Q on power-tool choice for trunk work (grinder or 'cut off tool'?)

[SU2]

I'm a bit confused here, it seems a 'cut-off tool' is just a grinder where the drive-shaft is parallel to the handle instead of perpendicular... I know I need more tools but wanted to start with something real basic (am going to be carving random deadwood pieces I have laying around, not actual bonsai!), I have a drill with tons of 'dremel-like' attachments but for removing larger stuff I'm pretty stumped in choosing between the grinder or cut-off tool, unsure if I can link specific products or not so I'll just say they're both the same price from a national, budget tool store, they're both real low-quality but for how cheap they are I'd sooner get something and experiment now, anyways the differences/specs:

cut-off tool - 3" max for discs (3/8" arbor), 20k rpm (120v), amperage not listed on site

grinder - 4 1/2" max for discs, 7/8" arbor, 11k rpm (120V), 5a

Both of them seem to take the same types of discs (obviously different arbor sizes and different disc-widths), even some saw discs (a 4" disc that's got chainsaw toothing as its edge!) Part of me feels like both would be able to help do things the other couldn't, but for now I'm only getting one and unsure which is the better choice..

I know I'll need a lot more gear (proper sawzall, proper rotary/multi-tool, etc) but I'm not at the point of working on bonsais yet I just want to learn for a while, am planning to do trunk work to a couple of my large (~1' wide) yamadori when they're re-potted so want to be ready at that point and getting some basic tools now to start learning seemed the smartest approach! Initially I was

Thanks for any advice on this!!!

 

[just.wing.it]

Straight one is a die grinder, 90 degree one is an angle grinder....
Either can be effective.
You'll want something smaller too, for the detailed work, like a dremel or flex shaft hobby tool.

 

[SU2]

[edited- I'm a moron they did list the amperage, the die-grinder is 3A and 20k rpm, the angle-grinder is 5A and 12k - I like the position of the wheel better on the die-grinder, but have zero clue how their varying specs (amps//rpm) affect them.. got the angled one and am about to go back to swap it for the die-grinder but having trouble guessing which would be more effective for trunk/wood stuff... I know I'll probably get both eventually (and a real dremel/rotary tool and a sawzall, it's getting easy to see how you could drop $500-1k on a good 'basic trunk power tool set' between several tools and all their accessories! For right now though just want something 'basic' to start experimenting with

 

[flyinmanatee]

Well there's always Craig and his list. I got a Dremel and accessories at a garage sale. Harbor Freight until ya figure out your preference, then upgrade to a better quality. A scout is frugal.

 

[drew33998]

Die grinder is more versatile. Angle grinder is for larger projects. Id like to see someone work a shohin with one. On a side note those angle grinders are super dangerous. Tuck your shirt in and make sure its not baggy. Wear gloves and eye and ear protection. I had one rip up my shirt tore through it and shot up just missing my neck. Of course this was at the end of a 10 hour shift working with one where pretty much your hand is stuck in that position even after you let it go. Cant open or close your hand for a minute. I was super lucky. Some people have had their guts cut open when the grinder catches your shirt. Also be careful when trying to grind inside corners, the grinder can and will kick back at you. Had one do that too. Got out of the way of that one, but it cut its own cord. So i had to fix the damn thing. Back in my steel fab shop days.

 

[sorce]

https://www.lowes.com/pd/Dremel-400...MIi7_Cr9ir1QIVjx2BCh2zwAG4EAQYASABEgKRR_D_BwE

Link away bro!

That's the one I got.
Variable speed.
Good torque.
Good price.
Variable speed.
Variable speed.
VARIABLE speed!

Sorce

 

[SU2]

Well there's always Craig and his list. I got a Dremel and accessories at a garage sale. Harbor Freight until ya figure out your preference, then upgrade to a better quality. A scout is frugal.

A 'scout'? And I wasn't sure how this site felt about brands but yes Harbor Freight is what I was referencing, the other day I bought their 4 1/2" angle grinder https://www.harborfreight.com/4-12-in-5-amp-heavy-duty-angle-grinder-60372.html , was just starting to think the 3" die grinder may be more useful...it's got lower amperage (3A) but higher speed (20k rpm) (the angled one I bought has 5A power but just 11k rpm - I have no idea which would go through wood better when one's got better rpm, the other's got better amperage - ANY help understanding this electrical spec stuff would be hugely appreciated!!

And yeah I love craigslist and constantly buy/sell, just couldn't find what I wanted so got a drill at a 2nd-hand place (super-cheap but it's corded and 3.5A with variable speed motor (1.2k rpm)), I know that's equal amperage to the die grinder but only 5% the RPM total, although I'd be using dremel-type bits with it so am thinking its power will suffice...we'll see! I'll get a real rotary tool/dremel soon enough, my gut feeling now is that it makes sense to keep the angle grinder instead of trading for the die-grinder, since my drill+dremel bits can do a lot of finer work and the 4 1/2" angle grinder should be able to do all the harder work!

["then upgrade to a better quality" That's totally the plan, like the 4 1/2" angled one I have now and am probably just going to go open & test right now, am guessing I'll end up getting a better one sooner than later, am more just trying to get a 'basic' setup so I can see what's what, having literally zero experience with woodwork of this sort (am good with wood in general, just never worked on tree trunks!)]

 

[SU2]

Die grinder is more versatile. Angle grinder is for larger projects. Id like to see someone work a shohin with one. On a side note those angle grinders are super dangerous. Tuck your shirt in and make sure its not baggy. Wear gloves and eye and ear protection. I had one rip up my shirt tore through it and shot up just missing my neck. Of course this was at the end of a 10 hour shift working with one where pretty much your hand is stuck in that position even after you let it go. Cant open or close your hand for a minute. I was super lucky. Some people have had their guts cut open when the grinder catches your shirt. Also be careful when trying to grind inside corners, the grinder can and will kick back at you. Had one do that too. Got out of the way of that one, but it cut its own cord. So i had to fix the damn thing. Back in my steel fab shop days.

Thanks for the advice, I like to think I'm pretty safe in how I use power tools (have had some close calls before that left me scared-straight lol!), have clipped many cords (still have a dewalt circular saw that's probably had its power cable patched/repaired/sections-replaced over 3-4x now!)

Thanks for the thoughts on the die grinder being more versatile, I hate having gotten all these opinions and am now starting to think contrary to them - see, with a drill + dremel bits, I can do a lot of 'tighter-area' stuff, so for now I'm thinking that my drill+attachments will let me do finer work and the angle grinder do large/bulk work, this should hopefully be enough to give me an idea of what's best for me before going and getting dewalt/milwaukee/etc level gear (or ryobi - I know they're not as nice but they do seem the best value and, for non-commercial uses, am sure they're sufficient (with dewalt/milwaukee just being [expensive]overkill!)

 

[SU2]

https://www.lowes.com/pd/Dremel-400...MIi7_Cr9ir1QIVjx2BCh2zwAG4EAQYASABEgKRR_D_BwE

Link away bro!

That's the one I got.
Variable speed.
Good torque.
Good price.
Variable speed.
Variable speed.
VARIABLE speed!

Sorce

That's awesome and is exactly the type of thing I'll be getting next (was kind of thinking the 3" die-grinder would function both as the dremel/finer tool *and* bulk tool, didn't realize that the lack of variable speed was sure to be a deal-breaker for using it for fine work!), am definitely thinking it makes sense to keep the 4 1/2" angled grinder, get a proper dremel like that one next, and a 'mini sawzall' type product last..

You say 'good torque' - could you please give me a simplistic/elementary explanation of how you determine that? I see it's 1.6amp and 5k-35k rpm... I see the amperage and rpm listed on most of these products but gotta say I'm utterly clueless how to interpret them (I know what the words mean, am just unsure where the benefits of amperage and rotation speed diverge, which one is better for what things, etc - you say 'good torque', the way I'd thought it worked was by analogy to a car's engine, with amperage being torque and rpm being horsepower, if that makes sense.. if I could change the rpm or amperage of any particular tool I'm just confused how that'd effect its function, any elaboration/clarification you could provide would be hugely appreciated!!

 

[A. Gorilla]

RPM is how fast it spins. Torque just a rotational version of force.

Amps would relate to how much torque could be produced. RPMs themselves doesn't take much energy to produce.

"Torque" could also be thought of as: "How much force it would take to bog down the tool and make it stop spinning?"

There is such a thing as too much. Imagine the grinding bit taking too big of a bite and instead of just stopping for a second, it breaks the shaft of the bit or sends the tool flying from your hands, or even starts spinning the damn tree around.

 

[drew33998]

My dremel is just not enough torque to get through hard woods. It is great for fine detail work though. Shohin boxwood. Very hard wood.

 

[sorce]

Wood stops Harbor Freight tools.

Not the Dremel.

That's torque.

Sorce

 

[SU2]

Wood stops Harbor Freight tools.

Not the Dremel.

That's torque.

Sorce

Please tell me you're exaggerating? I finally realized it made more sense to keep my angle grinder (as it's 5A versus 3A on the die-grinder - I'm still confused how the die grinder spins twice as fast when it has just 60% the power/amperage going to it..), but now you've got me afraid to go play with it!! (as I can't return it once I use it ;p ) Please tell me if you're being hyperbolic or not, I mean I know HF tools are very entry-level and I don't expect it to last long-term, I'm really just trying to get started, to learn the tools and techniques, but if I go out there and start messing with it (as I was planning to like in the next couple hours!) and it can't even go through wood then it's useless to me!

God I hope you're exaggerating!

 

[SU2]

RPM is how fast it spins. Torque just a rotational version of force.

Amps would relate to how much torque could be produced. RPMs themselves doesn't take much energy to produce.

"Torque" could also be thought of as: "How much force it would take to bog down the tool and make it stop spinning?"

There is such a thing as too much. Imagine the grinding bit taking too big of a bite and instead of just stopping for a second, it breaks the shaft of the bit or sends the tool flying from your hands, or even starts spinning the damn tree around.

Thank you, that's very useful! To be clear though, in comparing those two grinders - 3A with 20k rpm versus 5A with 11k rpm, the 5A wins-out hard because of almost doubled torque/power, right? (am confused why there wouldn't be correlation between amperage and rpm though, I mean if you put twice as much power to the shaft then wouldn't it spin twice (well not exactly twice) spin more? If the 3A spins almost twice as fast, is that extra speed worth anything? If I understand you correctly, amperage is what matters and rpm is almost a 'by-product' in this case, no?

Also, what are your thoughts on Sorce's post, that harbor freight stuff won't go through wood? I'd decided to keep my 5A / 11k rpm angle grinder, was going to mess around on some driftwood scraps this afternoon, am now afraid to use it (voiding ability to return it) after reading his post! Hoping it's hyperbole..

 

[wireme]

I'm not sure if the chuck on a cut-off tool is the same as a die grinder? May not hold the same bits? The ones I've seen also have stubbier noses so looks like they are more difficult to reach into tighter spaces.
I've never looked into it really or used a cut-off tool but I have wondered how similar the two tools are. Does anyone here use a cut-off tool in place of a die grinder? They are easier to find here and I recently gave my die grinder away in a misguided fit of generosity!

 

[sorce]

God I hope you're exaggerating

LOL!

Did you find out yet?

Hopefully all your digits are intact!

My buddy bought me a cheap one from there...
Yes....wood stopped it!

That place is the epitome of why America/Earth sucks.

They are easier to find here and I recently gave my die grinder away in a misguided fit of generosity!

Now all those iffy collects are gonna bang with growth!
Hears to your Karma!

Sorce

 

[drew33998]

Its bea

Thank you, that's very useful! To be clear though, in comparing those two grinders - 3A with 20k rpm versus 5A with 11k rpm, the 5A wins-out hard because of almost doubled torque/power, right? (am confused why there wouldn't be correlation between amperage and rpm though, I mean if you put twice as much power to the shaft then wouldn't it spin twice (well not exactly twice) spin more? If the 3A spins almost twice as fast, is that extra speed worth anything? If I understand you correctly, amperage is what matters and rpm is almost a 'by-product' in this case, no?

Also, what are your thoughts on Sorce's post, that harbor freight stuff won't go through wood? I'd decided to keep my 5A / 11k rpm angle grinder, was going to mess around on some driftwood scraps this afternoon, am now afraid to use it (voiding ability to return it) after reading his post! Hoping it's hyperbole..

Force=current x wire length x magnetic field.

The rate at which a motor spins has more to do with the windings and the number of poles or magnets than anything. But yes the current is one of the factors that will determine force.

 

[SU2]

LOL!

Did you find out yet?

Hopefully all your digits are intact!

My buddy bought me a cheap one from there...
Yes....wood stopped it!

That place is the epitome of why America/Earth sucks.



Now all those iffy collects are gonna bang with growth!
Hears to your Karma!

Sorce

I tried it, I used a really thin/flat disc and an ~8-10mm thick aluminum oxide cartridge, the power was definitely underwhelming* but it certainly worked, I was able to carve chunks out of the driftwood I was practicing on (hmm, I wonder how much of a strength difference there is between dried driftwood and wet hardwood inside a trunk?), I carved the general shape I set out to carve (and then finished it off using a 1 1/2" wire wheel drill bit, gave a really good grain real easily.

I imagine the discs meant for wood- sanding discs with the angled sanding pads; chainsaw-edged discs; rubber-pad-backed sanding discs; etc - perform far better BUT worry greatly that, since they'd 'bite' harder, the 5A power of this thing may no longer be 'enough' (right now I'd say it was about as weak as it could've been w/o me immediately feeling buyer's remorse lol)

(*this was a 5A model and only cost $20, they have 6A for $30 and 7A for $40, am thinking I should trade-up..... I only used it for ~5min total (did a very small carving area), am pretty sure I could put it back so it looks unused... I went there originally to get the $15 model (3.5A iirc), am utterly clueless I figured that if they could go through steel then wood would be no problem and figured I was getting more than 'needed' getting the 5A, am now thinking it's the lowest anyone should get and that a 7A angle grinder of this size (4 1/2") for anyone doing woodwork is probably a good starting point! Would that be a fair assessment? Right now the upgrade/swap to 7A seems like it'd do what I need, if this 5A unit is going to perform worse when I put wood-working discs on it which I fear is gonna be the case...)

 

[drew33998]

If it works why change it?

 

[sorce]

$20,

The one I had was like $8. Real poo!

Keep that for what it works for.
Dremel for Xmas!

Sorce