Cam Over OR Not.

[fguffey]

I spoke to an RCBS tech, and he recommended just letting my carbide die gently "kiss" the shell holder before the press cams over

You do understand if the RCBS Rock Chucker cammed over the die would move away from the shell holder.


And then there is that part about the Rock Chucker linkage kicking the ram back at the bottom, logic says if that is true the top of the ram kicks forward. Now I ask what does that do to the die if the shell holder grinds against the bottom of the die and if the carbide ring is recessed what happens to the bottom of the die.

I understand there is no propose for operating the ram under a no load condition meaning the case aligns the shell holder with the die.

F. Guffey

 

[IWAC]

That is interesting - what press do you have? If I understand what you said, that means your press is definitely dropping the ram back down some after the cam over center. My Rock Chucker does NOT do that.

Mine is a pre-LNL Hornady...the exact same one the one the fellow shows in post #16. My previous press was an RCBS Jr, and it cammed over, too.

 

[mdi]

No offence to anyone, but I think this "cam over" issue started out as just the ability for a press to go beyond TDC and reloaders chose to use this "design mistake" to their advantage...

 

[BBarn]

Neither of my Rockchuckers or my Lee Classic Turret cam over. It’s really easy to test a single stage press for cam over.

With no die in the press, lower the press handle all the way until it stops. With a shell holder installed, grab a die (preferably a non-carbide one to prevent damage). Thread the die in until it contacts the shell holder. Now gently try to raise the press handle. If essentially no resistance is felt as the handle is raised, the press isn’t camming over. If raising the handle requires more that gentle pressure, the press is camming over.

 

[AR-Bossman]

No offence to anyone, but I think this "cam over" issue started out as just the ability for a press to go beyond TDC and reloaders chose to use this "design mistake" to their advantage...

100%. Basically "cam over" is when all SLOP in the system has been squished out and you are now over stressing all the moving parts by metal to metal contact as if you were doing something good.

This is predicated on dies being poorly designed and not doing their job before reaching this condition.

 

[f451]

Cam over

I think that the Rock Crusher style loader, when talking about cam over and die set up, is used for consistency on each shell re-size. From what I can gather here, people are talking about cam over as something to put excessive force on the die with the press piston. Unless your shooting a match grade chamber, this is probably not a wise thing to do.

Now this is ONLY my opinion and I know you want as close tolerances as possible for shooting long range or for extreme accuracy. Under 500 yards, this should not be a problem. But when you start to really reach out there, a very minute difference in the load makes for huge changes.

Hunters should stay with what works for them the best, be it fire formed cases or neck re-sizing. These are more than adequate out to 300+ yards for most hunting. Using the cam over technique to get the absolute consistency you need for long range is again going to be up to the shooter.

I personally do not use the technique on any .308 I have except one. It is a 26" Remington 700 long range tactical the tolerances on it are very extreme. I do a full length, very tight re size on all new brass and then use that brass in this rifle only. Brass out of any other rifle I have will not fit but this brass will fit, after firing, with room to spare!

 

[BBarn]

Strictly speaking, cam over is a function of the press and has nothing to do with die adjustment. Adjusting dies to compensate for sloppiness or flex in a press is a different issue.

 

[mdi]

100%. Basically "cam over" is when all SLOP in the system has been squished out and you are now over stressing all the moving parts by metal to metal contact as if you were doing something good.

This is predicated on dies being poorly designed and not doing their job before reaching this condition.

I didn't want to offend anyone by using "slop". Machinsts and mechanics know this is just a term for "tolerances" but lots of reloaders think it's an insult...

 

[Mauser69]

100%. Basically "cam over" is when all SLOP in the system has been squished out and you are now over stressing all the moving parts by metal to metal contact as if you were doing something good.

This is predicated on dies being poorly designed and not doing their job before reaching this condition.

Dies do not have any moving parts. Even poorly designed dies. Any slop is in a poorly designed or worn out press. Properly setting up the dies and understanding the importance of compensating for this slop is how a knowledgeable reloader compensates for this problem.

 

[AR-Bossman]

Dies do not have any moving parts. Even poorly designed dies. Any slop is in a poorly designed or worn out press. Properly setting up the dies and understanding the importance of compensating for this slop is how a knowledgeable reloader compensates for this problem.

I have quite a few dies with moving parts...

 

[Metal God]

Basically "cam over" is when all SLOP in the system has been squished out and you are now over stressing all the moving parts

I'd think a press that cams over actually puts less stress on the parts . Think of it like this . If you put 100lbs of pressure on a non cam over press . That press is being over stressed by about 80lbs because you only need about 20lbs to size the case . Now put that same 100lb load on a cam over press and how much is it over stressed ? None , because it cams over at 20lbs and never gets to the 100lbs of pressure .

 

[BBarn]

It’s clear from some of the posts in this thread that press cam over is misunderstood, something I find disturbing. The same end results can be achieved with virtually any press, whether it cams over or not, with suitable die adjustment. The only real difference is, a cam over press requires somewhat more care in die adjustment to prevent damage and unnecessary stress on the press and dies.

 

[gwpercle]

If I need full contact for maximum resizing, I only go a light cam over. Very light ! I do not stress my Pacific Super Deluxe cast iron C press or linkage unduly . If I need additional sizing , I use a thinner shell holder or , as a last resort , remove a few thousandths from the bottom of the sizing die . Other ways to get additional shoulder setback than springing a press.

 

[Walkalong]

A press that cams over reaches a point where it puts no more additional stress or force on the ram, vs one that does not and continues to put whatever pressure you are using on the ram.

 

[Boombotz401]

I read not to cam over carbide dies so I setup my pistol dies so a pice of paper slides between the shell plate and die when raised


Rifle dies I just use a FL die and bump the shoulder back about .002 -.005
Never found the need to cam over


Sent from my iPhone using Tapatalk

 

[Walkalong]

If a press is designed to cam over, that is how the dies should be set up. You don't have to have a die contact the shell holder to cam over the mechanism.

Welcome to THR

 

[BBarn]

A press that cams over reaches a point where it puts no more additional stress or force on the ram, vs one that does not and continues to put whatever pressure you are using on the ram.

My Rockchuckers and Lee Classic that don't cam over do not continue to increase ram pressure once the mechanical limit is reached. At their mechanical limit the lever pivot block bottoms against the link bar, so any additional force is applied to the the bar and pivot block, not the ram.

 

[fguffey]

At their mechanical limit the lever pivot block bottoms against the link bar, so any additional force is applied to the the bar and pivot block, not the ram.

When the linkage hit the limiters the ram is kicked back; because the ram is solid and one piece if the ram is kicked back at the bottom the ram at the top is kicked forward. Then it should be asked what aligns the ram with the die. When I am sizing a case the case aligns the ram with the die.

And then there is that thing that is going on under the table with the linkage. Somewhere in about 1930 a company designed a pair of pliers that were called 'leaver locks'.

F. Guffey

 

[Walkalong]

At their mechanical limit the lever pivot block bottoms against the link bar, so any additional force is applied to the the bar and pivot block, not the ram.

So a mechanical stop that limits handle movement.

 

[fguffey]

So a mechanical stop that limits handle movement.

No, it is a designed lock up system. When the linkage gets tangled up the press is locked and it goes into a bind. The bind forces the ram back toward the rear. When the ram is kicked back at the bottom the ram at the top is kicked forward.

I am not the fan of abusing a press so I avoid jamming the linkage to gather.

F. Guffey

Again, I have modified one Rock Chucker to cam over; problem I can not use that press with an auto advance attachment.

 

[243winxb]

From RCBS instructions. Just follow instructions for you die set. Note when the lock ring is set.

 

[Walkalong]

No, it is a designed lock up system. When the linkage gets tangled up the press is locked and it goes into a bind. The bind forces the ram back toward the rear. When the ram is kicked back at the bottom the ram at the top is kicked forward.

I am not the fan of abusing a press so I avoid jamming the linkage to gather.

F. Guffey

Again, I have modified one Rock Chucker to cam over; problem I can not use that press with an auto advance attachment.

Mechanical stop, designed lock up, same thing.

I have never managed to tangle up my press linkage. That sounds hard to do without breaking the poor thing.

"Cam over", or what ever one wants to call it, is always such a fun discussion.

 

[fguffey]

I have never managed to tangle up my press linkage. That sounds hard to do without breaking the poor thing.

I have no way of knowing if I am talking to a reloader that reloads or someone that claims to be a reloader and does not have a press. Long before I mounted a press to a bench, table or stand I turned the presses upside down just to see how they worked. The one thing that did not escape my notice is the Rock Chucker linkage driving the ram back at the bottom; a reloader with investigative skills and a curiosity should wonder what effect the kick back was having on the ram at the top and bore alignment.

I have at least 4 Rock Chuckers, none of my Rock Chuckers cam over; if they did it would be a design failure because all of Rock Chuckers were designed to be used with a Piggy Back attachment. Two of my Rock Chuckers are installed on Piggy Back 11 attachments. My Piggy Back attachments are auto advance. My Piggy Back attachments will not work on a press that cam over. I know no one is going to ask ‘how can that be?’. I did not design the Piggy Back press, RCBS did, when RCBS made the Piggy Back press they built it with a ‘one way clutch’; meaning the auto advance system can only rotate in one direction, if the ram changes directions the press will lock up because of the one way clutch.

243wimxb, I have two sets of instructions form RCBS, one set is for the cam over press, the other is for the non cam over press. The instructions for the non cam over press are different from the instructions for the cam over press. The rock Chucker does not cam over. The die in the cam over press is adjusted after the ram is raised.

The popping sound is the linkage colliding. Many years ago a company designed pliers that locked when closed, the company called the pliers ‘leaver lock’. The additional ¼ turn of the die after contact loads the press by a guestimate of .017”. What that means the top of the press is pushed up and the bottom of the press is pushed down causing the press to spread in the center. Under a no load condition the ram would deflect to the rear causing the ram to kick forward at the top. Under a load condition; the press would be sizing a case, the case prevents the ram from kicking forward but that does not change the linkage at the bottom from causing a ware spot on the linkage when the press goes into a bind.

F. Guffey

 

[Walkalong]

Thanks for clearing that up.

 

[Captaingyro]

Under a no load condition the ram would deflect to the rear causing the ram to kick forward at the top. Under a load condition; the press would be sizing a case, the case prevents the ram from kicking forward but that does not change the linkage at the bottom from causing a ware spot on the linkage when the press goes into a bind.

Let me see if I'm understanding this: when you set up the press to cam-over, it's under a no-load condition (i.e., there's no case offering resistance to the upward travel of the ram). Later, when you're sizing a case, the resistance of the case may result in the press NOT camming over, since the resistance offered by the case may cause the press to flex just a bit before the cam-over is achieved.

Is that correct?