Cordless Angle Grinder for chasing stone wall? Plus can I use a mortar rake with stone?

[Oxbow16]

Hi all

 

I've got some lead work coming up and will need to chase the stone wall for the flashing.  I'm planning to get an angle grinder and use a 10mm thick blade like this:

 

https://www.amazon.co.uk/gp/product/B08CY465GJ/ref=ewc_pr_img_2?smid=A213SFYA0CUE59&psc=1

 

Or 

 

https://www.amazon.co.uk/gp/product/B08CY32NQ4/ref=ewc_pr_img_1?smid=A213SFYA0CUE59&psc=1

 

(or the 125mm equivalents if I get a larger grinder).  

 

My question is will a cordless angle grinder be powerful enough or am I better getting a corded model?  If going cordless, my preference would be DeWalt 18V as I've some other gear of the same.  

 

One other question....  If once I've cut the chase it isn't quite deep enough and I can't get deeper with the grinder and disc, could I use this inside the chase to make it a little deeper?  Just to be clear, the chase will be a straight line (parallel to the roof below), and will be cut through both mortar (lime) and the stone itself, as the wall is random stone.  

 

https://www.screwfix.com/p/mortar-rake-8mm-x-40mm/31307

 

Any help most appreciated.

Cheers

[SteamyTea]

8 hours ago, Oxbow16 said:

10mm thick blade

More like 2mm thick.

 

Lidl have some cordless angle grinders.

 

I would go corded, a small one.

[Conor]

Cordless grinders are fantastic, I love my Makita, but for that job you'll be replacing batteries every ~20mins. Get a corded 5". Cordless still worth having and might be useful for awkward bits in and around eaves etc.

[markc]

+1 on the above, I love my cordless tools but angle grinder just doesn’t have the humff or battery life for anything other than little quick jobs, plus battery grinders stop fast and heavy discs can (do) spin themselves off and disappear into the sunset at the most inconvenient times

[Oxbow16]

Thank you very much for the replies, that's really helpful.  

 

Anyone have any thoughts on using the mortar rake to add extra depth (as per OP)?  

 

1 hour ago, SteamyTea said:

More like 2mm thick.

 

I'm not sure what you mean tbh?  I'm pretty sure the discs in my links are 10mm thick.  

 

 

Thanks again

[markc]

17 minutes ago, Oxbow16 said:

Thank you very much for the replies, that's really helpful.  

 

Anyone have any thoughts on using the mortar rake to add extra depth (as per OP)?  

 

 

I'm not sure what you mean tbh?  I'm pretty sure the discs in my links are 10mm thick.  

 

 

Thanks again

10mm discs are horrendous to use, much easier to use a standard (much lower cost) disc and do a few passes. Easy to make deeper by scraping a chisel or similar in the groove, if the old mortar doesn’t crumble and come out easily it doesn’t need replacing and better left holding the bricks

[Thorfun]

if purchasing specifically for chasing walls have you considered a double disc jobby?

 

https://www.amazon.co.uk/EINHELL-ITALIA-TH-MA-1300-Mauernutfräse/dp/B00IYEEXR0/ref=asc_df_B00IYEEXR0/?tag=googshopuk-21&linkCode=df0&hvadid=309904160813&hvpos=&hvnetw=g&hvrand=17036672168689129604&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1007850&hvtargid=pla-421346012760&psc=1&th=1&psc=1

 

2 lines in one go is surely better than one?

[Oxbow16]

1 hour ago, markc said:

10mm discs are horrendous to use, much easier to use a standard (much lower cost) disc and do a few passes. Easy to make deeper by scraping a chisel or similar in the groove, if the old mortar doesn’t crumble and come out easily it doesn’t need replacing and better left holding the bricks

 

I'm not replacing mortar, I'm cutting a chase to fit lead flashing.  And it's a "random rubble" stone wall, so no bricks.  The chase will be a straight run and so will go through mortar in places (lime), and the stone itself in other places.  

 

For the same reason, I'm not sure scraping a chisel would work, especially when trying to get more depth in the chase where the cut is into stone.  

 

I have been considering using a thin blade and and making two cuts.  In fact, that's what I thought I HAD to do before I found the thicker blades.  But because of the nature of the stone wall with it's bumpy undulations, and because the work will be in an awkward place, I was concerned about how parallel I will be able to get the two cuts.  Hence why I thought a single cut with a thicker blade made more sense.  Having never used one though, I take on board what you're saying about them being horrendous to use!  

 

 

@Thorfun - thanks for the suggestion and the link.  I had considered one of those, and perhaps I should again.  What put me off was the fact I'm only likely to need it this one time.  Whereas an angle grinder I'm sure I'll find uses for in the future.  The 30mm channel depth is a bit less than what I'd prefer, although perhaps other makes/models would offer more?  And I have read mixed opinions on these chasing tools, with some folk saying they prefer to use an angle grinder.  The bottom plate and side of the machine could potentially make keeping the straight cut easier (using a piece of wood attached to the wall as a guide).   But I'm not sure in practice if that would work on a non-flat stone wall...  Food for thought though.

 

Many thanks

 

 

[Thorfun]

27 minutes ago, Oxbow16 said:

@Thorfun - thanks for the suggestion and the link.  I had considered one of those, and perhaps I should again.  What put me off was the fact I'm only likely to need it this one time.  Whereas an angle grinder I'm sure I'll find uses for in the future.  The 30mm channel depth is a bit less than what I'd prefer, although perhaps other makes/models would offer more?  And I have read mixed opinions on these chasing tools, with some folk saying they prefer to use an angle grinder.  The bottom plate and side of the machine could potentially make keeping the straight cut easier (using a piece of wood attached to the wall as a guide).   But I'm not sure in practice if that would work on a non-flat stone wall...  Food for thought though.

don't take that link as gospel! it was just the first one i found from Google. i think you might be able remove one of the discs so can use as a standard angle grinder in the future if required. sounds like you have a lot of research to do. 😉

[Dave Jones]

standard diamond blade is fine for lead, mortar is soft as buggery and smaller blade gives you a bit of wiggle room so as not to nick the bricks.

 

cordless much safer, you dont want extension leads on the roof really.

[Oxbow16]

Thanks, but as I've said a couple of times, it's not brick, it's a solid stone wall.  And because the chase and flashing will be straight rather than stepped, the cut will be into the lime mortar in some places, and the stone itself in others.  

 

Interesting the different opinions on whether the cordless will have enough power or not...  

[Dave Jones]

cordless is ok if you have other tools in the range to share the batteries. I have dewalt kit and the 54v battery is more powerfull than the mains, amazing. But a bit pricy if you only have 1 or 2 tools.

[Oxbow16]

Probably a bit overkill to share with my cordless drill and impact driver set 

 

And by the sounds of it using the grinder with 18V 3ah batteries won't bring much joy or success?  

 

Many thanks

[SteamyTea]

I have a selection of angle grinders, one small cordless, a small one, a medium one with speed control and a very large one.

The big boy scares the hell out of me when slicing concrete slabs up.

The little one, 700 W, is very easy to use as it can be locked on, means one handed usage.

 

But don't try using one up a ladder, when a cutting disc grabs, there is a lot of inertia in the disk, and even 700W is like pushing 700 kg a metre, in one second.

So if you weigh 100 kg, you will have moved over a metre before you even have time to realise what has happened.

 

Edited August 29, 2023 by SteamyTea

[Oxbow16]

Thanks for the warning  

 

An update... I sent the manufacturer an email RE the two discs linked in the OP... They said they think that the Turbo version (second link) would be better suited than the segmented (first link). And also, that although it is hard to tell, I may need 4-5 discs for the 7-8 metres I need to do. Does that sound right?

 

Cheers

[SteamyTea]

26 minutes ago, Oxbow16 said:

And also, that although it is hard to tell, I may need 4-5 discs for the 7-8 metres I need to do

Seems a lot.

I have cut many meters of stone and slate with a single disk.

 

27 minutes ago, Oxbow16 said:

better suited than the segmented

I have used both and never noticed any difference.

 

Did you check that it is really 10mm thick and that is not one of the spindle sizes?

[Oxbow16]

12 minutes ago, SteamyTea said:

Did you check that it is really 10mm thick and that is not one of the spindle sizes?

 

It's what it says.  But to be certain I will just double check with the manufacturer...  

 

Cheers

[SteamyTea]

I found a fourth one.

Way too much choice.

 

[joe90]

5 hours ago, Oxbow16 said:

I may need 4-5 discs for the 7-8 metres I need to do. Does that sound right?

 

NO, I have the same diamond blade I have been using for years (not full time) cutting stone, concrete and even steel!!!

[Oxbow16]

4 hours ago, SteamyTea said:

I found a fourth one.

Way too much choice.

 

Certainly more choice than I currently have   

 

 

4 hours ago, joe90 said:

 

NO, I have the same diamond blade I have been using for years (not full time) cutting stone, concrete and even steel!!!

 

Interesting...  Can you see or do you remember which disc that is that you have?  

 

 

Cheers

[TonyT]

Watch out for old blades they have a use by date on the blade😁

[joe90]

1 hour ago, Oxbow16 said:

Can you see or do you remember which disc that is that you have?  

No, all marks are rubbed off, not an expensive one, medium price diamond blade.

[Gus Potter]

On 28/08/2023 at 23:41, Oxbow16 said:

One other question....  If once I've cut the chase it isn't quite deep enough and I can't get deeper with the grinder and disc, could I use this inside the chase to make it a little deeper?  Just to be clear, the chase will be a straight line (parallel to the roof below), and will be cut through both mortar (lime) and the stone itself, as the wall is random stone.  

Lots of good points regarding type of grinder but preparation is the key to a good job.

 

I used to be a builder before I got into SE stuff so here is how I would cut a raggle in a nice stone wall that is compliant and is going to look good and professional.

 

Stone walls often have a tendency to disintegrate when you start to cut chase for lead, but you want your lead work to look good and not leak.

 

I would start by fixing a level bit of 100 x 25mm thick timber to the wall using screws and rawl plugs where I want the top of my chase to be. Next I favour a 9" grinder with a standard diamond disc, I think the kerf width is about 2.0 - 3.0 mm.. the kerf is the width of slot that the disc cuts. The 9" grinder has more power but is also much more controllable (I have two of these 9" grinders but only one smaller grinder for this reason) as it has big handle to grab onto and a bit of self weight that stops it jumping about.

 

Mark the disc with a pen to give you the depth of cut. Go for 25 -30 mm on average into the stone if you have a good thick wall. Now you have to judge this as the stone will not be flat but you are looking for a penetration into the stone of 25.0mm to comply with the regs.. and the Cookson / Calder good leadwork guide.. which is your Bible on this.  Download the Cookson or Calder guide to good lead work... if that is the only thing you do... it will save you money and grief!

 

The main thing is that the depth of cut will vary.. this is because when you come to fold your lead into the chase it needs to be straight to look good but the wall will be in and out a bit! That is part of the reason for the 100 x 25 timber.

 

Next move your 100 x 25 timber down by 20mm and repeat the above. You'll find that the timber has "suffered" a bit when you cut the top but that is ok, and that is why I cut the top chase first.. which is the bit you see.

 

Now you have two cuts in the masonry. Get a chisel and carefully break out the stone between the two cuts and clean the back of the chase out, then brush / clean off dust.

 

You should now have a cracking good looking chase for your lead that has not damaged the stone.

 

The next bit is preparing the lead flashing and fixing it into the chase. This is a diferent skill and can be done in a couple of ways not least.

 

With my traditional hat on I use little strips of lead rolled, folded and wedged in to anchor the flashing, then point up with mortar to seal completely. The flashing need a good bit of preparation so you have a task ahead if you want to start dressing and folding the flashings.

 

How you fold the lead into the chase is really important. I could try and describe but it would take ages.. try looking on U tube. This is a skill that is passed down the generations, I learnt it form a lead worker hands on... It's not in a book!

 

See the Cookson guide. I form the bends that go into the wall a bit like a cavity tray... hard to describe here without writing a massive essay.

 

I think if you are asking about a grinder size and discs then you have a bit more to learn about how you do these flashings to make them last and water tight. Lead working is a skill that takes many years to perfect so please don't take this the wrong way.

 

Keep asking questions!

 

If you do this and grasp the basics then your grinder question will resolve it's self.

 

One last thing.. make sure you get Patination oil and treat both sides of the lead or you will end up with massive stains down the roof!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[saveasteading]

Can you explain more on the purpose of the flashing?

Masonry is usually coursed to some extent. Is there a nearly horizontal bed of mortar you could flash into?

[joe90]

On 28/08/2023 at 23:41, Oxbow16 said:

the chase will be a straight line (parallel to the roof below), and will be cut through both mortar (lime) and the stone itself, as the wall is random stone.