Fowler or Bowers Centering Microscope intructions wanted

gjrepesh · May 27, 2021

I have a Fowler centering microscope that I would like to learn how to calibrate. Fowler has no info since the tool is no longer sold although they said it was made by Bowers. I'm hopeful someone can explain calibration or post a copy of the instructions. See attached photo of my scope. Thanks.

John Garner · May 27, 2021

I've encountered 2 flavors of centering microscope: 1) having a single-line reticle that can be adjusted along an axis that is perpendicular to the reticle line, and 2) having a cross-line reticle that can be adjusted along axes parallel / perpendicular to the reticle lines.

The adjustment process is similar. Start by chucking the microscope in the machine spindle, then fix a target dot to the machine table. Do what you need to do to center the microscope reticle on the target, with a) the reticle lines very nearly parallel to the table motions, and b) the eyepiece set so that you can see it BEFORE AND AFTER rotating the spindle 180 degrees.

Zero the DRO or the graduated collars on the lead screws, and verify that the target is still centered on the reticle lines.

Now rotate the spindle a half turn and adjust the table to put the target back on the reticle lines. Note the DRO or graduated collar values.

Move the table to the midpoint of the two reticle-on-target locations, then use the microscope's reticle-adjustment screws to center the reticle on the target.

Check your work.

It should go without saying, but a microscope having a cross-line reticle allows both table axes to be adjusted to center the workpiece target without rotating the spindle, while a single-line microscope reticle requires rotating the spindle 90 degree between the two adjustments of the table.

Oh, yeah . . . Some centering microscopes use a fixed (not operator adjustable) reticle, placing the operator adjustment between the microscope and its chucking shaft.

John

gjrepesh · May 28, 2021

John, Appreciate the info. I'll give it a go soon.

Ray Behner · May 29, 2021

gjrepesh said:
John, Appreciate the info. I'll give it a go soon.

I've got the instruction sheet on my Skoal. It may work the same. I scanned it, but can't figure how to send attachment with PM e-mail. Send me yours if you wish.

donie · May 29, 2021

It appears to be similar to the Perkins Elmar scope for the Moore jigbore.
I found the best "target" to adjust the 50X scope is to lock the table, make the smallest mark with a tiny drill bit on ground or polished metal, then insert the scope. and center the cross hairs, rotating the scope in the spindle, and viewing, should show any mounting error.
I have used a straight shank on the scope, to try it out on other machines, and this is the problem.
As the Moore tool shank is special designed to repeat to near perfection, the R8 system does not for example, in fact its terrible, making these scopes almost useless! That is why they have nearly disappeared from the market.
The scopes are common with jigborers, the Moore scope is capable of around .0002" repeatability, but, its not easy to judge an edge, or other features to go from under magnification. A sharp edge, looks ragged and hard to judge at 50X.
The key to success, is repeatable installation after removal.

John Garner · May 29, 2021

donie --

The goal is not to put the reticle on the mounting-shank centerline, but instead to place the reticle on the spindle centerline -- making the shank-to-spindle non-repeatability moot.

John

Joe Gwinn · May 29, 2021

donie said:
I have used a straight shank on the [centering] scope, to try it out on other machines, and this is the problem.
As the Moore tool shank is special designed to repeat to near perfection, the R8 system does not for example, in fact its terrible, making these scopes almost useless! That is why they have nearly disappeared from the market.

Do you think that the advent of DROs had anything to do with it?

The scopes are common with jigborers, the Moore scope is capable of around .0002" repeatability, but, its not easy to judge an edge, or other features to go from under magnification. A sharp edge, looks ragged and hard to judge at 50X.
The key to success, is repeatable installation after removal.

I have and often use a Skoal 45x centering scope bought many years ago. These were and are still made in Korea. I use it on my Millrite MVI vertical mill for picking up reference points or edges, then use the Jenix DRO (also Korean) from there. (With edges, the trick is careful lighting, so that there is a sharp light/dark boundary to focus on.)

As for being useless for a R8 spindle, how's that? The same repeat inaccuracy will afflict both scope and cutting tools the same, so the scope will be adequate for the task, unless the machine is far more accurate than the scope.

I have an integral R8-ER25 holder (Maritool), so I can get ER25 centering accuracy, so long as I leave the holder in place on the spindle.

When I bought that scope, it was $70 on sale. Now, MSC sells the same scope for $400 (item #06539332). Wonder why, or is this just MSC being helpful? Or auctioning new old stock to the desperate for what it will bring?

donie · May 29, 2021

This is the problem, "length" the body of the finder combined with the focal distance may be over 6" from the spindle nose.
If one can consistently hold close tolerance at the end of a 6" ground rod in a R8 collet, or solid end mill holder, then there will be little problem.
Otherwise, the finder has to be calibrated every time it is installed.

CarbideBob · May 29, 2021

donie said:
...
Otherwise, the finder has to be calibrated every time it is installed.

Assume calibrated means centered to spindle rotation axis, is this not SOP?
How close can one tweak it in? Line width and all that.
Nice scope on a Moore is neat but show me your six-sigma graph over 50 checks.
I so doubt .0002 very much but do agree this a way above average setup.
Bob

Joe Gwinn · May 29, 2021

donie said:
This is the problem, "length" the body of the finder combined with the focal distance may be over 6" from the spindle nose.
If one can consistently hold close tolerance at the end of a 6" ground rod in a R8 collet, or solid end mill holder, then there will be little problem.
Otherwise, the finder has to be calibrated every time it is installed.

I most often use the scope in an Albrecht keyless or Jacobs ball-bearing super chuck, both being mounted on a R8 to J33 arbor, and it certainly works for that. I bet that the R8 collets are not as good, and the R8-ER25 is better.

The MVI was good to maybe 0.0005" when brand new - it's no Moore Jig Borer.

ignator · May 29, 2021

I have a HECO spotting scope. Here's a jpg of the instructions;

The yellow sheet is an addendum indicating only the horizontal line of the graticule is to be used.

donie · May 29, 2021

CarbideBob said:
Assume calibrated means centered to spindle rotation axis, is this not SOP?
How close can one tweak it in? Line width and all that.
Nice scope on a Moore is neat but show me your six-sigma graph over 50 checks.
I so doubt .0002 very much but do agree this a way above average setup.
Bob

If you tried using one, you would understand, no fucking graphs and 50 dumb assed checks needed, it is just an aid to use the machine that is all it is.
Or simpler still, can a 6" rod be consistently chucked in a collett and run true at the end? If that works, then no problem with the scope, and good luck with that!

And, there it is, the Moore scope, the square part is the adapter for the Moore jig grinder.
Having the jigborer and scope for nearly two decades, the better application are more for measuring objects that are difficult to gage any other way, determining angles, when used with the rotary table, and alignment of objects on the table. Lookin at a scribed line, looks like a crooked nasty scrape.
When the scope is removed, and then returned, it is exact, as intended. These things on regular machines is not so popular, for the alignment reasons. Thus, they have disappeared from the market.
I posted these photos here a couple of years back. The first one, I somehow got of the reticle.

The inner circle of lines is spaced .002"
The outer circle is spaced .005"
The cross hairs are double, showing a space of .0005" between them-when focused on a work piece.

A practical measuring application here, it was requested the dimensions and angle of the rear sight dovetail slot on a Chi-com version of the Russian Tokarev military pistol, for custom replacement.

Using the optical sight, the machines DRO, and the rotary table, the slot was measured with reasonable accuracy, without removing the pistols rear sight.

The optical finder does not have to be centered with the spindle for measuring. For spindle to work location, it does.

gjrepesh · May 30, 2021

I appreciate all the input. You have pointed out issues such as the collet that can through this process off. Thanks.

Dahoud62 · Jan 11, 2023

gjrepesh said:
I have a Fowler centering microscope that I would like to learn how to calibrate. Fowler has no info since the tool is no longer sold although they said it was made by Bowers. I'm hopeful someone can explain calibration or post a copy of the instructions. See attached photo of my scope. Thanks.

Hi, I'm with Fowler. That was made by Bowers and was discontinued back around 1980. I've looked through all my old instructions and I don't have anything to help you. Sometimes I get lucky with these old tools and have something. Sorry, not this time.

ieracer · Mar 11, 2024

gjrepesh said:
I have a Fowler centering microscope that I would like to learn how to calibrate. Fowler has no info since the tool is no longer sold although they said it was made by Bowers. I'm hopeful someone can explain calibration or post a copy of the instructions. See attached photo of my scope. Thanks.

I have the original Bowers manual, i know this post is old but if you want a copy, I'll scan and send it to your pm.

Joe Gwinn · Mar 11, 2024

ieracer said:
I have the original Bowers manual, i know this post is old but if you want a copy, I'll scan and send it to your pm.

I'd suggest scanning it and providing it to the Vintage Machinery website.

Richard Cranium · Apr 3, 2024

Joe Gwinn said:
I'd suggest scanning it and providing it to the Vintage Machinery website.

ieracer said:
I have the original Bowers manual, i know this post is old but if you want a copy, I'll scan and send it to your pm.

Imagine my surprise! Here's a 2021 'string' to which there is a March of 2024 response noting the very thing I'm looking for! The instruction manual for the Bowers Centering Scope. If you would care to scan the manual I can assure you that I am most anxious to receive it. I have one of these scopes acquired years ago but I've been afraid to trust it as I've no way to calibrate it. I am just a garage guy so the other answers here are beyond me. This device may be the best solution for the pedestrian garage mechanic. My current project involves holes drilled to both sides of an object along a common axis. You can see the problem. Again, if you'd care to scan the manual I'd love to have it. And I will thank you!

Richard Cranium · Apr 5, 2024

Joe Gwinn said:
I'd suggest scanning it and providing it to the Vintage Machinery website.

ieracer said:
I have the original Bowers manual, i know this post is old but if you want a copy, I'll scan and send it to your pm.

Imagine my surprise! Here's a 2021 'string' to which there is a March of 2024 response noting the very thing I'm looking for! The instruction manual for the Bowers Centering Scope. If you would care to scan the manual I can assure you that I am most anxious to receive it. I have one of these scopes acquired years ago but I've been afraid to trust it as I've no way to calibrate it. I am just a garage guy so the other answers here are beyond me. This device may be the best solution for the pedestrian garage mechanic. My current project involves holes drilled to both sides of an object along a common axis. You can see the problem. Again, if you'd care to scan the manual I'd love to have it. And I will thank you!

Fowler or Bowers Centering Microscope intructions wanted

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