HF angle grinder.

[Coach James]

A few days ago, I cut two of the feet off our oldest set of parallel bars to make a set of pit bars. I have some other grinders, but I wanted to try out a new HF grinder I got on sale and see how it held up to a heavier job.

I was at my mother's house, about an hour from mine, needed a grinder so I went to HF and got this one.

http://www.harborfreight.com/4-12-in-5-amp-heavy-duty-angle-grinder-60372.html

The job at my mom's was short and no real test.

The P-bar feet are hollow but pretty thick steel. I haven't measured the thickness yet, but it is over 1/8" thick. Cross section is ~1" by 4". The cut off pieces are heavy.

I used a 1/16" thick cutting wheel. I started by making repeated passes over the top of the each foot, then cutting down the sides then underneath.

Since the bars were in an area where our gymnasts would be walking, we had to contain the metal shavings as well as keep sparks from falling on the mats and carpet.

I also forgot my ear plugs so I had to stuff cotton in my ears.

Total cutting time was ~ 50 minutes: 30 on the first foot and 20 on the second. Oddly, the wheel seemed to cut faster after it had been used for a few minutes. The grinder never bogged down or got too hot for me to touch anywhere.

Not sure why the pics are sideways. They are normal on pic viewer.

 

[JJThrasher]

Those grinders aren't great, but they will get the job done.

 

[malibu101]

On the wheel working faster after use.....
The diameter of the wheel has become smaller after use (wear), resulting in a faster RPM of the edge of the wheel, resulting in a bit faster of a cut.

 

[bcradio]

Glad to hear you got it done. I certainly use my hf grinder hard and have had no problems with it thus far.

 

[L.Cheapo]

On the wheel working faster after use.....
The diameter of the wheel has become smaller after use (wear), resulting in a faster RPM of the edge of the wheel, resulting in a bit faster of a cut.

Wouldn't the edge speed of the wheel be slower as the wheel wears down? As diameter decreases, tip speed also decreases.

What a smaller wheel will likely have is more torque, as the motor has less of a lever arm to work against.

 

[astroracer]

I have a half dozen of the HF grinders. Work them all hard. Never had a problem with them other then the oldest one I have (probably 20 years old) has a broken motor fan. Still runs, just clangs a bit when it starts up.
Mark

 

[winlinmac]

Can't beat $10 for a Drill Master Angle Grinder.

 

[flat tire]

mine lasted about 60 days

 

[winlinmac]

There is one fundamental aspect this forum has taught me is that you get what you pay for. There's no doubt about that these days.

There are some exceptions though when you may get lucky.

 

[Bill Bowman]

Wouldn't the edge speed of the wheel be slower as the wheel wears down? As diameter decreases, tip speed also decreases.

What a smaller wheel will likely have is more torque, as the motor has less of a lever arm to work against.

Your logic is flawed. Think of a small trailer wheel going down the road at 70 mph. Spinning like a biatch! Now think of a semi truck (22" tire) going 70 mph.

 

[B_Bimmer]

One of those things I got tempted into by price, bought it as a cheap backup. It broke the first time I used it. I was actually kinda releaved. The plastic felt like cheap **** in my hand and it vibrated way more than my Milwaukee or my dad's old Milwaukee that has been worked hard and put away wet for the last twenty years. Both those are still going strong. If I had something easy that needed done far from home, I suppose I would buy another, but with the full knowledge that it would be left on site when I was done.

 

[ovrrdrive]

HF grinders are great for what you pay for them. I've been absolutely punishing one of the orange one's I bought about 10 years ago and it's holding up great. It started making some noises last year so I gave it a brush change and it's been fine ever since.

I'm sure some of you guys know your tools but a few of you really **** at math. At a constant rpm the outside edge of a new cutting wheel is moving faster than it is on a used, smaller wheel. Say the outer circumference of a used wheel is (round numbers for example) 4" while on a new wheel it's 5". If they turn the same rpm the newer wheel will cover an extra inch for every revolution. IE the outer edge is moving faster than it is on a used one. In the tire example the smaller tire is turning faster rpm.

 

[freddyford]

My orange unit needed the cord replaced as it somehow created a short. Other than that I can't kill it, and I've tried. I'm guessing by running it very hard the cheap cord overheated and melted internally creating the short I had. Even the brushes are lasting.

 

[FigureItOut]

At a constant rpm the outside edge of a new cutting wheel is moving faster than it is on a used, smaller wheel. Say the outer circumference of a used wheel is (round numbers for example) 4" while on a new wheel it's 5". If they turn the same rpm the newer wheel will cover an extra inch for every revolution. IE the outer edge is moving faster than it is on a used one. In the tire example the smaller tire is turning faster rpm.

I'm glad someone pointed it out. In your example any point on the circumference of the 5" wheel will cover actually about 3 more inches, and be traveling about 33MPH faster, at 11,000 RPM.



Sent from my SAMSUNG-SGH-I337Z using Tapatalk

 

[Farmall450]

At a constant rpm the outside edge of a new cutting wheel is moving faster than it is on a used, smaller wheel. Say the outer circumference of a used wheel is (round numbers for example) 4" while on a new wheel it's 5". If they turn the same rpm the newer wheel will cover an extra inch for every revolution. IE the outer edge is moving faster than it is on a used one. In the tire example the smaller tire is turning faster rpm.

He's exactly right. The tire example is no bueno here, the "hub" is always moving at a constant speed.

 

[xela456]

As the diameter is smaller so is the circumference. So for a 4.5 inch blade, for every RPM you are dragging about 14 inches of abrasives across the the material. Wear it down to 3 inches and your only moving around 9.5 inches. So, basically a new disc will technically cut much faster than a worn down blade.

My goto cut-off machine is a 6 inch metabo quick-cut which is around 3 years old, it has lived a hard life and been repaired a few times mostly cord related. However the most powerful grinder/ cutoff i have is a dewalt D28140 6 inch paddle grinder, doesnt bog down at anything and is very comfortably in the hand despite its' large size.

 

[Kev442]

I have had decent luck with the older blue 9.99 HF grinders, only one has died. The newer black drillmasters not so much, they died pretty quick. I started buying them at Menards for a little bit more to get a two year warranty.
I am now going to start replacing them as they die with a bit better brand name, but I greatly prefer having 2 or 3 set up with different disks vs one nice one that I would have to change over constantly. It helps that I rarely run them for longer than 10 minutes at a time.

 

[99LeCouch]

My blue HF grinder works decently for what it is. And the once in a blue moon it gets used.

 

[kunkernator]

Those maroon grinders are near bulletproof. I abuse the **** outta mine, never had an issue. The black ones on the otherhand, are junk.

 

[madison069]

Where y'all getting the bushings for the orange angle grinder? Mine is still going but it's making noise. I actually bought a dewalt angle grinder to replace it but never took it out of the box since the orange one is still going.

 

[zendriver]

mine lasted about 60 days

Hope you returned to for another one. It has a 90 day warranty.

 

[anndel]

Hey it worked, that's all that matters and that project was done.

 

[Ign]

Yikes, kinda scary how some people think about surface speed here.

Go find a machine shop and either
a) go stand next to their biggest lathe (likely a faceplate) at, say, 20 *spindle* RPM and tell me you're not scared shitless of getting tangled up in that thing. I used to run an American w a 60" faceplate and even at 22rpm it looked like it was doing 1200 rpm

2) go to any CNC lathe with a program that shoots for constant surface speed. As the work (diameter) gets smaller, the spindle speed ramps up dramatically (most notable during parting ops) to maintain a constant surface speed.

Bottom line, on a grinder spindle speed is fixed so a smaller wheel is spinning more slowly at its OD as it has less ground to cover per revolution. This is why - for me - new abrasive cutting wheels kick *** and they struggle more as they wear, because 1) they're going slower and 2) you're asking less wheel to do the same amount of work.

 

[Ign]

This is also why - almost universally- as diameter of abrasives increases spindle speeds drop. Look at the RPM of a 7" grinder (maybe 6 to 8000rpm?) vs a 4" grinder (10,000 rpm) or 2" wheels for use in a die grinder (up to 30k rpm). Likewise a 14" abrasive saw is around 4000 rpm. If you tried to spin that 14" wheel at 10k the surface speed would be so great it'd explode.

Likewise a 4" wheel at 4000 rpm wouldn't net any worthwhile results - just too little surface speed.

 

[Pipe]

Mine has surprisingly held up fine for years(the orange one). I have looked at dewalt bosch and fein for when it gives up the ghost. The vibration isn't terrible but of course those other brands listed run smoother.

 

[wildbill23c]

I have a 4" angle grinder from HF, probably about 7 or 8 years old, I've used it a lot and it still works great. I've had a couple tools from HF fail early on, a belt sander, and a drill bit sharpener, but everything else still works very well even after being used for several years.

 

[stage20]

My orange unit needed the cord replaced as it somehow created a short. Other than that I can't kill it, and I've tried. I'm guessing by running it very hard the cheap cord overheated and melted internally creating the short I had. Even the brushes are lasting.

same here. i had 2, buddy had 2 or 3. my last one now has an issue with the cord. if i wiggle it, it will work. i just need to get around to replacing the cord.

as for the old drill master blue ones, i still have one of those too. its not very stout. i can stall it or bogg it with little effort grinding, but it wont die.
i keep it in the back of the truck for emergencies.

the newer ones they have im just not fond of the shape or the switches.

im a dewalt guy so to speak, but i use makita grinders for work everyday. for the price they are great. power and fit my hand well.