Home Built Surface Grinder

Based on my above height assumptions, this is what I'm planning:

  • 1.5''x0.75'' plates for on top of the slider (aluminum)
  • milling into the tooling arm by ~20.4 mm to adjust height of 2.5'' chuck to center of 75 mm wheel.
  • Mounting the wheel 1/2'' off of tooling arm (this seems to be where the center of my tracking in on my machine)


I've never mounted a contact wheel to a tooling arm before... do you just thread the tooling arm and put spacers (washers) in between the bearing of the wheel and the tooling arm to space it out as you want?
 
J. Keeton said:
I've never mounted a contact wheel to a tooling arm before... do you just thread the tooling arm and put spacers (washers) in between the bearing of the wheel and the tooling arm to space it out as you want?
Click to expand...

That'll work. The easiest way (less likely to screw it up) is probably to drill through the tooling arm. This way you don't need to both drill straight - and tap straight. :D

62BazRx.jpg
 
Stromberg Knives said:
That'll work. The easiest way (less likely to screw it up) is probably to drill through the tooling arm. This way you don't need to both drill straight - and tap straight. :D
Click to expand...

Cool deal! Thanks for the tip and method explanation. I've gotten decent at the drilling and tapping straight (that is if it will fit in my mini mill). I generally drill the hole, then while everything is still lined up, put the tap into my mill chuck and get it started by hand turning the chuck (with the power switch off!).

The drill though and nylon lock nut option does seem easier though! Probably stronger too...

I can't wait to get the pieces in! Thanks again.
 
So based on some awesome correspondence with Stromberg Knives Stromberg Knives I've made some modifications in order to minimize the depth of which I'll need to mill into the tooling arm.

With a 5/8'' x 1.5'' plate on the top, and a 1/2'' x 2.25'' plate on the bottom, and a 2.5'' magnetic chuck; I'll only need to mill into my tooling arm by 10.8 mm



I plan on using 1/4-20 bolts to attach the top plate to the back of the magnetic chuck and 3/8''-16 handles for the pivot.

Let me know if I'm missing anything... Thanks for the help!
 
I'm going to make a few changes to mine. A 6x3" wheel, and I'm going to attempt making my own feed/table out of some 1/2" and 3/4" 6061 I have leftover.

I saw Ken H's pictures, anyone else have pics or plans of their DIY feed they can share? Just looking for ideas.
 
Thanks a million for the information provided in this thread! And major thanks to @Jesse Latham , K Ken H> , john april john april , and especially Stromberg Knives Stromberg Knives for his email correspondence. Really helped clarify some of the finer points.

For anyone else looking to build one of these, I hope this video can be of some use. I tried to stand on the shoulders of giants (yall) and put this tutorial together in a clear and concise manor. If I missed anything please let me know!

There is a parts list with current links in the description of the video along with some PDFs I used to build off of.


I can't wait to get some serious use out of this thing!
 
Good video and a job well done. When you're giving credit, don't forget OneArmed, the guy who started this whole thread. While he's not been around lately, he sure deserves credit for starting this whole SGA idea of homebuilding a clone of Travis's SGA.
 
Ken H> said:
Good video and a job well done. When you're giving credit, don't forget OneArmed, the guy who started this whole thread. While he's not been around lately, he sure deserves credit for starting this whole SGA idea of homebuilding a clone of Travis's SGA.
Click to expand...

For sure, sorry I forgot the OP! This thread is epic.
 
You might try SuperGrit.com, on a closeout catalog they have some 80YF grit 2-1/2"X 72" AO belts at a good price (10 for $20), and some 150Y grit ceramic 2X72 belts ($4.50 each). Look about mid way of page page #9, for item #9-L and 9-M.

I've not tried either of those items yet, but do plan an order soon. I've ordered from SuperGrit a couple of times in past with good results.
 
I messed around with four post HT'ed blades today (pre bevels). I got pretty decent results on them. I will stay that I think I trashed one chasing warps around.

I think my conclusion (like Stromberg Knives Stromberg Knives advised me) is to get the warps out first! Before heading this advise I tried to shim the warp like this (didn't work too great):




Finish is nice though:






Just for curiosity (and my learning!), what is yall's Standard Operating Procedure when using your SGA? (blank prep, warp management, belt progression, feed rates, #of passes (spark judgement), etc)


Cheers,
JK
 


So far these are my results. I surface ground 3 knives post HT... Granted I was learning the machine here so I ended up taking of more than I should have on them. (especially the top one)

To mitigate any warping issues and to see how true my SGA was I took a piece of .25'' plate and surface ground it (@ the bottom there).

The x marks where I measured with the mic. The circled number is the "max variance" across the points I measured.



So it looks like I'm right at 1 to 2 thousandths of an inch accuracy across these pieces. Two interesting things just looking at this sheet is that the lower measurement on the tang is consistently smaller... and the center measurement on the bottom two knives is the largest across the knife.

What do yall think?

Cheers,
JK


EDIT: That bar is about 7.5'' long
 
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1 to 2 thou is pretty good and is in the same ballpark as rest of us get in general use. You did lightly touch the surface of the magnetic chuck with belt before doing any grinding? That's important, and should be a long time before it needs doing again.
 
Okay, I’m getting close and can see the finish line. Or so I thought... I mounted my 6”x3” serrated contact wheel to the tool arm and thought it was really close to perpendicular checked my drilled hole with a machinist square) and it seems balanced. As I got the rail assembly closer to mounted, I could see some indicators that made me think the rubber on the wheel wasn’t perfectly even-possibly thicker towards one side of the wheel? I later checked the bolt with a machinist square and it’s definitely not perfectly square, but when running with the belt on it, there wasn’t any noticeable “wobble”, etc.

Then I got the rail assembly mounted. I decided to begin surfacing the chuck against the wheel and noticed the process wasn’t as smooth as I would’ve thought it could be... As the handle gets closer to the wheel (more of the rail and chuck are extended below the wheel) there appears to be some bouncing in the extended part. Which makes me think the concentricity of the wheel is off just enough to cause me a problem....

So, any thoughts? Mine is on a KMG and the rail is mounted at around a 45 degree angle. I threaded the 1/2” hole in the tool arm and started the tap using my mill, turning it by hand, to help keep things perpendicular for the first bit, until several threads were there as a guide, then finished by hand in a vise. Thot I had been careful enough, but guess somehow I went wrong... I’m thinking of opening the hole up to a clearance hole and getting a longer bolt and using a nut on the exit side. The bolts I’ve had have mostly a full 1/2” shaft with only the last inch threaded. But, if that doesn’t straighten things up, maybe I’m stuck drilling new mounting holes for everything? That would definitely suck at this point...but I really want this tool to work. Anyone ever have a problem with the rubber on the wheel not being even thickness? I need to narrow down if I have a separate problem with the wheel, as well. Also, how fast do you a guys run your grinder? I have a vfd and had it under 50% by a little ways. I don’t know if faster or slower is better?

Thanks for any suggestions.


Jeremy
 
gudspelr said:
Okay, I’m getting close and can see the finish line. Or so I thought... I mounted my 6”x3” serrated contact wheel to the tool arm and thought it was really close to perpendicular checked my drilled hole with a machinist square) and it seems balanced. As I got the rail assembly closer to mounted, I could see some indicators that made me think the rubber on the wheel wasn’t perfectly even-possibly thicker towards one side of the wheel? I later checked the bolt with a machinist square and it’s definitely not perfectly square, but when running with the belt on it, there wasn’t any noticeable “wobble”, etc.

Then I got the rail assembly mounted. I decided to begin surfacing the chuck against the wheel and noticed the process wasn’t as smooth as I would’ve thought it could be... As the handle gets closer to the wheel (more of the rail and chuck are extended below the wheel) there appears to be some bouncing in the extended part. Which makes me think the concentricity of the wheel is off just enough to cause me a problem....

So, any thoughts? Mine is on a KMG and the rail is mounted at around a 45 degree angle. I threaded the 1/2” hole in the tool arm and started the tap using my mill, turning it by hand, to help keep things perpendicular for the first bit, until several threads were there as a guide, then finished by hand in a vise. Thot I had been careful enough, but guess somehow I went wrong... I’m thinking of opening the hole up to a clearance hole and getting a longer bolt and using a nut on the exit side. The bolts I’ve had have mostly a full 1/2” shaft with only the last inch threaded. But, if that doesn’t straighten things up, maybe I’m stuck drilling new mounting holes for everything? That would definitely suck at this point...but I really want this tool to work. Anyone ever have a problem with the rubber on the wheel not being even thickness? I need to narrow down if I have a separate problem with the wheel, as well. Also, how fast do you a guys run your grinder? I have a vfd and had it under 50% by a little ways. I don’t know if faster or slower is better?

Thanks for any suggestions.


Jeremy
Click to expand...
Hey Jeremy, I actually had two different wheels that I had to send back before I got one that worked right. one the rubber was 'out of round' (kinda egg shaped) and the other the bearings didnt turn freely from the factory. So it is VERY possible that your rubber is not right. Where did you buy your wheel? Have you taken a square and laid it on the top of your wheel and flat against the side? If the wheel was bought on Amazon ( like mine were) tell them of the issue and they will replace it. It sounds like you did everything right. Heck, I didnt use a mill or a drill press when doing my tapped hole for the wheel mount and it turn perfectly concentric.

Also, I know it seems like it is WAY close to the linear stage, and it is! but you SHOULD only be turning the dial to take thousands of an inch off.

Let us know!
 
gudspelr said:
Okay, I’m getting close and can see the finish line. Or so I thought... I mounted my 6”x3” serrated contact wheel to the tool arm and thought it was really close to perpendicular checked my drilled hole with a machinist square) and it seems balanced. As I got the rail assembly closer to mounted, I could see some indicators that made me think the rubber on the wheel wasn’t perfectly even-possibly thicker towards one side of the wheel? I later checked the bolt with a machinist square and it’s definitely not perfectly square, but when running with the belt on it, there wasn’t any noticeable “wobble”, etc.

Then I got the rail assembly mounted. I decided to begin surfacing the chuck against the wheel and noticed the process wasn’t as smooth as I would’ve thought it could be... As the handle gets closer to the wheel (more of the rail and chuck are extended below the wheel) there appears to be some bouncing in the extended part. Which makes me think the concentricity of the wheel is off just enough to cause me a problem....

So, any thoughts? Mine is on a KMG and the rail is mounted at around a 45 degree angle. I threaded the 1/2” hole in the tool arm and started the tap using my mill, turning it by hand, to help keep things perpendicular for the first bit, until several threads were there as a guide, then finished by hand in a vise. Thot I had been careful enough, but guess somehow I went wrong... I’m thinking of opening the hole up to a clearance hole and getting a longer bolt and using a nut on the exit side. The bolts I’ve had have mostly a full 1/2” shaft with only the last inch threaded. But, if that doesn’t straighten things up, maybe I’m stuck drilling new mounting holes for everything? That would definitely suck at this point...but I really want this tool to work. Anyone ever have a problem with the rubber on the wheel not being even thickness? I need to narrow down if I have a separate problem with the wheel, as well. Also, how fast do you a guys run your grinder? I have a vfd and had it under 50% by a little ways. I don’t know if faster or slower is better?

Thanks for any suggestions.


Jeremy
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Maybe you could use a dial indicator to get a rough idea of how much wobble there is without load. It's not going to be perfect with a serrated wheel, but maybe with a heavy belt turned inside out, you could turn the drive wheel by hand and see if you are dealing with 5 thou or 50. Just a thought, not sure how practical that is.

I have not had great success with the through hole in the tool arm. The threaded hole was much more rigid for me. A slight misalignment should not really matter anyway. Surfacing the chuck should take care of that.

If there is bouncing in the extended part of the rail, maybe the bearings in the rail system need to be adjusted. Have you checked to make sure those are tight?
 
Thanks very much for the help. I took my square to the outside of the wheel and I was a bit surprised to see that the rubber appears to be square to the hub. Mostly surprised because it was bought off the Chinese website. I rotated the wheel a bit at a time and kept checking, but it appeared to be good all the way around. When I spun the wheel by hand and sighted over the top of it, I could see a slight rise and fall of the rubber at the edges. But-if the rubber was evenly applied, shouldn’t it look even (no rise and fall) as its rotating even if it wasn’t mounted perfectly square? I don’t know, my head is starting to hurt thinking about it...

The bearings for the rail assembly seem to be good and solid, the rail doesn’t have any wiggle room when sliding on it. I may mess with the feed rate for the table, too. I know I was a little hurried and wanting to grind off the aluminum on the chuck and took some bigger bites than I probably should have. Even so, that little variation in the rubber of the wheel I can see when rotating is possibly going to drive me bonkers....


ETA:
I went out and did some more looking and decided to check the grade 8 bolt. It’s threaded for the last 1.5” or so, the rest of the bolt is 1/2” round. I put it on my granite plate and it appears to have a slight bow in it. Put my machinist square to the shaft and can see the lack of straightness. I put it in my mini lathe, but couldn’t really detect runout on the bolt head when it was spinning. I suppose the bolt would be the logical first place to start. Guess it’s another trip to the store, this time with my machinist square...?

Jeremy
 
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gudspelr said:
Thanks very much for the help. I took my square to the outside of the wheel and I was a bit surprised to see that the rubber appears to be square to the hub. Mostly surprised because it was bought off the Chinese website. I rotated the wheel a bit at a time and kept checking, but it appeared to be good all the way around. When I spun the wheel by hand and sighted over the top of it, I could see a slight rise and fall of the rubber at the edges. But-if the rubber was evenly applied, shouldn’t it look even (no rise and fall) as its rotating even if it wasn’t mounted perfectly square? I don’t know, my head is starting to hurt thinking about it...

The bearings for the rail assembly seem to be good and solid, the rail doesn’t have any wiggle room when sliding on it. I may mess with the feed rate for the table, too. I know I was a little hurried and wanting to grind off the aluminum on the chuck and took some bigger bites than I probably should have. Even so, that little variation in the rubber of the wheel I can see when rotating is possibly going to drive me bonkers....


ETA:
I went out and did some more looking and decided to check the grade 8 bolt. It’s threaded for the last 1.5” or so, the rest of the bolt is 1/2” round. I put it on my granite plate and it appears to have a slight bow in it. Put my machinist square to the shaft and can see the lack of straightness. I put it in my mini lathe, but couldn’t really detect runout on the bolt head when it was spinning. I suppose the bolt would be the logical first place to start. Guess it’s another trip to the store, this time with my machinist square...?

Jeremy
Click to expand...
The bolt is not spinning, so it should not matter if it is slightly crooked as long as the wheel is held firmly in place. Have you tried taking the chuck off and grinding by hand at high speed? That might tell you how bad the vibration is.
 
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