Disc sander vs wide-belt sander

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Wapiti

Joined
Sep 25, 1999
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I have been working on a design and assembling the parts for a disc sander when a thought occured to me;
Why do most makers favor a disc sander in the shop over a wide belt sander (like a 4x or 6x belt)?
Is it mainly because finer grit sandpaper can be used on the disc, and metal cutting sandpaper can be used? Both features that are not as simple to pull of in 4x or 6x belts?
Now, understand that I have never used a disc sander, so that might be part of where my questions are comming from (lack of experience).
It seems that wide flat grinds could be had on the wide belts, and it would be easier to switch grits.

I guess this question has come up for me bacause the main reason I have not added a disc sander earlier is it seems like a pain to replace the paper when I need to switch grits.
At this point I see the main value of a disc sander in my shop would be for flattening handle slabs, and maybe occationally flattening a blade bevel.

At this point I do most of my final flat sanding on a sanding plane (marble).

Anyway, was just curious what other's thoughts were on this.
Thanks again,
Brome
 
They both have their uses. Now remember, the standard knife makers grinder is a 2X72. The 4" sander is good for flat work. I use it a lot to round the ends of steel. If you start on the edge and arc your arm the same for each side, you get a near perfect round on the end.
It's also better to flat sand the handle scales.

The disk grinder is better for hogging metal. It allows you to get right up to the tang and hog away. I also find the horizontal disk better for things like double edge daggers. Some people can't do it that way.

I have a number of grinders. From 12" belts to 1". I have several disk grinders 4" to 9" and in different speeds.

It's not unusual, especially when I'm making a part, for me to move back and forth between all of them.

If I could only have one grinder though, it would be my homemade 2X72.

If you need something while you are building that, go to Woodcraft, buy their $15.00 9" disk and pit it on a junkyard 2 hp motor.
 
One thing I don't like about a disk is that the closer you get to the center, the slower it cuts. I've used my 6" disk sander for grinding chisels and some things like that any it just didn't want to put an even bevel on. On a bigger disk its not going to be as prounounced, but it still happens. Surface speed decreases as you approach the center (where you have rotation, but no lateral movement of the grit which is what does the cutting).
On a wide belt with a platen, you don't have this. So it makes some things easier. At least starting out, before you learn to compensate on the disk.

I do like a disk for a lot of things and would not want to be without one though. I guess what I'm saying is its best to have both :D
 
Matt, I user a 6X48 belt for preforming and flat grinding (it has a 9" disk that I almost never use).The belts are readily available from Pop's.Prices are almost the same as a 2X72 belt.I have a 9" cast iron,horizontal disk set up to run very slow, 0 to 180 RPM.It has a spray mist.I use it for sharpening and for getting exact flats.I can get disks to 8000 grit,and polish pads to 100,000 grit.If you go 6X48 get a good unit.The underpowered econo units are a waste of time and money.Like Pete said,your first real money should be for the best 2X72 you can afford.
SA
 
One thing I don't like about a disk is that the closer you get to the center

There's a trick to it Matt. Start your blade and pull back. The entire blade gets the benefit of the high speed outer edge.

The speed differential can actually work to your benefit in some cases.
When you grind on the belt grinder, (or at least for me) the 1/3 toward the tip seems to always reach 0 grind first.

I can go to the disk and complete the grind without over grinding the thinner tip section.

When I go to the slow, finish disk, I just use the pull back method to keep everything even.
 
Is it possible to remove dips and low spots using the disc sander? Not that I don't like using 180 grit EDM stones :).

Matt
 
Yes, in fact it's easier for me to get a final flat on the disk sander than on the 2" belt.
 
Like Peter, and Matt said. You just can't get a true flat with the belt grinder. You have a moving belt, over a stationary platen. It will never be really flat.
That is mostly eliminated with a disc sander.

Taking tapered tangs as an example, I rough the taper with a 40 grit belt(after heat treat) on the vertical platen on my belt sander, and use the disc to get it truly flat.

It always has a slight convex, or dips from the belt grinder, even with a pyroceram platen liner. The disc gets them right out.:eek: :D
 
Thanks for the information and the thoughts.
I am actually pretty good with the 2x72 grinders, for now
( http://www.stoneandsteel.net/tools.html ).
Have a modified Grizzly and a KMG, both serve me very well.
Still plan other modifications to the Grizzly, but that is another story.

Peter nap, thanks for the recommendation on the discs at Woodcraft. I was actually contemplating shelling out the big bucks for one of Rob's discs; they are nice. Would have to see if he still has any of the old flat ones he used to make, as I would be using it to flatten handle slabs and don't need the 1 degree bevel.

Well, I will give it some more thought.
Sounds like it is definitely a worthwhile grinder to add to the ones I have.
And I already picked up a 1.5hp DC motor and controller from my favorite scrap yard, so I am mostly there (though not convinced variable speed isn't a little overkill for a disc sander...).
Anyway, thanks again for the help,
and you folks have a great Thanksgiving; I know I have a great deal to be thankful for.
Brome
 
Could someone explain the 1 degree bevel as far as what it does that a true flat disk will not do? Many thanks.
 
My understanding is that the one degree bevel allows a person who is grinding a blade (or anything) longer the the radius of the disc to extend that blade beyond the center of the disc, without the other side of the disc catching the blade.
But that is just my understanding; I have never used one.
Brome
 
I expect someone will give a better explanation but.....

The very center of the disk is almost useless. Worse when you grind slightly off center it cams the end of the work around like an eccentric wheel. The bevel causes the blade to miss that center zone. As far as I can see, the only real disadvantage is that you reduce the disk size some. No biggie since the portion eliminated can't be used.
 
Go with the variable speed.It is a must when flattening ivory and bone,as well as many woods.The 1 degree bevel does exactly what Wapiti said.It keeps the sanded item from grabbing the rising side of the disk.It can prevent a nasty accident when grinding a blade.
 
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