• Gabriel Christy

Tools of the Trade: Rule and Compass Part 2

To continue from yesterday’s post, we’ll discuss how we applied these same geometrical concepts to lay out our new water wheel. One of the beauties of compass geometry is its scalability; so long as you’re able to make a compass large enough, the techniques remain the same.

To lay out our wheel, we needed a flat, preferably level, surface. Normally this would be the floor of the shop.[1]

However, our mill’s floor warps significantly with the seasons. We had to come up with a different method and, as usual, history offered us a solution.

This is a photo of the water wheel at Mabry Mill (Part of the Blue Ridge Parkway National Park) being rebuilt in 1942.[2] The millwrights built a level surface with posts driven into the ground around the circumference of their wheel. This allowed the workers to both lay out and build the wheel at a comfortable working height and on a level surface.

We recreated this in our shop with a series of 8 stands built by both staff and volunteers.

Once these were completed, we laid out sheets of ⅛” plywood in a rough octagon. We later realized this was too flimsy for the kind of work we’d be doing, so we replaced it with 1 ½”thick Douglas fir panels.

To lay out the wheel we created a large beam compass, with one section pinned to a center post.

With this we scribed the outer and inner circumferences. Finally we had a 15 ½’ wheel to work with.

Using a chalk line, we struck the centerline for the wheel. Then using the beam compass, we followed the same process we did in the last post, continually dividing a section in half until we had 8 equal parts.

Finally, to lay out our bucket boards, we stepped out 7 divisions of one of the 8 sections. We used a smaller beam compass to do this, approximated the distance we needed, and stepped out across the outer circumference of the wheel section.

We then adjusted slightly until we had exactly seven divisions across the section.

Next we walked out across the whole wheel, which gave us our bucket locations.

Now we just have to finish building it!

Again, I would normally invite everyone to come visit us in the Millwright Shop, but it’s currently closed due to COVID-19. We will be continuing to post here on the blog, and we’ll be doing more Facebook Live videos, so be sure to follow us on Facebook. Stay safe, and check back here next week!

If you’d like to take the next step and get involved in the shop once this has all calmed, please contact us at:


Telephone: 610.459.2359

Find us on Instagram @newlingristmill1704

Look for us on Facebook @newlingristmill


[1] Greenbank Mill waterwheel construction 1998-1999, image courtesy of Tony Shahan.

[2] Blue Ridge Parkway National Park, “Challenges,” Mabry Mill - Milepost 176, Burks Fork, Virginia.


Blue Ridge Parkway National Park, “Challenges,” Mabry Mill - Milepost 176, Burks Fork, Virginia.


Message to Our Community

As events develop with the COVID-19 virus, Newlin Grist Mill (NGM) continues to closely monitor the situation and follow guidance from the CDC and all levels of government including social distancing and restrictions on gatherings. The NGM has taken the following steps through May 31:

  • The NGM Visitor Center, Archive, Blacksmith Shop, Millwright Shop, and public restrooms will be closed;

  • All tours, programs and events have been postponed or cancelled during this period;

  • Pond Fishing will remain closed until further notice;

  • The Fishing Breakfast has been cancelled;

  • Rentals and photography sessions are being cancelled for this period of time;

  • There will be no Volunteer Wednesday Workdays;

  • The trails will remain open but parking is limited

Decisions concerning additional closings will follow based on the developing situation. Please check back for updates.

While the trails at Newlin Grist Mill remain accessible while the site is closed due to the COVID-19 pandemic, we do want to remind everyone of a few things:

  • Continue to observe proper social distancing when you are on the trails. If you are ill or have been around anyone who is ill or has been exposed to the virus, please remain at home. If you arrive and find that the parking lot is crowded, please postpone your visit to another time.  

  • Please remember that all dogs must be on a leash that is held securely by the owner at all times. This is a township law, and it is to protect the health and safety of all park visitors (human and canine) and the wildlife in the park.

  • The park contains unique habitats that are home to sensitive plants and animals, some of which are being monitored through ongoing scientific surveys.  Please stay on the trails to avoid disturbances (wading, dip netting, collecting, rock throwing etc.) that could damage wildlife and vegetation. 

  • Remember that collecting of any kind, including plants and animals, is prohibited in the park.

We appreciate your understanding and support during this challenging time.

Newlin Grist Mill   l  219 South Cheyney Road   l  Glen Mills, PA 19342   l   610.459.2359   l   © Copyright 2014-2015 Newlin Grist Mill. All rights reserved.