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Disc/Belt Sander RPM?

pak

Cast Iron
Joined
Oct 31, 2007
Location
Miami Fl, USA
I am looking for a new 6” x 48” belt/12” disc sander. I notice that, depending on the make/model, there is a choice between 3450 RPM and 1725 RPM, driving the belt at 5000 and 2500 SFPM respectively. Which speed is more appropriate for metal working in aluminum, steel and SS?

Thank you.

Drew
 
Well, there you go. We all have different experiences, I guess. In the last few years I've replaced all my sanders and grinders with 1750 RPM (except my Baldor diamond wheel one, which I think only comes as 3450). Much more enjoyable for me. Slower stock removal, yes, but not a scary to be up close to.

But then I'm getting older and slower, too. . .
 
I cannot decipher David's comment. As a rule,the slower motor is for woodworking.However,I have a variable speed motor on my square wheel grinder,which is useful when doing delicate work,such as finishing up the grinding on a knife blade,when you do not want to cut a dollop out of a nearly finished bevel. Got the 1 1/4 H.P. D.C. motor and drive unit from Surplus Sales (?) Catalog for a lot less than elsewhere. They are new Leeson motors and controls.
 
I had a 1725 RPM 12" disc grinder / 6 x 48" belt combo. The belt speed was way too slow for finishing metal. It always left a scratchy finish. I upgraded to a Burr King 760 (3450 RPM motor, 8000SFPM belt) and it leaves a smoother finish with 180 grit than the slow machine left with 300 grit. It also removes material faster. Generally I love it. I also went to a 20" 1725 RPM disc grinder and that seems about right. The 12" disc at 1725 RPM, just did not remove stock the same way.

As far as bench grinders go, I prefer the slower 1725 RPM models to the 3450s in 8" or greater wheel diameter. (The slow machines are especially nice for use with wire wheels, they just don't throw as many wires.)

The below is from the Burr King website FAQ

Question: What abrasive speeds are best for which materials?

Answer: In general abrasive speeds from 4000 to 8000 surface feet per minute are recommended for mild steels and aluminum. Abrasive speeds from 3000 to 6000 surface feet per minute work well with stainless steels and cast irons. Exotic materials such as titanium generally prefer speeds below 2000 SFPM. Plastics and other polymers usually prefer speeds below 2000 SFPM. Woods and similar fibrous materials are often best ground below 6000 SFPM. Grinding speeds are determined by the material to be ground, the finish desired, and the abrasive used.

As far as brand goes:

Belt Sanders: Burr King
Disc Grinders: State / Apex / Master
Bench Grinders: Baldor (although I like the Daytons as well and I usually do not like Grainger stuff)
 
2Slow: Good info. It helps narrow the field. I will take a look at each of these this week.

Has anyone seen this product? It has some interesting videos, but very expensive for something that seems easy to build. Do a search on "beaumontmetalworks" on YouTube.

Drew
 
The Burr King 760s are very expensive and it is hard to justify the new price. I only paid $350 for mine, but I got a good deal at an auction. I really like the machine, but would not pay much more than $500 for one in nice shape.

-Joe
 
I looked at the Burr King 760 along with their other models. That's a nice machine. My options are all over the place now. I'll have to give this some thought.

Drew
 
this is an old thread but i joined this blog site to ask a question i think i've already answered.
i have a mastercraft 4x36 inch belt sander with a disc sander on the side.
after reading this thread and looking up other models i figure this little bitty i got probably runs an rpm around 1700.
it works better than by bench grinder at shaving off steel from my untempered leaf spring i'm making into a bowie knife.
the problem is i went through a belt in no time. i've bought a few more and will estimate the costs of belts after i do some more "shaving"
i'm making a jig for my bench grinder to shave off the steel in a bit more controlled fashion.

i dont want to spend (nor have in my shop) a huge dedicated belt grinder. the cost is a bit high as well. how significant a difference is a dedicated belt grinder for shaping blades vs this little mastercraft with a 36 inch belt?
I am hoping it's the quality of the belts i put up, but wasn't sure.

i think i can grind a bit more with the bench grinder (after finishing my jig) then flatten out the blade with the belt sander.

what do you think?

i am just a backyard amateur putterer.
i get most of my experience from my old profession and DIY on youtube.
I was a maintenance test pilot in the army and did only hands on sheet metal work in school (officers didn't do hands on repairs). I did inspect and i did have an awesome machinist in panama, and i watched him at work a lot.
 








 
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