What's all the fuss over "Cam Over"?

Status
Not open for further replies.
Allow me a minute to run on a bit. Think of a rubber band & a rubber ball. If you squeeze a ball or stretch a rubber band they are under force & fight to get back to there at rest shape. Metal does this also. This is how bolts hold. A nut is used to stretch/crush the bolt to pull/shove to hold something in place. Large bolts that you can't get enough force to stretch the bolt by turning the nut requires a hydraulic cylinder to stretch the bolt then run the nut down & release the jack to allow the nut to hold the spring of the bolt.

So the question was can you get any more press after the shell holder contacts the die. The answer is yes but you need all of the leverage of the press.

My vote is for cam over.

Now to side track. Explain why I keep seeing eat your heart out fguffey.

Unless I'm taking it wrong it isn't appropriate & seems like it would be against forum rules.
 
So the question was can you get any more press after the shell holder contacts the die. The answer is yes but you need all of the leverage of the press.
Click to expand...
Yeah, after contact, you can make the press flex more all you want, up until it breaks. What's the point?

Cam over may very well be a great way to increase the leverage of a press. Why can't we just say that?

You could get a degree in BS from reading this thread. It's painful.
 
I wasn't aware of any fuss about cam over? Is this something us old timers should be aware of? I try my best to avoid cam over, but sometimes it's just an unavoidable circumstance.

Maybe I should consider adjusting my dies so they only push the shoulders back enough to maintain proper head space.

Seriously though, cam over is simply an effect of what some presses do depending on how much adjustment is needed to properly form / size the brass for the firearm being loaded for. Cam over is by no means a determining point of adjustment which should be used as a guidline. I have an old RCBS single stage I use primarily for bottle neck resizing that doiesn't cam over at all. Just an example of how effective using cam over as a description of proper resizing die adjustment, it's not.
 
Last edited:
Yeah, after contact, you can make the press flex more all you want, up until it breaks. What's the point?
Click to expand...
Yep.

"Cam over" is simply a mechanical spot where the lever action of the handle moving down stops moving the ram upwards, so that no matter how hard you push down on the handle after that point, all you will do is damage things is you crank down harder.
 
Cam over is a term meaning the ram has gone up far as it can go and then ram starts back down. All presses I have ever looked at does this, some more than other. It's the only way to get a consistent travel upward every time. In all of the die sets I own, the instructions tell you to run the ram all the way and stop, not cam over to set the sizing die.

Like Walkalong said, continuing on after the ram as cam over does no good. Any more travel you think your getting is moving the ram down......
 
Kingmt, nothing like having two standards.

More surprising to me, with all this talent, and owners of RCBS Rock Chuckers and throwing around a term like CAM-OVER, not one of them can/will measure the amount of cam over, I said the RCBS ROCK CHUCKER jams over, crams over or locks up, it matters not to me what it is called, point being, if the RC cams over, measure the amount of cam over. Then there was the video filmed at Cabala’s and the mass hysteria, not one owner of an RCBS RC came to the aid (save one) and displayed knowledge of the design and function. The jam over/cram over pushed the ram over at the top without a die and or shell holder, and again, the reloading world blamed China.

Again, I can modify a RC press to cam over, cam over would be a good thing, if there was some way to get the reloaders to understand putting a press into a 9 line bind is not necessary, for them to understand that they would have to understand there are times the case wins.

The case can win because of bad habits, the case can win when the cases ability to resist sizing exceeds the ability of the press to size the case, and that is the reason I said I can determine if the case was sized before I lower the ram.



More surprising to me, with all this talent: Before the gimmick die called bump I made forming dies from ugly die that were too cheap to pass up, ugly on the outside, great on the inside. Dies I made, like the bump die had/have case body support, again, it is not possible to form/move/bump the shoulder of a case ‘back’ without without case body support.

But, I did notice a change in definition, seems there is a movement to call jam-over, cram-over and lock up----CAM OVER.



F. Guffey
 
This topic is of interest to me as I was trying to resize 1k 7.62mm casings that had been fired in a MG. Try as I might with seven different presses (non of them being green or red/silver), I could not fully resize them and get the shoulders back enough to safely chamber in my M1A.

I measured the press flexing with a finger gauge and found that all presses flexed .0015 or a bit more with both Forster and Hornady dies. I could get cases fully resized by running them thru the once and waiting a few seconds, then sizing a second time.

My solution was to take my Hollywood Senior Turret and screw the tie bar down tight, which eliminated press flex and allowed me to get the shoulder measurement I needed.

However, I also considered the possibility that the dies were too long to adequately fl resize the casings and considered contacting someone with a surface grinder and taking .005 off the bottom of the die. Would this solve the problem of incomplete sizing?
 
From a previous post I indicated my RC cams over, and that I recalled making a couple mods to give it a bit more travel for 375HH. Well, I checked out the press and lo and behold I modified it for both down stroke travel and also milled a bit of metal from the toggle to allow it to go over TDC. I set the dial gauge on and it goes over TDC by a bit under .001". I like this because there is never question about the ram reaching top stroke, no matter how high the handle force is. For me the RC is pretty accurate if I back a die off a bit, with a given case / load its within a thou. For the lnl-ap I have to ensure die to ram contact at the size and seat stations otherwise its all over the map. I also place a rubber washer on the ram to help seat the pins etc. and it helps this press alot.
it takes a several hundred pounds to compress the washer so it presses the shell plate onto the base, seats the base onto the ram, and stresses the links. I made a post about that earleir with some measured results.
 
Kevin, It is never necessary to grind a die and or shell holder, it is never necessary to purchase a set of Redding competition shell holders, those that sell Redding shell holders disagree, those that have already purchased Redding shell holders for the purpose of adding to the length of the case from the head of the case it’s shoulder may not have been able to increase the length of the case any other way. Then there is 1858, he was not happy, seems he did not get what they promised, I found a set for $5.00, I checked them, they were off a total of .003, things like that have never locked me up.

Before you grind the die, add a .005 shim between the deck of the shell holder and head of the case, when using RCBS dies it is possible to add a .011 thousands shim between the case head and and deck of the shell holder, but if you are using other shell holders check to see if there is enough clearance, anyhow, if you find it is necessary to grind the die, checking with a feeler gage will let you know if it will work and how much is necessary to remove.

I have a grinder, it is used to make pilots, tapers, erosion type gages, head space gages and for length of anything I can chuck up, it also is a butt cutter, it is water cooled and is adjustable in thousands. Point being, I have never found it necessary to grind a die and or shell holder. There is a difference between old shell holders and modern shell holders, any how, if you decide to grind the die, I will make a one time offer, but first I will exercise a right to determine the ability of the die to size a case back to minimum length/full length size with a shell holder that has a deck height of .125.

F. Guffey
 
The problem with cam over is like that on a vice grip. You tighten the screw, it doesn't grip enough, tighten it more and before you know it, you tightened it too much and it won't release or it breaks something.

Tightening a die on a press that has cam over can crack a carbide die or lock it up.
 
Last edited:
When you run out of ideals, out of desperation, purchase another die? Not desperate but I did purchase a new set of dies, 8mm-338 Winchester, at half price. I made the 338-280 dies out of ugly/cheap dies, like people I find no with ugly on the outside.

F. Guffey
 
fguffey said:
Kingmt, nothing like having two standards.

F. Guffey
Click to expand...

I don't understand.

fguffey said:
The case can win because of bad habits, the case can win when the cases ability to resist sizing exceeds the ability of the press to size the case, and that is the reason I said I can determine if the case was sized before I lower the ram.

F. Guffey
Click to expand...

I agree.

Gloob

No BS there it is all truth. Why do you think the press stretches?
 
If people would read the front part of their reloading manuals we wouldn't be having this discussion.

"WHY" would anyone want to "OVER" resize their cases?

Does anyone want to buy a Cam Over Drill? :rolleyes: (it will bump, jump and rock and roll) :D

hand20cranked20drill.jpg
 
"WHY" would anyone want to "OVER" resize their cases?
Click to expand...

Because

This is important if you have a rifle with a short chamber or if your die is short or your shell holder a bit too tall.
Click to expand...

Also, in the case of the 9mm, the more you size the longer the case gets. Being that 9mm are too short to begin with, getting all the length you can is a good thing. Chambering a .740" case in a .762" chamber is not conducive to good accuracy.
 
Tightening a die on a press that has cam over can crack a carbide die or lock it up.
Click to expand...

Only if the carbide sticks out the bottom of the die. That is not an issue with most dies.
 
The problem with cam over is like that on a vice grip. You tighten the screw, it doesn't grip enough, tighten it more and before you know it, you tightened it too much and it won't release or it breaks something.
Click to expand...

For the purpose of achieving maximum amount of sizing, you don't have to have the press camming over that much. .001" to .002" is enough and does no harm.
 
Kevin, It is never necessary to grind a die and or shell holder, it is never necessary to purchase a set of Redding competition shell holders, those that sell Redding shell holders disagree, those that have already purchased Redding shell holders for the purpose of adding to the length of the case from the head of the case it’s shoulder may not have been able to increase the length of the case any other way. Then there is 1858, he was not happy, seems he did not get what they promised, I found a set for $5.00, I checked them, they were off a total of .003, things like that have never locked me up.
Click to expand...

I disagree. I had to grind my 9mm shell holder to get the die to size the cases to get them to be .748"+.

I like my Redding competition shell holders. They make sizing a breeze. I typically use the +.008" one to get my bolts to close snug. They are dead on. Maybe your buddy got a POS set.
 
It is necessary for my rifles. .002 between the shell holder & the die & I can't close the bolt. I can get them in my sons rifle with a little force then chamber them in mine but it is a pain & once in a while they stick after fired. The other guns it just won't work. I just got a AR & some of the cases still didn't chamber with the press camming over. I haven't dug into it yet to find out why. As fguffey said "sometimes the press wins & sometimes the case wins". If the press is camming over then most of the time the press wins. I would have to use a dial indicator or something if I didn't have that bump to tell me I got a full size. You can add a shim to the top of the shell holder if you like. I used to only FL new to me cases so not that big a deal.
 
This thread is making my head spin.

I hope everyone realizes that if a press "cams over" it will do so whether the shell holder touches the die or not. Camming over just indicates that the ram has gone beyond top dead center and is going down.

By setting the press the cam over at some load to get the press to cam over, in theory, you are taking up all the looseness in the ram mechanism as well as flexing the frame about the same and therefore the case is sized the same every time.

If you do not load up the ram and remove all the looseness in the system, different cases, as they are resized, will affect the amount of resizing.

If you do set the press to have the shell holder jam against the die without camming over, then you should rig up a torque wrench to insure you are applying the same force to the system with each case.

Is it enough difference to make a difference? Some say it is, some say it isn't.
 
Status
Not open for further replies.

Similar threads

B
  • Locked
press cams over center
Replies
8
Views
1K
ironworkerwill
ironworkerwill
L
  • Locked
RCBS Neck sizing die ?
Replies
13
Views
3K
gamestalker
G
jmorris
  • Locked
How much force does my press exert?
2
Replies
49
Views
4K
HB
HB
H
  • Locked
Sizing Cases?
Replies
20
Views
851
NMexJim
NMexJim
Z
  • Locked
What am I doing wrong w/ resizing?
2 3
Replies
64
Views
4K
308sc
3
Back
Top