Messages

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I believe the problem to be in the locking pivot joint of the multi-base.
Even if I crank that thing down to an uncomfortable level of tightness, there is still a lot of flex right at that joint, and it isn't creating a perfectly parallel surface even without any pressure applied.
I even dismantled the pivot to ensure there wasn't anything in there causing a bad seating, and everything looked fine.
I don't believe a ~1" diameter locking ring with a single bolt is good enough to hold this as securely as it should.
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I'm wondering if your MB-100 is defective?  I just dug mine out, (admittedly, don't use it much) and the pivot joint on mine locks solid.  I don't have any detectable play.

Maybe post a short video of what you're seeing?

Won't be home this evening, but I'll see if I can capture it on video tomorrow.

To elaborate, i wouldn't call it play in the mechanism. Once it's locked down, there isn't any slop in the interlocking ridges, no rattling rotational movement. It's just....bendy.

Mounted to the machine, puting any light to medium pressure on the USB, i can see a small amount of flex through the whole unit, mostly at that pivot joint,i think

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... software to measure absolute angles and settings down to fractions of mm and degrees...
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I've said for some time now (as have others), this degree of accuracy ain't happenin'. 

Carry on....      

So.....we should all be saving ourselves hundreds of dollars by skipping all these inaccurate jigs and just freehand grind everything? 

I'm being a bit hyperbolic, of course.  As I was in the previous post too.
I don't care if I can't dial this in to 18.0 vs 18.25 degrees.
What I care about at this point is the last sentence in my previous post...if I can't hit the same spot every time I place the jig against the rest and touch the wheel, then this multi-base isn't worth the cost, or the frustration.


This morning I kind of got it working, but not in a way that I'm happy about.
Again, this is a skew chisel in the SVS50.  Set up meticulously in the jig, checked for any twist by using a ruler to ensure equal distance from edge of jig to tool on both ends of each side.
I reduced the protrusion of the chisel and the height of the USB to as low as i could go without the screws hitting the grinding wheel, and i turned the USB around so that I'm staying over the 2 legs of the bar (which will work for this jig, but not for others)
This gave me the absolute tightest setup i could muster, with the least amount of flex (though, there still is some at the angle locking joint on the multi-base)
I then locked the bar in place by turning the screw over the threaded leg till just snug, then tightened the screw over the smooth leg, then finished tightening the one on the threaded leg.  This is how I always do it, and it works fine every time when mounting the USB directly to the machine.
But, once locked down in the multi-base like this, the bar is not quite parallel to the side of the wheel.  Through trial and error, I had to intentionally twist the USB while tightening it down, in order to make it parallel.

I believe the problem to be in the locking pivot joint of the multi-base.
Even if I crank that thing down to an uncomfortable level of tightness, there is still a lot of flex right at that joint, and it isn't creating a perfectly parallel surface even without any pressure applied.
I even dismantled the pivot to ensure there wasn't anything in there causing a bad seating, and everything looked fine.
I don't believe a ~1" diameter locking ring with a single bolt is good enough to hold this as securely as it should.


Again, it's not about accuracy of the chosen bevel angle, it's about consistency.  And i don't think i'm being overly critical when the amount of play I'm seeing here can literally keep me from reaching the apex across the entire length of the blade (which is only a little over an inch long).  After all, isn't the whole idea behind using jigs that you can repeatedly get quick touchups without a) having to grind an entire new bevel each time, or b) spending 20 minutes fiddling with, and forcing things into place to find the lucky spot where you got it to line up once before?

Certainly not expecting .0002" here, but I would think better than .02" (.5mm) overall wouldn't be within the realm of the impossible.
If I knew someone with an end mill, i would just have the hubs cut down to equal backspacing and call it a day.  Short of that, yes, custom spacers are still the other option I'm considering.

This is sharpening, not toolmaking. how much precision is required?

For the thousands of dollars many people put into these systems, systems that boast precision and repeatability above all else, i would say "all of it".  All that promised precision is required 
Looking at all the branded and user created jigs, software to measure absolute angles and settings down to fractions of mm and degrees...that almost seems like a silly question lol

Taking the wheel width issue completely out of the equation, this was my issue from this weekend:
I was working on setting a new bevel on a skew chisel. 1/4" thick HSS, with a 30° skew.
Using the SVS50 with the standard USB, on the face of the wheel, the hollow grinding was no problem.  I could flip and grind as many times as needed, and every time it hit perfectly.  In the end, each side had one continuous grind pattern.
Switch to the multi-base and side grinding.... And I've spent ages chasing uneven grinds.  A straight, flat edge, grinding against a flat wheel, and I can't for the life of me get full surface contact in a single pass.  I'm now well beyond the point were I could've done this faster by hand.

Because of the multiple joints, between the multi-base he the USB, it's not just a question of the bar moving closer to the wheel and dropping the angle a bit...that, i could deal with.
Instead, the flex causes twisting in multiple directions.  Wiggle it one way, and the bevel angle changes.  Wiggle it another, and you grind away the tip, or the heel.
And this is with using as light a touch as I can, while holding just tight enough to keep the jig against the bar, and applying just enough pressure to make it cut decently.

Keeping the tool/jig closer to the legs of the USB helps in some regards, as does locking the multi-jig closer to the machine. This is probably why i didn't notice this at first, when using other jigs.  But doing something like a skew chisel only lets you start near the legs for one side...when you flip it, you're now over the (very flexy) far end of the tool rest.

The only way I can think of to resolve all that flex, would be to have a tool rest that is somehow supported on both ends.  Which, of course, would be impractical for every other jig that requires sliding over the bar.

I don't even care about the wheel width issue at this point, but it's driving me bonkers that i can't grind a tool, lift it off the wheel, set it back down without changing anything, and not be grinding on the same plane as I was just seconds earlier.

Finally got around to emailing tormek at the end of last week, and just heard back from them this morning. 

Was told the wheels themselves can vary up to 0.2mm in width (along the rim), and that they couldn't quote me all the other tolerances for backspacing, offset, etc.  But they're saying an overall difference of 0.5mm would still be within spec.

They signed off with "I am sorry, but it is very difficult for us to have tighter tolerances than that. This surface is not our primary grinding surface.", so I guess that answers the question; when they talk about consistency for swapping between wheels they're talking for face grinding only, not side grinding 


After spending more time with it this weekend, I'm coming to find that 0.5mm variation in the wheels isn't that big of a deal anyway...because I'm seeing WAY more flex than that from the USB when mounted in the multi-base   

I was really looking forward to how easy this setup was supposed to make it for me to get flat bevels on all my turning tools....but at this point I've gotta say I'm not all that impressed, and am glad I bought the stuff used and didn't pay the full blown retail for most of it 

[definitely]

I would suggest purchasing the new two locking screw design XB-100.

Y'lnow, i was debating about going that route instead, just this morning.....and then it occurred to me, i have one of these mounts already, out on the porch on my BGM-100 (for the high speed grinder, that I haven't used in ages).  I might just swap that over this weekend, if I find some free time.
Or wait till next week for a new mount and upgraded water tray to be delivered.  The side grinding definitely doesn't play well with the old SG2000's original water tray.....especially after i increased the speed of the machine today lol

Good question about the acceptable tolerances from the factory. I'll see about getting motivated to send that email this weekend too, if time allows.

Yeah, I'm sure there are workarounds.  Again, it just surprised me that they were off like this, but i can set the angles okay if i re-adjust your reach wheel.

So far, I've only been using it to work on a set of chisels.  I could see a custom block for the USB height and chisel projection being the answer for that.

I'm hoping that i can use the turning tool jig and angle setter when it comes time for those, but I haven't even started looking into that.


Today I just discovered a new problem - the USB is shifting because the multi-base is racking in the mount after I lock it down.....because my old SG2000 only locks one side of the bar.  So, time to drill and tap that for a second lock screw 

make a spare and your first one will never fail..........

Ken

LMAO  now there's some solid truth, right there 

Yup, that's exactly what I meant by "Now if only I had a metal lathe to cut new backspacers to match each wheel" 

Sadly, i don't have the equipment to do that....I might know someone with a 3D printer who could help, but I wouldn't have expected plastic would hold up for that part?  Even my metal backspacer is showing some signs of wear....
Could be worth a try though 

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So, it seems 1 notch on the micro adjuster is equal to about 0.25mm of bar height, is that about right?  I know that info is out there somewhere, but I don't recall.
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Yep... that's correct.

Glad it's solved... well figured out anyway...

Thanks for the confirmation on that.

Now if only I had a metal lathe to cut new backspacers to match each wheel......something tells me trying to shim with 0.2mm and 0.5mm washers isn't going to be a great long term solution lol

Yeah, I'm just looking to see where a difference may or may not be.

Well, lunch break didn't happen, but got the measurements done tonight. The answer is the differences are a little bit on every surface lol
Different wheel width on 1/3, different backspacing on each, different depth from the face of the wheel to the surface for the nut. Most importantly, different overall hub to face widths.


I took the time to take averages of all measurements taken at 4 points on each wheel.

Outer ring wheel widths:
Coarse: 50.28mm
Fine: 50.12mm
Extra Fine: 50.12mm

Actual height from hub face to wheel face:
(measured with your granite plate/depth Guage suggestion, but with the hub sitting up on a 1-2-3 block, so the offset isn't factored.  This would simulate actual measurements while mounted to the machine.)
Coarse: 50.36mm
Fine: 49.86mm
Extra fine: 50.16mm
Largest difference of 0.5mm

After that, i mounted each wheel to the machine and confirmed measurements using the USB.  The differences between the distance to the wheel faces matched the measurements above perfectly.

Keeping track with the micro-adjuster as I went, i found the following...
To keep the distance to the USB the same, using the coarse wheel as the baseline of 1:
Switching Coarse to Fine, need to lower the USB 2 full notches.
Switching Coarse to Extra Fine, need to lower USB about 1.25 notches (in other words, if going from Fine to Extra Fine, would need to raise the USB about 0.75 notches).

So, it seems 1 notch on the micro adjuster is equal to about 0.25mm of bar height, is that about right?  I know that info is out there somewhere, but I don't recall.

I'll use this as a rough guide, but will still double check with the marker when switching wheels.

Just for a bit of reference I measured the width of my diamond wheels (using the depth gauge to a granite flat surface)  I averaged  50.4mm on the DC to 50.2mm on the DE.  (So that accounts for one of your 'clicks' on the microadjust I guess).

Maybe the reality will be to realize there is a difference when changing wheels, and adjust accordingly?  Just out of curiosity, does Tormek actually say you can switch wheels without adjusting? (Maybe it's an assumption we're making).   After all, you should only have to go thru all 3 wheels once... then touchups should only take one.

I had also thought about using a depth gauge and a granite plate, but ruled it out once i realized one of the hubs is higher than the wheel, and the other two are lower, so even that wouldn't give a proper view of how they compare when mounted.

I don't actually know if they ever specifically came out and said about switching without adjusting.  I just remember seeing that discussed as a big benefit of the diamond wheels....granted, I'm sure that's mostly on relation to the outer diameter not changing when the wheel wears down, like the stone ones do.....but, yeah, i guess I just assumed there'd be a high level of accuracy for the side grinding as well.

I'll report back once I get my measurements taken on my lunch break

I seem to have a different opinion of Tormek support than some of you.

I don't mean to imply they aren't supportive, i know they are.  I simply figured this wasn't something to pester them with.
I'll consider it, after i get my measurements really nailed down here.

The only fix I can think of, after getting everything measured out, would be adding custom washers between the back of the wheel and the spacer that sits between the machine and the wheel. But they're need to be very precisely machined, and i'd have to keep track of them for swapping on with each wheel.

But that's if I want to be really anal about it, I suppose.  It's not all that hard to just re-color the bevel and adjust a bit as needed between wheel swaps

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That doesn't account for the amount of adjustment you're having to make.  Measuring the shaft should account for this plus any difference in stone width.  If nothing else, it should tell you how much adjustment you'll need to make between wheels a bit more accurate than the Sharpie method.

I'll be curious what support has to say.

You're right, it doesn't give the whole picture...there has to be a difference elsewhere as well.  But with the machined inset on the outside of the wheels, the shaft protrusion wouldn't give the full story either. I would assume the other difference is in the width of the wheel itself, but that's a little difficult to measure exactly, without risking damage to my calipers from the diamonds.

I'll see if I can rig something up later today to measure the absolute location of the sides of the wheels while mounted on the machine.

As I mentioned to Ken, i didn't bother with contacting support because these wheels were bought used.  And, for that matter, they're mounted to an old SG2000 that I bought about 5 years ago, and who knows how old it was at that point lol  The only thing I've ever had a warranty on is a couple of the jigs 

Kavik,

You should email Tormek support. (support@tormek.se)

Ken

I was more just curious if this was a common issue.  I would've contacted them if these were brand new wheels, but being that I bought them used....I wouldn't really expect them to have much to say about it?

Can you measure how much the shaft sticks out after you mount a stone?  Might give you a clue if it's the offset?

A good idea, but i went a different approach.   Straight edge across the center of the back of the wheel, across the hub, with feeler guages.

• Coarse wheel - hub is .004" higher than the edges of the wheel
• Fine wheel - hub is .006" lower than the edges
• Extra Fine - hub is .003 higher than the edges

Doesn't sound huge, but definitely enough to make a difference, and makes it not quite so "swap wheels and keep all your settings the same" as they advertise, unfortunately