Liquid Wrench saves the day...

Restoration can be a painfully slow process when life keeps getting in the way!  Work piling up at the office and grass growing like crazy due to an early spring has kept me away from the toolshed, but I finally managed to get back to the DeWalt 780 and try to figure out a problem that I was having with the miter function.  Try as I might, I couldn't get the miter lock to release so that the radial arm could be rotated on the column.

Although I have a photocopied version of the DeWalt Instruction and Maintenance Manual for this saw, the photos leave a lot to be desired and the instructions just didn't seem to jive with any of my attempts to unlock the arm.  Further complicating matters, my manual lacked a parts list or schematic, so I had no corresponding visual representation of how the component parts were supposed to function.

Through a bit of trial and error and more than a few Google searches, I discovered that the DeWalt 7730 is, in essence, the 10" version of the DeWalt 780.  Although there are some discrepancies between the two, I was able to find a schematic of the 7730 which did provide some additional direction.

What the arm needed more than anything was a good soak in penetrating oil.   A fellow member of the Woodworking Talk Forum suggested that I do so and lightly "vibrate" any of the suspect areas using a block of scrap wood and a hammer. I sprayed a very liberal amount of Liquid Wrench on all of the component parts and along the underside of the column and then let it soak for a number of days before returning to it. When I did, I again sprayed all of the component parts and then tapped them using a small dowel rod, concentrating primarily on the miter latch, pin and spring.

I then backed out the two miter adjustment screws on either side of the pin and applied a bit more Liquid Wrench.  Giving the external handle a good push, the latch pin popped out of the 90° stop on the column and the arm swung around. A bit more Liquid Wrench was sprayed to the uderside of the column and the arm is now functioning reasonably well.  Given how gummed up the arm was, I doubt that the original owner ever did more than use this saw for straight crosscuts. With a bit more cleanup and some lubrication, it should be as good as new. 

I did learn a few important things relative to adjusting the saw as a result of getting the arm to free up...the most important being that the two miter adjustment screws are critical to aligning the saw at 90° for good straight cuts.  If the adjustment screws are not properly tightened down, you will get some side-to-side play in the arm; if they are too tight, it is very difficult to release the miter latch.  I found that by tightening them up all the way and then backing them off about ¼ - ½ turn, I could correct for both problems.

Once the saw is cleaned up and ready for alignment, I'll adjust the crosscut at 90° by placing the leg of a rafter square against the back fence and aligning the blade to the tongue.  Any lateral adjustment can be easily made by loosening the two miter adjustment screws, moving the arm into alignment with the square and then re-tightening the screws to lock the arm in place.

Again, big thanks to my woodworking brothers at Woodworking Talk.com for their good advice!