Using a disc sander with shelf

[DIYalot]

Hi. I'm making a home-made disc sander with a shelf in front of the disc. I'm going to be using diamond pads to take make and polish 60mm cubes from Yorkshire sandstone. Firstly, is it correct to assume that although only 50mm of the disc with show above the shelf (assuming the shelf is halfway up the disc) there should not be a problem getting pretty nigh on perfect cubes?

Secondly, is it kosher to place the shelf below the halfway point of the disc? Say 60mm to the disc edge that the work will be in contact with, 40mm below the shelf? I'd like to use diamond pads greater than 100mm dia., say 180mm dia. but not seen any.

EDIT: Just seen some 180mm dia. diamond pads on Ebay.

 

[Burnerman]

Nothing wrong with your theories at all, but it is conventional to have the rest at centre height but it isn’t vital.....but only use one face of the disc that is pressing the material against the rest for safety.
I do think you are expecting quite a lot from such a small disc though so I’d certainly practice first as the outside of the disc does tend to remove material quicker than the inside - there again I’ve never used discs on stone.
Are there any belts available for something similar to a Machine Mart linisher.....maybe easier if there is.
Watch out for the heat generated!
Just a thought!
John

 

[DIYalot]

Hi. Just noticed that one can get diamond pads 180mm diameter, because I've just seen some on Ebay. It might make sense to get a 180mm aluminium backing disc, and use 180mm dia. diamond pads.

 

[Burnerman]

I think that would be a good move.....how are you fixing the faceplate to the motor?
John

 

[DIYalot]

I intend to weld on a 14mm dia. stud onto the spindle of a washing machine universal motor and use an arduino speed controller (based on "Arduino universal AC motor speed controller" as per Arduino Projects). When finished I'll probably upload the project to Arduino Projects.

 

[Burnerman]

Not wanting to be a wet blanket at all, but I’m a bit concerned about the balance of the disc and the tendency for it to run out of true.....I guess you don’t have access to a lathe.
John

 

[DIYalot]

Hi. Currently I do not have a lathe. Actually, it might be feasible to get an adapter of sorts made and fit it into the recess you see on the spindle, and pin it.

 

[Burnerman]

Presumably the diamond pads come with a backing plate, hence your reference to a 14mm stud, the same as an angle grinder/polisher?
Again, very accurate machining of an arbor required to avoid a wobble!
Just had a thought.....I seem to recollect a 14mm spindle turned to fit into a normal corded drill somewhere. What RPM are we dealing with?
John

 

[Burnerman]

https://lilleytileandstone.co.uk/ru...MIqLK22I-a5gIVGeDtCh2_-g0hEAQYDiABEgLnIvD_BwE
Always worth looking at other options!
Good luck with your project.
John

 

[DIYalot]

Hi. I think I can get an aluminium backing plate with velcro, and the pads are affixed by way of velcro. I've been looking here for the backing plate:
https://www.elitestonetools.co.uk/shop/velcro-foam-backing-pads-m14-lfas4
Speed: About 2500 RPM.

 

[Burnerman]

Yep, they will do nicely....all you have to do is to mount them onto a drive motor. 2500 RPM is bloody fast if the machine is out of balance and will hardly be usable I fear so whatever system is used it will have to be good!
John

 

[Tigercubrider]

What about dust?
We are having a sh1t load of trouble in our wood workshop due to ineffective dust collection/extraction
Stone dust could be even worse

 

[Ryler]

Water application is the usual method when cutting or polishing stone.
Won't work well with the OP's method. Likely to get electrocuted.