Home Built Surface Grinder

razor-edge-knives said:
Is anyone else getting some serious convex action on the ends of a piece or around holes? It's like the rubber on the wheel is compressing on the main portion of the blade but right where it comes on or goes off of the blade it's curved really bad (I'm getting about .035" between both sides!) . I'm thinking it's because of the 70 duro wheel - need something harder.
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How many thousandths of an inch (or MM) are you moving for each advance? How much thickness are you removing each pass?

I seldom move more than 3 or 4 thou each advance, and remove only a thou or two each pass and don't have any rounding of the sides, or dishing of holes.
 
Ken H> said:
How many thousandths of an inch (or MM) are you moving for each advance? How much thickness are you removing each pass?

I seldom move more than 3 or 4 thou each advance, and remove only a thou or two each pass and don't have any rounding of the sides, or dishing of holes.
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I was doing about 8-9 thou, good point I'll try that
 
i only go 1 thousand each pass. i have really skinny arms and if i try to take too much off my skinny arm cannot keep the same speed when pulling the table across the contact wheel :rolleyes: if i try and take off 5 thou, sometimes the resistance is too much and the table will stop for a second and cut a deep spot o_O
 
hardness of the wheel, amount of material removed each pass but also the grit size of the belt has an effect on the amount of rounding. I found that with a 36 grit belt there is less rounding wenn you remove to much at once, than with a 120 grit.
 
I can't understand why there is need for a rubber contact wheel in a surface grinder. Do you know why?
A steel wheel would not "round the edges" of the piece as a rubber wheel can do. A stone wheel works well (better) for SG even if it is rigid and brittle.
Is the reason related to the chance a steel wheel could expand by heat build up and throw out the depth of cut? Or the possibility of hogging the material justifies the compromise of using a rubber wheel?
 
john april said:
good point stezann, a hard wheel should give more consistent results ?
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I get very consistent results with a rubber contact wheel. I'm not sure what a hard wheel would do, I would imagine you might have more and faster heat build up. If you don't get too aggressive advancing the chuck, it's a non issue.
 
john april said:
i only go 1 thousand each pass. i have really skinny arms and if i try to take too much off my skinny arm cannot keep the same speed when pulling the table across the contact wheel :rolleyes: if i try and take off 5 thou, sometimes the resistance is too much and the table will stop for a second and cut a deep spot o_O
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He ain't lying. He's like a stick figure.
 
Kevin McGovern said:
I get very consistent results with a rubber contact wheel. I'm not sure what a hard wheel would do, I would imagine you might have more and faster heat build up. If you don't get too aggressive advancing the chuck, it's a non issue.
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I do imagine a harder wheel would be more consistent, as long as it was running very true and balanced. Unfortunately I don't know where to get one or I probably would... But even on that piece I had you SG for me I did notice some convexing at the ends (which was a non-issue for me since I was using a piece in the middle, and was super thankful that you did it for me! ;)). Just saying that I think with any soft-ish wheel it will be somewhat of an issue because there will be compression.
 
razor-edge-knives said:
I do imagine a harder wheel would be more consistent, as long as it was running very true and balanced. Unfortunately I don't know where to get one or I probably would... But even on that piece I had you SG for me I did notice some convexing at the ends (which was a non-issue for me since I was using a piece in the middle, and was super thankful that you did it for me! ;)). Just saying that I think with any soft-ish wheel it will be somewhat of an issue because there will be compression.
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I probably got a little over zealous with that since I was removing so much. There's a reason I NOW know not to advance too much per pass...
Glad it worked out though.
 
Yes, a stone wheel does offer a good bit finer finish than a belt will, BUT - you have to take fine passes with a stone wheel, it must be kept dressed properly, and they are expensive. Changing wheels is a bit more hassle than changing belts also. Stone does work good on a "real" surface grinder, but you don't normally "hog" with them either. OR - I didn't many years ago when I was using one.

A metal wheel rather than a rubber/poly coated wheel would be a lot like grinding on a metal wheel. To get the feel for that, try a bit of grinding on your drive wheel and you'll find out quickly why you do want a rubber/poly coated wheel for grinding.

Ken H>
 
It may have been covered already ( I haven't read every page) but a lathe trued 100 Durometer wheel would be very solid and should cut smooth.
 
Kevin McGovern said:
I probably got a little over zealous with that since I was removing so much. There's a reason I NOW know not to advance too much per pass...
Glad it worked out though.
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Ahhh copy that! Yeah it was a lot to remove for sure ;) Thanks again for doing that for me!
 
razor-edge-knives said:
Now to just find one =)
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The same seller that is recommended for the wheel in this thread will make you one with 90 durometer for the same price. There is an extra 2-3 weeks added tim because they don't keep them in stock. Just message them before ordering. Quick response. I've got a 90 duro on the way.
 
^^^^^^Thats what I did, as well. They said it would take a couple of extra weeks wait time to make it, but other than that, there was no extra charge or anything. I need to look at the order, but I think I got the 6” wheel...?

Jeremy
 
I finally have my SGA build going thanks to the folks here. A special thanks to Stromberg as well for the email correspondence and tips along the way. I'm using 3/4" aluminum plate that I had on hand for the magnetic chuck and got the slots all milled out. I think it's 15.5" long and I'm loading it up with a bunch of the N52 magnets. I got a contact wheel from the place mentioned by one of the other guys; I waited a little extra time so I could get the hardest rubber (95) on the wheel. I'm not sure if I really needed it to be 3" wide, but I got it that way thinking it would give me the extra distance to track the belt back and forth a bit. I've got some 1/2"-20 threaded rod that I'm going to use to attach the wheel to my aluminum tool arm as well as for the fixture that I will make to move the chuck towards/away from the contact wheel.

Before:




After:




The rail:




And, the wheel:




Hopefully it all goes together okay. I need to cut out some more aluminum for the attachment plates for the magnetic chuck and do the pivots for the tapered tang option. Then, it'll be figuring out how I want to make the little "sled" thing that it'll all ride on; I've got a little t-track that I'll use to help keep everything aligned as it screws forwards/backwards. Can't wait to see how it ends up working and if I can get the same good results as everyone else. Unfortunately, I've got stuff going in the coming weekends, so not sure when I'll be able to get this finished up, but it'll be before I make the next folder....hopefully... :).

Jeremy
 
I think you did good getting the 3" wide wheel - that's what I wound up with. I like it better, there's more room for the belt to move. AND - if I get some 2-1/2" wide belts the wheel will handle them nicely. A 2" wide belt really doesn't do a good job on a 2" wide blade, there needs to be a bit of belt hanging over the sides of the blade for best work.

Good luck with rest of build.
 
Thanks, Ken. I need to think out the rest of the parts and how it’ll all go together. Then get to cutting, drilling, and tapping. And I really need to make sure the hole for the contact wheel in the tool arm stays nice and perpendicular :confused:.

Jeremy
 
what about wheel size ? what are the advantages and disadvantages of small and large wheel sizes, if any ?
 
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