So...fairly structural lest my uncle wants his truck bed to fall apart while he's driving down the road :)

I've seen how the chevy beds bolt together which is complete crap, since I have to weld mine together.
 
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