Hotblast Furnace ?

Are your grates connected together with a slide-together square stub into a square socket in the middle of the fire box?? If so if this socket is sloppy, your rear grate will have a lot less movement than the front grate.. You may try using thin steel strips, like the size of a finger nail file to wedge in the sloppy socket-joint..
This may improve the shaking action in the rear grate..

Best of luck,, Greg L
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Greg I gotta say you're right on top of this.I have 5 grates and because they're just rough cast I pick grates that don't have a sloppy fit.
I emailed us stove and asked if they made grates for nut coal in my furnace.They said no.
It's such a simple grate system(they just slide in) I've always wondered if some other grates would fit.
DON

I just wanted to chime in on a progress report;
I fired up the hotblast Fri. noon with about 35# of coal.Last night shook it down(5 or 6 shakes) got 1/2 ash pan.Loaded it with another 25# of coal.With the windows open,fan in the window and wife rolling her eyes I was set for the night.Sat. morning shook it down (12 shakes) got 3/4 ash pan and loaded another 25# of coal.I'm burnning mystery coal no clinkers red ash EZto light,seems like good coal.Seems like grinding 3/16" off the grates so they move (tip) more is the ticket for this beast.We'll see how it acts latter in the season when you get more clinkers.No jamming of grates so far(shook down nice and EZ).
DON