The lowly abrasive cutoff wheel. Best type? Best technique?

I’ve used cutoff wheels for many years (so l’m an expert right?) on my 7” Makita (nice)



most of the time and sometimes on my 4.5 older Milwaukee (OK) angle grinders. Most of my use involves cutting gates ranging from 1/2” x 1” to 1.5” x 2” in size on my cast iron castings. I also use them to score castings that need to be scrapped.

I typically use a plunge-cut vs scoring-cut technique as that seems to be the quickest. But I am starting to wonder if the pressure involved in plunge cutting may be causing excessive wheel wear and shortening wheel life. (I was looking for tips on YouTube and came across this video which looks at scoring vs plunging on THIN material: which indicates scoring is better by far for durability but is somewhat slower)

I am also looking for thoughts on optimal blade thickness (I have been buying 1/16” ) abrasive grain size, and brand preferences that folks with experience might have. I have considered diamond blades, but from what I can glean it sounds like they are slower and cost per cut may be greater.

Just looking to improve my methods and tools…. Thanks in advance for your advice.

Denis

rule #1: pull the grinder. it seems most people dont.
rule #2: keep rpm up.

diamond grit wheels many say ok for sheetmetal but are much slower cutting on thicker stuff.
diamond grit overheated will burn, diamond is carbon and will burn if hot enough.
CBN or even tungsten carbide grit maybe better than diamond at times especially with steel
and iron
.
how deep wheel in part that if wheel deep in sheetmetal and sheet vibrating, breaks wheel down
faster. if wheel shallow in sheetmetal and sheet not vibrating as bad, wheel might last a lot
longer
.
thinner wheel cuts faster but wears faster, so many use thinner wheel for sheetmetal
.
grinding wheel binder comes in different hardness soft wheel cut faster but wears faster.
hard binder wheel might last a lot longer but if it takes 10x longer to cut maybe thats not wanted

Jason over at Fireball Tools did a video about technique vs wheel life and time to cut.

https://youtu.be/hid9bDnSeok



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I have been pretty happy with Pferd. I probably go thru a dozen or two a year, of the thin ones- .045, inox. But we mostly use em on stainless, so the inox is worth it to me.
I have had employees, for close to 40 years now. One of my jobs, as boss, is to always put the guards back on if somebody has removed one. Never lost a finger yet.

dian said:

rule #1: pull the grinder. it seems most people dont.
rule #2: keep rpm up.

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I was never actually taught how to use a grinder, but I always pull it towards myself. Cuts seem more stable that way. In a plunge cut, it puts the point of contact closer to you, which I think reduces chatter.

I've had good luck with the .040" Pferd wheels. Last set I got was from Amazon Germany. Certain items can be cheaper if you are ordering a bunch.

$1.15 each 1mm x 125mm
PFERD 69198290 1,0 mm Trennscheiben Box – 50 Stuck | 125 x 1,0 x 22,23 mm | fur Stahl und Edelstahl (INOX) : Amazon.de: Gewerbe, Industrie & Wissenschaft

dian said:

rule #1: pull the grinder. it seems most people dont.
rule #2: keep rpm up.

Click to expand...

I was never actually taught how to use a grinder, but I always pull it towards myself. Cuts seem more stable that way. In a plunge cut, it puts the point of contact closer to you, which I think reduces chatter.

I've had good luck with the .040" Pferd wheels. Last set I got was from Amazon Germany. Certain items can be cheaper if you are ordering a bunch.

$1.15 each 1mm x 125mm
PFERD 69198290 1,0 mm Trennscheiben Box – 50 Stuck | 125 x 1,0 x 22,23 mm | fur Stahl und Edelstahl (INOX) : Amazon.de: Gewerbe, Industrie & Wissenschaft

jerholz said:

Jason over at Fireball Tools did a video about technique vs wheel life and time to cut.

https://youtu.be/hid9bDnSeok

Ya, that’s the video I linked in the first post. ;-)



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Click to expand...

Ries said:

I have been pretty happy with Pferd. I probably go thru a dozen or two a year, of the thin ones- .045, inox. But we mostly use em on stainless, so the inox is worth it to me.
I have had employees, for close to 40 years now. One of my jobs, as boss, is to always put the guards back on if somebody has removed one. Never lost a finger yet.

Click to expand...

I’ll need to try some to compare to the Makitas I’ve been buying.

newtonsapple said:

I was never actually taught how to use a grinder, but I always pull it towards myself. Cuts seem more stable that way. In a plunge cut, it puts the point of contact closer to you, which I think reduces chatter.

I've had good luck with the .040" Pferd wheels. Last set I got was from Amazon Germany. Certain items can be cheaper if you are ordering a bunch.

$1.15 each 1mm x 125mm
PFERD 69198290 1,0 mm Trennscheiben Box – 50 Stuck | 125 x 1,0 x 22,23 mm | fur Stahl und Edelstahl (INOX) : Amazon.de: Gewerbe, Industrie & Wissenschaft

Click to expand...

Looks like there is a concensus building for Pferd.

Denis

I used to plunge cut, a friend showed me the benefits of doing a scoring cut a few years ago, I think it works better, straighter lines, and wheel lasts longer, no more sudden disintegration, your mileage may vary.

Cubitron wheels. When plunging, or in your break thru pass of scoring (same thing at that point) you notice when the wheel goes from being cutter to cuttee. Only way to stop it is to go back to far side on scribe cut and pull grinder towards you, rolling the edge of the end of plunge cut. Then push grinder with plunge cut. You will soon find the point to reverse push/pull before wheel goes into disintegration mode.

Cubitron, does not glaze and is better on the wrist and forearms with less vibration. Also cuts a lot faster.

memphisjed said:

Cubitron wheels. When plunging, or in your break thru pass of scoring (same thing at that point) you notice when the wheel goes from being cutter to cuttee. Only way to stop it is to go back to far side on scribe cut and pull grinder towards you, rolling the edge of the end of plunge cut. Then push grinder with plunge cut. You will soon find the point to reverse push/pull before wheel goes into disintegration mode.

Cubitron, does not glaze and is better on the wrist and forearms with less vibration. Also cuts a lot faster.

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Sounds like a nice wheel. Pricey. Best deal I saw was min order 50 at 6.50 a wheel for 7”. Do you have any favorite suppliers?

I use Cubitron belts on my 2X72 grinder and really like them. Great belts.

Denis

We get the 4 1/2 thru one of our weld suppliers. Welsco out of west Memphis Arkansas. They are never the cheapest but do same day rush delivery of band saw blades and keep our sizes in stock- well worth the extra price.

Just looked at amazon, odd price on the 5” (close enough for 4 1/2 inch grinder). 3M Cubitron II Cut-Off Wheel 66539, T27 5in x .09in x 7/8in: Abrasive Cutoff Wheels: Amazon.com: Industrial & Scientific

memphisjed said:

We get the 4 1/2 thru one of our weld suppliers. Welsco out of west Memphis Arkansas. They are never the cheapest but do same day rush delivery of band saw blades and keep our sizes in stock- well worth the extra price.

Just looked at amazon, odd price on the 5” (close enough for 4 1/2 inch grinder). 3M Cubitron II Cut-Off Wheel 66539, T27 5in x .09in x 7/8in: Abrasive Cutoff Wheels: Amazon.com: Industrial & Scientific

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Thanks for the information. I would be buying 7” wheels as I find them, at least in other brands and likely Cubitron too, to deliver a lot more cutting per dollar cost. I also need the reach of the larger blade because of the location of the cuts I need to make. And finally, I much prefer the power and heft of the 7” grinder. So far, the best price I’ve found is from AirGas online store at about 9 dollars.

Denis

i use 1 mm pferd too. i get them in a 10-pack for under $10 whenever on sale at the local harware store.i doont remember breaking one.

Joe Gwinn said:

Looking at the high-speed video of the workpiece vibrating madly as the plunge cut was made, but not while grooving, it struck me that if one prevented that wild vibration, reasonable wheel life could well be achieved. Something as simple as a piece of wood under the workpiece might do the trick. Thicker workpieces could also help.

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I think you are on the right track with minimizing vibration (multiple high speed impacts) on the wheel. This is I suspect analogous to the difference in the very long wheel life of a smoothly engaging/cutting surface grinder wheel vs the much shorter life of a bouncing bench grinder wheel.

I remember making a thickness grind on the periphery of a not well supported 10” saw blade on a surface grinder. There was a lot of vibration of that blade which just ate up the SG wheel until I put supporting discs sandwiching and effectively damping the blade vibration. Once the blade was no longer vibrating the SG wheel did its job easily and broke down very slowly as is usually seen. Had I had a high speed camera, I am pretty sure a small shower if abrasive granules would have been seen with each vibration impact of the wheel on the undamped blade.

I think the abrasive wheels are designed to withstand steady sliding engagement but not instantaneous point loading. I have noticed rapid cutoff wheel breakdown if I get deep into a cut and the wheel gets pulled hard into the cut. This kind of loading is much more likely with pushing into a cut than when dragging the blade in a cut as the friction of the cut tends to pull the wheel deeper into the cut when pushing vs climbing out when dragging.

Listening for more tips…

Denis

I tried several different kinds of cutting wheels that I got for a good price on the internet, I was not happy with life. At the recommendation of my local welding supply shop I tried walter, it seems to work way better than the others, last much longer, cuts faster and does not self destruct, costs around twice the price but well worth it in my opinion. For the grinders I have, I don't gain much going from the 4 1/2 inch to 7 inch grinder because of the larger gear box on the larger grinder. The 4 1/2 cuts faster with less HP and muscle power.
I do not think pferd was one of the ones I tried but I ended up with a box of 25 of the walter (about $5 ea) so I will mot be buying any more for awhile.

I will have to pay more attention to pulling vs pushing, usually I am trying to follow a line so it comes down to how can I safely see where the cut is.

Gard said:

For the grinders I have, I don't gain much going from the 4 1/2 inch to 7 inch grinder because of the larger gear box on the larger grinder. The 4 1/2 cuts faster with less HP and muscle power.

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Well, your comments got me wondering if I was just imagining a difference between my vintage Milwaukee 4 1/2 and my Makita 7 pictured in my first post. Though I bought the Makita new a couple yrs ago, it is also of vintage design as Makita has not changed its construction since introducing it 25 yrs ago —-with the design said to be so successful no changes were needed or allowed. (Too often I’ve witnessed brand names previously synonymous with quality go steadily down hill while MBA’s milked the name for money by constantly cheapening tool design.)

So, I clamped a 1” round bar of 1018 in my vice and timed a cut with my Makita and Milwaukee with the exact same blade brand and grit (60 AlOx) in each. The Makita cruised through in 15 secs and the Milwaukee labored through in 31 secs. Probably all 4.5’s don’t perform the same just like all 7’s or 9’s aren’t going to be the same. But the performance difference in the two I have is pretty clear. Additionally the 7 wheel had changed very slightly in diameter whereas the 4.5 might have had enough blade left to get through half a similar cut.

I would like to see how much times would be shortened using coarser grits and using Cubitron or similar “high performance” abrasives. My guess is the Cubitron would kick ass. If anyone cares to post time results with their setups it would be of interest to me and likely others as well.

One other side note: the 7 produces such a large shower of sparks, I’ve learned to wear a leather apron or else be careful to keep my jeans (genes too) out of the line of fire. Otherwise I end up with a 2 or 3” smoking hole in my pant leg.

Denis

Walter is very high quality too. We never have much Walter around here, because, for 20 years or so, their West Coast reps have been crappy. In the last couple years, something has changed, as my (not small- 25 stores) local welding supply is FINALLY able to actually get products from Walter. I think in the USA, Walter was mainly focused on really big manufacturers, not retail customers.

Cubitron is the best wheel I have ever used- expensive yes, so are carbide cutting tools.

They cut cool and don’t stink and might last twice as long.
As far as cutting technique- I like to keep the wheel moving back and forth so I do not concentrate heat to one spot.

We did a test with a grinding wheel sales guy proving it was cheaper to use Cubitron wheels. We made a few weld passes on some coupons and weighed them, weighed the wheels and timed how long it took to grind flush. After grinding we weighed the wheels to check how much material we used and converted to cost, then weighed the coupons and came up with a labor figure for removing x amount of weight. The Cubitrons saved about 20 to 30% in labor and material over a conventional abrasive.