Throw/orbit on the PC7424?

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itskrees

New member
Hi everyone,



I plan on using my pc7424 throughout the sanding process of respraying my miata. The only issue is that I'm unsure as to what the throw is on the machine..which is usually indicative of what part of the process it would be used in (surface prep, priming, or finishing) when it comes to sanding. From what ive read, 3/8" throw is ideal for surface prep before primer, 3/16" is for leveling the primer before spraying base coat, and 3/32" is for damp/wetsanding orange peel. I tried calling Porter cable today and they couldn't find an answer.. would anyone on here happen to know the throw of the machine? Thanks in advance!



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itskrees said:
Hi everyone,



I plan on using my pc7424 throughout the sanding process of respraying my miata. The only issue is that I'm unsure as to what the throw is on the machine..which is usually indicative of what part of the process it would be used in (surface prep, priming, or finishing) when it comes to sanding. From what ive read, 3/8" throw is ideal for surface prep before primer, 3/16" is for leveling the primer before spraying base coat, and 3/32" is for damp/wetsanding orange peel. I tried calling Porter cable today and they couldn't find an answer.. would anyone on here happen to know the throw of the machine? Thanks in advance!
Click to expand...



It features a 5/16" diameter stroke, and will work well for all the sanding jobs you've mentioned. I've used mine paired with 36 grit discs to smooth concrete, with 4000 grit discs to final sand automotive paint, and all sorts of tasks in between.



The orbit size comes into play when you are either working on an area that does not physically allow you to use the machine due to its movement (a 6" sanding disc used in an area smaller than 6-5/16" across), or when you cannot easily control unintended tilting of the machine.



In my opinion, it's the latter that causes the sanding industry to recommend small stroke machines for fine sanding. For example, if you happen to be sanding a flat surface and you tilt the machine, the edge of the sanding disc will dig into or gouge the sanding surface. This will be very noticeable on a finely sanded surface.



Further, all other things being equal, a machine featuring a small stroke will cause its backing plate to rotate more slowly than a machine featuring a large stroke. Because of this, a small stroke machine might be a bit easier to handle (possibly resulting in less edge digging), whereas the large stroke machine may be a bit more difficult to control if the backing plate is in fact spinning at a faster rate.



Use of an interface pad (a cushioned spacer placed between the backing plate and sanding disc) will absorb some machine tilt and likely negate some of the machine's motion, but the trade-off is well worth it. The sanding disc will contour to complex or curved surfaces much better, and won't negatively affect the sanding of flat surfaces all that much (if at all- it really depends upon the characteristics of the interface pad). Click the link to learn more about interface pads.



To the point: use high quality sanding discs, use slow machine speeds rather than faster, and for goodness sake... keep your discs clean!
 
Kevin Brown- thanks so much for the information! Your knowledge truely is an asset to the community. Im delighted to hear that my good old PC is up to the task, I guess that leads me to a couple other questions.



1)Since there is no polish involved, there is no "flashing" of any substance that would indicate when you have completed a sufficient number of passes. How would you know when to stop sanding?



2) Would I continue to work in a 2x2' area in a way similar to how I would work a polish on a DA? Keeping the speed at a 3-4, 1 rotation/second, moderate pressure, slow speeds, etc..



3) How long/often do you change the sanding disc? Im looking at the prices and it can hit anywhere from $75-$100 for a 20 pack of just 1 grit.



When buffing, I find myself usually having to change pads two-three times when using an LC orange pad, sometimes less when using white or blue. Would the same go for sanding, where I'd only need like 3 80 grit, 3 330 grit, 2-3 600 grit, 2-3 1500 wet, and 2 3000?



Again, thanks for the info, and if anyone else would like to chime in as well I'd greatly appreciate it!



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itskrees, I would try talking to KB directly (not through this forum) -- he can't make the offer here (rules apply) but he can set you up with everything you need for your project, one-stop shopping style. ;)
 
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