|Forum topic by MrUnix||posted 06-21-2014 09:12 PM||659 views||0 times favorited||9 replies|
06-21-2014 09:12 PM
A couple of weekends ago at a yard sale, I ran across a Delta 40-601 18” scroll saw that I couldn’t resist taking home with me. It worked, but it couldn’t keep a constant speed and varied from dead slow to super fast. The PO told me that it had a bad speed sensor and had already yanked it out (it was sitting on top of the machine). Other than that, it was in great shape, had it’s original metal stand, a quick change kit (new – still in the box) along with about a hundred various blades (most still new in unopened packages). For $35 I figured the blades and quick change kit alone were worth it.
So, I got it home and started looking for some place to get a new sensor. Doing the research, I noticed that the majority of speed problems with these saws was not the sensor, but the ‘speed control rotor’ that the sensor works with to determine rotational speed. Seems they were made of some kind of bakelite material and had a habit of breaking apart. I got around to opening up the machine and sure enough, the rotor was gone, but the metal hub was still there. Grrrr.. Ok, yet another one of those parts that is no longer available. However, I did garner from my digging around the net that the sensor picked up a magnetic pulse from the rotor, so I got a wild idea to try and make one to replace it with.
The rotor is about 2” in diameter, so I got out my 2 1/4” hole saw and threw it in a drill press. I had some scrap hardwood (cherry I believe) and made the circle, then used a forstner bit to make a hole for the metal hub. I dug up a small rare earth magnet in my box-o-junk and embeded it on the edge, glued in the hub and gave it a try.
To my surprise, it worked! But I’m pretty sure it’s running much faster than what the speed indicator tells me, and maxed out, the thing feels like it wants to explode (way, way too fast!). However, the slowest speed it runs at is just about as slow as I would ever want to go, and I can ramp it up for larger stuff if needed.. so all in all, I’m pretty happy with it.
(You can see the speed sensor installed just above the rotor)
Now.. my question for those of you in the know.. I am pretty sure that those original rotors had more than one magnet in them, but not sure how many or how big. I would love to have an original to examine, but if someone who has one of these saws could just tell me what theirs has, that would be fantastic. It’s pretty easy to get to.. you just remove the four screws holding the gear box cover on the bottom and it’s right there. By rotating the gears and using a piece of metal, it should be pretty easy to figure out how many embedded magnets are in the rotor.
Any help would be GREATLY appreciated!!
-- Brad in FL - To be old and wise, you must first be young and stupid