Saw anvil?

A two foot piece of train rail.

Nice rising DT’d leg on you workbench by the way.

-- Love thy neighbour as thyself

Train rail will get you the mass, but the top is crowned, not flat.

A piece of Flat Bar or square bar would be nice and it comes in widths from 1” up to 6” and in thicknesses from 1/4” to 4”.

Steel weighs roughly .29 lb per cubic inch.
So, if you want a 25 to 30 lb block you will need about 86 to 103 cubic inches.
If you start with 2” thick x 4” wide that is 8 cubic inches per inch of length.
So a 12” long, 2” x 4” flat bar will contain 96 cubic inches; and weigh 27.8 lbs.
I think this would be the minimum chunk you would want to use.

Any steel supply house should be able to sell you a piece of flat bar like this for $0.50 to $0.70 per pound.
They will probably charge you a cutting fee as well.

-- Michael :-{| Diapers and politicians both need to be changed often; and for the same reason.

I buy short metal bars on ebay sometimes. Prices can
be very good as they are scrap and thus no cutting
fees.

Shipping is often reasonable too as a small but heavy
steel bar still fits in a small priority mail box.

About that train rail 1) IF you can find some LEGALLY they do work. 2) The bottom of the rail is flat, merely use the top in a vise.

Again, LEGALLY find rail, as these usually belong to some Rail Road. If you know a MOW crew member, ask them for any short scraps of rail. MOW? Maintainence Of Way. These are the folks that work on keeping the rails in good order.

-- A Planer? I'M the planer, this is what I use

An I beam cut off from a construction site. Any old heavy table top off heavy machinery.

-- Superdav "No matter where you go - there you are." http://chiselandforge.com