Surface Grinder

#41
Thanks!

Do you strip the abrasives at the splice for the higher grit, which have thinner backing?

I've seen the technique being mentioned a couple of times when using SGAs.
 

KenH

Well-Known Member
#42
Do you strip the abrasives at the splice for the higher grit, which have thinner backing?
Never thought about that - seems like I did read something about that in trying to reduce the bump. That is something you'll just have to try for yourself to see your thoughts.
 
#43
I'm pretty new at this milling business. I saw your magnetic chuck which looks nice.

How do you mill those slots so nicely? What kind of end mill would I use? Full width and several passes to get the depth? A pilot slot with a more narrow end mill and then finish with the correct width?

Thanks!
 

KenH

Well-Known Member
#44
It all depends on which milling machine you have and how much cut it can handle. I used a 3/8" endmill and took full depth each pass. If you're using a mini-mill I'd expect it to handle 3/8", but how deep each cut would be I don't know. If you're using the 10mm width, .375" works out about right - the magnets are not a full 10mm.
 
#45
Thank you guys for the inspiration!

I've been looking for a better way of surface grinding, my process today involves my belt grinder, disc grinder and surface plate. But it's time consuming and not really giving me the precision I'd like. So I came across One Armed's build, and then KenH's and knew I had to build one myself. I sourced the parts a while ago but haven't had the time to get it all together. But I managed to get it done today. It was a fun build with a lot of small challenges for a non machinist. I learned a lot making it. Thanks KenH for the tips about milling, I sourced a 10mm 3 flute 45 deg helix carbide end mill made for aluminium, it was like cutting hot butter, even with my mini mill.

I'm also waiting for some 75x2000 mm (3" x 78") belts. I built the SGA with a 75x200 mm (3"x8") serrated wheel so I can take full advantage of the 60x400mm (2,36" x 15 3/4") magnetic chuck. A lot of my knives are 50-60mm wide. This means I don't have to track the belt up and down for full coverage.

The components I sourced:

Magnets
https://www.aliexpress.com/item/15-...Rare-Earth-Neodymium-Magnets/32398053200.html

Linear stage sliding table
https://www.aliexpress.com/item/Man...al-Linear-Translation-Stages/32612615636.html

Linear slide rail
https://www.aliexpress.com/item/1pc...ulti-axis-core-linear-Motion/32842691822.html

Contact wheel
https://www.aliexpress.com/item/200...isher-Wheel-Sanding-Belt-Set/32381815454.html

Chuck and plates
The magnetic chuck is made from AW-2007 aluminium. The holding plate for the chuck and the mount plate for the slide rail is made from O1 tool steel.

The linear stage sliding table was a little less precise than I wanted. If I were to build it again I would probably get this one instead:

https://www.aliexpress.com/item/GGP...4-Ball-Screw-Linear-Rail-CNC/32806395029.html

So I had to take it apart and lap the pieces for a tighter dovetail fit. I now have a runout of about 0.02mm (~0.0008") across the slide. And I decided to get a lot of magnets on the chuck since they're only 4mm. And it seem to have done the trick, the grip is fantastic.

I also put the two stops at the correct distance for easy tapered tangs, just like Wuertz SGA.

I decided to build the whole package on the same tooling arm for more rigidity.

Now that everything seem to be in perfect working order, and with the precision I want. I'll probably make it a little prettier, round some corners, gun blue the O1 and so on.

Edit: I did the finish work today, so I replaced the pictures with the updated ones.

Here are some pictures.









 
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KenH

Well-Known Member
#50
You did really good with that build, and good with the photos. I especially like the contact wheel mounted to the tooling arm. Since I saw OBG's setup with his contact wheel mounted to contact arm I've been thinking about doing the same thing. BUT - I'd have to resurface my magnetic chuck. Due to the slop in the tool arm holders when my system is mounted the magnetic chuck wasn't exactly square to the contact wheel. Once I surfaced the magnetic chuck it's now square, but I'm not sure the "slop" will come out to exactly the same every time. I might just move my contact wheel to the tool arm like you've got. I do think that's best.

Again, GREAT JOB!

Ken H>
 

One Armed

Well-Known Member
#51
Awesome work currenthill! Clean, CLEAN build! That's 3 of us now. Just normal guys with a passion,(and not a lot of money in my case!), and KNEW they could build this! Warms my heart to see people sharing my love for building things. I'm so happy to have posted here.
 
#52
Awesome work currenthill! Clean, CLEAN build! That's 3 of us now. Just normal guys with a passion,(and not a lot of money in my case!), and KNEW they could build this! Warms my heart to see people sharing my love for building things. I'm so happy to have posted here.
I totally agree! I’ve looked at SGAs for a while but thought it would be too hard to build one myself.

I really do appreciate you sharing your build, it was very inspiring!
 
#53
Hi guys!

I've been using the SGA with 3 inch belts for a couple of days now. It's great! I can do all my pattern sizes without tracking the belt. It's nice to be able to flatten tangs so quick and easy now, no more hand rubbing on the surface plate. But then it struck me, I still need to hand flatten the scales on the surface plate.

So, back to the drawing table. I made a quick and dirty prototype holder this morning. It works perfect, I might make some minor adjustments and make it a little prettier. But it flattens my scales superfast and precise. It's a real time saver!

It's got a 2mm (5/64") steel backplate for attachment to the magchuck. It can do scales up to 60x140mm (2.4"x5.5"). Minimum depth in this configuration is 5mm (0.2"), but I could grind it thinner.





 

KenH

Well-Known Member
#54
I see you're like me - the more you use the SGA, the more uses you find for it. That's a good looking attachment and a good idea. Does the 3" belts work good with the normal 2" (usually 2-1/4") tracking and drive wheels?
 
#55
You're correct, the 3" belts would be too wide for the standard wheels (or rather, the belt would hit the grinder when centered).

So I cut them at 2.5". That way it covers the 2.4" magchuck perfectly, while it'll still fit the wheels fine.
 
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KenH

Well-Known Member
#56
Currenthill, got a question for you - when you move the slide .003", make a couple of passes so it seems to be ground good, does that .003" movement remove .003" from the metal?
 
#57
Currenthill, got a question for you - when you move the slide .003", make a couple of passes so it seems to be ground good, does that .003" movement remove .003" from the metal?
That is actually a really good question. I have so far solely been measuring relatives, not absolutes. I would have to do some test passes to know.

What is your experience on the matter?
 

KenH

Well-Known Member
#58
I've not done any real testing - had to take the dial indicator off to use elsewhere. BUT - the little bit I did it seemed sorta like .006" feed might get an honest .003" of actual metal removal? I was thinking the metal removal would be closer to feed distance, but perhaps wear on belt? Perhaps not making enough passes grinding to remove all metal to the depth of feed? Not sure, that's why I was asking you :)
 

One Armed

Well-Known Member
#59
Removal will ALWAYS be less than feed with this type of surface grinder. Remember we are using a rubber contact wheel, and the belts have a cloth backing. This combination gives "flex". Whereas full size surface grinders use stone wheels. So the work is LITERALLY stuck between a ROCK & a HARD PLACE!:D LOL!

Ken, I would think most will see about the numbers you did. An approximate 2:1 feed to removal ratio.

Currenthill, another great idea my friend! I have just been using a piece of steel and superglued scales to it, for grinding flat! But I'm going to build exactly what you came up with! Thank you!
 
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