Welding Tips and Tricks

Hi,

I have an old Makita 9523nb 4" grinder. I bought some thin cut off abrasive discs 1.2mm thick and they won't fit properly. By that I mean it's impossible to have the flanges contact the disc to lock it down tight to the shaft, so that there is no looseness / play when the machine is running. I have actually run it as best I could but all that happened was that the centre metal washer in the disc tore out and the disc just ran loose on the grinder shaft like a hoola-hoop, which ovalled the hole.

I'm not so bad that I bought discs with the the wrong arbor hole size. The machine and the discs are the 5/8" 16mm common size so that's fine. But the issue is that the standard inner and outer flanges of the grinder seem to be designed to accept a disc that is not less than 2.5mm thick. I have run heaps and heaps of 2.5mm cut-only abrasive discs with no issue other than they do wear a bit quick as they all do.

I've read on a few other forums about the same issue and some have said that you just flip the lock nut but this isn't my issue. Others have had little spacers made up so that the 'top' of the inner flange is level with the base. Others have also said you just grab another disc, run it down to almost nothing left and use that as a 'backing plate' / spacer. But I'm thinking that there is a better way.

Also, are angle grinders meant to run cut off wheels at all? I read on another forum that someone queried with a manufacturer (ryobi) about a similar issue and they said that grinders are not intended to be run with cut off wheels. I have done heaps of cutting with the 2.5mm wheels and as long as you position the disc in the right spot relative to the job it's safe enough. Although with my old machine with the thumbswitch style I think it would be happy to spin across the bench and chase you across the floor like an angry snake if you ever dropped it while it was running.

Also what are really thin discs like to cut with? I've got the impression that they will cut faster than a thicker disc like the 2.5mm I'm used to. Just worried that being so thin that a decent side load will split them and send bits of disc into places they should not go.

I've never had such issues running cut off discs that are 0.045" thick in my grinders (1.2mm). I just flip the outer washer so that the centering lip is out (since it is only used with ¼" (6.4mm) hard grinding discs. It is very well possible that your grinder wasn't meant to be used with thinner discs. I use thinner discs on an air cut off tool, which uses 1/32" discs (0.032). They cut really fast because they have to remove less material, but at the same time, they don't last long. It's a balancing act. What is your idea for "the better way"?

5vzfehilux wrote:Hi,

I have an old Makita 9523nb 4" grinder. I bought some thin cut off abrasive discs 1.2mm thick and they won't fit properly. By that I mean it's impossible to have the flanges contact the disc to lock it down tight to the shaft, so that there is no looseness / play when the machine is running. I have actually run it as best I could but all that happened was that the centre metal washer in the disc tore out and the disc just ran loose on the grinder shaft like a hoola-hoop, which ovalled the hole.

I'm not so bad that I bought discs with the the wrong arbor hole size. The machine and the discs are the 5/8" 16mm common size so that's fine. But the issue is that the standard inner and outer flanges of the grinder seem to be designed to accept a disc that is not less than 2.5mm thick. I have run heaps and heaps of 2.5mm cut-only abrasive discs with no issue other than they do wear a bit quick as they all do.

I've read on a few other forums about the same issue and some have said that you just flip the lock nut but this isn't my issue. Others have had little spacers made up so that the 'top' of the inner flange is level with the base. Others have also said you just grab another disc, run it down to almost nothing left and use that as a 'backing plate' / spacer. But I'm thinking that there is a better way.

Also, are angle grinders meant to run cut off wheels at all? I read on another forum that someone queried with a manufacturer (ryobi) about a similar issue and they said that grinders are not intended to be run with cut off wheels. I have done heaps of cutting with the 2.5mm wheels and as long as you position the disc in the right spot relative to the job it's safe enough. Although with my old machine with the thumbswitch style I think it would be happy to spin across the bench and chase you across the floor like an angry snake if you ever dropped it while it was running.

Also what are really thin discs like to cut with? I've got the impression that they will cut faster than a thicker disc like the 2.5mm I'm used to. Just worried that being so thin that a decent side load will split them and send bits of disc into places they should not go.

-- Turn the nut "backwards" with the flat side to the disk. I have been doing it for years with thin cutting discs, flap discs, rust/ paint remover wheels etc as most of them are too thin to use with the nut flange in without a spacer. I use the thin 3/64" x 4in cutting disc in a dedicated 5" cheapo rat tailed grinder with a rear paddle switch and side handle simply because I can get a good grip and control while cutting. The thin discs work great, fast cutting without a big heat buildup. The trick as I see it with these discs, as they are fairly delicate, is proper operator positioning and control much the same as welding in that you need to have a good solid stance to control and feed it smoothly. Bit of a learning curve but worth it. As with any grinder accessory NEVER operate it so if the disc demos it's not spinning in line with the operator and wear gloves and safety glasses.

homeboy wrote:Turn the nut "backwards" with the flat side to the disk.

This ^^^^ works on my Milwaukee and also on a Metabo with a non-tool-free nut.

You can at least see how it would contact by flipping it around. Not sure what type of nut you have, so not even sure you can do that...

Thanks always for the replies. Pics will tell the story better. Now I am thinking it's nothing more than the inner flange is too worn out, but not sure if getting a new one would solve it, as it would take a lot of material to bring it back up to where this all would work.

Below (bottom pic) is the bare inner flange. It can only go on one way as there are little cut-outs on it that match up with the notches in the grinder shaft so it all is locked and spins together. The issue is that the inner section of this flange in the centre that rises up, is too high. To properly fit, the flat surface that the disc rides (the worn chewed edge bit) would have to be at the same level or at least much nearer to the top of the inner centre section.

But as per the second pic, it isn't and with the outer flange wound on, the gap between the flanges is still too big, because a combo of the inner flange disc riding surface being too low and the outer flange/locknut recessed side not being recessed enough. You can sort of see the gap in the first pic. Flipping the nut upside down from this pic makes it worse because the inner 'ring' of that nut actually sits higher than the outer 'ring' (hard to see from the pic).

I've seen this problem, but a different nut resolved it. The arbor has that section raised, one thing you could try to putting a washer under the disc to raise it up above that section, then tighten the nut down. Your other option is to get the threaded hub cut-off wheels. Or yet another option, get a disc with a smaller bore in it, one that will fit over the threads but not the metal section. What size is the threaded arbor, and what size is the metal at the base?

If the thread is 5/8-11, get 5/8" bore cut-off wheels.

Here you go, 4" x .040" x 5/8" Metabo cut-off wheels, less than $1 for steel, less than $2 for alu at Lehigh Abrasives

Aluminum
https://www.lehighvalleyabrasives.com/b ... t655810000

Steel
https://www.lehighvalleyabrasives.com/b ... t655324000

You need to replace the nut set to one that’s capable of using thin wheel. That set is only for 1/4 inch thick wheels. You need a lower nut, (the one closest to the grinder) that is flat. I’ll post pictures of the ones I use. You just flip the top nut over if you swap between thin wheels and thick, or flap discs. They even work good with the .040 thin wheels.

Here’s a link to some.
https://www.amazon.com/Grinder-Spanner- ... V2G78TY3T4

Fantastic, thanks for that Poland308 and everyone, gives me a few options.

My machine isn't listed on that actual amazon page but it still may work. The 4.5" makita model (9524) is and mine (9523 - 4") is the 5/8" shaft size so it might be a goer.

I found the nut set for the 9523 on Amazon.ca," not available at this time"! The bottom nut is threaded to the shaft, not a slip on type that Poland posted. It's a discontinued model. Personal opinion, to save the headaches on Amazon.com alone there are several choices of new 4.5-5in grinders that will do what you need for 2-3 times the cost of the nut kit alone that you may not be able to find. Comments were that it's much easier to source the 4.5-5in discs than 4in also.

Something else to consider... I stopped using those types of cut-off discs because they lack the internal "bushing". It has been my experience too many times these type of discs are more prone to fracturing and slinging deadly Ninja stars through the air when they crack. And they do crack. Also, they tend to wallow out at the hub which unbalances them and leads to deadly accidents.

I've seen these fly across job sites and embed themself into the side of a truck, having barely missed humans. Your mileage and experience may differ.

I would agree thin discs require more care than regular ones -that said - all off hand grinding discs can break if used incorrectly - with basic precautions they should not pose an unacceptable risk - I assume your grinder is old enough they did'nt allow for the modern 1mm slitting discs but the only thing you need to do is reduce the height of the inner flanges shoulder or increase the counterbore depth on the outer flange - either would be a minute or two's work if you own or have a buddy with a lathe - if you don't then take off the flanges & stack 5/8 washers on the spindle till you can snug the inner flange back on with the shoulder just higher than the thread - now just switch on the grinder & gently run a smooth file across the shoulder ( clamp grinder in a vice & take due care ! ) till you reduce the height of the shoulder to a point that the disc can be clamped without the flanges quite touching in the middle.

Well I took the machine and disc into a higher-end tool shop a couple of days ago and it turns out they had inner flanges in stock. I thought I might as well get a new one so I could run the thick discs ok, as the old one was pretty worn and then I could move onto to sorting out the thin disc issue. But I wasn't thinking it would fix the problem, as it would just be the same dimensions as the old one but in new condition.

Turns out it did! Below is a pic of new vs old.

The guy at the counter test-fitted the thin disc and said good to go and also interestingly told me that the outer flange/lock nut DOES NOT need to be cranked down super - tight. He said they tighten up a bit when in use and all that's needed is a secure tension with the pin wrench but def not a crankdown like your life depends on it. I have always done the opposite and this prob contributed to the wear on the inner flange. It looks like a fair chunk of the inner flange's thickness / height is some sort of rubber bonding that may help with gripping the disc and reducing shock and vibration and over time it will wear down anyway, but I may have sped up the wear rate by overtightening over the yrs.

Anyway, test drove it on a 2 inch cut thru 4mm gal plate and it worked a treat with no heat marks less sparks and def faster and lighter than the 2.5mm disc. Came away pretty stoked and thanks again for all the help.

The only type of grinder disc I ever use a wrench on is the thin cutting disc and then only well snugged up simply because they are so thin that it's easy to crack the disc if trying to hand tighten. Anything else off and on by hand only. Good to see you got an easy fix.

If you ever decide to replace the actual shaft in that thing, don't be afraid to call Makita because they will do that at a price you won't believe. And it will be back in your hand in 2 days. Call their customer support and they will fix damn near any tool they ever made, and it'll blow your mind how many service centers do they have and how fast they turn the parts around. I know here it's two days and that's shipping it out ground. And it comes back ground. Literally it arrives there at the service center, gets fixed and packed back in a box and is shipped back out the same day. I've had three repairs on all three have been that way.

I used a large flat washer with the hole sized to fit.