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View Full Version : Unusual sine bar - advice on gage blocks

PStechPaul
12-14-2014, 06:01 PM
I bought an interesting sine bar on eBay a few weeks ago:

http://i.ebayimg.com/images/i/281493093966-0-1/s-l140.jpg
http://www.ebay.com/itm/281493093966

And I also got a set of adjustable parallels that I figured I could use with this instead of gage blocks for moderate accuracy:

http://i.ebayimg.com/images/i/191417723992-0-1/s-l140.jpg
http://www.ebay.com/itm/191417723992

I probably don't really need these, but they seemed like a good acquisition at the time, and inspired by the class lessons on sine bars. Now I am considering a set of gage blocks, and I will also need to get a granite block to complete my inspection and set-up system. I might also need a height gage and other things, but I may actually have some old tools that will work for that:

http://enginuitysystems.com/pix/Old_Tools_5.jpg

For the gage blocks, we were introduced to the standard 81 block set, but I have also found a couple of inexpensive sets with smaller numbers of blocks, and wonder if they would be good enough:

and

http://www.ebay.com/itm/281511180931

The first link includes a block that is a half-tenth:

2 blocks: 1.000" & 0.1005"
9 blocks: 0.1001" to 0.1009" in step of 0.0001"
9 blocks: 0.101" to 0.109" in step of 0.001"
9 blocks: 0.110" to 0.190" in step of 0.01"
3 blocks: 0.200", 0.300" & 0.500"
3 blocks: 1.000", 2.000" & 4.000"
1 block: 0.10005"

I'm not sure of the advantages of the 81 block set over these with smaller numbers of blocks. It seems that either would be capable of the same range of measurements, but perhaps the set with less blocks would take more than four to obtain certain values.

This seems to help answer the question:
http://www.mansontool.com/merchant2/merchant.mvc?Screen=PROD&Product_Code=RS9A1&Category_Code=Gage_Blocks

Optics Curmudgeon
12-14-2014, 06:39 PM
You want to use the minimum number of blocks to get to the stack size you need. The larger sets make that easier because they have more intermediate sizes, at higher cost.

Fodenman
12-14-2014, 07:00 PM
Here's a random number 3.845"

With 9 blocks it takes 6,with 81 blocks you can do it in 3.

oldtiffie
12-14-2014, 08:40 PM
Here is some useful advise regarding the accuracy and sizes of slip gauge sets:

http://en.wikipedia.org/wiki/Gauge_block

An "81" Grade "B" set will cover most requirements as will a Grade "B" surface plate.

If you are looking at real consistent accuracy you will need to consider tool calibration as well as ambient conditions in the "Inspectorate" area.

PStechPaul
12-14-2014, 09:52 PM
For most purposes, especially with a sine bar, I doubt that I would need anything more precise than 0.002", and I can use the adjustable parallels and a digital caliper or micrometer to get close enough for most angles I would ever need to make. For instance the sine of a 33 degree angle is 0.544639 and for a 6 inch sine bar that would be 3.2678". Suppose I used a caliper and set an adjustable parallel to 3.266". That would be an angle of 32.979 degrees. If it were 3.269", the angle would be 33.013 degrees. So an error of 0.003" in height or 0.003/3.2678=0.019% produces an angular error of 0.034 degrees out of 360 or 0.0094%. So I doubt I would need the high precision gage blocks, although I could use them to calibrate my micrometer and calipers and be pretty sure of 0.001" accuracy. I don't have a good environment either, and the variations in temperature would be significant, and the high humidity would probably cause the blocks to rust. I think I'm talking myself out of buying them.

Now I'd like to learn more about how I might be able to use the sine bar other than just for measurement. It would probably be more useful to me to use it as a part of a tilting vise for milling angles. It has a single T-slot that I could use with clamps, and maybe I can use the tapped holes to attach it to the milling table at an angle as needed.

oldtiffie
12-14-2014, 10:11 PM

http://i200.photobucket.com/albums/aa294/oldtiffie/Sine_bar/Sine-bar_setting1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Sine_bar/Sine-bar_setting2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Vise/Vise2.jpg

PStechPaul
12-14-2014, 11:17 PM
Good information. I think I would be able to make a base for this sine bar to make something like the sine vise you show in the last image.

http://i200.photobucket.com/albums/aa294/oldtiffie/Vise/Vise2.jpg

Here are some better images of what I have:

http://enginuitysystems.com/pix/tools/Sine_Bar_1682.jpg

http://enginuitysystems.com/pix/tools/Sine_Bar_1683.jpg

oldtiffie
12-15-2014, 12:27 AM
For most purposes, especially with a sine bar, I doubt that I would need anything more precise than 0.002", and I can use the adjustable parallels and a digital caliper or micrometer to get close enough for most angles I would ever need to make. For instance the sine of a 33 degree angle is 0.544639 and for a 6 inch sine bar that would be 3.2678". Suppose I used a caliper and set an adjustable parallel to 3.266". That would be an angle of 32.979 degrees. If it were 3.269", the angle would be 33.013 degrees. So an error of 0.003" in height or 0.003/3.2678=0.019% produces an angular error of 0.034 degrees out of 360 or 0.0094%. So I doubt I would need the high precision gage blocks, although I could use them to calibrate my micrometer and calipers and be pretty sure of 0.001" accuracy. I don't have a good environment either, and the variations in temperature would be significant, and the high humidity would probably cause the blocks to rust. I think I'm talking myself out of buying them.

Now I'd like to learn more about how I might be able to use the sine bar other than just for measurement. It would probably be more useful to me to use it as a part of a tilting vise for milling angles. It has a single T-slot that I could use with clamps, and maybe I can use the tapped holes to attach it to the milling table at an angle as needed.

You have got a very grip of reality and common sense here as many or most real everyday tolerances are quite wide and achievable on most machines - and that applies to a lot of stuff that can be done by hand or flame cut and/or off-hand ground if needs be.

The trick is to analyse the job or requirements and find the best tolerance range and class of finish to get the job done. Once you have that you can work through your range of methods of achieving the end result required in the most practical, effective way and with the least effort and time needed.

If I wind up with a method or requirement that seems a bit demanding, it is a signal to go back and re-think it all again - from "square one".

If it suits, it is quite in order to fabricate a job - or part of it if needs be - to get a satisfactory result - there may be no need to "machine" it at all.

Some times a New machine" may not be needed as an exiting "lesser??" machine may be quite adequate if the operator/user/HSM-er were to improve his skill-sets to the level required.

bob ward
12-15-2014, 05:31 AM
I have a sine bar and no blocks. I typically use the sine bar for angles <10°, and for that, a piece of round turned to the required diameter works just fine.

J Tiers
12-15-2014, 08:03 AM
Anyhow, that's NOT a sine bar.... it's a "sine plate", and the t-slot is useful for actually attaching a part to be machined to the plate. A sine "bar" is more of a reference tool.

While it is fashionable to state that you don't need accuracy better than "X", it is important to make a distinction between dimension accuracy and angular accuracy. Angles may need very good accuracy, for instance a taper for a morse, B&S, etc socket. Whatever your degree of "NASA" tolerances, you still need the parts to fit together, and you can't have the taper shanks wobbling loosely.

Plus, the use of at least some gage blocks for tool calibration is very helpful and necessary if you ever make parts that must be 'to print" without having the other part to fit to. That can be simply for your own purposes, it need not be for pay.

mklotz
12-15-2014, 11:03 AM
For most purposes, especially with a sine bar, I doubt that I would need anything more precise than 0.002", and I can use the adjustable parallels and a digital caliper or micrometer to get close enough for most angles I would ever need to make. For instance the sine of a 33 degree angle is 0.544639 and for a 6 inch sine bar that would be 3.2678". Suppose I used a caliper and set an adjustable parallel to 3.266". That would be an angle of 32.979 degrees.

It's easy to generalize the error analysis of a sine bar.

The equation of a sine bar is:

h = L * sin(A)

where:

A = desired angle
L = length of sine bar (between roll centers)
H = stack height

Taking the derivative wrt 'h' we have:

1 = L * cos(A) * dA/dh

so the angle error (dA) in terms of the stack height error (dh) is:

dA = dh/(L*cos(A))

A = 33 deg
L = 6 in
dh = 0.0018 in = (3.2678 - 3.266)

so dA = .0003577 rad = 0.0205 deg

which agrees favorably with your error of 33 - 32.979 = 0.021 deg

Toolguy
12-15-2014, 12:16 PM
You can use the sine bar or plate in the mill vise by setting the angle on the bed of the vise and either clamping the material in the vise (if wider than the sine bar) or clamp the sine plate in the vise and clamp the part to the plate.

oldtiffie
12-16-2014, 12:49 AM
Angle plates are very handy and will measure very accurately (to just south of a slip gauge - in a good set) in increments/multiples of 0.25 degrees (~ 1 in 230 or 0.0044 per inch) and they can be visually interpolated to quite an accurate degree.

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Angleplates1.jpg

These digital protractors are calibrated to the same accuracy as that of a digital protractor (0.1 degree ie = 1/10 degree = 1 in 573 or 0.002" per inch). And they are easier on the eyes when you are trying to read them then trying it on a vernier caliper.

So, considering the angular accuracy required, a sine bar may not be needed or justified as there are perhaps better suited alternatives for your job.

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Angleplates3.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/measuring/Angleplates3.jpg

J Tiers
12-16-2014, 08:25 AM
Just remember that for a taper fit, an angle difference giving an error of a thou or two at one end is the same as a mile.... the taper will rattle, and will only hold if forced in very hard, which is not a good idea.

If you need only ordinary accuracy, why bother? Just get an angle fixture with a degree scale and get on with life. Or set that thing as accurately as you care to, using adjustable parallels, a protractor, gage blocks, etc, and proceed.

Paul Alciatore
12-16-2014, 01:01 PM
Another reason for using the minimum number of blocks that the larger sets allow is that the error accumulates with each additional block used. If each block is +/-20 uMeters, then a stack of three blocks will be +/- 60 uMeters while a stack of 6 would be twice that or /- 120 uMeters.

Since the idea of using blocks is to get the maximum accuracy, it is best to use as few blocks as possible. Thus the larger sets are more desirable.

Looked at another way, a larger set can be of a lesser grade and still meet a desired level of accuracy. Thus, a larger set may be more economical.

You want to use the minimum number of blocks to get to the stack size you need. The larger sets make that easier because they have more intermediate sizes, at higher cost.

PStechPaul
12-16-2014, 05:05 PM
I can see where tapers need a high degree of angular accuracy, but a tapered piece would probably require a set of centers for the sine block. It's probably even more accurate to coat the piece with layout dye and use a known female taper to determine fit. Mostly I am questioning why I purchased this item in the first place. It was probably because I had just completed the homework assignment on sine bars and we used the instructor's own sine vise with an adjustable parallel instead of gage blocks to set the angle for grinding a 20 degree feature on the vise we were making. But the tolerance was +/- 5 degrees, and for that a cheap protractor could be used.

Now I'd just like to be able to find a good use for this thing, or it will just get shuffled around and put in a box or drawer and end up rusting or get lost. A set of gage blocks might be more useful, even if just to calibrate my calipers and micrometers. I'd need a granite surface plate to use them for height measurement, and maybe I'd also need a proper height gauge. And the list of tooling goes on, although I may never actually need any of it for my present and foreseeable projects. I'm a toolaholic!

oldtiffie
12-16-2014, 06:29 PM
I can see where tapers need a high degree of angular accuracy, but a tapered piece would probably require a set of centers for the sine block. It's probably even more accurate to coat the piece with layout dye and use a known female taper to determine fit. Mostly I am questioning why I purchased this item in the first place. It was probably because I had just completed the homework assignment on sine bars and we used the instructor's own sine vise with an adjustable parallel instead of gage blocks to set the angle for grinding a 20 degree feature on the vise we were making. But the tolerance was +/- 5 degrees, and for that a cheap protractor could be used.

Now I'd just like to be able to find a good use for this thing, or it will just get shuffled around and put in a box or drawer and end up rusting or get lost. A set of gage blocks might be more useful, even if just to calibrate my calipers and micrometers. I'd need a granite surface plate to use them for height measurement, and maybe I'd also need a proper height gauge. And the list of tooling goes on, although I may never actually need any of it for my present and foreseeable projects. I'm a toolaholic!

Bingo!!

Good call Paul - a real bulls-eye.

I all too often wish I'd asked myself that question before I bought stuff instead of after.

Perhaps I really just wanted it without really needing it!!

Arthur.Marks
12-16-2014, 06:34 PM
Mostly I am questioning why I purchased this item in the first place.
If I am to be completely honest, this is the only use I've had for mine that ever truly required it:
http://i771.photobucket.com/albums/xx357/Arrak_Thumrs/Schaublin%20items/DSCN3663.jpg (http://s771.photobucket.com/user/Arrak_Thumrs/media/Schaublin%20items/DSCN3663.jpg.html)

It was to prove the exact angle of a historical, proprietary "2° taper." I've learned enough to not trust proprietary mfr. tooling to be as simple as it is commonly named. In this case, though, it was---spot on 2° to extremely close tolerance (4° included angle). Actually, I sort of like this setup over a centers based one. It strictly indicates off of the taper without introducing any error which may or may not be integral to the male + female centers of the tooling. This piece has no female center on the small of the shank. The rotating center point also has bearings with clearance (design is loaded by contact with the workpiece) to contend with.

oldtiffie
12-16-2014, 11:45 PM
Just a thought - and a reminder.

If you are using your machine/mill (or what-ever) table and are setting the sine bar up using the table movement, you will need to ensure then the side/s of the sine bar are (very!!) parallel to the machine table bed axis (as you would when setting a vise up as parallel on a mill table).

If you don't get it that way you will have brought in "compound (ie many) angles".

If you are not using the machine table axis or are setting up on a surface plate it will not matter as there will be no compound angles.

oldtiffie
12-17-2014, 06:14 PM
Just for a change and for interest, here are more pics of a variety of "sine bars".

PStechPaul
12-17-2014, 06:34 PM

I didn't see any that were quite like mine, particularly the T-slot.

There were no applicable hits for "cosine bar", but there are tangent bars:

http://dreadnoughtproject.org/tfs/index.php/Tangent_Bar (there is a cool video of its use):

http://www.hhip.com/precision/gages/angle-gages/angle-tangent-bar-set.html

and there is a bar in Tangent, OR: