Let's talk about carbide blades and cooling them during overhead work.

[six-point socket II]

Let's assume the pre owner of your house used an ridiculous amount of concrete nails, set with a powder actuated tool, to fasten a wooden substructure to a concrete ceiling.

This one fooled me, because it came right out when I forced the "two by four" down.

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The reality is, with brute force you actually only force the washer and "two by four" over the head of the nail. And sometimes even the washer remains stuck and only the "two by four" gives up eventually.

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If said pre owner then also thought it was a great idea to glue styrofoam to an extensive part of the raw ceiling before installing the substructure - albeit not everywhere - you might start to think about alternatives before using an angle grinder with cut-off wheel that will send sparks flying and create a lot of heat.

To better understand the issue why these concrete nails are not easily pried out (especially in comparison to concrete pins used for electrical and other installations), I put on quite a bit of PPE and forced one out. It required an incredible amount of force and was incredibly dangerous, so don't try this at home - chances the nail breaks and shoots through the room are really high!

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Now the bended tip of this concrete nail was not caused by my efforts to pry it out, it happened while the concrete nail was set. It hit rebar or gravel inside the concrete. This illustrates why some, that did not bend, came out when demolishing the substructure and others remained in place.

My research showed that currently available concrete nails, offered by specialists in this field like Hilti, are mostly hardened to about 49 hrc per corresponding technical documentation.

So that left open the possibility of using carbide blades on either an oscillating multitool or reciprocating saw. Which can be used for materials/metals with a hardness of up to 50 hrc max. . Now "my" nails are from the late sixties to early seventies, and everyone knows: everything was better back then. So  chances are some are hardened to over 50 hrc some might be well below.

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My first 4 tries with the oscillating multitool were a classic fail. I didn't even go all the way up to speed 6, but even at my lowest speed test using speed 2 and plenty of movement while cutting I didn't produce less sparks after a couple of seconds of sawing than an angle grinder and cut-off wheel. Additionally the blade lost (actually burned out) a few teeth. (Now it's not that I hadn't seen this happening before on a different application of the same style blade.)

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I needed cooling. Now I do have coolant in form of aerosol sprays for drilling and other applications - but overhead that would make a great mess all by itself, add the high speed of oscillating saw blade or reciprocating saw blade - not fun.

I knew there were coolants in form of solid, wax like, sticks but I had never used them before. My friend and dealer gladly sold me one from a reliable lubricant manufacturer and I was able to continue my research on how to remove these hardened concrete nails as easy as possible, without creating a big mess with either the coolant or dust/debris from using the angle grinder with cut-off wheel and of course without overheating/ creating a fire hazard in regards to the overuse of styrofoam on my ceiling.

Additionally I ordered a carbide reciprocating saw blade, especially suited for hardened (50 hrc max.) thick-tough metal, with him.

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Details with wax on.

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So the coolant did what it was supposed to do, it kept both blades from overheating and also the remains of the concrete nails cooler than before. Especially when the saw blades where given an insignificant amount of time between cuts, it helped to reduce the sparks to an absolute minimum, sometimes even no sparks at all. Re-applying the coolant every few cuts was smooth and easy because of the solid form and easy to handle applicator.

The oscillating carbide saw blade didn't lose any additional teeth, the reciprocating saw blade didn't lose any teeth to begin with.

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So I think carbide really makes a difference in applications like this, and greatly expands the use of oscillating multitools and reciprocating saws, but the need for cooling is not stressed enough.

Not only to make these more costly blades (compared to regular bi-metal blades bought by 10/25/50 packs) last longer but also for safety (if need be) and an overall more pleasant/easy cutting experience.

Kind regards,
Oliver

 

[Packard]

It may not apply here, but in the metal stamping industry it is a well established fact that some lubricants will erode carbide.

There are special water soluble oils to use with carbide.  They appear to be expensive, but get diluted by as much as 15:1.

I am for years out of that industry, so I can’t point you in any specific direction.

 

[six-point socket II]

That is a highly interesting topic!

A quick search provided this document, where they try to solve it the other way around by making a more corrosion resistant carbide.

->https://www.boehlerit.com/fileadmin/user_upload/PDF/Hartmetall_Carbide.pdf (Page 14)

I will look deeper into this. Thanks for pointing it out!

Kind regards,
Oliver

 

[tsmi243]

That's good info to know, but I think a Dremel and a 5gal bucket would be my weapon of choice here. 

 

[Michael Kellough]

Thanks Oliver!

I tried cutting some thick stainless with a carbide blade similar to the reciprocating blade above without lubricant and the teeth came off.

I left out the most relevant detail, without lubricant the blade got so hot the braze melted and the teeth came off. The blade blank then wore away and and became a valley between the remaining teeth at the ends of the blade.

 

[Laminator]

I've had very limited experience with this kind of nail but I discovered (probably in sheer desperation) that bending back and forth  by hitting with a hammer snaps them off fairly easily. The hardened steel doesn't bend much before breaking.

 

[Ron B]

I would get a 4 1/2" grinder and put a metal cutting disc in it and just cut them off.  You can buy a Harbor F. grinder for less than $20.  So what you are spending on blades that are wearing out, you can buy another tool. 

 

[Cheese]

I would get a 4 1/2" grinder and put a metal cutting disc in it and just cut them off.  You can buy a Harbor F. grinder for less than $20. 

+1...

The small carbide blades are nice to use when cutting into real plaster walls, the blades last forever.

 

[hdv]

I think Oliver wrote that he hesitated to do just that because he didn't want to create too many sparks or too much heat in that room with all the styrofoam around...

 

[usernumber1]

a grinder is a more proper tool, this is a bit silly. protect your work area with sheathing or simply cover the surfaces you don't want the sparks to get to.

 

[MikeGE]

I would get a 4 1/2" grinder and put a metal cutting disc in it and just cut them off.  You can buy a Harbor F. grinder for less than $20.  So what you are spending on blades that are wearing out, you can buy another tool.

It might not be obvious, but Oliver lives in Germany.  There are no Harbor Freight stores on this side of the Atlantic Ocean and no place to buy disposable $20 grinders.

 

[six-point socket II]

I've had very limited experience with this kind of nail but I discovered (probably in sheer desperation) that bending back and forth  by hitting with a hammer snaps them off fairly easily. The hardened steel doesn't bend much before breaking.

Yes and you send them shooting through the room. And if the nail does not break exactly level with the ceiling, you're still stuck with a piece sticking out that needs to be removed.

I would get a 4 1/2" grinder and put a metal cutting disc in it and just cut them off.  You can buy a Harbor F. grinder for less than $20.  So what you are spending on blades that are wearing out, you can buy another tool.

Sadly I can't go into a Harbor Freight, but I get what you mean. Good thing for me, I do have an angle grinder and a large selection of different cut-off wheels/ consumables for it.

a grinder is a more proper tool, this is a bit silly. protect your work area with sheathing or simply cover the surfaces you don't want the sparks to get to.

I'd agree that the angle grinder would have been the more convenient tool. And if that was purely a concrete ceiling I wouldn't have hesitated to use mine. But with about 14 of 17 square meters covered in styrofoam, nails poking out basically everywhere - I'd love to learn the proper way of sheathing/covering a work area like that. And how that will be quicker/ more convenient than what I did. Maybe I am silly after all. Who knows?

And before someone asks, the styrofoam is glued. Fully glued over the whole area.

Kind regards,
Oliver

 

[tsmi243]

Here's the best option, but might not be available in Europe yet

 

[six-point socket II]

That is actually a great idea. I was wondering what you meant by using a bucket. But sure, cut it, put grinder through, it will contain the sparks & minimizes the area exposed to them.

Learn something new everyday. Thank you!

Kind regards,
Oliver

 

[usernumber1]

LOL  that's good BKT 400 REBQ

 

[rst]

One of the new Milwaukee vacuum accessories, Milwaukee AIR-TIP Dust Collector 49-90-2022, is a wide funnel shaped attachment that suctions to the wall and vacs dust or grinding debris.

 

[Michael Kellough]

One of the new Milwaukee vacuum accessories, Milwaukee AIR-TIP Dust Collector 49-90-2022, is a wide funnel shaped attachment that suctions to the wall and vacs dust or grinding debris.

And sparks?

 

[Banana]

This is a good post.  I have no idea why I've never tried a cutting oil on my metal cutting oscillating blades (or a wax etc.).  We do so for drill bits to greatly speed the cut and keep bits sharper longer so why not oscillating blades.

 

[Crazyraceguy]

Thanks Oliver!

I tried cutting some thick stainless with a carbide blade similar to the reciprocating blade above without lubricant and the teeth came off.

I left out the most relevant detail, without lubricant the blade got so hot the braze melted and the teeth came off. The blade blank then wore away and and became a valley between the remaining teeth at the ends of the blade.

Stainless steel can be quite a tricky thing to cut or drill. The nickel and other elements of the alloy can make it more gummy and stringy, which are tough enough to deal with, it also holds the heat which is damaging to the tools. Double whammy.
Carbide can take the heat better than high-speed steel, but chip-welding is a concern too. That's where the lubrication helps. Cobalt drill bits work well for drilling it.

Breaking the nails, may damage the surrounding concrete, since it was technically already violated by the powder gun in the first place.

 

[six-point socket II]

I found another nail in the part of the ceiling with the styrofoam. I took the angle grinder to it. Exactly what I did not want to happen did happen - albeit in a controlled environment with safety measures in place and precautions taken.

I'm not posting this for the sake of an argument. I won't have it. I have zero interest in that and I respect everyones opinion and personal choice on how to work/ get something done.

Nail cut off with the angle grinder. As expected quite a bit of the styrofoam melted/burned. The fumes, even after one cut, were nauseating. Should not have removed my PPE so quickly.

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But the really dangerous part is this:

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As you can see now, even though it was just one cut, the heat/burn (whatever you wanna call it) had already traveled further than the easily visually confirmed & directly impacted area. It traveled below the surface of whatever the pre-owner had smeared on the styrofoam and no bucket is going to contain this if it happens.

Kind regards,
Oliver