Sprue cutting is not good on my new RCBS mold/s

[saxguy]

I have recently purchased a couple of RCBS steel molds, both for “Keith” style boolits. .357 and .44 (four cavity).
I fitted them to Lee handles, after milling the handles down to be a good fit to the molds.


I cleaned and cast from both, after carefully de-buring one or two of the edges using a cratex rubber strip (by hand), and obviously degreasing the molds carefully.


Overall I am very pleased with the molds, as they drop bullets which are quite uniform over the four cavities respectively. One problem however, is that the sprue cutter on both the .357 and .44 is riding up over the last sprue (the one farthest from the handles), and too be honest, I am really having to give the cutter some seriously hard whacks to get it to cut through. I have been spoiled by my years of using the Lee dies, with the cam action of their six cavity mold cutter/s.


When I look at the cutting edge on all of the holes, it appears not sharp, but maybe a 64th of a blunt edge (not sure how to describe it better. I was wondering should I grind/lap the sprue cutter holes so that they have a sharpness to the cut? Is this normal for RCBS molds?
I am so that afraid that a few hundred or so operations using such hard blows, it will start to have a negative effect on the molds.

Any advice guys?

[No_1]

Call RCBS but be ready to send them in if you do and possibly not get them back. Other option is aftermarket sprue plates - If you are happy with your molds this may be the way to go. Check the Vendor Sponsor section for a seller.

[saxguy]

Call RCBS but be ready to send them in if you do and possibly not get them back. Other option is aftermarket sprue plates - If you are happy with your molds this may be the way to go. Check the Vendor Sponsor section for a seller.

...so would you say they should be "sharper"?..... I live in New Zealand, and the cost of posting them back to the US is half the cost of new molds unfortunately.

If its a case of just honing the cutting edge, i can do that, but i didnt want to do any work to brand new molds if i am missing something more obvious.

[saxguy]

... the bulging spur left on the fourth boolit after sprue cutting, is around 8 to ten thou (I measured a few)...

[saxguy]

I did a little digging, and i have found old threads relating to blunt RCBS mold sprue cutters.... guess it is quite common. I'll bite the boolit and lap 'em out I guess.

[runfiverun]

or just open them sooner.
opening them sooner will allow you to not whack them with a stick or have that bounce from the glancing blow quite often encountered from a not so straight smack.
the bounce allows the cutter to ride up and over the hard sprue nub.
you can also do the double smack where you close the plate back up and whack it again this will quite often cut that nub off.

i use a gloved hand [thumb actually] to open my sprue cutters once the mold allows me to do this i start keeping the boolits from the mold.
i then focus on getting that same feeling each time i open the mold.
if i get deeply torn sprues i slow down, if it's too hard i need more heat in the mold/plate.
if i ever so slightly smear the base, it comes out flat without a nub at all.

[theperfessor]

Does RCBS sell 4 cavity molds now? That was always my complaint, that they only had two cavity molds.

[saxguy]

Does RCBS sell 4 cavity molds now? That was always my complaint, that they only had two cavity molds.

Yep they do.

I have only ever used Lee molds before... been using them for over thirty years with no real issues. Just getting back into reloading after a long stint away (UK stupid laws) and having moved to a country where i can shoot pistol again. Thought i would like to try "Keith" boolits, so went with the RCBS molds.

[Bullshop]

I have a bunch of RCBS molds that I have purchased over about 35 years. They are all single or double cavity. I have never seen any RCBS mold with more than two cavities.
I have an Ohaus mold which is the predecessor to RCBS and this mold has three cavities but it is for round ball.

[geargnasher]

or just open them sooner.


This.

Gear

[williamwaco]

Cast faster, keep them hotter, cut them sooner.

[saxguy]

Whooooah…. HOLD THE PRESS
I have a HUGE apology. The molds are Lyman.:oops:
I have been buying quite a bit of new reloading gear, some of it RCBS, and for some reason it stuck in my brain that the molds were RCBS.
What a foolish mistake, my humble apologies to RCBS and everyone here reading this.
So, that said (and head hung very low), the problem remains, but the manufacturer now correctly identified.

Sorry…. Again.

[geargnasher]

You can sharpen them with a ball or cone grinder in a drill press, or my favorite way is a 60-degree countersink mill in a drill press. Follow up by dressing the underside of the sprue plate flat again as the pressure from the mill will dimple the plate a bit and scratch your blocks.

Or, do what Run and WW said. They're pistol bullets, no worries. Cut them right as the sprue flashes over dull, they should pop out and leave little "goat arses" right in the middle of the bullet bases.

Gear

[theperfessor]

If RCBS ever makes pistol molds in four cavity versions it will cost me a bunch of money! They have a number of good designs and every one I've had has been very good quality.

At least I'm not losing my mind or totally out of it.

[saxguy]

If RCBS ever makes pistol molds in four cavity versions it will cost me a bunch of money! They have a number of good designs and every one I've had has been very good quality.

At least I'm not losing my mind or totally out of it.

Hahaha.... Yes, it's okay for you, I'm the one with loose marbles rattling around.

The molds I bought a few months ago, and it was only recently I found the time to get them up and running. I remember at the time I was procrastinating over which to get... RCBS was in the running. I seem to think that maybe it was because I couldn't get a four cavity from them.... not sure...

Anyway, very sorry for misleading you, my foolish mistake. All I can say is, I haven't really got enough time for anything at the moment, but thought I could at least get a bit of reloading done.... I shouldn't try and rush things.

[MT Chambers]

Doesn't matter, the Lyman 4 cavity are excellent molds and for me are my bread and butter and none have ever given me grief, it takes longer for them to fully heat up and that's when the sprue cutting is trouble free even if done with the gloved hand.

[leadman]

I use a countersink bought from Home Depot to finish cutting the tapered hole in the Lyman sprue plates. Angle is not entirely correct but it takes so little out of the bottom of the hole that they work fine.
Don't know why Lyman can't get these right.

[Buckshot]

I use a countersink bought from Home Depot to finish cutting the tapered hole in the Lyman sprue plates. Angle is not entirely correct but it takes so little out of the bottom of the hole that they work fine.
Don't know why Lyman can't get these right.

.............Saxguy, I fully concure with the above. All you are wanting is to put a bit of a keener edge on the spruehole itself. The taper on the spruecutter is 90º. Since all you want is to sharpen the hole any cutter (60 & 82º) are common and will do this, and carefully done by hand is entirely satisfactory. Just do not get too carried away as making it 'knife sharp' would weaken the edge and cause further undesirable problems.

...............Buckshot

[.22-10-45]

1+ on using hand power for c' sink..most home/hobby drill presses have far too much rpm even on lowest setting. Gearnasher mentioned dressing underside of plate..a flat piece of steel..or better yet thick glass & 350-400 grit emory paper..working the plate in a fiqure 8 motion will both de-burr sprue holes & nicely flatten underside of plate. Best of luck!

[saxguy]

Well thanks for all the replies fellas. I have since done one of the molds (the .357) sprue cutter with a countersink in the drill press. I then polished out each hole with 80/120 grit grit on a wooden dowel also in the drill press, followed by a de-burr/flatten of the plate underside. Havent tried it yet, but it stands to reason that it will be better.

Next job, lapping out the boolit bands a couple of thou. I have that one figured, just need to have time enough not to have to rush things.

[Buckshot]

Next job, lapping out the boolit bands a couple of thou. I have that one figured, just need to have time enough not to have to rush things.

.............Just remember while 'lapping', that sharp features (corners, edges, crimp grove) will be the first affected. Also the lube grooves which are 'inside' the cavity will also receive more attention from the lapping then the drive bands, which are on the outside of the cavity.

..............Buckshot