MetalworkingFun Forum

ok so yes im a bit of a dumb bugger with a lot of things .keeping in memory all I basically did all my life was build bike motors and fabrication of frames exhausts ect
firstly big thanx for all the help and replys you all have given its a lot to take in but it is getting through the thick skull .
my son wants me to make him a belt sander I have 3 different pulleys for the 1/2 hp motor but im not sure which will give it the best speed eg; 2600rpm ]a mate recommended]
1st pulley is 3inch ..2nd is 2inch 3rd is 4inch
my question is which will give my boy the best speed
my way of thinking is it don't matter as the motor only spins at one speed so the pulley bolted to motor wont change belt speed but hey im on a lot of meds so I more than likely could be wrong
any info would help
cheers

Cutting speeds for belt sanders are typically calculated in SFPM (surface feet per minute) or in meters per minute in the civilized world.  One can perform a Google search for belt sander plans and literally come up with dozens of examples.  Here's one result:

http://www.toolcrib.com/blog/2010/05/12-...ess-sander

I'd start by deciding just what type & size of belt sander you'll build and find out the preferred belt speed.  Then you can start calculating what size of pulleys you need.

What is the motor rpm?

not sure tom I got it few yrs back at a yard sale but it spins bloody fast

Have a project speeding up the belt speed of a wood sander. Pretty standard common belt sander found everywhere, 8 disk 6 x 48 belt. Here are pictures, remove the disk, replaced the belt drive pulley, double the size of the motor drive pulley. 

How does it work?

1 did speed things up as common sense tells ya

2 better metal removal

3 does it stall .......... to much feed, yes and that was not new it stalled before I modified it, so no biggy

4 Next step, at some point when I find one, will increase the HP of the motor, I believe this one is 1/3. Want to step it up to 1 hp 110ac,  3400 rpm

5 belt tracking was not affected, still holds as before, a little tweaking here and there is alway in the game.

Conclusion:

I wanted to keep the 6" width just my preference, it works better than therory says it should. 


greg

Hate to burst a bubble, but in general wood requires much higher cutting speeds than metal.

I have a 3/4hp motor on my Delta/Rockwell 6" wide belt & 12" disk and I really really have make the effort to stall the sander.  The belt will slip and the motor keeps on running.

One thing that really concerns me is the unguarded belt & pulleys.  One Oh ***** could result in the loss of finger(s) or thumb.

If wood work takes higher belt speeds, then why do belt grinders run so fast?  Second, I am actually smart enough to not put my fingers in a running machine.

Ok, so a 3/4 hp motor is harder to stall, seems logical to me. What's the point you are attempting to make?

Kindly be concerned about your own safety, thank you very much, I was born at night but not last night.  

greg

I'm not an old hand with belt grinders but my single-speed 4" belt- made for metal work- burns wood unless one is extremely gentle. I have always been of the understanding that this is because the belt speed is way too fast for wood. One of the projects that has been on my list for a long time is a variable-speed belt grinder / sander run via VFD.

Ron, changing the pulley size will indeed change belt speed because the belt is moved by the circumference of the pulley- thus a drive pulley with a 12" circumference will move a belt 12" per revolution, which if coupled to a driven pulley with a 6" circumference will make that pulley turn twice to move the circumference that same 12".
If you are able to find out an ideal grinder belt speed in feet per minute (someone on here will probably know, if not, Mr Google almost certainly will) then it is a matter of working out the ratios of your drive train in relation to your motor RPM, to get the required speed at the surface (i.e the circumference) of the drum that drives your belt.
If you find yourself struggling with this, I'm sure you could get some help here to work out what pulleys you need. The info needed would be (A) the motor RPM, (B) the size of the drum or wheel on the grinder, and © the required belt speed.

The RPM of your motor will be on the name plate, along with the voltage, horsepower etc. If this is missing or unreadable, I have a dial RPM gauge that you could borrow for the cost of return postage if you like.

Pete

(09-02-2016, 10:35 PM)pepi Wrote: [ -> ]If wood work takes higher belt speeds, then why do belt grinders run so fast?  Second, I am actually smart enough to not put my fingers in a running machine.

Ok, so a 3/4 hp motor is harder to stall, seems logical to me. What's the point you are attempting to make?

Kindly be concerned about your own safety, thank you very much, I was born at night but not last night.  

greg

most of the production belt grinder, I seen and used are between 3600 to 8000 fpm, I've seen in a catalog a version that went to over 10,000 fpm. A belt break at that speed has to be exciting. I have a 2 x 48 Jancy RadiusMaster, that runs at 3600 fpm, that will remove metal at an alarming rate. Belt speed is only part of the equation, high quality belts are a absolute necessity, I use nothing by Norton, with ceramic grit on a fabric backer. Cheap belts render a belt grinder almost useless.

I have a Rockwell/Delta 6 x 48 belt sander, that speed is about 1200 fpm, a good unit, but rarely used, since the Jancy arrived in the shop.

THANX PETE O WILL LET YOU KNOW ONCE I HAVE A SCAN OF THE MOTORS ID TAGS IF ANY ive wanted to make something like this anglegrinder sander as it owould be great for sanding pipes ect but the son said the stationary belt sander/grinder is what he wants/needs
btw happy fathers day to all that have dads still with us .I don't drink fullstop but will have a bit of a beer for my dad as he passed in april from asbestos cancer he got while in the forces from 46 to 75  and missing him heaps