I thought it was time I revisited a project I started Halloween of last year. The below is the story and build, but the TL;DR can be found in this video.
I created a 3D printed part that allows you to swap rakes in the Pumpkin Master electric pumpkin carver.
You can check out the video then jump to the STL file and print your own: https://drive.google.com/open?id=0BzY3yLosRyyxMzAxdFo3Y3ZHTUU
Almost a year ago I saw this Tweet by @indiecom showing @jimylongs
modified electric pumpkin carving saw that was turned into a power rake. It was
dubbed the pumprake or pumpkey depending on who was commenting. I am still not
sure of the official name, but I liked pumprake - https://twitter.com/indiecom/status/728806259248369664
After much consternation with a set of calipers I was able to model and 3D print the plastic end for the saw blades. These can be used to hold modified rakes making them interchangeable.
Just in time for Halloween I’ve tested the parts on the old
version and new version of the Pumpkin Master carving tools. You should be able
to find these carvers wherever fine Halloween gourds are sold.
Check out the video above. I also documented the build
process in this blog post. If you are just interested in the STL file to make your
own click here. The STL can be modified in TinkerCad, printed at home, or sent
to services like Shapeways for printing. I use TinkerCad and then send it
directly to Shapeways for printing from inside the TinkerCad interface.
Happy Halloween and Happy Picking! Tweet @eanmeyer to let me
know if you print the part and how it worked for you!
Tinkercad Link - https://www.tinkercad.com/things/aPNNGu5nNaJ-pumpkinlockv5
Thingiverse Link - https://www.thingiverse.com/thing:2551598
Build Process
Measuring
First, I spent a fair bit of time measuring all the nooks
and crannies on this tiny part with a set of digital calipers.
My trusty-ish Harbor Freight digital caliper and Moleskine and some whiskey (not pictured).
Modeling
Fast-forward many hours in TinkerCad and we get the 3D
model. Yes, this is very much a “draw the rest of the owl” moment. However, I
am publishing the STL so you don’t have to go through this part of the build.
You can jump right to my TinkerCad build here: https://www.tinkercad.com/things/aPNNGu5nNaJ-pumpkinlockv5
Send to Print
I like TinkerCad because it directly integrates with
Shapeways. I don’t own a 3D printer. However, I’ve sent many parts to Shapeways
for printing. You can see this part was successfully printed once. Shapeways
will take about a week to get you the part. The part arrives laser sintered and
aren’t made via the filament printing process.
A Wild Part Appears
About a week later the parts showed up.
Because they are laser sintered the small hole the rake will
go in often has powder packed into it that needs to be cleaned out. Use a pin
or needle to clean this out by scraping out a bit at a time until you can see
through the hole.
You can see in the photo where I am holding it the slot is hard to see. Look at the 3D render to see where the hole is more clearly.
There may be loose material in the hole you need to clean out with a pin.
Preparing the Rakes
Now we need to measure the tools. The 3D printed part has a
hole running through it to mount the rake in. This means we need to cut away
some material from the rake. 
I took some measurements to grind down the rake.
The internal measurements of the hole used to mount the rake are approximately 18mm
x 2.75mm x 0.55mm. After marking off the metal to grind away we are ready to
head to the garage.
Metal Work!
Next, comes some metal work. You could do this with a small
metal saw and file if you don’t 
I’m not sure which approach would work better, however, I
used the bench grinder first as it conveniently makes a right angle for me when
grinding away material.
However, you could use the angle grinder to cut off
most the handle first. Take your time with this part and have a plastic cup with
water or cooling oil near by to dip the part in. Too much grinding can warp or
weaken the part.
Now we use the angle grinder to cut away the handle.
Back to the bench grinder to take the burs off.
Finally, we take the end that will get inserted into the 3D
printed part and taper it into a knife
I choose to think of it like one of the plastic cocktail swords you find in drinks. This shape will allow you more easily insert the rake into the adapter. 
This is a lot like the tang on a blade fitting into a knife handle.
Fitting using your Imagination
This is where I don’t have photos because holding a hammer and a phone became… problematic. I will likely print a few more and update this with a photo or two. However, the below should describe the process adequately.
The final step is to mount the rake with the rake end inside of a bench vice. If you don’t have a bench vice a wood clamp secured to something sturdy could work. After securing the rake with the “tang” side up gently tap the adapter into place with a hammer.
If you removed too much material from the rake use 3D print safe glue on the rake, insert into the adapter, and let it dry.
Try and get the rake “tang” all the way through the 3D printed part. You can see in the video how my first city rake is wobbly because the part isn’t fully seated. The triple peak rake in the video doesn’t have this issue.
At this point the rakes should be ready to use! The new rakes should insert in the exact same way as the saw blades. 
As mentioned in the video I tried these in both the new and old version of the Pumpkin Master electric saw. Hopefully it works for you too!
Tweet me @eanmeyer to let me know if you used the part, how it worked, and if you have any suggested changes.
