A degree wheel for the Atlas/Craftsman 6X18

[SG51Buss]

...eBay item 111483477188 is a Starret metal flat tape in imperial & metric which are usually fairly accurate at 60 o F ...

Yeah, I like that. Found them under "Starrett Stix", around $10.





That last one is marked in millimeters, so no need to add the extra 'zero'. Just need to cut off the first 360 millimeters and slice it down the middle. Might need to subtract a little from the disc's diameter to account for the tape's thickness...

 

[wa5cab]

John beat me to it. 22/7 is close enough for most machining but it is off by one in the third decimal place.

22/7 = 2.142857143...
Pi = 3.141592653...

:whistle:

Robert D.

That's interesting Robert ... I was taught at the Electrical & Mechanical Engineering Apprentice college that I attended for 3 yrs was that 22/7 was the right equation that's why it never works out as a decimal .

I'm intrigued , can you point me to any places that explain how it is derived please? .

 

[SG51Buss]

I like to be as accurate as possible when using Pi, easy enuff when you have a 'Pi' button on your calculator, but that can be unnecessarily picky for some tasks. Like when Kirk asks Spock "How long 'till we reach Alpha-Ceti-6?", and Spock responds "Precisely 2 days, 4 hours, and 7.623 minutes".

If you used a metric tape, precisely cut to 360mm, what disc diameter would you need, rounded to the nearest 0.001", which is practical enuff for this task?

Using the 'Pi' button, giving extreme accuracy: Diameter = 4.511"
Using my favorite, Pi = 3.14159: Diameter = 4.511"
Using Pi = 3.1416: Diameter = 4.511"
Using Pi = 3.14: Diameter = 4.514"
Using Pi = 22/7: Diameter = 4.510"

If I was trying to precisely fit bushings or press-fit parts, I'll use the 'Pi' button. But here, we're trying to wrap a tape around a disc, hopefully with little-to-no visible gap or overlap of the ends, and account for the tape's adhesive and thickness. For this, 22/7 is good 'nuff...

 

[Mark_f]

) I am going to buy one of those tapes.4.511 seems a good enough diameter for me.

Mark Frazier

I like to be as accurate as possible when using Pi, easy enuff when you have a 'Pi' button on your calculator, but that can be unnecessarily picky for some tasks. Like when Kirk asks Spock "How long 'till we reach Alpha-Ceti-6?", and Spock responds "Precisely 2 days, 4 hours, and 7.623 minutes".

If you used a metric tape, precisely cut to 360mm, what disc diameter would you need, rounded to the nearest 0.001", which is practical enuff for this task?

Using the 'Pi' button, giving extreme accuracy: Diameter = 4.511"
Using my favorite, Pi = 3.14159: Diameter = 4.511"
Using Pi = 3.1416: Diameter = 4.511"
Using Pi = 3.14: Diameter = 4.514"
Using Pi = 22/7: Diameter = 4.510"

If I was trying to precisely fit bushings or press-fit parts, I'll use the 'Pi' button. But here, we're trying to wrap a tape around a disc, hopefully with little-to-no visible gap or overlap of the ends, and account for the tape's adhesive and thickness. For this, 22/7 is good 'nuff...

 

[SG51Buss]

Okay, here's a jpg of the degree wheel marking tape. Unfortunately, the max resolution of forum uploads is 1280 pixels. When I printed my tape, on a 300 dpi printer, the 7.2" tape image used about 2160 dots. So, simply scaling and printing this jpg image will result in loss of resolution, and the degree lines may appear mis-aligned.



Also attached is a zip file containing 3 versions of this image in bmp, gif and jpg. A 4th file in this zip is DegreeWheel.igr, which is the original drawing in Intergraph SmartSketch format. So, if you have this application (which came pre-installed on many PC's), you could load the file and get a better printout.

 

[Round in circles]

I give up :whiteflag: . I just spent 5 hours trying to print a scale from several software programs. I got close , but me and this computer are not getting along.:banghead::banghead: . I'm going to the shop and do what I do best, cut metal and make chips. I got along 45 years without a degree wheel , I guess I'll make it till I die without one too.


Mark

Mark,
Don't despair .

Gradomatic v10 .....is an easy way to get a scale that can be marked to indicate 1 mm is 1 degree along the edge of an A4 printed sheet and have a little 3 mm wide margin as well ( you might need reading glasses to start developing it for a scale /ruler strip though . ( Gradomatic 's prime use is to make accurate graph paper )

NutnBits .com is where to pick it up .

There is a menu that asks you what colours , line styles and line thicknesses you want to play with .

I've use the thinnest black lines possible for the 1 mm points and size two lines for the red intermediate lines ( every five mm ) and dark blue for the 10 mm grid lines . ( I have a laser colour printer so can get really fine lines if needed ) .


If you use both long sides/edges of the printed sheet you can make two paper scale rulers of 180 mm /180 degrees
It only took me three prints outs to find the right setting up

If you still can't make head nor tail of things drop me a PM with your full name address and zip codes etc. & I'll send you a couple of printed sheets via snail mail from this side of the pond.

 

[Round in circles]

Yeah, I like that. Found them under "Starrett Stix", around $10.

View attachment 87527

View attachment 87528

That last one is marked in millimeters, so no need to add the extra 'zero'. Just need to cut off the first 360 millimeters and slice it down the middle. Might need to subtract a little from the disc's diameter to account for the tape's thickness...

You can reverse the tape when it's cut to 360 mm and do a trial and error turning down of the disk diameter at ambient temperatures, then once it butts up nice and tight clean & wash the disk to remove all traces of oil etc ,let it cool to ambient temp again stick the tape on it .Secure the tape inplace with a bog standard clear sticky tape

Just make sure the disk is made of steel not aluminum or brass due to coefficients of expansion differences .
Once the tape adhesive has cured for a couple of days it should be possible to turn off the unwanted portion . If that is thought too scary make a slipped over screwed on finger tight outer ring to hold everything in place before turning it off. Once the excess tape is off remove the outer keeper ring .

Whilst looking for the metric measure in the UK online stores I happened to find the Starrett tape measures site , SM44ME is a 1.2 metre long self adhesive tape jobby , it should be cheaper than a 12 foot long one & less wasteful unless the longer ones are restarted numerically after every meter of length then you get three 1.2 metre tapes for the $10 .

I haven't found a UK stockist yet but there may be other solutions , such as getting a friend to roll a quality bright steel 1 metre long metric ruler ( I have one of these as it was fairly cheap) into a band and slicing at right angles it at 360 mm point. Then once trued up epoxy gluing it to a steel disk or fix it hammer fit screw rivets in drilled holes or even sweating it on with a SS solder whilst it's held tight to the disk with some twisted wire

 

[SG51Buss]

Here's that GridOmatic:

http://www.nutsnbits.com/nutsnbits_000060.htm

 

[John Hasler]

Here's that GridOmatic:

http://www.nutsnbits.com/nutsnbits_000060.htm

Another resource:

http://www.printfreegraphpaper.com/

 

[Mark_f]

I have an idea I am going to try . It involves engraving a disk using my rotary table. It will be extremely tedious and time consuming but really nice if it works. But it will have to wait till my latest project is done which should be a few days.

Mark Frazier

Mark,
Don't despair .

Gradomatic v10 .....is an easy way to get a scale that can be marked to indicate 1 mm is 1 degree along the edge of an A4 printed sheet and have a little 3 mm wide margin as well ( you might need reading glasses to start developing it for a scale /ruler strip though . ( Gradomatic 's prime use is to make accurate graph paper )

NutnBits .com is where to pick it up .

There is a menu that asks you what colours , line styles and line thicknesses you want to play with .

I've use the thinnest black lines possible for the 1 mm points and size two lines for the red intermediate lines ( every five mm ) and dark blue for the 10 mm grid lines . ( I have a laser colour printer so can get really fine lines if needed ) .


If you use both long sides/edges of the printed sheet you can make two paper scale rulers of 180 mm /180 degrees
It only took me three prints outs to find the right setting up

If you still can't make head nor tail of things drop me a PM with your full name address and zip codes etc. & I'll send you a couple of printed sheets via snail mail from this side of the pond.