I got a 125mm guard from ffx for our Milwaukee, the 115 never been back on
Any downside to buying a 125mm angle grinder rather than a 115mm one
- Thread starter marcusthehat
- Start date
Will the lower circumference of the 9" disc worn to 4.5" not lower the m per second speed!?
- Location
- East Essexshire
I went with Metabo because there's a really good dealer very near me, and I like the idea that if there's any problem I just dump it on their counter and let them sort it out.
They've been excellent. I'm not sure whether there's any difference in the grinders of other makes, but I know the impact wrenches have a much lower spec than Milwaukee. I've got the biggest 600Nm one, and it's been perfectly adequate for what I need, with a 1" drive airgun for the heaviest jobs.
marcusthehat
Member
I have not tried or used the Milwaukee, but I cannot fault the Metabo's, neither the LTX Drill nor the impact screwdriver, bought as a package.
mth
mth
- Location
- Lancashire
Make sure its the brushless version. They are excellent
Digester Man
Member
Has the 125mm got a thicker body? If so might be less ergonomic if you are trying to use it one handed whilst holding something in your other hand
Steevo
Member
- Location
- Gloucestershire
Like you i’m sure there is no difference in the grinder, just a different guard!
But for some reason we’re already on page 2!
marcusthehat
Member
Re the speed rating nonsense when swopping worn down 9" discs to a 115/125mm grinder, rated at higher rpm's than the 9".
The 9" disc only needs to be spinning 1/2 as fast as the 115mm, to give the same rim speed/cutting velocity.
Ergo the 115mm grinder probably is rated at twice the rpm's, but no odds for the reduced 1/2 size disc, which will now simply have the same rim speed.
Simples, I imagine.
mth
The 9" disc only needs to be spinning 1/2 as fast as the 115mm, to give the same rim speed/cutting velocity.
Ergo the 115mm grinder probably is rated at twice the rpm's, but no odds for the reduced 1/2 size disc, which will now simply have the same rim speed.
Simples, I imagine.
mth
I've got a cordless Metabo grinder along with a host of other Metabo cordless and corded tools and it's the same grinder just a different guard for a inflated price, in fact the 150mm they do is the same as the 115 and 125. The 125 will come with a 115 guard so pay your money and take your choice, where Metabo stand out is their batteries.
Paddington
Member
- Location
- Soggy Shropshire
Anyone got any recommendations for a 115/125mm grinder stand, to use it like a chop saw ?
- Location
- Derbyshire
I often agreed with people over not using 9" discs in smaller grinders, but just out of boredom did some calculations.
Dewalt 240v 9inch grinder, 6600rpm 5inch disc rim speed is 97mph
Dewalt 240v 5inch grinder, 11500rpm 5inch disc rim speed is 170mph
Dewalt 240v 4.5inch grinder, 11000rpm 4.5inch disc rim speed 146mph
Dewalt 18v 5inch grinder, 7000rpm 5 inch disc rim speed 103mph
And having seen a couple of worn 9 inch discs explode in smaller grinders, the above is the reason.Shouldn't be too bad in a 18v model though
marcusthehat
Member
Clarify your first entry please,
or perhaps rather, what is the rim speed with a 9" disc in a 9" grinder?
Actually since 6,600 is well more than 1/2 of 11,000, so the 9" rim speed at 6,600 is higher than 4.5" rim speed at 11,000.
EDIT;
No calculations needed, since comparing 4.5" with 9" .
yes?
mth
or perhaps rather, what is the rim speed with a 9" disc in a 9" grinder?
Actually since 6,600 is well more than 1/2 of 11,000, so the 9" rim speed at 6,600 is higher than 4.5" rim speed at 11,000.
EDIT;
No calculations needed, since comparing 4.5" with 9" .
yes?
mth
Last edited:
simmy_bull
Member
- Location
- North Yorkshire
225mm disk circumference is 706mm x 6600 = 4650 m/s
115mm disk circumference is 361mm x 11000 = 3970 m/s
Grassman247
Member
TheTallGuy
Member
- Location
- Cambridgeshire
It's all well and good quoting linear speeds, but the critical factor actually comes down to the angular velocities and the forces generated from that which increase in proportion to the square of the velocity. I have often argued against the business of rating discs on linear speeds as that rating is based on running at the nominal diameter & just confuses matters.
marcusthehat
Member
But since the 9" is already rated at higher rpm's than the 4.5", each for a brand new disc,
a worn down(but obviously undamaged) 9" disc fitted to a 4.5" with a 6600/11000 lower rotational speed,
should be unburstable.
yes?
a worn down(but obviously undamaged) 9" disc fitted to a 4.5" with a 6600/11000 lower rotational speed,
should be unburstable.
yes?
TheTallGuy
Member
- Location
- Cambridgeshire
As long as the disc is rated for the rpm of the grinder & the disc is in good condition it should be okay, but bear in mind that the disc has been used and may have been damaged.
- Location
- Derbyshire
Either I'm not reading you correctly or you're getting mixed up??
9 inch grinder 6600 rpm, 4.5 inch 11000rpm almost twice the speed!! When that 9 inch disc is worn
down its still doing 6600rpm regardless of what size it is, you then put that disc in a 4.5 inch grinder and nearly double its rotation!! Thats why its bad practice to put them in a smaller grinder when they are worn, unless that grinder is rated at the same rpm as the bigger one.
I don't know what the manufacturers say or what they will take, but I do know from first hand experience of seeing it happen that they can and will shatter. Whether they were bad discs to begin with or it was the speed difference I don't know, but seeing it go and the state of the lads arm from the shrapnel its not a risk that I will take for the sake of a few quid.
- Location
- Derbyshire
Back to the OP, I'd go for the 5 inch. We have both sizes of dewalt between out team on track, and the 5 inch seems to cut better, faster and obviously lasts longer.
Steevo
Member
- Location
- Gloucestershire