# Surface grinder wheel balancing from scratch, and on the cheap:



## ErichKeane (Aug 20, 2020)

I have a surface grinder, it is awesome. But I've never felt like a balancing setup was worth the cost, which basically amounts to the cost of the machine!

SO, I'm going to try making one from scratch. That's right, everything. For this, I need 3 parts as far as I can tell:

A U shaped balancing frame. These seem to run $500 on their own, but are pretty simple looking. The only important part is that it is 3-point levelable, and that the rails are coplanar. I have two thoughts on how to do that, and might end up trying both . I'll use the surface grinder, plus make it adjustable.

Second: an arbor. Presumably these are typically hardened. I'm just going to try turning one out of 12L14 and see how it does. The key here is going to be getting the taper in the middle correct. 

Third, I need a way of balancing the wheels. The drill-bit mechanism seems silly, and the balancable arbors are expensive. Instead, I have an idea on how to cheaply/easily make my sopko style HHIP arbors adjustable based on a design I saw elsewhere.

I ordered stuff, and finally started working today. Not much work done, but it's a start 

This is the material to the balancing fixture/frame. $30 of drops on eBay, downside is I think it is A36. I picked up 3/4" for the bottom and 1/2" for the sides. I'd put good money on this being way too thick on the bottom, but I'm going to go with it. Since my bench is a softwood table, the extra weight sounds like a good idea.


 First step was squaring up the base plate. I used my flycutter on two sides to get something I could put against my jaws, then flycut the top/bottom. Finally, used an endmill for the other two sides.


Here it is shaped and mocked up with the other plates. Final dimension is a little under 6" square by 9/16" thick. I still have some work left to do on this obviously, but my next step is probably to do the same on the next two pieces.



While that was happening, I faced and center drilled a ~7" piece of 12L14 for the arbor. I'll end up turning between centers when I get to it.


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## graham-xrf (Aug 21, 2020)

There is poetic justice in using a machine to make stuff to ultimately balance itself later.


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## ErichKeane (Aug 21, 2020)

Alright, a little more work today. I started by milling 4 of the faces of the sides (including the two big ones). Then, I used the surface grinder to make them the same thickness. the two were not too close, and the fly cutter dug in a few times, so I ended taking a lot of each side.




Then I chucked up a surface grinder arbor in the lathe to set the taper attachment. While doing so, I noticed a couple of necessary lathe repairs (tightening some gibs, taking the play out of the taper attachment, etc. It took a while, but I'm down to less than a 1/2 thou off.  This will be useful later


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## graham-xrf (Aug 22, 2020)

Hee Hee - he's really hardball meticulous, isn't he?  
Everything he touches on the way gets tweaked up to the nuts before he lets it proceed!


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## ErichKeane (Aug 22, 2020)

graham-xrf said:


> Hee Hee - he's really hardball meticulous, isn't he?
> Everything he touches on the way gets tweaked up to the nuts before he lets it proceed!



Good grief, you have no idea   My last thread I started (about the surface grinder part) actually started because of this project!

I went to start fly-cutting the bottom plate, which required changing the belt on my mill. As I did that, the cast Iron washer under the tightening bolt cracked. SO, I went over to the lathe to turn a new one, then to the surface grinder to clean it up, just to notice it was broken.

I feel like this scene: 



 is my spirit animal.


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## 7milesup (Aug 22, 2020)

OMG!!!  that video is too damn funny.  I had never seen that before...


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## graham-xrf (Aug 22, 2020)

@ErichKeane  : Nope - sorry, but your case is worse in it's own way, because you let the sequence of tasks become infinite loop circular!


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## ErichKeane (Aug 26, 2020)

A little more work today on the base! I took the sides and milled them flat and equal sized (which will help later! 

Then, I milled the slots for the sides to fit into on the bottom, drilled some holes to bolt the sides to the bottom with (I might get someone to weld this before too much longer!), And drilled/tapped the adjustment screw holes.  I'll probably end up cutting the single one down a little so it doesn't risk hitting the grinding wheel.


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## pontiac428 (Aug 26, 2020)

The TI-89 is the greatest calculator ever invented.
You can take it... from my cold, dead fingers!


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## Janderso (Aug 26, 2020)

Good idea. I need one too.

Did you see this one ?


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## ErichKeane (Aug 26, 2020)

I didn't see that one! Though, I suspect mine is going to be somewhat similar. I'm building adjustable rails in a way that I'm pretty excited about, that I think you all will like!

I also don't have balancing arbors, so I have to make those too


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## graham-xrf (Aug 27, 2020)

ErichKeane said:


> I didn't see that one! Though, I suspect mine is going to be somewhat similar. I'm building adjustable rails in a way that I'm pretty excited about, that I think you all will like!
> 
> I also don't have balancing arbors, so I have to make those too


That video has a rabbit-hole of its own! At the end, it runs to him using the grinder to make an outrageous OTT milling vise, and your thread has me going all over the place.

#1 @pontiac428 The Ti-89 Graphing Caclulator. Nostalgia! For everyday calculating, I ended up using HP Reverse Polish. It cuts through complex bracketted scientific calculations. Now, we have smartphone apps that can run rings around the old calculators, though they don't have the charm, and need to be coddled, because of the investment on "other stuff" on them, quite aside from the price!

#2 That guy's skills, precision, and video-making production are all exceptional. Reminds me a bit of Clickspring (Chris Ramsay) except maybe for the ambient lighting level, and that he lets you see his hands, and himself.

#3 A 0.01mm indicator is 0.0004" - so slightly smaller than a half-tenths type.
     A 0.002mm indicator is 79 milliionths !!! 

#4 What is going on when he is "tapping" on the spindle while indicating it. Does it "move"? Is it "adjustable"?

# 5 I am thinking that what he calls "gray (grey?) cast iron" is probably what I think is "semi-steel".

#6 I have to learn more about "soft jaws" esp in relation to CNC

All that stuff above is only about the thoughts it provokes in me. What will it do for Erich?
@Janderso  Jeff, showing a guy like Erich a video like that is just madly digging his rabbit-hole deeper for him. The poor guy is now probably out there looking for a 0.002mm indicator, and thinking on plans for what else in his shop is going to need the services of his surface grinder!


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## ErichKeane (Aug 28, 2020)

A little more progress today. I got the sides drilled/tapped and it bolted together! I think this part is now ready to be welded before I can do anything else.  After it is welded, I'll probably grind the screws flush.


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## NortonDommi (Aug 28, 2020)

ErichKeane said:


> I'm building adjustable rails in a way that I'm pretty excited about, that I think you all will like!


One ready source of edges is planer blades, they come precision ground and are not expensive.


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## ErichKeane (Aug 28, 2020)

NortonDommi said:


> One ready source of edges is planer blades, they come precision ground and are not expensive.


Oooh!, that is a REALLY good idea that actually makes my post-weld thoughts that much easier!  I actually HAVE a couple of 18" planer blades I could use (assuming I can find a way to drill holes in HSS easy enough  Or, have a design that uses clamping force instead!) that might work perfect!  thanks for the idea!

My plan had been to use some ground-rod that I have, and put 2 bolts in each side.  Basically, each side would have 2 bolt holes, 1 through that would have corresponding threaded hole in the fixture.  The other would be threaded through the rod (with no corresponding hole) that would push against it, similar to the design of gib adjustments on mills.

But I have some interesting thoughts now on how to make fine adjusters for some planer blades!


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## graham-xrf (Aug 29, 2020)

Its a (nice) jig for holding two edges to have a grinding wheel roll around on in a balancing operation.

Does it need to be welded?
Bolted together would seem to be enough for the balancing support role. I suspect that welding it could introduce all sorts of distortions that could bring about the need to re-flatten the bottom, turn it over, and re-do the tops. Of course, if you have already welded it, the point becomes moot.

You are to be doing several extra operations to give it a feature I am, so far, not understanding. Of course I could be just plain wrong, so maybe there is something to learn here.

I am also curious also about the value of having the top edges "micro-adjustable". Yes yes - do use the planer blades! I love the idea!  Agreed also that they need to be a tad "moveable" initially in getting them fixed to the U-section, but once made parallel in 2 axes, and clamped hard, they can stay fixed. After that, having 3-point adjusters under the whole jig seems the obvious thing to do.

Thinking this through, it seems to me the prime requirement is to arrange the tops of two beveled straight edges be exactly on the same plane, and clamp them there.

Given that the top edges are relatively narrow, if not sharp, the contact to the wheel arbor/axle is just a small point, then it would not matter if the edges under splay a little along their lengths. There is not the need to make the edges be any better than nominally parallel in the same direction as the axle is rolling. It will roll anyway.


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## ErichKeane (Aug 29, 2020)

graham-xrf said:


> Its a (nice) jig for holding two edges to have a grinding wheel roll around on in a balancing operation.
> 
> Does it need to be welded?
> Bolted together would seem to be enough for the balancing support role. I suspect that welding it could introduce all sorts of distortions that could bring about the need to re-flatten the bottom, turn it over, and re-do the tops. Of course, if you have already welded it, the point becomes moot.
> ...



The welding isn't necessary, it is more to make it 'permanent' and repeatable.  I could definitely get away having it be bolted together ONLY (and that was my initial plan).  My order-of-ops was going to be to do the tops AFTER welding for that reason, since my plan for the rods wasn't super adjustable.  The bottom doesn't have to be flat though, only the top (which has to be close enough to adjust in).  The bottom is held up by the 3 bolts, so its flatness is meaningless.

That said, I can now think there are some advantages to having this be a 'break down'-able device.  Since I'm using planer blades now, I think I have the advantage of being able to adjust them MORE, so the extra range of motion might make this worth while!



graham-xrf said:


> I am also curious also about the value of having the top edges "micro-adjustable". Yes yes - do use the planer blades! I love the idea!  Agreed also that they need to be a tad "moveable" initially in getting them fixed to the U-section, but once made parallel in 2 axes, and clamped hard, they can stay fixed. After that, having 3-point adjusters under the whole jig seems the obvious thing to do.
> 
> Thinking this through, it seems to me the prime requirement is to arrange the tops of two beveled straight edges be exactly on the same plane, and clamp them there.



Well, getting them into the same plane is the only goal.  I intended to make them as adjustable as possible so that getting them into the same plane is as easy as possible. This way the 'tops' of the device being even isn't necessary. The adjustment was simply to attempt to get them flat in these 2 axes.  I have an even nicer (though a little more complicated to machine) way of micro-adjusting them up/down now that I'm using planer blades!



graham-xrf said:


> Given that the top edges are relatively narrow, if not sharp, the contact to the wheel arbor/axle is just a small point, then it would not matter if the edges under splay a little along their lengths. There is not the need to make the edges be any better than nominally parallel in the same direction as the axle is rolling. It will roll anyway.



Yep, thats exactly it.  Making them coplanar is the only requirement as far as my understanding.


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## homebrewed (Aug 29, 2020)

I've been following this because I also have been thinking about a wheel balancer.  It would only be used on occasion so I don't want to spend much $ or time on it.  The planer blade idea is brilliant.  But just to stir the pot, supported linear shafting isn't too far off, pricewise, either:  for example.  If you can find just the shafting it should be even less money.  You won't cut yourself on it, either.

Regarding the co-planarity issue.  Do you have a surface plate?  You could use that as the reference plane for your planer blades or rods.  Flip your balancer upside-down and support the body so the blades have some room to settle down to the surface plate, then bolt them in place.  But now I've handed you something else to make (those supports).    Or perhaps a pair of machinist jacks could be pressed into service for that.


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## graham-xrf (Aug 29, 2020)

homebrewed said:


> I've been following this because I also have been thinking about a wheel balancer.  It would only be used on occasion so I don't want to spend much $ or time on it.  The planer blade idea is brilliant.  But just to stir the pot, supported linear shafting isn't too far off, pricewise, either:  for example.  If you can find just the shafting it should be even less money.  You won't cut yourself on it, either.
> 
> Regarding the co-planarity issue.  Do you have a surface plate?  You could use that as the reference plane for your planer blades or rods.  Flip your balancer upside-down and support the body so the blades have some room to settle down to the surface plate, then bolt them in place.  But now I've handed you something else to make (those supports).    Or perhaps a pair of machinist jacks could be pressed into service for that.


Fast! Cheap! Accurate! 
Also, I think, probably very much like what Erich is actually going to do. When it's upside down, he can use his micro-adjusters to get them right.

I have not yet picked apart every aspect of grinder wheel balancing. Yes indeed, if the majority bulk of the wheel is not at right angles to the shaft, you can imagine the wobble. Theoretically, it could still be "balanced" so far as non-vibration spinning in one plane is concerned, but even when the circumference is trued with a diamond, it is still scuffing axially on the surface. So fixing this either by tilted shimming, or using one of those adjustable arbors where you rotate two slant washers relative to each other to set it up true, I can believe those are expensive!

Non-uniform weight lumps within the wheel? This whole deal is exactly like balancing a car wheel, with the added refinement that we further don't allow a perfectly balanced disc that ends up with it's surfaces not much within the spatial confines of a mathematical geometric disc on axis.

I am not sure about "drilling" bits out of a disc is OK. Adding epoxy in special places seems less harmful. I still feel I am somewhat ignorant on this. I still have to read and explore more to get up to speed. Meantime, there are bound to be HM members who have been through this, and can say exactly what _not_ to do to a grinding wheel.


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## ErichKeane (Aug 29, 2020)

homebrewed said:


> I've been following this because I also have been thinking about a wheel balancer.  It would only be used on occasion so I don't want to spend much $ or time on it.  The planer blade idea is brilliant.  But just to stir the pot, supported linear shafting isn't too far off, pricewise, either:  for example.  If you can find just the shafting it should be even less money.  You won't cut yourself on it, either.
> 
> Regarding the co-planarity issue.  Do you have a surface plate?  You could use that as the reference plane for your planer blades or rods.  Flip your balancer upside-down and support the body so the blades have some room to settle down to the surface plate, then bolt them in place.  But now I've handed you something else to make (those supports).    Or perhaps a pair of machinist jacks could be pressed into service for that.


The nice part is I have BOTH used planer blades AND precision ground shaft rod   I like the planer blades, since mounting them is way easier.

the surface plate is essentially my idea of how to calibrate them.  I'm going to flip it over, and bolt them in place. The idea of micro-adjust is to save me from having to elevate it in some way (though, 2 1-2-3 blocks are probably sufficient....), but I guess I can add that later.!



graham-xrf said:


> Fast! Cheap! Accurate!
> Also, I think, probably very much like what Erich is actually going to do. When it's upside down, he can use his micro-adjusters to get them right.
> 
> I have not yet picked apart every aspect of grinder wheel balancing. Yes indeed, if the majority bulk of the wheel is not at right angles to the shaft, you can imagine the wobble. Theoretically, it could still be "balanced" so far as non-vibration spinning in one plane is concerned, but even when the circumference is trued with a diamond, it is still scuffing axially on the surface. So fixing this either by tilted shimming, or using one of those adjustable arbors where you rotate two slant washers relative to each other to set it up true, I can believe those are expensive!
> ...



Basically, the problem with grinding wheels is they aren't uniform density, so you have to move/add/remove weight to balance them. There are a few different mechanisms to do so (including hubs that have weights that move!).  The drilling bits out of the wheel is the 'common' way, but I'm not going to do that, it scares me that I could break it easily.  Adding epoxy seems time consuming! 

My idea is to essentially turn my 'cheap' non-balancing hub into a balancing hub by either modifying or replacing the nut.  I think I can just drill/tap it in a number of places for set-screws, like these: https://www.kineticprecision.com/all-about-balancing-rings

THOSE rings are expensive, and I think there is no reason I couldn't do the same on the nut instead!  The question i've got is whether I want to increase the diameter of the nut, or just use it as-is.


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## homebrewed (Aug 29, 2020)

I have seen two reasonable (to me) approaches to balancing a grinding wheel.  One uses an arbor with holes in a circular pattern where weights can be installed.  The other uses a two-piece arbor with a channel inside, and free-to-move bearing balls are placed in there.  The latter is a kind of dynamic balancing system, while the former is a static one.

An online search will find numerous examples of both of these as a DIY.

Neither of these will address a wheel that wobbles.  My impression is that most problems can be addressed by the static or dynamic balancing schemes, along with dressing the wheel.

I have read of folks balancing wheels by removing material but that scares the heck out of me!  I DO like the idea of using something like epoxy but I'm not sure how you'd apply it. OH, now I get it -- use epoxy putty....it cures fairly slowly so you could adjust the balance.  Hopefully it sticks well enough, eh?


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## graham-xrf (Aug 29, 2020)

I have not the kit to be balancing stuff (yet), but I know I am going to have to do all this - so I think it through.
Start with a notional grinding wheel. Let us take these on one at a time.

*1. First location on the shaft.*
The "hole" is bigger than the shaft. It can be a bit this way or that, regardless the internal non-uniform weight balance.
It is held between "blotting papers", presumably to spread the clamping force from six highly stressed local contact points.
The disc of the wheel besides being eccentric, may also not be perpendicular to the shaft. You could "make it so" by dressing the sides, and rim, to in effect "carve out" a smaller concentric wheel out of the bulk of the starting wheel.

*2. Radial balance*
This would be the weight distribution that makes it "roll" on the jig. If this balance is fixed first (by one of several methods), it all gets undone by the first dressing. It becomes physically perfectly circular at the rim, despite that it was caused in the first place by the whole disc not being concentric on the shaft, but clamped between the "blotters". Only the outer rim is circular. The hole in the middle is eccentric, and there is now more weight on one side. Start again!  The wheel has to be such that repeated dressings are not going to make it go unbalanced.

I think the wheel densities just might be a bit better than we credit them for.
Saying that repeated dressings which require regular re-balancing is inevitable, and blamed on "non-uniform density" within the wheel, may be wrong. It might well be partly down to internal non-uniform densities, but clearly, repeatedly dressing the outside of a balanced wheel to make it circular, when the centre hole is even slightly not in the middle, will make it go unbalanced about the axis. This with a certainty that is way more inevitable than unknown internal non-uniform densities being removed from the rim in tiny amounts.

*3. Axial balance.*
Even if you balance a wheel (several methods), such that it won't roll on the blades, and even if the density through the wheel was supplied by the perfection fairies and elves, if the wheel disc is not physically at right angles to the shaft, (i.e. swash-plate wobble), there is a problem, though less than we might think. Relative to the axle, there is no theoretical acceleration of masses  back and forth along the direction of the axle.
There is an axial "scrubbing motion. Except for a blurred look, in theory, it spins OK - that is until the first attempt to dress the side.
Even the smallest change to one side that is not replicated on the other will bring about the Father and Mother of axial vibration! Remember, we started with a balanced swash-plate!

At the least - for that reason, I have to read again the virtues of the _*kineticprecision.com*_ kit. I suppose they are experts, and they have it all figured out. It's just that I haven't fully understood what they do. Adding a ring clamped to the wheel, so to become part of the wheel. with ability to add weights in the form of grub screws seems to be what they are up to, and an obvious way to balance without drilling, nor adding material (except grub screws).

*Dynamic axial balance*
There is also the need to discover and compensate for a weight to one side of the wheel, somewhere in it's disc. This weight may be be compensated for to stop a roll on the jig, but slings back and forth along the axis. There are good tricks to compensate this also, some of them exotic. A quick 'n dirty I once tried with a car wheel was to suspend it from centre like a plumb bob, and set it spinning. I have no idea if this would work on a little grinding wheel.

*4. About swash-plate adjustable rings.*
An old and effective idea. Replace the blotter compression big washer discs each side with two stacked together. They be thicker to accommodate that they have a tilted side each. I am sure one could make a pair by turning them, then grinding off one side of both set down together, at a few degrees tilted. Tilted sides placed together, so they cancel, then rotated relative to each other up to a desired tilt. There needs to be some way of rotating them..

a) Relative to each other, to adjust the amount of tilt, and ..

b) Both together relative to the grinding wheel, to put the tilt in just the right place to take out the wobble.

I think there needs to be a matching pair put on the other side of the grinding wheel, set 180° relative the those on the other side.
With all this, we have a nearly straight wheel, that is in with a chance.

Only now, after dressing,  the arbor stays with it, and we get to balance it. If the centre hole is reasonably on the axis, you can likely dress again, and keep dressing, until either centre eccentricity, or internal non-uniformity, or a combination of both, catches up with you.

If I got this wrong, let's hope I discover what really happens soon.


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## ErichKeane (Aug 29, 2020)

SO, I got a few hours in the shop, and I have some progress!

For the life of me, I couldn't find the old blades to my 6" jointer, but I DID find my 18" planer blades  I spent a few minutes with some scotchbrite and a stone cleaning them up.  They were covered in a lot of wood pitch, so windex helped with that.  I didn't bother cutting them down yet, but I will eventually...



First, I drilled 5 holes for the set screw.  Why 5?  Because I had 10 bolts!  In retrospect, I'm probably going to shorten or buy much shorter ones, but 10-32 bolts seemed fine for now.  This was the most time consuming part, because for some reason despite drilling/milling reasonably well, this material seems to tap terribly.




I have a 1/8" cutter that I made an arbor for a few months ago, so I cut a 500 thou deep slot down the side.  The blades fit in a little tight, but loose enough I can slide them with my hand.  I figured thats a good fit, and I can find a thin stone for the inside of the slots if I need to make it better.



I did those steps 2x.  However, the 2nd one came out worse due to 2 mistakes:
1- I messed up one of the bolt hole locations.  They are .300 off the side, and located at 2.500, 1.250, 0, -1.250 and -2.500 on the Y axis as cut.  I messed up and drilled one of them at 1.500 instead of 1.250, so its a 1/2 inch off.
2- I forgot to tighen my quill until the slot cutter was already about 1/4 of the way.  By the time I noticed, it had 'climbed' 50 thou, so the slot is 50 thou off center.
However, neither of those problems are a deal-breaker for a shop-project, so lets keep going 

This is how I got the blades co-planer (also, you can see how ridiculous 18" blades are).  I tried putting a stack of blocks inside and then getting the blades level from there, however I found that just putting the blades straight down on the surface plate, then tapping them with a lead hammer got me perfect contact all the way across!  Because of this, I'll likely leave them ~2-3" over-length when cutting them to make this part easier (likely, just cut an 18" in half ).



Finally, I leveled it on my bench to see how the adjustments worked.  I used a pair of parallels to do the other direction, and just my 8" starrett (bought for this purpose, and likely about 75% of this project's cost!) for the other.   First I leveled it with the 2 on the same side, which went really quickly.  I found myself happy I used the fine thread (3/8-24 I think!), as it made dialing it in simple.

Then, I put the parallels on, and flipped the level the other way and leveled it in that direction with the other screw.  I confirmed back and forth with the level in both directions, and is dead-on!

Overall, leveling took ~45 seconds.  It took longer to find my level 



I think i've still got 3 things left to do on this :

1- Paint!  I have some blue and orange somewhere, as well as some green hammerite.  I hope I can find the latter, and paint it with that.

2- Cut the blades down.  I think I can just use my cut-off wheel and cut 1 of the 3 blades in half and be perfectly happy here.  ~8.5" seems about perfect, the overhang will give me plenty of room to tap them for co-planer reasons.

3- Made some sort of blade-guard.  I might just do this with some spare oak, but this thing looks like a death machine while in storage. I think I'll just grab some wood scraps and make something that fits nicely over the blade.


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## graham-xrf (Aug 29, 2020)

Unless you propose to stash the Starrett somewhere, and never use it again, don't put the cost of the Starrett entirely on this project.


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## ErichKeane (Aug 29, 2020)

graham-xrf said:


> I have not the kit to be balancing stuff (yet), but I know I am going to have to do all this - so I think it through.
> Start with a notional grinding wheel. Let us take these on one at a time.
> 
> *1. First location on the shaft.*
> ...



I think you're putting more thought into this than necessary, I think what you call 'radial' balance is the only one that really has an effect. In fact, even THAT only matters when dealing with wheels greater than ~5-6 inches in diameter.  Typically people just skip doing it on anything smaller.  

#1 is handled by dressing the wheel, as is #3 if it ends up being important.  The "wobble" in that way is minor enough (particularly with well made wheels) that I don't think people tend to worry about them.

For #4, The nice part about the blotters is that they are compressable, so you get greater hold.  Using any sort of metal washer is typically going to be worse off.

That said, thats based on my minor-understanding of the process. Someone like benmychee or others can correct us


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## graham-xrf (Aug 29, 2020)

ErichKeane said:


> I think you're putting more thought into this than necessary, I think what you call 'radial' balance is the only one that really has an effect. In fact, even THAT only matters when dealing with wheels greater than ~5-6 inches in diameter.  Typically people just skip doing it on anything smaller.
> 
> #1 is handled by dressing the wheel, as is #3 if it ends up being important.  The "wobble" in that way is minor enough (particularly with well made wheels) that I don't think people tend to worry about them.
> 
> ...


OK - I can also be practical.
Fully understanding something is not overthinking it when in practice, one does just enough of what it takes to get it to work.

My whole point was it is that the act of dressing the wheel, making it "circular", is what puts it out of balance, and makes all the balancing work moot, if what it started with was a weights-compensated, fully balance wheel with the central hole even slightly off the middle.

I use the terms "radial" and "axial" to differentiate the directions in which the wheel shakes.

I just love your really serious lead "adjuster"


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## ErichKeane (Aug 29, 2020)

Perhaps the wrong word choice... More meant that from a practical perspective, only the 1 direction matters. From a truely practical perspective, even that one doesn't matter for a hobbiest like me


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## ErichKeane (Sep 2, 2020)

So I spent the last 2 days learning FreeCAD (I'd previously only done mechanical drafting in 7th grade, and typically my drawings are on a piece of scrap paper or white board!). So,  Attached!

For the drawing, the conversion to PNG from SVG messed up, but I don't care enough to look closer


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## tq60 (Sep 4, 2020)

How will you use this?

The axle resting on the top?

Must be perfectly level to work. 

Real unit is similar except it has a pair of overlapping wheels on the sides that allow the axle to rotate in place.

Need 4 ball bearings like 38KDD, then bolt to opposite sides of each wall.

Sent from my SAMSUNG-SM-G930A using Tapatalk


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## ErichKeane (Sep 5, 2020)

tq60 said:


> How will you use this?
> 
> The axle resting on the top?
> 
> ...


I've seen that style as well, but I'm trying to emulate the sopko version: https://www.mscdirect.com/browse/tnpla/65107047

Here is someone balancing the same way:


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## graham-xrf (Sep 5, 2020)

Several things about this.
 I'm pleased for him that he got such a nice finish. What I could see was his surface grinder, or parts of it, moving  relative to the background. Maybe all surface grinders do that in the face of reversing inertia, I don't know, but here is the place to ask.

I see the tops of his jig are drill rod, or something like it. Still theoretically a tiny point contact with the round arbor, so minimal rolling friction. It just looks a lot less deadly than the very convenient re-purposed planer blades. If the rails were drill rod, I guess they would have been glued, or secured in some non-distortion way.

I am surprised that it took that much removal from both sides to get it balanced. Of course, the closer to the middle, the less is the stress, offset by the closer to the middle, the more that needs to be removed. I have to say everything in my logic resists drilling out anything, and I remain to be convinced there is not a better way. I defer to those with the experience who can say that drilling on a ringing good grinding wheel is no big deal, and it works just fine.

For a  wheel that needs eight chunks like drilled out, it speaks of a wheel that was not so sweetly set concentric to the arbor in the first place!
I have not done it yet, but I think a little calculation of the imbalance plotted vs amount off centre may be revealing.
The same calculation leads inevitably to vibration forces for a given RPM.
Going yet further, it yields the tensile load for a given wheel width and radius.

We only need the first of those. I think that the whole heavy wheel, off centre by even a tiny amount, may be worth a whole lot of drilled hole mass removal. I just don't know yet if this is so. Either way, I so dislike giving a grinding wheel such a focused weak region stress raiser, I would go some way to seeking an alternative. Can one add mass reasonably conveniently?

OK - it's just my opinion, and I don't want to be just an armchair critic. I will have to do something like this soon.
I am happy too be told otherwise from those who know more with some certainty.


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## graham-xrf (Sep 6, 2020)

My weigh scale gadget tops out at 500 grams, and I don't have any spring balance or other handy kit. When it comes to weights of machine stuff, I either find it easy, rate it in grunts+puffs, compare it to 25kg bags of cement, or resort to something with mechanical advantage!

Can someone help with the approximate weight of a grind wheel, and mention it's nominal diameter, width and centre hole?
Thanks

[Edit: I remembered. There is a balance thing in the kitchen with weights, for baking and suchlike. Still a no-go, because if I get busted trying to put anything like a (used) grind wheel from out of the shop on it, there will be hell to pay! ]


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## ErichKeane (Sep 15, 2020)

Ugg... well, I still haven't gotten anything done in a while.  We had some family over 2 weeks ago, and immediately after the fires in Oregon started, so air quality outside sucks.  Hopefully I'll get back into the shop soon enough to make the arbor/arbor nut.


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## graham-xrf (Sep 15, 2020)

ErichKeane said:


> Ugg... well, I still haven't gotten anything done in a while.  We had some family over 2 weeks ago, and immediately after the fires in Oregon started, so air quality outside sucks.  Hopefully I'll get back into the shop soon enough to make the arbor/arbor nut.


Go a little easier on yourself Erich. You have my sympathies about the fires you folk have to endure.
Human's are smart, and can tell when something is up, even from quite small signs. I happen to be one who thinks the signs are pretty much compelling!

I have also been distracted by domestic stuff, one darn thing after another, ending up this morning with the lady of the house after me to "do something" because of water making it onto the kitchen floor from "somewhere under the sink/ water softener region". Yuk!
Just when I was ready to be sneaking off to where the machine stuff with the nice aroma resides!

I know that when you get the arbor together, you will let us know. When you actually grind a surface, rub it over with a stone that has been rubbed against another (stone), reveal the pattern, and take a picture. Meantime, I will attempt the calculation about off-centre balance. I still have pretty much big negatives about drilling eight chunks, four a side, dead opposite each other, into a ringing wheel.


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## ErichKeane (Sep 22, 2020)

Alright, a little progress on the arbor!  I am going to the calculations I made in my drawing, at least where they are important.


I'd already put centers in each end, so the first step was to turn it down to roughly 1" all the way across.  I obviously couldn't get that last section under the dog, but that is not going to matter since I'll get it when I flip it around.



The next step was to turn each 'end' down to a rough dimension.  I'm going for .500, and I don't want to change my cross-slide/compound when I go to cut them (basically, don't change my setup if at all possible to make them the same!), so I cut each down to ~.515, which is enough to get the threads done, and still enough that I can take that cut without deflecting the tool too much.  Since I'm between centers, flipping it around is trivial enough.  I got the center-section set to the right 'width' here as well:







Next, I wanted to separate the threaded section, so that I could cut the taper.  So, I turned that down to a touch under .625 (book says .6239) with a left-to-right tool (never remember which is which...) in prep for 5/8-18.





Next, I cut the taper.  I'd previously indicated-in my taper attachment, so this was as easy as tightening 2 bolts, and going to town!  I used the power feed + the same tool (left to right) and cut until the dykem from above was removed and so that the 'intersection' was about right.  I'd chamfered the end just a little to get rid of the burr, and put a little slot in the transition for my threads to start.







Finally, I cut the threads.  I have a 'stop' built into my lathe, which is super handy so I used that, then used the compound for a 29.5" infeed.  I did a scratch pass, and realized I was WAAYYY off!  I was at 13 TPI, not 18!  Turns out, I'd read the 'Thousandths-per-rotation' chart instead of the 'Threads Per Inch' chart.  Fortunately, I checked after my scratch pass to make sure.

I used an indicator to get my .034 DOC over a few passes.  The tough part was that I was starting from a single-point spot between the two sections, so I had to make sure I hit my thread dial EVERY time!  There was no chance to stop/restart if I messed it up.  Fortunately, it went right!  I cut to my DOC using the indicator, then used my thread pitch mics to confirm, then used my thread-wires to confirm again.  All seem right at the top of the range.

I'm going to make my nut separate, so I can fit that to the threads.




I have 2 more ops left, turn the 'right' side down to final dimension, then, without moving the cross-slide, flip the part and do a single more cut there.  Then, I'll consider this part done, and I can move onto the nut!


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## ErichKeane (Sep 26, 2020)

My wife had a few things she wanted to do the last few days, so I only got about 2 hours the last 3 days.  SO, I didn't snag many good pictures.

First step was to cut the 'long' pieces down to 500 thou (actually ended up about 2 thou under). I started on the 'thicker' side, and did 1 cut plus a spring pass.  Then, without moving the compound, flipped the part around between centers, and cut the other side + a  spring pass:




TODAY, I built a nut for it out of aluminum, I did a knurled outside (a hex seems like it would not be balanced), and single-point threaded the inside. The 1.5" long threads ended up being too long, so I cut the nut down to ~1", and 'counter bored' one side about 1/2".  I'll still have about 1/2" of threads, so that should be fine.


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## Tim9 (Sep 27, 2020)

I’ve spent way too many days overbuilding stuff ( tools) that really doesn’t need to be heavily built.
  I’m now of the mindset...KISS
anyway...not knocking your build. It’s a well done balancer. And if that’s what floats one’s boat...more power to you.
That said... here’s the balancer I’ll build when I need one. It’s really simple.
Grinder wheel balancer


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## ErichKeane (Sep 27, 2020)

Tim9 said:


> I’ve spent way too many days overbuilding stuff ( tools) that really doesn’t need to be heavily built.
> I’m now of the mindset...KISS
> anyway...not knocking your build. It’s a well done balancer. And if that’s what floats one’s boat...more power to you.
> That said... here’s the balancer I’ll build when I need one. It’s really simple.
> Grinder wheel balancer


I'd actually seen that one when I was researching how to do this one.  I liked the JB Weld trick on the surface plate, but wasn't confident enough in my ability to get it right 'the first time'.

That said, your balancing replacement nut is almost exactly what I'm going to do!  I'm likely going to modify the 'factory' nuts instead of making new ones, but thats about exactlly what I'm going with.  What lead you to choose 5/16-18 if I can ask?

Side note: Thats a fantastic looking Burke Millrite!  I've got one of the first powermatic ones, but mine spent a long difficult life in a high-school, so its not nearly as nice as that one.


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## Tim9 (Sep 27, 2020)

Eric, don’t get too envious. I didn’t overpay for my Millrite but it surely wasn’t pristine. I had to do a good bit of work on it. I had to replace the spindle bearings and when I got in there, I found out they were already replaced. To make matters worse, I had an odd issue in which the quill was kind of flopping around ... moving in and out about an 1/8” . Lots of signs of metal worn out where the bearings seat inside the quill/ spindle.
I seem to have fixed it and it’s holding up, but I was really concerned that maybe my mill was toast. But, as I always say.... I’d rather be lucky than good. And I lucked out because it’s holding up well. Then I attempted to regrind the spindle r-8 taper. I had a lot of runout or whatever it’s called. My collets were micing something like 8 thousandths out. It’s now about 2 to 3 thou out now.
   And... it looks good because i repainted it. But it’s good now and I like it.
Maybe one day I’ll try to hard turn it to get it closer to zero.


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## ErichKeane (Sep 27, 2020)

Tim9 said:


> Eric, don’t get too envious. I didn’t overpay for my Millrite but it surely wasn’t pristine. I had to do a good bit of work on it. I had to replace the spindle bearings and when I got in there, I found out they were already replaced. To make matters worse, I had an odd issue in which the quill was kind of flopping around ... moving in and out about an 1/8” . Lots of signs of metal worn out where the bearings seat inside the quill/ spindle.
> I se to have fixed it and it’s holding up but I was really concerned that maybe my mill was toast. But, as I always say.... I’d rather be lucky than good. And I lucked out because it’s holding up well. Then I attempted to regrind the spindle r-8 taper. I had a lot of runout or whatever it’s called. My collets were micing something like 8 thousandths out. It’s now about 2 to 3 thou out now.
> And... it looks good because i repainted it. But it’s good now and I like it.
> Maybe one day I’ll try to hard turn it to get it closer to zero.


Ah, I was lucky that after replacing my spindle bearings that it is in great shape. My ways on the other hand are toast, particularly on top of the knee, but the X axis is bad too. If I get the gibs tight enough to remove excessive "twist" of the x axis, I lose about 6" of travel at both ends.

Plus my table is rough. I spent a while at one point with some flat stones so it isn't too bad, but I'm jealous of your flaked top


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## Tim9 (Sep 27, 2020)

By the way Eric, that video isn’t my build. I was just showing the one I will copy once I get to that stage. To many other irons in the fire right now.
   Anyway, I’m guessing he used fine thread because it’s less likely to unscrew. and probably a good idea to make sure the side with the “screw weights” is on the side of the grinder which doesn’t allow the rotation to unscrew the set screws. Probably not critical, but back in the old days.... Chrysler vehicles had right hand lug nuts on one side of the vehicle and left hand lug nuts on the other side. The engineers didn’t want the lug nuts unscrewing while you’re driving down the highway. Doubt it would happen and a little blue Loctite would solve it anyway. But, wouldn’t hurt to design it that way if possible I guess.
fwiw...as I edit this... I’m laughing at myself. The whole set screw designed on left or right is just typical of those rabbit holes I go down. Probably doesn’t really matter but I tend to overthink all this stuff. Not a great personality trait.


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## ErichKeane (Sep 27, 2020)

Ah, I misread that! I thought that was you in the video 

Mine ends up being very similar, the JB Welded rails were concerning to me because I didnt want to get to the end and have it screwed up! Instead, using my planer blade + being able to reset it whenever seemed to be less likely to get screwed up!

I had been thinking 1/4-20 instead, but didn't have good reason. So when in the video he used 5/16-18, I thought there might have been justification.


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## Tim9 (Sep 28, 2020)

Eric...I wouldn’t overthink what anyone uses as far as bolts and threads. Half the time...we use what we have on hand so we don’t have to run to a hardware. It’s more a move of convenience  than rational analyzing best practices.
  Especially when thinking about a set screw for a weight to balance a grinder wheel. Nothing structural there.


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