couldnt find another thread to put this on so ill ask here which will probably be a good thread for new people and dumbasses like me who still cant use there tools properly hehe.

i got a ton of grinder discs at the engineering thing and found a few are a tad wobbly when i install them, about 3 of them shake pretty noticably. any body else notice this?

also when using cutting discs what is the correct way to use them. couldnt find any in my books about cutting with a grinder. only grinding.. im pretty sure im doing something wrong as the cuts ive made in box section are approximately twice as thick as the disc itself (i think thats because im not holding it straight) and its taking forever to cut through the box, im talking about 3-5 minutes. should the disc be spinning into the cut or away from it when cutting?

and also nick, how did you get that awesome finish on the lexan using the file? cant remember any more. i tried 'flame burnishing' and it turned somewhat nasty
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www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

Well Glen, using an angle grinder isn't rocket science. Those loose discs are you're main problem. If they wobble up and down it'll mean that you havn't done the nut up enough or there's something wrong with the bearings in the grinder. If its done up tight enough you shouldn't have any problems.
If the disc moves up of down while your making a cut the top and bottom surfaces of the disc may bite into the sides of the cut and flick the grinder out to one side. This also happens if you twist the grinder slightly while making a cut. This can be very dangerous if you arn't paying attention and has scared the @$#& out of me while grinding. Just make sure the disc is securerly held onto the shaft and keep the grinder straight with the cut and keep paying attenetion.
As for going with or against the rotation, I havn't really noticed a differance to the effect of cutting. I spent 3 hours cutting out the 4 parts for the claw Adversary was using at the Annihilator and I was swinging the grinder around to all sorts of angles trying to cut into the corners and didn't really notice anything.
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Get Some!!!

Secretary of the Queensland Robotics Sports Club inc.

Hi Glen. I cant quite remember the filing, but I probably used a technique called "draw filing'. You use a fine file, put it on the material edge at 90 degrees (like you were going to file it the usual way), then you draw the file along the material edge without letting it move from side to side.

I hold the file at both ends and only use a light downwards pressure. You will get longer, stringy plastic filings with this method and a brushed look on the material. you can round the edge a bit by tilting the file either way, but it doesn't work so well on a sharp edge.

Withthe disk cutting, you could be holding the disk at an angle off 90 deg. to getthe wider cut, but its probably cause its taking so long to make the cut.

It sounds like you are grinding the steel away rather than cutting it - the less material in contact with the blade at any point the faster the cut. It might not be the right way to do it, but I try to keep the disk cutting thru the steel like a circular saw cuts thru a thin sheet. All the action is going on at a very small point and the saw teeth are passing thru the sheet at around 90 deg. to the sheet. that makes it sound harder than it really is - I could show you in about 10 seconds. Also, you need to apply a fair amount of pressure. If the angle grinder isn't slowing down a bit, its not cutting as hard as it could.
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

quote:

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Those loose discs are you're main problem. If they wobble up and down it'll mean that you havn't done the nut up enough or there's something wrong with the bearings in the grinder

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quote:

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If the disc moves up of down while your making a cut the top and bottom surfaces of the disc may bite into the sides of the cut and flick the grinder out to one side. This also happens if you twist the grinder slightly while making a cut. This can be very dangerous if you arn't paying attention and has scared the @$#& out of me while grinding.

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quote:

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Hi Glen. I cant quite remember the filing, but I probably used a technique called "draw filing'. You use a fine file, put it on the material edge at 90 degrees (like you were going to file it the usual way), then you draw the file along the material edge without letting it move from side to side.

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quote:

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It sounds like you are grinding the steel away rather than cutting it - the less material in contact with the blade at any point the faster the cut. It might not be the right way to do it, but I try to keep the disk cutting thru the steel like a circular saw cuts thru a thin sheet. All the action is going on at a very small point and the saw teeth are passing thru the sheet at around 90 deg. to the sheet. that makes it sound harder than it really is - I could show you in about 10 seconds. Also, you need to apply a fair amount of pressure. If the angle grinder isn't slowing down a bit, its not cutting as hard as it could.

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For cutting box section and steel in general, buying a cheap $80-$120 14inch cut off saw is magic. I use ours for everything, from 50mm x 50mm x 4mm steel down to polypipe and wood (Using wood is a laugh and a half )
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https://www.halfdonethings.com/

Wish I had a web cam to show you what I can't describe properly . The 'flick' problem sure is scary, but can be avoided for most cuts (anyone know what the proper term is?) When you are making a cut thru thin material its always best to cut with what I would call the trailing side of the disk. If you relaxed your grip, the grinder would push itself OUT of the cut and away from you. When you accidentally move the cutting point past the top of the disk and onto the leading side, you can get the disk trying to make a supper aggressive cut, grabbing the material and then flinging the job, the grinder, or you all around the room!

That's too many words describing a simple thing, so the short advise would be to cut so you have so the grinder wants to pull away from you and you have to pull it towards yourself to keep it cutting. That way, if the grinder grabs, it flys away from you and on one gets hurt.

Not sure I understand the wobbling problem - could it be you have disks with too large a mounting hole? My old grinder has a small spindle and when i accidentally buy a disk with a larger bore, I cna never thighten the grinder up enough to keep the disk spinning on center.
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Australian 2015 Featherweight champion
UK 2016 Gladiator champion

It helps if the material is held in a vice.

Well i'll just add something I have found for me the faster I try to grind the less use I get out of the disks so I take it slow most of the time.... that's just me lol got no proof but it's a tip I got from the hardwear store and seemed to work.
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Team KO

According to my engineering theory book, your suppose to work the disc hard so the abbrasive comes loose of the bonding agent and causes frictiong against the metal allowing it to cut and generate heat.
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https://www.halfdonethings.com/

Well i noticed on a discovery channel show i love called american chopper that for thin steel tubeing and thin ali chekerplating they use a cutting wheel for it all and ever curves and crap.

I bought 2 cd thickness oens from bunnings and so far have cut bolts, 10mm plus thick solid steel shaft with no real probs and will use it for sharpening the weopon blade probably and cutting teh edge (not grinding it on).

SO far i have had no problems and the purchase of thes discs are a dream to use and make life easier. I love them.

I checked at the store though the disc would fit perfectly on the UX1 grinder. I took the disc and placed it on the grinder on display and spun it with my hand and then when i was convinced it felt good i bought it. No probs and much neater and easier work.
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Andrew Welch, Team Unconventional Robotics

just a bit of a problem today with my xu1 grinder (i can see you all laughing now lol, a problem with an XU1 tool!)

basically there is huge sparks coming out the sides where the brushes are, and i can hear an electrical "cracking sound" thats a bit like arcing.

i changed the brushes suspecting thats what it is but it still does the same thing so im guessing theres some metal inside the motor causing the problem.

could anybody who has taken an XU1 grinder apart give me some advice as to how i get access to the motor without destroying the thing.

i tried to get to it by undoing the black case on the back, but only the speed controllers and switches are under that part.

any advice HUGELY appreciated, as i really need my grinder working now lol.

thanks in advance
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www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

You should get some sparks not much though.

If your getting a lot of sparks then, not wanting to upset you any more, but it would be that the motor has a problem

The only time I ever see excessive sparks from the brushes are caused by a couple of things that I know of.

1. Faulty brushs
2. bad commutator
3. dirty commutator (unlikely due to being reasonable new)
4. short in the windings (drawing to much current)
5. brushs not run in (the arc in the brushs should match the arc of the commutator. ( circumference ))

and the winner is for the most common fault causing sparks I have had with a AC motor is

Drum roll

Number 4
short in the windings (drawing to much current)
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It's all about the destruction.

i doubt its 1 or 5 because i replaced the brushes and the original brushes where fine-ish. id only used my grinder maybe 15 minutes total usage.

im trying to get to the motor to rule out number 3 but 2 and 4 seem reasonable :S
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www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

3 is very unlikely.

I have only seen it happen acouple of times and they where on very old motors, that had been sitting around not doing much in a very bad inviroment.

but it is a posibility.
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It's all about the destruction.

ah i gave up on the xu1 and bought a big 900w ryobi deal. really cheap at only $46 as well.

ill probably hack the xu1 at the next event to figure out what its problem is.
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www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz