The birth of my twins!

i4Marc

i4Marc

Joined
Oct 19, 2011
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Um, ok, they're just disc sanders but I'm still a proud papa. Just finished them an hour ago. They are identical except that one has a flat disc and the other has the 1˚ bevel (thanks Nathan!). They are 1HP 115V reversible 1750rpm. The design sprang from an idea another member here shared with me (thanks Barry). I added some features of my own. They can be used horizontally or vertically. The reversible hand rest is very sturdy in the vertical position, height adjustable of course, and can be used with the work rest in the horizontal position. The reverse switch will come in handy although I wish it were also variable speed. I'm going to see if I can figure something out with that. The motor will be used with a foot switch so I can use both hands to pre-position the blade before turning on the motor.












Update: New and improved. Now with speed control!

 
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Man Marc those are sweet! I know you haven't used them yet since your shop is so clean at that spot. Get to using them and that will change quickly!
 
My only suggestion would be to change out the nuts on the height adjuster for the work rest with hand knobs. That will make adjustments and paper change faster and easier.
 
Thanks Barry. I'm looking forward to getting them dirty today. They were based off of your set up. Thanks for sharing that.

Stacy, I thought initially about using wing nuts but I was afraid they wouldn't generate sufficient clamping force. I don't want the rest to slip. I guess I was thinking small. Hand knobs is a better idea. I will look into sourcing some.
 
Chris,

The 1˚ bevel is so that there is no reverse direction drag on the opposite side of the disc. If you are sanding a longer blade that crosses the center of the disc it will want to spin. The bevel creates just a slight clearance on the back end so that does not become an issue.
 
Whoa, get rid of that rheostat... you'll kill your motors! :eek:

The stands look nice though. :) :thumbup:

How do you hold them down?
 
Grrrrrrrrrr. Thanks Nick. How did I know that would be too easy? I have the open cage design so that in either orientation clamps can be used to secure them to a bench. They don't "walk" much in the horizontal position unless you are pushing hard but in the vertical position clamps are a must because they will twist with the start up torque. I haven't weighed them but they are heavy, maybe 45 lbs or so.
 
That photo shows two things that will never go together...a low cost motor controller ( virtually useless) and a capacitor start motor. Don't try and run it that way.
 
One thing you might want to do is lower the work rest below the center line. At the center and above the piece will feel like it is being pushed sideways off the disc and below the center line the pull is down across the blade not out the side.
 
Yeah, thanks Stacy. I'm not going to use the controllers. Dumb newb mistake.

That's interesting Barry. I will modify the work rest to be adjustable in that regard.
 
I made some changes to the work rest as suggested. I lowered the work table level to below the center line of the disc. I also enlarged the work rest and added an additional adjustment. The work rest can now be adjusted for parallel to the disc. The hand knobs are on order.


 
They run great Barry but without variable speed they are a handful. The motors run very strong and smooth and the discs are super nice. Even at 1750 rpm they are just too fast. They heat up a blade quickly. I guess a light touch and frequent dips in the water bucket are in order. I tried feathering adhesive with the discs but found it too lumpy under the paper for my taste. Maybe it was just the cold temps in my garage wouldn't allow the adhesive to spread evenly enough? Anyway, I tried a re-positionable spray adhesive which works much better. I also tried using a 1/16" thick neoprene rubber layer on the disc to absorb any bumps or irregularities under the paper but that turned out to be a bad idea. When the spinning disc pushes the blade against the hand/work rest it has nowhere to go. The blade is held in place by the immovable rest and the hard surface of the disc. When I added the rubber surface to the disc I now had a surface that gives slightly. The blade was still held by the rest but the slight give of the rubber allowed the blade to find its way under the rest and now we have a flying blade (and ruined paper). Not good.

If anybody wants to pass along helpful tips for using disc sanders feel free to pass them along. ;)
 
It doesn't take much of the feathering adhesive to stick paper down. I use business cards to smooth it out and that works pretty good. Sorry to hear they aren't working out like you had hoped! The learning curve of the disc seems to be a lot higher than on a grinder. Being able to slow down the rotation would be a big help learning how to use them. As far as tips I don't have enough experience with mine yet to offer any except practice, practice, practice.
 
I would be in a world of hurt without variable speed and a reversing switch. I run mine pretty darn slow.

I don't grind blades with a tool rest on the discs. I need to be able to work the blade around at varying angles.

Feathering adhesive has hands down been the best adhesive for a 9" disc IME. The cold temps might be the issue. How are you spreading it out? I use heavy card stock or business cards. The guy that lived here before us left a box of 2,000 shiny finish business cards... they work perfect. :D
 
I think the cold temps are the problem with the adhesive Nick. I'll try doing a test application in the house where it's warmer to see if there is a difference. I'm spreading it with a small plastic drywall spackle knife. The motors are wired for reverse so that helps but man, I'd love to have variable speed. I do all my bevel grinding freehand on the belt. I was going to use the discs for finish refinement as well as for flattening guards, handles, spacers etc. As you can see from the pics it will be easy enough to pop off the work rests so I might try using the discs without rests.
 
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