My Modifications‎ > ‎

Apron Mod

Early on I found that chips would get down in the apron gears and even the Half nuts.  I found this mod on the web and decided to try it.   Unless you are like me and just like doing this kind of stuff you can get this little plate from for just a few bucks. Their P/N is 2960 and is made of sheet metal but gives you the basic plate.

Mine was made from a piece of 1/8" acrylic I had around the shop.  I won't go into all the steps to remove the apron but a good practice I use is:  mark every piece with a fine sharpie before removing them.  That will at least give you a starting point during reassembly.

Once it was off I inspected the gears and their bearing surfaces (because the Saddle and drive handle were a bit sloppy for my liking) then cleaned everything up real good.  Next, with the gears out I cut a cardboard template of the shape by laying the apron face down on the cardboard and tracing with a pencil.  Leave a bit of material at the top where the pinion drive gear is outside the casting.  I measured from the bottom side of the apron to the center of the pinion drive gear, and from the edge of the half nuts.  Then transferred them to the template for the hole for the rack pinion gear.  I mic'd out the OD of the pinion gear and cut the hole with a gasket punch.  Note: I left about 1/16" clearance from the half nuts (See Picture).

Next was to transfer the template to the acrylic and cut it out.  I did not drill the holes for the screws as I wanted to do a 2nd OP on them so I could place them where I wanted them.  I cut the the rough shape with a jig saw and then cleaned up the edges with some sand paper to its final shape.  I think I might have used a Dremel a bit with a small sanding drum also as I had left some excess material around the larger gear at the top where it's exposed.  One thing to note: when drilling the hole for the drive gear, as you will note in the pictures, use a Forstner bit and go real slow and don't let it overheat by lifting it up and down as you drill it.  You can see the little crack in mine at about 11 O'clock...a bit over zealous on my feed.

Once it was pretty clean, I assembled the gears and laid the acrylic into place and decided on the hole locations you see.  I only used two, 8-32 flat head sockets as I didn't want to go into the upper right thinner area and didn't have a proper flat head 4-40 at hand.  I marked the acrylic and drilled the pilot hole then used a transfer punch to mark the apron.  I drilled and tapped the Apron and then used counter sink on the acrylic to flush up the flat head at assembly.  The depth of the pilot hole in the casting was about 1/4- 5/16".  This will give you about 6 threads into the casting after tapping.  I also had a couple of 8-32 taps but no bottom taps so I ground the end down on one of them to resemble a bottom tap.  Tapping cast iron by hand takes patience and a steady hand (another reason not to use 4-40's), so take your time.  Also the countersink in the acrylic wasn't quite thick enough to flush the head so I went a little deeper into the acrylic and followed into the apron just a skosh to flush it all up.  It doesn't hold the planet together so I put a little Loctite mild (222) on the threads during assembly.  The acrylic actually lays very flat on the surface of the apron even though I only used 2 screws.

Last thing was to clean everything up and lube the gears (white Lithium Grease) and reassemble the apron.  I ended up shimming the crank handle about .025 with a washer to take up the slack in the drive set (kind of a thrust bearing).  Also add a bit of lube to the rack and be sure and align your rack and pinion as straight on as you can during assembly to minimize backlash and wear.

That's about it!  A simple add-on that helps ease maintenance and wear.  Also keep in mind if you make the accordion way cover it will pretty much keep all the Swarf (Chips) out of the works.