Every mold is an individual, they are all different and depending on size of both the cavity and the blocks the temperature that the mold wants to cast will vary. Jones blocks are very large and hold heat well also a .40 cal cavity will want to cast at a lower temperature than a .32 or a .25. 
  As far as wait time to shear off the sprue if you use a lead / tin alloy once the sprue goes solid a 2 or 3 count and it should be hard all the way through. If you are using a alloy that contains antimony the alloy will go through a slushy stage you must wait longer to get a clean cut.
  This is a good time to mention doing something to maintain your sprue plate. Most mold manufacturers that use commercially supplied blocks use plates supplied by the same manufacturer. Quite often they are punched out on a press and then countersunk. The holes in the sprue plate should be sharp! If they are not sharp they will not cut they will tear. Take some time and make sure your edges are sharp if not lap them on a lapping plate this will also flatten the plate you may be shocked the first time you lap a plate as to how not flat they are.

40 Rod

40_Rod, what is a lapping plate?  I'm a computer guy and know very little of the things that are common knowledge to gunsmiths and machinists

Thanks,

Chris.

gunlaker wrote on Mar 29^th, 2016 at 2:43pm:

Told ya so   Chris, Put some 320 - 400 grit sand paper on something flat and solid such as piece of  glass plate.  work it around a little to smooth, flatten and take off any burrs.  You can use a little water for lube. If it is really bad, start with a courser grit.  A WORD OF CAUTION not too course.  All those scratches from the courser grit will need to be smoothed back out.

Every two piece mold has a burr at the edges of the cavity. The duller the cutter the bigger the burr. When you cast bullets the cavity gets dirty from dirt/dross in the lead. Dirt will build up along the burr and cause sticking. As stated earlier, bullet molds can be off center, magnifying the problem.

I use a microscope and an Exacto knife to remove the burr.  Simply running a hardened piece of tool steel along the burred edge may solve the problem. A piece of drill rod? Music wire? 

       
              Joe.

U R welcome.  While you have that flat plate and fine grit paper, you can touch up your plane irons too 

I would not do anything more to a Paul Jones mould than a very minor polish to get rid of the flash, and steps to keep it away, as described.

Jones owned a tool-grinding shop down in LA and decided to make his own moulds when he couldn't find what he needed for his Schuetzen and BPCR shooting.  He made cherries for Redding's first black powder moulds and used the relationship developed to buy their finished but uncut blocks for his own moulds.  Word of mouth and the tiny ad he ran:  "When you care enough to send the very best--Downrange" got him a back order situation for the rest of his career.

Every set of Redding blocks, which was already good enough for Redding moulds, was ground on all surfaces for right angles, finish and fit, and a third alignment pin attached.  Sprue plates were similarly ground to fit. He rough cut the cavities with cherries like those he sold Redding for their finish cavities, but lathe-bored the cavities on his moulds to final dimensions, and checked the dimensions by casting bullets out of the alloy the customer specified and putting them on a comparator before they left the shop.  A Jones mould will barely show a parting line and the runout is typically below the limits of the measuring instruments.

So before setting up your glass plate and sandpaper, hauling out your files, scrub brushes, Exacto knives and steel scrapers, ask yourself "Is my Mickey-Mousing around really going to improve this mould, given what has gone into it already?"

Hey thanks for all the info. I really like the Paul Jones story,Thanks. I did polish the bottom of the sprue plate. It was flat and cleaned right up with 220 then 320 paper on a surface plate. I did notice something about the sprue hole the counter sink is not all the way to the bottom of the plate to form a knife like edge. It stops short 1/32" or so.
That doesn't seem right. But I am not having any trouble with cutting the sprue it cuts nice and clean. I will keep the temp lower and look for burrs, maybe try the Scotch Brite.