Hey guys. Can you help me determine if I can just buy a simple circular cutting bit? Or help me source a more appropriate bit?
I bought my wife a car. Because of her work supplies, I need to install cargo panels in the trunk area so her work supplies don’t tear up the back of the vehicle.
The dealer instructions say you need to use a 6 mm rotabroach. From what I can tell, it’s really just a tiny hole cutting bit, but you use this instead of a twist drill for a cleaner cut through the back of the seats and side panels.
Can you recommend a purchase? I have to drill 25 holes…I assume a hand drill with a steady hand a drill block is sufficient, but not really certain what bit to buy.
In my experience a “rotabroach” is designed for non-circular holes with a nutating cutter.
It seems the industry also defines a circular milling type cutter as a roatabroach.
The big advantage of these in your application is likely to be a truly round hole regardless of material thickness. Conventional twist drill holes in thin sheet metal will not be truly round. Whether that matters in you application is hard to say. It might be critical, or might just be a fussy engineer.
What kind of car, and what kind of fasteners are being used?
@TBJK Tim, thanks for letting me know. By chance are they hollow bits? The rotabroach bits seem like precision hole saw bits. And it is rivets. It is the first time I’m handling rivets, so that should be fun…
No they are a cross between a unibit and drill bit. They make pretty decent holes.
It looks like you can get the mandrel and 6mm rotobroach for less than about 50 bucks. Personally if it were me, I’d try the vortex and see how it looks. But hey that’s just me.
I suspect the reason they may have specified a rotabroach is the fact that there may not be a lot of depth available in the top layer of sheet metal.
Unibody construction results in many closely spaced sheet metal layers and the point you need a hole may have another panel a few mm behind it. That panel may provide the only barrier to the outside and cause leaks and whistles.
$750 labor only, or parts and labor? If only labor, I’m betting it’s a no-bid because many mechanics don’t like doing interior trim jobs, and it may be that they know the book is painfully optimistic. Or it may be their shop hour rate is $250/hr.
There are lots of truly impressive horror stories on the interiors of cars people bring in for service. Full Hazmat gear isn’t enough protection. That and pistols, ammmo, drugs, biohazards, chemicals (identified and not.)
I am looking forward to trying out this bit. When I’m done using it, I’ll probably pair it up against my cheap home saw bit and a twist bit and see if I can feel any difference
Looking further online, I noticed other companies are calling these annular cutters. I came across the Milwaukee version on Northern tool
So big wonderment on my end, how does one “center punch” for keeping these on target? The annular I’m accustomed to seeing usually go into larger machines, typically magnetic or otherwise robustly anchored “presses”, and one carefully measures it all out. If this uses a handheld drill motor, in the back hatch of a car, I’d imaging getting the 'ole in exactly the right place, without the bit going on walkabout, shall prove quite challenging. Earnest to hear about your experience/solution
The mandrels have a spring loaded pin in the center. The one I used required more than a little force to hold in place. A center punch dimple was enough to get it started. Once you were cutting it was no longer needed until it punched the slug.
That helps, some. It shows using a 3mm drill bit for a pilot hole first, then the 6mm rotabroach. It doesn’t really touch on the ‘how to hold the rotabroach, the advertising copy for which loudly proclaims no zero-speed center material removal and therefore superior to twist drilling, centered’. Curious…
Hm.
The Yootoobs I dug up DO show the centering pin (eventually - I have no idea why that’s such a secret! but it seems like an afterthought/byproduct of showing off other stuff) but nothing about it being spring loaded… Interesting. Thank you!
