how large is the big hole...if it's like 5 inches you can weld a floor flange for 2" pipe in it then use 3" conduit to make your air pipe used a 2" niple screwed in the floor flange use a 2" union plug welded in the 3" conduit air pipe weld up a drop gate and a right angle air inlet. set the whole thing in a table with a hole cut out ...
the blacksmith Depot has some http://www.blacksmithsdepot.com/Templates/cart_templates/cart-detail.php?theLocation=/Resources/Products/Supplies/Safety_Equipment/Gloves is this what your looking for?
I have two a slash pein and 3 1/2 -4 lb rounding hammer old style (square) both are nice
the finish is nice the handle is the same type as the Hofi one would expect that as Hofi showed them how to make his style they just expanded it to meet the American market,from what I can see.
I found a new one in a pawn shop for $40.00 a few years back needless to say it went home with me before the guy could change his mind.it was not as big as yours but a Wilton
A good spoke shave works really well if one does not have a draw knife. as for plans for the shaving horse I know Mother earth news had plans also Roy Underhill the Woodwrights series had plans I think even foxfire series had them.
here a google search http://www.google.com/search?q=free+shaving+horse+plans&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a
most of the lawn and garden chairs I've see or owned were either 3/8 or 1/2 depending on where you bought it most seem to use expanded metal for the seat and back . the old ice cream parlor chairs were made of 1/4 stock
instead of a spike I used one of the bolts you find along the tracks I cut the dome of the head off and welded a handle on and drilled the hole then then drifted from the bottom and filed a radius on the mouth so the nail will release...works good for me also I cut a section of leaf spring then filed a notch about 3/8 wide in the center with the cutting edge about 1/16 below the surface so it will not cut all the the way through so as not to cut your hammer face.
heck got to Lowe's and get a big nail ..already has a head on one end; slide it in, measure it, and cut it off, then heat it up and form the other side.
might try something like this with larger holes as small lumps of coal will clog up the small holes http://www.centaurforge.com/Cast-Iron-Tuyere/productinfo/TUYERE/ or here from ebay
http://cgi.ebay.com/Blacksmith-Tuyere-Plate-Iron-Forge-Repair-Item-/270660778515?pt=LH_DefaultDo