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Manually Built Final Sled


#1

I was having a hard time with a temporary (and maybe inaccurate) sled making my final sled that needed to be accurate (chicken or the egg). So, I decided to make my own sled by hand as best I could. If still off maybe I’d have a better chance at getting a more accurate final sled. I have yet to make that final sled because my hand made one seems to work just fine.

Here are some pictures of the build.

I started with creating a simple print out with some circles to aid in positioning things. Taped it to the board then drilled a 1/4" hole dead center in the circle middle.

Then a quick scrap piece of wood became my circle jig that has a 1/4" hole in the middle spaced 9" from the center of the hole to the inside of my router bit (giving me a 18" sled when done).

Then round and round stepping the bit down each pass.

All cut.

Then using the same 1/4" hole, I placed my 1/4" bit in that hole for aligning my router to the center of the sled.

Then, using the print out circles, I placed my ring upside down so I could center it “exactly” in the middle of the sled/bit. I was careful to keep the same brackets in the same spot just in case they were slightly different.

A center punch helped get holes right where they needed to be.

Then all the holes where drilled or had pilot holes drilled for bolts/screws.

Center hole for router bit clearance was next. Yup, you guessed it - same 1/4" hole (although this one didn’t really need to be centered).

Cleanup time. I used a chamfer bit to router the outside sled edge and inside circle edge. I also heavily rounded all counterbore holes to help them not get caught on previous cuts.

Time to place the bricks. This I could have made a little better/easier but I placed these by eyeballing it with some measurements to make sure they were somewhat symmetric.

Then I opted to put on numerous coats of polyurethane to seal the wood, create a hard surface to prolong sliding life, reduce friction slightly as it glides and creates a smooth surface for saw dust to fall off. Make sure it dries for a few days after your last coat to get it good and hard.

Then everything was installed. Z-axis holes were drilled after everything was mounted.

I’m quite pleased with how it turned out and feel like I did the best I could to get everything centered by using the same 1/4" hole and template. I’m starting to cut some test cuts and I’ll update on how accurate it is. I’m curious about the center hole roll test @Dustcloud has mentioned. Thanks to everyone for your tips and inspiration.

Edit: Also, just for completeness, I sanded the inside edge the ring bearings ride on to remove the bumpy paint. Glides great now. I also sanded the inside router base to help the router go up and down for Z-axis then applied some light grease to the same housing and the Z-axis screw rod. I am using a bungie for positive Z-axis engagement attaching to the handle bolts (without the handles).


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#2

That is one nice piece of work! It will be the first thing I do when I get back to my machine. Thanks so much for sharing your build process in such a clear and thoughtful way.


#3

Just turned my router on and plunged it into some material. First test was rotating the sled about 25° to the left and right. It’s slightly hard to do without artificial moving the sled. My results were a hole that was slightly horizontally obround by about .4mm.

The second test (new hole) I rolled it to its extremes (which will never happen in real life) and got about .6mm horizontally off obround circle. I would contribute most of this to tolerance of built parts, a slightly out of round factory ring and human error when placing things (although I don’t know how I could have got it more accurate than the approach I took).

Not sure how this stacks up to others. This test was done about dead center on the machine (motors 10’ apart).


#4

Hi Jayster!

Just finished the sled rebuild per your solution… Just doing my rotation test with the router running and a .1 inch cut, there is a big improvement, about a 1/16" vertical diflection over about 45 degress of rotation in both directions… Much better than my previous sled. A lot of work, but hopefully for the good!

Thanks!


#5

That’s great to hear! Thanks for sharing that. How much deflection did you have before?

Edit: I was more off horizontally on the sample plunge hole - are you the same?


#6

No, my deflection was about 1/16" vertical. Before the deflection was at least the width of the bit, maybe more, and “c” shaped,. I tried fixing it on the old sled by messing with the router mounting holes, but it only got worse. Your post came at just the right time. Maybe you have read the string about getting round circles… There I posted my latest benchmark results, which are much better…

Thanks again!


#7

Do you still happen to have a copy of your circle template that someone else could print out? It could come in handy for centering.


#8

Circles.pdf (11.0 KB)

Here is what I used. The only important thing is that the circles are all concentric and there is a center point.