Questions for those who gave surface grinders running belts

[deker]

I'm contemplating picking up a surface grinder I've found a good price on, but it's only worth it to me if I can run belts rather than stone wheel. The reason for that is that my major use for it will be to grind damascus to finished thickness myself rather than send out my grinding to a shop. It's a 3ph machine so I'd have to set up a VFD or swap the motor. I'd lean towards a VFD in that case honestly.

So, I've got a couple of questions for folks who have done this.

- How tough was it to adapt a wheel to the spindle and set up tracking? The one I'm looking at is a Brown & Sharpe #2.
- How much steel can you take at a pass? I'm figuring on roughing with 36 grit and then switching to 3M Gator belts since they grind so cool and even.
- Anything else I should know?

Thanks,

-d

 

[John L]

I switched out a harbor freight surface grinder to belts. It took a couple of hours and it runs great. The motor was not powerful enough so I hooked up a two hrspwr motor and pulleys to the opposite end of the arbor from the stone. It works great. I make slipjoints and do not need to hog material...but with a 36 grit belt you cetainly could. The quality of the mag chuck is important if hogging as you create quite a bit of friction and the materials being ground want to move. I simply place another thinner pc of steel behind the pcs being ground and throw the arm on the chuck and it works pretty well. Now..this chuck is pretty lousy one also...it came with the Harbour Freight unit. I have heard that some people think that these units are not qccurate...but when I checked mine initially I gound four different pcs on all four corners and they were all within a thou. Good enough for me. I use mine to clean up heat blades and springs after heat treat.

 

[Ed Caffrey]

Heres a link to pics of my surface grinder that was converted to belts shortly after I purchased it: http://edcaffreyms.jalbum.net/Surface Grinder Conversion/

If I can set it up, anyone can. Besides ensuring that you have a quality fine pole mag chuck, its also very important to utilize a very hard wheel....if you planning on running a contact wheel, use a 100 durometer. Some folks have even forsaken contact wheels and had staight aluminum wheels. The problems with standard 70 or 90 durometer contact wheels is that because your applying down pressure in a surface grinder situation, if the wheel is softer, it will "cup" causing whatever your grinding to come out convexed (low on the edges and and a high spot down the middle).

I personally do like the Gator belts on the surface grinder...more often than not they will acquire a groove in the belt where it contacts the work piece...if you move the contact any at all (side to side), it will leave high/low lines down whatever your working on.

As far as how much you can take at a pass...with a 50 grit belt and slow passes, I can manage .010 to .020 if I'm careful and slow.

 

[deker]

Thanks for the info Ed. I've got a couple more questions for you. First off, which durometer scale are you speaking of, A or D? I was just looking at Sunray wheels and they have 70A and 70D. 70A seems very soft (somewhere between a car tire and a tap washer), and 70D seems much harder (described as "hard as a golf ball"). 70D would be the obvious choice, but I'm wondering if the wheel you're using is 100A or 100D.

Is your idler crowned?I see the tracking adjustment, but I can't tell if the wheel itself is crowned.

Also, are you able to prep all of your steel effectively to thickness? What I'm looking for is to avoid paying the blanchard grinding shop hundreds of dollars if I can do the work myself. Since I'll never be able to afford or power a blanchard grinder, this is the next best thing.

I like the attachment method for the arm BTW, looks very effective and completely non-destructive to the grinder itself.

Thanks!

-d

 

[Ed Caffrey]

Ya know....I'm not really sure about the scale. I know the wheel is 100 durometer urethane, and I can apply enough down pressure to stop my surface grinder, and still not get any "cupping" on the work piece.

There is a slight crown on my idler wheel.

Yes, on prepping my steel. I can hold within 1/2 thousandth with this set up, and its also the machine I use for precision grinding billets for other makers.
The machine itself was $999 with free shipping when I purchase it, and I spent approx. $250 more setting it up for the belts. I really like the economics of using the same belts as my grinders, plus the convenience of not having to take the time and trouble of changing grinding wheels when I want to achieve a finer finish.

It might take a while to make up the difference if your out sourcing your grinding, but its really nice to have the machine sitting in your shop and be able to use it whenever you need to.