Pattern Routing for Fenders for a Toy
July 1993 Woodworkers Journal.
This is a long detailed blog on pattern routing. I am making a 1920 style Runabout car for the Mason Dixon Woodworkers toy distribution. We usually make about 1300 toys each year that we give to 25 different charities, for them to distribute to the children that they represent at Christmas time.
We work every Wednesday, 50 weeks of the year. We are funded by community support in our area, $10.00 here $500.00 there. We have been privileged to have some lumber donated to us so that cuts down our expenses.
This year I decided that I was going to make a toy at home in my shop. I found a 1920 Style Runabout in an old woodworking magazine and it seems like a great toy to make. I was able to pick up some Mahogany at a workshop that makes custom doors and windows. He allows me to take all scrap less than 34 “ long. In the last few months I’ve probably picked up 400 Bd ft of Mahogany Most of it 2” thick some 3X3’s and some 1”. Since all of their MFG is done in metric measurements the wood is about 50mm in thickness.
I’ve resawed and cut most of the parts. I’m using mahogany for most of the car and Sapele for the seats, radiator and trunk deck. That gives a different color for the car.
But we’re here to talk about the fender pattern jig. In the past when making parts like fenders, they are all cut on a bandsaw and sanded and every part is a different size. I wanted to stop that. I wanted matched parts and a consistent way to assemble the toy.
The fenders became my problem child. I don’t like routing against the grain in an uphill cut. Chipout is always a problem that is about to, or already happened. And for small thin parts, shattering becomes a constant reminder of keep all ten attached and blood not visible.
So I wanted this jig to be only a straight or downhill cut. This is how I accomplished that task.
I made Mahogany fender blocks 2” X 10 “ X ¾” thick. I drilled 2 holes in the middle so the blocks could be used on the left or right side of the car. This kept me from having to have 2 different parts at the start.
I used a Triton tool that drills 2 holes for dowels 32mm apart. It works like a biscuit jointer or the Domino tool.
So I mounted wood in my vise to allow me to put my part on and drill the holes very quickly. I was able to drill both holes in about 6 seconds and could keep that up for about 20 parts. Then stack the completed ones and get a new supply, rest my wrist and do it again.
Somewhere in that process the tool changed one of it’s measurements.
The holes were supposed to be about 1/8” from the edge and it slid to over ¼” during this process. Over half way through, I noticed it and reset the tool. So I’ve got some wood variations to contend with.
All of the parts were drilled. I then took pencil and drew a fender on one of the wood blocks and cut it out and sanded it to become my master.
You can see the effect of the off drilled holes.
Since the Dowel holes don’t go all the way through, I need a left side part and a right side part. I took a piece of ½” mdf and made a duplicate with holes all the way through it. I cut the mdf part using a pattern router bit with the bearing on the top. The two pieces were aligned using dowels in the holes.
I then used the MDF pattern to draw the fender on my blocks of wood. I then cut about 1/16” outside the line on the top of the fender.
I started to make jig # 1. It would allow me to cut one portion of the downhill cut on the front and back fender. Since the dowel holes were in two different places clamp block had to allow for the differences in spacing. I put in my hand cut master, clamped it down and cut the base of the jig with a top bearing mounted router bit. The router bit was not allowed to touch any other places on the jig except for the 2 downhill cuts.
I now started on jig #2. I turned my master part over so that I could cut the other top edge of the fender also in a downhill cut.
But, my mounting holes for the pattern are not on the top so I made a block that would have holes for the fender and lock the block into my clamp plate. I used a long dowel to go through my plate, the mdf jig and into the bottom holes. This insured that the top plate would hold a fender piece in the same position whether the holes were up or down. This way I could use 4 jigs instead or 8 jigs.
Once all of the plates were cut and mounted for jigs numbers 1 and 2, I cut a couple of fender pieces. I needed these to make jigs 3 and 4. I wanted to use actual cut parts for the next fabrication and not my master part that I used for jigs 1 and 2.
Cut the first downslope.
Cut the second down slope.
On jigs 3 and 4 the clamping plate was modified to match exactly the profile that was cut on jigs 1 and 2. I drew the profiles and sat in front of a spindle sander to make the clamp blocks fit exactly the profile that I cut on jig 1 and 2.
Using dowels and the parts cut on the first jigs, I glued down the clamping blocks. I then took my master piece and cut the appropriate profile in the jib base to allow for downhill cuts on the inside of the fenders.
I used the bandsaw and cut the profile just outside the line so the the router only has to take off a small amount of wood. Again I needed left and right mounting blocks on the top of the clamp plate on jigs 3 and 4.
Once I cut a full set of fenders I slightly modified the router jigs to bring the edge created on jig 1 to match up to the cut on jig 2 without having a difference in height. A slight touch of the sander and the parts match perfectly.
It takes about 5 seconds to route the part on each station, It takes longer that that to get the part on and off the jig. I’m lightly sanding the dowel to allow the mount block to slide on and off easily, instead of using a screwdriver to pry it off.
My next jog will be to separate and mark left side and right side parts and band saw the top edge. I’m not bandsawing the bottom edge at this time because I want the extra wood bulk to keep the piece from flexing until the top surface is routed.
So it will be mark band saw, jig 1 right, jig 1 left, jig 2 left, jig 2 right The first operation doesn’t use the mounting block the second one does. So I’ll finish the jig 1 process first before I go to jig 2. Then bandsaw for the jig 3 and 4 process.
Here are the pieces as they might be.
If any parts and not understandable let me know and I revise of make additional comments.
I sat down tonight and drew the pattern on 250 parts for 125 cars Keeping them seperate for left and right side. Now to bandsaw almost to the line.
-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware firstname.lastname@example.org †