Thread: Tool Time (ROS)

Congratulations Tim, I suspect your Ryobi was no longer random nor orbital, just a sander.

No. It still does all three things - random, orbit & sanding.
But very loudly.
& not terribly effectively.
The emphasis is definitely on random & orbit rather than sanding.
It's in the bin now.
How's Coquina coming along?
I really will have to wander around one weekend when I'm not working.
AJ

Please do, I've had a few distractions recently so things have slowed but hope to get some paint on soon.

The quick way of comparing them is to check out the amp rating on the label. More amps (or watts) means more nuts. The Makita very likely has a bigger motor, which can deliver more torque to the paper.

260W Ryobi vs 300W Makita
The Makita is nearly double the weight, which probably helps it put more watts into
moving the paper, and less into making noise or moving the user's hands.
Same thinking as unsprung weight on a car.
Makes perfect sense now.
cheers
AJ

The Makita is about 15% more powerful then the Ryobi, which can easily account for the difference, plus possably better engineering, so it delivers more cutting action.

15% isn't a very big difference is it Paul.
I've also decided the watts consumed as per the label are very different
to the watts applied to the job. Not talking incremental improvement in
performance here. More like a multiple of 5 or 10 times faster cutting.
Far more than a 15% higher nominal maximum power consumption can
account for. And I wasn't using full power on the Makita either.

So we conclude 'hidden' better engineering, actually makes an enormous difference
to the effectiveness of the humble ROS. Worth every cent of the higher price,
several times over. And because it is 'hidden', it is hard to believe the difference
it makes on the job.

Had a very similar experience yesterday comparing the cutting rate of the
same drill bit in a new-ish 'high-end' Black & Decker vs an elderly Metabo of
lower nominal power draw. Considering all the machine has to do is spin the
bit while you hold it against the job, again the difference was astonishing.
So now I need to kill the B&D...

DA sanders are fairly difficult to engineer and get a good product. The problem isn't getting it to vibrate, but to vibrate and random orbit without shaking the user's hand off. Having had more then one of these apart for whatever reason, there's some major differences the way they handle each issue. I have a professional grade Porter Cable 6" that is really well made. It doesn't shake excessively, cuts very well, has good dust extraction, etc. I have others, but none have taken the engineering choices seen inside the Porter Cable. It has a full bearing (sealed) at each end of the motor, while most just one, on the output shaft side and bushing on the commutator side. The dust extraction fan is seperate from the motor cooling fan and the shaker is propely counter weighted, so it doesn't "egg out" the plastic housing with use. Very clever engineering and you see this inside good tools. Take apart a Fein or a Bosch and you'll see what I mean.

Good random orbit sanders rely on a one way bearing for there efficiency.

there is a pivot thet the disk rotates on, this rotates off centre.

some of the more primative random orbit sanders leave it there and rely on surface friction and good luck for the sanding action.

As soon as you introduce the one way bearing it increases the sanding efficiency considerably.

I would go as far as to say that modern random orbit sanders are nothing of the sort...they are far from random....they are in fact planetary sanders.

Oh BTW..... best thing you can do to a random orbit sander is toss the distbag and get it hooked up to a vacume cleaner.

cheers

Now this makes some sense.
The Ryobi, if powered without friction against the pad, turned into a high speed
disc sander. Too much friction & it orbited but hardly rotated.
(Note the use of the past tense..)
The Makita doesn't care whether the pad is frictioned or not - rotation is constant
relative to motor speed. Once the warranty is expired, I shall have to pull it apart
to examine this "one way bearing" thingy. Sounds interesting.

As for being a planetary sander... It's a good sander, but you'd be a bit
ambitious to tackle a whole planet with it.
AJ

Originally Posted by b.o.a.t.

The Ryobi, if powered without friction against the pad, turned into a high speed disc sander. Too much friction & it orbited but hardly rotated.

Sounds exactly like my Ozito which was never any good as the velcro pad wore out in about 10 minutes. Seemed like I achieved more by hand sanding than using the ROS on my strip kayak. Must have another search for the receipt as it really deserves to go back.

Thanks for starting this AJ (and thanks to the contributors) - I now know what I'm looking for in a ROS .

you dont have to pull the machine appart to sus out the one way bearing......just turn the unpowered ansder upside down and rotate the pad by hand.....it will free wheel one way but not the other.

As fas as the bearing...there is nothing to see..it just looks like any other bearing.

It is quite expected that the one way bearing may fail and cease to be a oneway bearing in some cases

I have replaced the bearing assemby in my metabo.....the two bearings on the shaft bushing cost me arround $100.
the one way was still working but the bearing had become noisy and had excess freeplay.
No grief in the matter I have given that machine a fair flogging.

If ya ROS is not making realy good headway...there is something wrong.

cheers