I got a honkin huge 1.250" thick by 18.68" diameter jig plate disc from SandSmachine: Cost $78.00

A cheap Penn State Industries steel faceplate for my PM lathe.

Everything else for the build I have on hand.

 

The jig plate is 36 pounds  nothing I can do is going to flex it.   It's just under my lathe max spin diameter of 22"

 

I tapped and drilled the jig plate for 1/4-20 helicoils with the detents in 10 places  Two of them were just to use for dogs to clamp the faceplate in place while I centered it and transferred the holes from the face plate to the jigplate.

 

Sadly and with much whimpering and whining I had to face the fact that my Drill Press didn't have the reach to get the job done so I used hand drills.

 

The Penn state faceplate was annoying because they made it so that the arbor of my lathe just poked through it by ohhh maybe 0.060" So I had to fabricate a 1.250" diameter  spot face in the center of the jig plate to clear that.

I used a  milwaukee metal cutting coring bit and a little spotfacing tool to chew the material out of the plate.   IT worked but was a PITA that I'd not have need to endure had Penn State just done it right 

Well, I did say it was  a cheap faceplate, so there you go.

 

Anyway after I mounted it there was a misalignment of about 0.040" TIR and I had to turn the jig plate on the lathe.  I used a Doug Thompson Bottoming gouge and the metal cut like Buttah.

I  used a little C clamp  on the  gouge to set the depth of cut so I wasn't just following the  circumference of the jib plate disc.  So it was an interrupted cut. I lubed it with paste wax. Worked great.

It is perfectly balanced. 

Face of the jug plate is flat within 0.005" TIR.  I could shim but I'll leave it.

 

Here's Pix

 

 

 

 

Now I gotta  get some Elmer's repositionable spray adhesive and a cheap widebelt from Supergrit to cut my discs from

And of course build a little plywood box to be the table.

I'll prolly apply some Formica I have around to the ply for durability

I had the same problem with a face plate and the protruding arbor. My solution was to add a steel washer and an anti-lock spindle washer 

 

 

between the shoulder of the arbor and the "rear" of the face plate. The thicknesses of both gave me enough length to eliminate the problem. And as an added bonus, I don't have to worry about ever again having to free a jammed faceplate on the headstock. I use the metal/teflon washer combination everytime I use my chucks or faceplates.

 

Woodcraft has a couple of sizes-

 

http://www.woodcraft.com/Product/149358/antilock-lathe-spindle-washer-1.aspx

 

Nice sander! I also like Supergrit. They are only about 30 minutes from here.

Thanks  It all came together pretty cheaply considering the cost of a good 20" disc  sander is around $2500 and my investment is less than a buck fifty even with shipping.     

 

I couldn't use an anti jam washer as I needed a truly repeatable dead flat metal to metal seat and one that will go back together dead true every time.   Anything other would mean that I could not get a flat or repeatable  spinning surface.

 

Precision is  one of the several reasons I rejected a spend-O-licious 20" power disc.  They are not as precise as one hopes them to be -  or so I am told by people who have been disappointed by theirs.