Received my Proportional Divider, but How-to?

The most useful thing that I use my proportional dividers for is finding the width that planks have to be tapered down to. You can do this without measuring and calculating by using the following method. Lay a strip of paper on the bulkhead that is to have the planks laid across. Mark two pencil lines accurately with a very sharp pencil, one at the keel end of the strip and another at the opposite end. You now have the total width of all the planks. If you want 9 planks in that space, set your dividers to 9 ON THE LINE SCALE. Then open them so that one LONG pointer is at one of the pencil marks and the other long pointer is at the other pencil mark. The distance between the SHORT pointers is the width that each of the 9 planks must be tapered to. You can, of course, use any number depending on how many planks you must fit onto the bulkhead. Basically, the numbers on the line scale divide a line into that many pieces. I would urge you to seek out an old pair of metal, engineering/draftsman’s dividers. They are more expensive than the plastic variety but they are absolutely beautiful and far more accurate for our hobby in my experience. I think that the plastic ones are aimed more at artists who use them to measure proportions by holding them out at arms length rather than sticking the pointers into solid materials.
 
Bob Cleek said:
The proportional dividers pictured by the OP are an inexpensive set most likely made in India or Pakistan for the brass curio trade. They are not "professional grade," but may be sufficient for modeling purposes. They are scaled for proportions in "multiples," "times two, times three," and so on. A professional grade set of proportional dividers will be made of German silver and those scaled for modeling will invariably be ten inches long over all. There are shorter models, commonly 6", 7", and 8" which are "useable," but lack the accuracy possible with the full size "universal" models scaled to set proportions in terms of their decimal equivalents. There are also very large, and for our purposes crude, proportional dividers used by artists and sculptors, which are too large to be useful for modeling purposes. If you have a proportional divider regardless of the scaling on the instrument, you can always "manually" set the proportion by drawing two lines of proportionate length (e.g. 1" and 2" long for 1:2 proportion) and adjusting the dividers so that the points on each end are set to exactly match the length of the respective lines. The divider will then be set to the proportion of the two lines.

I find proportional dividers essential because I find myself redrawing lines published in old books (Chapelle, etc.) that will be prints of larger drawings reproduced in the book, often without regard to scale. With a good set of proportional dividers, all you need is a single identified measurement on the original drawing (a scale is often included in the original drawing) and with your dividers set to your desired drawing scale, away you go! Just take a distance from the page in the book and the other side of the dividers gives you the distance to the scale you've set for your drawing. There are, as mentioned, a lot of other things you can do with them as well, such as drawing a square with the same area as a particular circle and vice versa, but I've yet to learn who really needs to do that. They are very handing for dividing lengths into equal increments for spacing planking runs, ratline spacing, stanchion spacing, and such.

I collect fine drafting instruments for my own use. Most I've bought on eBay and I check for listings frequently and note that the prices do vary wildly, depending on condition, quality and rarity. Condition may not always be a relevant factor if you are looking for a "user." Some oaf may have scratched his name into the instrument and/or the case may be in rough shape or missing. That can mean a $100 or $150 reduction, leaving what would be a "mint" $200 instrument going for only $50, yet be entirely satisfactory for use, nonetheless. Be forewarned that I started collecting mint condition examples of the finest manual drafting instruments made, primarily Keuffel and Esser's Paragon line, made in Germany and solid in the U.S., as far back as twenty years ago when CAD had almost completely replaced manual drafting in the professional workplace and manual drafting instruments were plentiful and not in demand. An active collectors' market has since developed, and prices have risen accordingly for the more desirable instruments which are now much less available. Alas, the really excellent examples are no longer manufactured.

The proportional dividers that you want to obtain for modeling use are the 10" pairs with "110 scaling" or "decimal scaling." These are referred to in the advertising literature as "universal proportional dividers" because with decimal scaling they can be used for any purpose possible rather than those scaled only for specific purposes like navigation. This universal scaling permits setting proportions in "decimal equivalents" (e.g. 1/2 = .50) These instruments will have rack and pinion geared adjustment and Vernier adjustment to decimals out to .0005 (If memory serves... perhaps there's an extra zero in there... don't hold me to it.) These instruments will be manufactured by Keuffel and Esser, Dietzgen, Post, and Bowen (among less commonly seen other brands) in straight point and right-angle point configurations (as pictured in post #2 above.) (You will likely never see a right angle pointed set on EBay. They are extremely rare.) The most commonly offered are the K&E 10" "Paragon" decimal scaled models. "Paragon" was K&E's top of the line series of instruments and the "110" decimal equivalent scaled dividers were only offered in the "Paragon" line. They are made of cold rolled "German silver," an alloy of nickel and copper, much similar to Monel and were hand fitted, each bearing matching part serial numbers. They were sold in silk velvet lined fitted cases. The back of the case in newer production models has a metal plate on the bottom with all the various decimal equivalents etched in it, which is quite helpful. Older models have a cardboard insert (often missing) that has the same information. (The information is easily found on line in any event and decimal equivalents are easily calculated on by a simple math formula or on any smart phone calculator.)

View attachment 465167

There are also commonly 6" and 7.5" proportional dividers. The 7.5" models do come with rack and pinion adjustment but not with the more accurate Vernier adjustment feature. They are, however, useable. The 6" models do not have rack and pinion adjustment and neither do some of the 7.5" models. Don't waste your money on anything that does not have rack and pinion adjustment. While useable, the "slide" adjustment models aren't anywhere near as accurate. Similarly, pay the few extra bucks for the "110" decimal scaling. The other proportional dividers have scaling that corresponds to fractions 1/2, 1/3, 1/4 and so on, and settings in between are "by guess and by golly." Also, you will see "Russian Navy" and "Weems and Plath" proportional dividers offered. Take a pass on these because they are "navigational dividers" and, although they work the same and are useable, they are scaled for "time" and "distance" proportions for use on maps and their scaling isn't useful for modeling measurement conversions. (You can adjust them for plans measurement conversions by comparison to a rule and/or tick strips, but this is rather tedious)

All K&E Paragon instruments are labeled "Paragon."
View attachment 465172

Note rack and pinion Vernier adjustment, and decimal scaling.
View attachment 465188

Very early "right-angle point" K&E Paragon branded universal proportional divider in old style case. No difference in function. Just a matter of style.
View attachment 465173

Early 20th century K&E Paragon branded 10" Universal Proportional Dividers.
View attachment 465184

Post branded universal proportional divider in pin-lock case.
View attachment 465174

Mid-20th century K&E Universal Proportional Divider in hard case with decimal equivalent and formulae chart on back. (Most commonly encountered type now.)
View attachment 465170

Very late manufacture K&E Paragon 10" universal proportional divider packaged as their "Mark I" line. Manufactured by Haff Instruments
View attachment 465171


In summary, what you want to look for on eBay is a Keuffel and Esser 10" "Paragon" proportional divider with "110" decimal scaling. They are relatively common because they were the "professional's choice" for many years. A "mint" example with an excellent case will sell for as much as $225, but very "clean" examples regularly go for around $125 at the moment. Examples that are a bit "rough," mainly due to a worn case, can be had for $75 or even $50.

If you work from drawings to the scale you are building (i.e. as with kit plans,) you can live without a proportional divider, but if you are working from plans in one scale (or no scale, as in many lines drawings found in old books,) you will be amazed at how you ever before lived without them. Yes, you can measure a distance and then punch that into a calculator and then measure off the result, over and over again, or you can set your proportional dividers once and then simply measure the drawing at one end of the dividers and have the proportional distance simultaneously provided between the points of the other end of the dividers. It doesn't get any faster or simpler than that.





Haff drafting instruments company advertising page and instructions for use of Universal Proportional Dividers. The finest, and near-only, drafting instrument manufacturers in the world were a handful of companies in Germany and Switzerland. One of these, Haff, made all of K&E's Paragon line, labeled for sale in the U.S. under the K&E label. As the prices were stated in euros, this advertisement was after 1999. Twenty-five years ago or so, they wanted 200 euros or about $200 for one retail.
View attachment 465189
Click to expand...
Thanks very much for the detailed explanation and recommendations. I found this information extremely helpful in narrowing down which proportional divider I will shop for. Thanks again for taking the time to share your expertise!
 
Bob Cleek said:
The proportional dividers pictured by the OP are an inexpensive set most likely made in India or Pakistan for the brass curio trade. They are not "professional grade," but may be sufficient for modeling purposes. They are scaled for proportions in "multiples," "times two, times three," and so on. A professional grade set of proportional dividers will be made of German silver and those scaled for modeling will invariably be ten inches long over all. There are shorter models, commonly 6", 7", and 8" which are "useable," but lack the accuracy possible with the full size "universal" models scaled to set proportions in terms of their decimal equivalents. There are also very large, and for our purposes crude, proportional dividers used by artists and sculptors, which are too large to be useful for modeling purposes. If you have a proportional divider regardless of the scaling on the instrument, you can always "manually" set the proportion by drawing two lines of proportionate length (e.g. 1" and 2" long for 1:2 proportion) and adjusting the dividers so that the points on each end are set to exactly match the length of the respective lines. The divider will then be set to the proportion of the two lines.

I find proportional dividers essential because I find myself redrawing lines published in old books (Chapelle, etc.) that will be prints of larger drawings reproduced in the book, often without regard to scale. With a good set of proportional dividers, all you need is a single identified measurement on the original drawing (a scale is often included in the original drawing) and with your dividers set to your desired drawing scale, away you go! Just take a distance from the page in the book and the other side of the dividers gives you the distance to the scale you've set for your drawing. There are, as mentioned, a lot of other things you can do with them as well, such as drawing a square with the same area as a particular circle and vice versa, but I've yet to learn who really needs to do that. They are very handing for dividing lengths into equal increments for spacing planking runs, ratline spacing, stanchion spacing, and such.

I collect fine drafting instruments for my own use. Most I've bought on eBay and I check for listings frequently and note that the prices do vary wildly, depending on condition, quality and rarity. Condition may not always be a relevant factor if you are looking for a "user." Some oaf may have scratched his name into the instrument and/or the case may be in rough shape or missing. That can mean a $100 or $150 reduction, leaving what would be a "mint" $200 instrument going for only $50, yet be entirely satisfactory for use, nonetheless. Be forewarned that I started collecting mint condition examples of the finest manual drafting instruments made, primarily Keuffel and Esser's Paragon line, made in Germany and solid in the U.S., as far back as twenty years ago when CAD had almost completely replaced manual drafting in the professional workplace and manual drafting instruments were plentiful and not in demand. An active collectors' market has since developed, and prices have risen accordingly for the more desirable instruments which are now much less available. Alas, the really excellent examples are no longer manufactured.

The proportional dividers that you want to obtain for modeling use are the 10" pairs with "110 scaling" or "decimal scaling." These are referred to in the advertising literature as "universal proportional dividers" because with decimal scaling they can be used for any purpose possible rather than those scaled only for specific purposes like navigation. This universal scaling permits setting proportions in "decimal equivalents" (e.g. 1/2 = .50) These instruments will have rack and pinion geared adjustment and Vernier adjustment to decimals out to .0005 (If memory serves... perhaps there's an extra zero in there... don't hold me to it.) These instruments will be manufactured by Keuffel and Esser, Dietzgen, Post, and Bowen (among less commonly seen other brands) in straight point and right-angle point configurations (as pictured in post #2 above.) (You will likely never see a right angle pointed set on EBay. They are extremely rare.) The most commonly offered are the K&E 10" "Paragon" decimal scaled models. "Paragon" was K&E's top of the line series of instruments and the "110" decimal equivalent scaled dividers were only offered in the "Paragon" line. They are made of cold rolled "German silver," an alloy of nickel and copper, much similar to Monel and were hand fitted, each bearing matching part serial numbers. They were sold in silk velvet lined fitted cases. The back of the case in newer production models has a metal plate on the bottom with all the various decimal equivalents etched in it, which is quite helpful. Older models have a cardboard insert (often missing) that has the same information. (The information is easily found on line in any event and decimal equivalents are easily calculated on by a simple math formula or on any smart phone calculator.)

View attachment 465167

There are also commonly 6" and 7.5" proportional dividers. The 7.5" models do come with rack and pinion adjustment but not with the more accurate Vernier adjustment feature. They are, however, useable. The 6" models do not have rack and pinion adjustment and neither do some of the 7.5" models. Don't waste your money on anything that does not have rack and pinion adjustment. While useable, the "slide" adjustment models aren't anywhere near as accurate. Similarly, pay the few extra bucks for the "110" decimal scaling. The other proportional dividers have scaling that corresponds to fractions 1/2, 1/3, 1/4 and so on, and settings in between are "by guess and by golly." Also, you will see "Russian Navy" and "Weems and Plath" proportional dividers offered. Take a pass on these because they are "navigational dividers" and, although they work the same and are useable, they are scaled for "time" and "distance" proportions for use on maps and their scaling isn't useful for modeling measurement conversions. (You can adjust them for plans measurement conversions by comparison to a rule and/or tick strips, but this is rather tedious)

All K&E Paragon instruments are labeled "Paragon."
View attachment 465172

Note rack and pinion Vernier adjustment, and decimal scaling.
View attachment 465188

Very early "right-angle point" K&E Paragon branded universal proportional divider in old style case. No difference in function. Just a matter of style.
View attachment 465173

Early 20th century K&E Paragon branded 10" Universal Proportional Dividers.
View attachment 465184

Post branded universal proportional divider in pin-lock case.
View attachment 465174

Mid-20th century K&E Universal Proportional Divider in hard case with decimal equivalent and formulae chart on back. (Most commonly encountered type now.)
View attachment 465170

Very late manufacture K&E Paragon 10" universal proportional divider packaged as their "Mark I" line. Manufactured by Haff Instruments
View attachment 465171


In summary, what you want to look for on eBay is a Keuffel and Esser 10" "Paragon" proportional divider with "110" decimal scaling. They are relatively common because they were the "professional's choice" for many years. A "mint" example with an excellent case will sell for as much as $225, but very "clean" examples regularly go for around $125 at the moment. Examples that are a bit "rough," mainly due to a worn case, can be had for $75 or even $50.

If you work from drawings to the scale you are building (i.e. as with kit plans,) you can live without a proportional divider, but if you are working from plans in one scale (or no scale, as in many lines drawings found in old books,) you will be amazed at how you ever before lived without them. Yes, you can measure a distance and then punch that into a calculator and then measure off the result, over and over again, or you can set your proportional dividers once and then simply measure the drawing at one end of the dividers and have the proportional distance simultaneously provided between the points of the other end of the dividers. It doesn't get any faster or simpler than that.





Haff drafting instruments company advertising page and instructions for use of Universal Proportional Dividers. The finest, and near-only, drafting instrument manufacturers in the world were a handful of companies in Germany and Switzerland. One of these, Haff, made all of K&E's Paragon line, labeled for sale in the U.S. under the K&E label. As the prices were stated in euros, this advertisement was after 1999. Twenty-five years ago or so, they wanted 200 euros or about $200 for one retail.
View attachment 465189
Click to expand...
Hi Bob,
Very interesting information on proportional dividers.
Thank you for taking the time to educate us on this topic, I didn't know there was that much to know about proportional dividers .
I have a pair of Tacro 4151 dividers that may not be quite as good as the ones you mention, although in my opinion made to a high standard and a joy to use.
Cheers,
Stephen.
 
To answer my question #3 : I purchase the ebook from ModelExpo for planking - Planking the built-up ship model by Jim Robert. I find it really more easy to to apprehend for my french minding and seem's really complete. I did not regret this purchase. The money saved was used to purchased the Rigging model ship praticum from Bob Hunt (Lauck Street Shipyard). It will complete my Rigging Period Ship Models book by Lennarth Petersson.

So, I am in the waiting for purchase a good Proportional Divider to replace the on from India showed uppward.

Thank you for all your inputs. Very appreciate stuffs were put here.
 
I just bought a pair of proportional antique vintage dividers made in Germany in 1910 by Dietzgen, with rack and pinion movement. You can set it precisely and fix the setting so it does not slip. Very nice, shows "Lines", "Circles", "Plans" and "Solids", 4 different scales as the earlier models displayed. I found the Indian brass made models not very precise for model ship building purposes, they lack all those things.
 
CIB said:
I found the Indian brass made models not very precise for model ship building purposes, they lack all those things.
Click to expand...
Yes, it seems any instrument made of brass (recycled shell casings?) in India or Pakistan, whether proportional dividers, compasses, sextants, spyglasses, and the like are intended more for use as desk paperweights than as precision instruments! God forbid anybody would ever attempt to go hardhat diving with one of those $200 reproduction "antique" diver's helmets they make!

1725066847604.png

www.ebay.com

U.S Navy Copper Finish Brass Diving Divers Helmet Solid Heavy Model Mark V 18" | eBay

Approx Size: 16" x 12.5" x 17" / 40 x 32 x 42cm. Model: Boston Mark V. Weight: 9.5 Kg.
www.ebay.com
 
Edit : right = fees

Hi,

I received my new Norris Proportional Divider today. HEre is two pics. I am really happy for this purchase, great difference compare to indian one. But 88 CAD plus 29 CAD tax and duties is a deception (for custom fees). Thanks again for your help.

20240912_125951.jpg20240912_130009.jpg
 
Last edited:
Here is how I use mine:
I divide my hull into bands. I then measure the width of the widest band to determine the number of strakes to fit in that band.
I go to one of the other bands, i set the width of the divider to the width of that band.
I then set the divider, using the line scale, to the number of strakes in that band( we did that calculation already).
As I add strakes, I will have to remeasure the width and adjust the number of strakes left in that band.
Using the small side of the divider, I draw a mark on the strake to show what width is required for that bulkhead.
I repeat for all the bulkheads that the strake goes through.
then I use an Exacto blade to trim the strake.


For fun i went to Micromark to see how much a good quality divider is. It is way too expensive so I will make due with the cheap Amazon one.
 
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Thank Jack for this infos. I also puchased Ebook from ModelExpo that explain all this process with really good explanation and I understand this level of english too. So, I will use it on the HMS Fly planking that is waiting to do in parallèl with my Belem. But Time is a rare ressource at this end of summer.

A+
 
Fish&Chip said:
Thank Jack for this infos. I also puchased Ebook from ModelExpo that explain all this process with really good explanation and I understand this level of english too. So, I will use it on the HMS Fly planking that is waiting to do in parallèl with my Belem. But Time is a rare ressource at this end of summer.

A+
Click to expand...
Yes, I have that one. It is really informative
 
Fish&Chip said:
Hi,

I received my new Norris Proportional Divider today. HEre is two pics. I am really happy for this purchase, great difference compare to indian one. But 88 CAD plus 29 CAD tax and duties is a deception (for custom rights). Thanks again for your help.

View attachment 470785View attachment 470786
Click to expand...

I just recently bought one:
(Describes a 1910 Vintage 7-1/4” Dietzgen “Superior » Proportional Divider 926 with Rack and pinion movement drafting drawing in a case made in Germany).

Proportional Dividers typically carried up to four scales, two on each face. "Plans" and "Solids" scales are less common and are mostly found on older instruments.
One small wheel to set it to the scale line on the divider, the opposite wheel moves it along the rack & pinion.

First quality proportional dividers have the indicators "Plans" and "Solids" engraved on the reverse side, in addition to the indicators "Lines" and "Circles" engraved on the front. For 2D line work, only the first two indicators are needed. Proportional dividers have points at both ends and can be opened into an "X" shape using a screw and nut that slide along a slot within the legs. The screw can then be tightened at a particular proportion to make scale drawings for engineering or architecture.

The "Lines" scale sets the two sets of pointers in direct proportion.
The "Circles" scale is used to inscribe regular polygons inside circles. The 6 lines up with the 2 on the line scale, which correlates to a hexagon having sides equal to the radius of the circle (1/2 the diameter). I suppose if I wanted a 30 degree
arc, I could use the same scale to take one sixth of a semicircle (using the radius for a semicircle, vs. the diameter for a full circle).
The "Plans" scale on proportional dividers allows shapes to be reduced so that their areas are in the ratio of the setting. For example, to draw a circle that's one third of the area of a given circle, the dividers can be set to 3 on the "Plans" scale and the long points set to the diameter of the given circle. The short points then give the diameter of the required circle.
The "Solids" scale performs a similar function for volumes. For example, to find the size of a cube which is one third the volume of a given cube, the hinge is set to three on the "Solids" scale and the dividers can then be used to scale of the reduced sides of the new cube.
Claude, Rolling Meadows, IL (USA)
 
Fish&Chip said:
To answer my question #3 : I purchase the ebook from ModelExpo for planking - Planking the built-up ship model by Jim Robert. I find it really more easy to to apprehend for my french minding and seem's really complete. I did not regret this purchase. The money saved was used to purchased the Rigging model ship praticum from Bob Hunt (Lauck Street Shipyard). It will complete my Rigging Period Ship Models book by Lennarth Petersson.

So, I am in the waiting for purchase a good Proportional Divider to replace the on from India showed uppward.

Thank you for all your inputs. Very appreciate stuffs were put here.
Click to expand...
that practicum is very useful. I got mine about a month ago.
 
i understand how presision can be important especially for small scale work. but not many can afford investing in an instrument most of us did without for so many years. the dividers are more useful when converting scales from plans to model.

so in that light, i think a cheap one will suffice for general model building.

i wonder how this would fair?...
 
paul ron said:
i understand how presision can be important especially for small scale work. but not many can afford investing in an instrument most of us did without for so many years. the dividers are more useful when converting scales from plans to model.

so in that light, i think a cheap one will suffice for general model building.

i wonder how this would fair?...
Click to expand...
That is the one that I have. It works for me, although the pointers could be a little smaller.
 
Jack Sparrow said:
For fun i went to Micromark to see how much a good quality divider is. It is way too expensive so I will make due with the cheap Amazon one.
Click to expand...
Glad you did! The MicroMark Tasco 6" proportional divider is junk. The Indian brass ones such as the one sold on Amazon for US$25 is not a serious highly accurate measuring instrument, either, but appears to be better than the MicroMark Tacro one and certainly more useful at nearly 10" long than the 6" MicroMark example which is extremely overpriced.

As mentioned previously, the best option is a "universal" decimally scaled 10" model. These were made by Haff in Germany, but marketed by Keuffel and Esser, Bowen, and others here in the US under their labels. These can be picked up on eBay for around US$75 for "users" in good shape to US$250 for "mint" collector's items. If that's too rich for your taste, quality-brand (Keuffel and Esser, Dietzgen, etc.) 7" and 8" proportional dividers with rack and pinion adjustment can be had on ebay for US$50 or less. These quality dividers won't be decimally scaled but can be manually set to any proportion desired by "setting to fit" proportional lines on a sheet of paper. In addition to the greater flexibility in scaled settings with the digitally scaled model, the 10" dividers give you just that much more "working size" to use. The shorter dividers will require more breading lengths down into segments because of their shorter capacity.
 
Bob Cleek said:
Glad you did! The MicroMark Tasco 6" proportional divider is junk. The Indian brass ones such as the one sold on Amazon for US$25 is not a serious highly accurate measuring instrument, either, but appears to be better than the MicroMark Tacro one and certainly more useful at nearly 10" long than the 6" MicroMark example which is extremely overpriced.

As mentioned previously, the best option is a "universal" decimally scaled 10" model. These were made by Haff in Germany, but marketed by Keuffel and Esser, Bowen, and others here in the US under their labels. These can be picked up on eBay for around US$75 for "users" in good shape to US$250 for "mint" collector's items. If that's too rich for your taste, quality-brand (Keuffel and Esser, Dietzgen, etc.) 7" and 8" proportional dividers with rack and pinion adjustment can be had on ebay for US$50 or less. These quality dividers won't be decimally scaled but can be manually set to any proportion desired by "setting to fit" proportional lines on a sheet of paper. In addition to the greater flexibility in scaled settings with the digitally scaled model, the 10" dividers give you just that much more "working size" to use. The shorter dividers will require more breading lengths down into segments because of their shorter capacity.
Click to expand...
really? wow. Talk about buyer beware.
Thanks for the heads up.
 
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