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10-11-2011, 06:46 AM #1
Attaching an arbor to electric motor
I hope you guys can help with this, because after a full day of searching I've come up with nothing. We have an aluminum extrusion shaped like an upper-case "E" and I need to mill off a few inches of the middle tab after the extrusion is cut to length. So we'll cut this E extrusion to 10' and then trim out ~2 inches of the middle tab from each end. The current (and dangerous) method is to use a circular saw to cut this tab. Its loud, time consuming an as mentioned before its somewhat dangerous and imprecise.
I was thinking of making a small dedicated station where this tab could be milled off. The part I'm having trouble with is finding a way to attach an end mill to an electric motor. Is there something out there that will attach to the output shaft and allow me to attach an arbor?
Just curious to hear your thoughts.
10-11-2011, 07:13 AM #2
Firget electric motors and attachments for endmills. Motor bearings are OK radially but they spring in and out up to 1/32".
Use two routers mounted in a fixture.
10-11-2011, 07:42 AM #3
Routers work very well on aluminum.
If you must start with a 56 frame electric motor with a 5/8" shaft, look at Shopsmith accessories for tooling with 5/8" I.D. and set screw fastening.
10-11-2011, 08:11 AM #4
Thanks Larry, that's exactly what I was looking for.
10-11-2011, 08:23 AM #5
Perske has spindle motors that have an optional 1/2" collet. The bearings are designed for stiffness.
10-11-2011, 08:32 AM #6
If you try to use an ordinary electric motor for this, you WILL be disappointed at the very least. You will go to a lot of work to make a fixture to mount the motor and once you're done you will have nothing to show for it.
On the other hand, a good (or even an inexpensive) three horsepower plunge router will do the trick. Make a U-shaped trough to hold the extrusions securely and SNUG but still allow the extrusions to slide freely through it. Make the trough long enough so that the extrusion is well-supported over its entire length. Add a little platform on top, and mount the router to it so that the bit is centered on the rib you want to cut. Use a "flat bottom" carbide router bit of appropriate diameter. Add a stop to limit the extrusion's travel into the trough to the amount you want to trim and you are done. To keep chips from flying around, you can add shielding and guards as desired, since you don't have to see the bit as it is cutting.
It's unclear to me how deep your cut will be. You mention several inches, but it sounds like this refers to the length of the cut, not the depth. If you are making a shallow cut, you can take it in one pass. Just adjust the router to the proper depth. If you are removing some serious metal, that's where the plunge feature comes in. Take several small cuts until the router hits its depth stop at your desired finish dimension.
In practice, slide the extrusion along the trough until the router bit cuts metal. When the extrusion hits the stop pull it back out and you are through. Experience will tell you how deep a cut you can make and how fast you can feed the material into the bit.
btw, get a variable speed router and run it at low speed.
10-11-2011, 09:09 AM #7
Steves router suggestion is good but I'd turn the idea round by arranging to fix the extrusion down and sliding the router over it. Plain bearing on round rail linear guide systems are pretty inexpensive and easily made up to suitable short lengths. Manual push in of a 10 ft length without it jumping out of place or tilting sounds a bit on tricky side to me. Certainly I got into terrible trouble on a similar sort of set up with 4 ft (ish) bars!
If you need multiple cuts many plunge routers have a rotating stop assembly which allows several depths to be preset. My cheapie has 5 settings.
If its a regular production arrange to set up two routers, one at each end. Quicker to scamper down than turn a 10 ft bar without knocking stuff or people. Frankly a 10 ft bar is best handled by two guys anyway so doing both ends simultaneously works.