Andrew Biggs
Moderator
Hi Airamp and Dave
Nope, I still can't visualise it
Cheers
Andrew
Nope, I still can't visualise it
Cheers
Andrew
Question: Microscope Stay in Focus
- Thread starter Kicker
- Start date
KCSteve
~ Elite 1000 Member ~
Andrew
As I recall the pictures posted when one of the low profile vises was being introduced, it's all in the distance between the top of the ring (where the actual pivoting takes place) and the bit of the work you're focusing on.
To take it to the extremes, if you take an almost full sphere with just a little flat spot on top that sits in a very low donut then when you tilt the ball only the bottom few inches are staying inside the ring and thus everything above that ring is changing plane.
If you take a sphere that's just barely more than half a sphere and set it into a ring that comes up almost all the way then when you tilt the ball most of it is already inside the ring and pretty much stays there, thus it's less likely the spot you're looking at is moving up or down by very much.
In fact, you should be able to get the effect of a low profile vise by making a high-rise ring. Replace the standard 'tire' with a piece of PVC pipe just about an inch smaller than the max diameter of the ball. Add a wide cap so it won't tip and make sure it's long enough the ball won't bottom out. Bevel the edge a bit to make it ride smoother and it should give you significantly less change in plane with the tilt. I might have to give this a try tomorrow on my day off.
As I recall the pictures posted when one of the low profile vises was being introduced, it's all in the distance between the top of the ring (where the actual pivoting takes place) and the bit of the work you're focusing on.
To take it to the extremes, if you take an almost full sphere with just a little flat spot on top that sits in a very low donut then when you tilt the ball only the bottom few inches are staying inside the ring and thus everything above that ring is changing plane.
If you take a sphere that's just barely more than half a sphere and set it into a ring that comes up almost all the way then when you tilt the ball most of it is already inside the ring and pretty much stays there, thus it's less likely the spot you're looking at is moving up or down by very much.
In fact, you should be able to get the effect of a low profile vise by making a high-rise ring. Replace the standard 'tire' with a piece of PVC pipe just about an inch smaller than the max diameter of the ball. Add a wide cap so it won't tip and make sure it's long enough the ball won't bottom out. Bevel the edge a bit to make it ride smoother and it should give you significantly less change in plane with the tilt. I might have to give this a try tomorrow on my day off.
Andrew Biggs
Moderator
Hi Steve
Unfortunately at high school science wasn't my strong point and this is up there with the molecular structure of Klingons
I'll be interested in your results.
Cheers
Andrew
Unfortunately at high school science wasn't my strong point and this is up there with the molecular structure of Klingons
I'll be interested in your results.
Cheers
Andrew
Here's how you compute the depth of field for a specific microscope focal length at the specified degree of vise tilt. This is for a scope with a 0.5x objective. Those of you using Zeiss scopes with a 0.63x objective must modify the conditional convergence sequence accordingly.
Donny
Elite Cafe Member
WAIT A MINUTE!!!!! My first engraving teacher always yelled at me saying " HEY this isn't rocket science DONNY BOY" Now we got Sam tossing around quantum physics equations and REALLLLLY hurting my public school ego :biggrin: But just cuz I'm not a quitttter I'm gonna take off my boots and try to solve this equation. Be back in...ok whats PI again?
Donny
Andrew,
All kidding aside you are good at drawing so if you take the picture of the dovetail low profile that I posted and continue the round base (8.6 inches D) 4.3R to a sphere you will see the center of the sphere is just about where the workpiece would be clamped (or top of the jaws.
Do the same thing with any other vise and you can see that the where the workpiece is compared to the center of the sphere (outside of the sphere).
Cannot be simpler than that.
Dave and I both have the dovetail vises and I also will prove it to anyone that stops by.
Ken Hurst's design of this vise is just Brilliant.
I really think that Sam's Calculations will be very important since these vises (only about 20 in exsistance) are rare and have not been remade to date. So bursh up on you math guys...
OR try it with 1/3 of a bowling ball vise. Or KCSteves Idea (Donny Kinda like Bryan's large ball diemakers vise..Same principal).
AirAmp
All kidding aside you are good at drawing so if you take the picture of the dovetail low profile that I posted and continue the round base (8.6 inches D) 4.3R to a sphere you will see the center of the sphere is just about where the workpiece would be clamped (or top of the jaws.
Do the same thing with any other vise and you can see that the where the workpiece is compared to the center of the sphere (outside of the sphere).
Cannot be simpler than that.
Dave and I both have the dovetail vises and I also will prove it to anyone that stops by.
Ken Hurst's design of this vise is just Brilliant.
I really think that Sam's Calculations will be very important since these vises (only about 20 in exsistance) are rare and have not been remade to date. So bursh up on you math guys...
OR try it with 1/3 of a bowling ball vise. Or KCSteves Idea
(Donny Kinda like Bryan's large ball diemakers vise..Same principal). AirAmp
Last edited:
Donny
Elite Cafe Member
AirAmp....I do fully understand what you are saying about the vise. The last one sold before I was in a position to buy so I ended up having Ray LeTourneau make me one of his...and I love it! I did like Bryan's vise too...and i probably got yelled at more than you
Donny
Donny
Andrew Biggs
Moderator
Sam, Sam, Sam
Now I get it
Cheers
Andrew
Now I get it
Cheers
Andrew
KCSteve
~ Elite 1000 Member ~
Yep, like airamp said, even with a higher setting base I still won't have as good a setup as the low profile vise. It all has to do with how far the work surface is above the pivot point.
If you stand a dime on the table and move then tilt it 45 degrees the highest point of that dime doesn't really move all that much. If you use a full-length pencil, that point moves a lot more. I took some measurements so now I know I need to get a piece of 5" OD PVC to use for the test but I also know that I'll be moving my work surface from about 5-6" above the pivot point to no less than 3". With the low profile vises the pivot point can pass through the center of your work piece (depending on how tall it is).
Still worth running my test though - it will help, the question is just how much and if it makes the vise any less convenient to use.
If you stand a dime on the table and move then tilt it 45 degrees the highest point of that dime doesn't really move all that much. If you use a full-length pencil, that point moves a lot more. I took some measurements so now I know I need to get a piece of 5" OD PVC to use for the test but I also know that I'll be moving my work surface from about 5-6" above the pivot point to no less than 3". With the low profile vises the pivot point can pass through the center of your work piece (depending on how tall it is).
Still worth running my test though - it will help, the question is just how much and if it makes the vise any less convenient to use.
KCSteve
~ Elite 1000 Member ~
Hey! It works! :banana:
I stopped by Lowes on the way home after picking up the ever-indulgent wife (I had the day off) and started poking around the PVC area. Unfortunately they didn't have anything at 5", just 4" and 6". Toward the end I found a 4" - 6" bushing and I was debating whether it work, whether I could grind it out a bit, etc..
Then I turned it over, and found this lovely little curve that looked like it would be just a perfect fit (and it was).
The picture even shows the nice curved side. For those really interested, click here
Brought it home and tried it out.
With the regular donut a tilt toward 45 degrees the work surface I had at the time was dropping 3 - 4 inches.
In the bushing the same tilt only produced a drop of 1 - 2 inches.
I stopped by Lowes on the way home after picking up the ever-indulgent wife (I had the day off) and started poking around the PVC area. Unfortunately they didn't have anything at 5", just 4" and 6". Toward the end I found a 4" - 6" bushing and I was debating whether it work, whether I could grind it out a bit, etc..
Then I turned it over, and found this lovely little curve that looked like it would be just a perfect fit (and it was).
The picture even shows the nice curved side. For those really interested, click here
Brought it home and tried it out.
With the regular donut a tilt toward 45 degrees the work surface I had at the time was dropping 3 - 4 inches.
In the bushing the same tilt only produced a drop of 1 - 2 inches.
Attachments
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PVCBushing.jpg
KCSteve
~ Elite 1000 Member ~
Ok, I had a moment this morning to grab some quick pictures with my phone. A little rough, but they show what I'm talking about.
In the first two you see the vise on it's normal donut. Upright the top is at about 6 inches. Tipped you can see that the work is running between 6 and 4 inches - and that's just across the width of the jaws.
Next you see a shot of the PVC bushing, showing the lovely curved bit the ball sits into so nicely.
Now you see the same pair of shots with the ball in the bushing. Sorry it's a little harder to see (I had trouble getting the yardstick to stay in place) but now we're at 7 inches upright and 7 - 6 tipped - a 50% reduction in the amount of depth change.
Of course, with a true low-profile vise the rotation point passes through the surface so you get much less movement.
In the first two you see the vise on it's normal donut. Upright the top is at about 6 inches. Tipped you can see that the work is running between 6 and 4 inches - and that's just across the width of the jaws.
Next you see a shot of the PVC bushing, showing the lovely curved bit the ball sits into so nicely.
Now you see the same pair of shots with the ball in the bushing. Sorry it's a little harder to see (I had trouble getting the yardstick to stay in place) but now we're at 7 inches upright and 7 - 6 tipped - a 50% reduction in the amount of depth change.
Of course, with a true low-profile vise the rotation point passes through the surface so you get much less movement.
Attachments
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IMG_20110811_062801.jpg -
IMG_20110811_062739.jpg -
IMG_20110811_062828.jpg -
IMG_20110811_062911.jpg -
IMG_20110811_062857.jpg
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