Rotary and 4" pads.....anyone ever use this combo?

WilliamHBonney · 04-23-07, 10:24

I bought a 2 3/4" backing plate for the rotary to use with my 4 inch pads that I have. I have a hard time controling the bigger pads and I figured that this would help. In addition I figured that I could get into troubled spots easier. Even though its a smaller surface area I think that I might actually be able to go faster as I can move the rotary faster (not RPMs wise) as I dont have to worry as much about hitting trim and other stuff.

Anyone ever use the smaller pads with the rotart and what is your experience?

Wetwerks · 04-23-07, 10:47

I've moved to 6" Edge pads on the rotary from the standard 8". Aside from being able to swap between the DA and Makita, I personally found them easier to control, and fit in tighter areas.

Walter
C0-owner

Accumulator · 04-23-07, 01:06

I really only use the 4" pads on the rotary for small-area spot repairs and for situations where the larger pads won't fit. A while back somebody posted a pretty compelling argument about why the smaller pads are both riskier (heat build-up) and less effective (correction-wise) than the larger pads. I forget the details of his argument, but they did correspond to my observations when using the different sizes of pads.

So use whatever works for you, but be careful and pay attention

WilliamHBonney · 04-23-07, 01:13

Quote:

Originally Posted by Accumulator

I really only use the 4" pads on the rotary for small-area spot repairs and for situations where the larger pads won't fit. A while back somebody posted a pretty compelling argument about why the smaller pads are both riskier (heat build-up) and less effective (correction-wise) than the larger pads. I forget the details of his argument, but they did correspond to my observations when using the different sizes of pads.

So use whatever works for you, but be careful and pay attention

Ok the heat buildup I can understand, but was less effective correction wise?

SpoiledMan · 04-23-07, 01:15

Accumulator I do remember that post about the heat dissipation and all that. I didn't and still don't buy it. Something that generates less heat in my *experience* doesn't need to be able to dissipate as much heat.

I've been using 4" pads when necessary for a couple years and haven't had a problem with them at all in reference to heat. I have polished such delicate items as the vents on the deck lid of 997's without issue. Does take some common sense and care though.

clnfrk · 04-23-07, 01:22

Quote:

Originally Posted by Accumulator

I really only use the 4" pads on the rotary for small-area spot repairs and for situations where the larger pads won't fit. A while back somebody posted a pretty compelling argument about why the smaller pads are both riskier (heat build-up) and less effective (correction-wise) than the larger pads. I forget the details of his argument, but they did correspond to my observations when using the different sizes of pads.

So use whatever works for you, but be careful and pay attention

I would agree wholeheartedly on the riskier factor when using 4" pads with a rotary, although I would have to totally disagree with them being less effective at correcting.

Accumulator · 04-23-07, 01:24

I've yet to have any heat-related issues so I can't speak with authority. I'm always being very careful and I don't have any heat-measurement tools

It did seem like the 4" orange pads were getting things pretty warm at ~1500 so I took that as a clue to, well, continue being careful

Worked fine on the M3's plastic, but I still found that argument compelling.

Quote:

Originally Posted by WilliamHBonney

Ok the heat buildup I can understand, but was less effective correction wise?

The whole size/speed thing reminded me of a lecture on disk-drive speeds from the early '80s. The outer portions of big rotating things move faster then the outer portions of *smaller* rotating things (they cover more ground in the same period of time), hence (in this context) the ability to do more work.

orngez · 04-23-07, 01:43

smaller pads technically do less correction...but being easier to control you tend to get the same level of correction in the end....the whole inner/outer rotating debate can continue if you want but just look at your pads and you will have your answer...where is the most polish building up because it is not fully breaking down?...the closer you get to the center of the pad...the more polish that is not broken down...so a larger pad like an 8 inch pad has a larger area of surface that does heavier correcting...maybe the outer 3 or 4 inches on and 8 inch pad compared to the outer 2 or 3 inches of a 6 inch pad...the percentage of pad that does correction is the same but a larger pad still has overall more correcting surface

qadsan · 04-23-07, 02:11

There are various machine factors at work here (time, speed, pressure, pad type & material, etc), in addition to other factors such as the aggressiveness of polish, environmental factors such as heat & humidity, material being worked, etc, but lets focus on the machine and pad size for a second.

Smaller pads have less surface area working against the paint / finish, which means there's more working pressure per square inch with a smaller pad. A 6" pad has more than twice the area of a 4" pad and this factor is especially important on dual action machines, hence the reason smaller diameter pads can offer more correction. A 4" pad has an area of about 12.57 in^2 where as a 6" pad has an area of about 28.27 in^2. An 8" pad has a whopping area of 201.06 in^2, or about 7 times that of a 6" pad and nearly 16 times that of a 4" pad!

When it comes to rotary machines, you’ve got another factor at work, which is the rotational speed of the pad. Even though you have a fixed machine speed of 1,500 RPM, the speed of the pad increases as its diameter gets larger. For instance, with your rotary machine set to 1,500 RPM, the outer edge of an 8” pad will be spinning at about 35.7 MPH or twice the speed of 4”. At 1,500 RPM, the outer edge of the 6” pad will be spinning at 26.7 MPH (~25% less than an 8” pad). Higher speeds increase friction, which in turn increases heat. While the smaller diameter pads increase the working pressure per square inch, you may need to increase the machine RPM to make up for frictional heat difference of their slower speeds.

What all this really boils down to is there’s no perfect universal rule that works for all products, machines, environments, etc, and you’ve got to use common sense, test methods and experimentation to find what works best for your specific situation. For instance, if you were using a rotary with an 8” pad at 1,200 RPM with good results, then you should probably increase the speed of the machine when using a smaller pad, but always work a test spot first to determine the process that works best for your given application. Even though the outer edge of an 8” pad will have a speed that’s twice that of a 4” pad, it doesn’t mean you should run the 4” pad at twice the machine RPM to get the same pad speed. You can’t forget that your 4” pad by its very nature of being smaller has already increased the working pressure per square inch and this has to be factored in with pad speed.

WilliamHBonney · 04-23-07, 02:11

Quote:

Originally Posted by orngez

smaller pads technically do less correction...but being easier to control you tend to get the same level of correction in the end....the whole inner/outer rotating debate can continue if you want but just look at your pads and you will have your answer...where is the most polish building up because it is not fully breaking down?...the closer you get to the center of the pad...the more polish that is not broken down...so a larger pad like an 8 inch pad has a larger area of surface that does heavier correcting...maybe the outer 3 or 4 inches on and 8 inch pad compared to the outer 2 or 3 inches of a 6 inch pad...the percentage of pad that does correction is the same but a larger pad still has overall more correcting surface

Believe me I would like to get the use out of my bigger pads but they tend to skip to much when I am using them.