1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

? Will any "O" type press cam over?

Discussion in 'Handloading and Reloading' started by ironworkerwill, Jul 11, 2014.

  1. ironworkerwill

    ironworkerwill Well-Known Member

    I've used Lee Challenger and Classic Cast presses and I don't think they were advertised to cam over, but they do. I'd like to hear from other "O" type owners.

    I suppose a ''C'' type would or could, but would it be bad for the press?

    I've never used a turret or progressive. I assume they will not cam over. Is this true?

  2. fguffey

    fguffey Well-Known Member

    I have Os, Cs, Us, I have variations. I have presses that cam over, I have presses that do not cam over, one very popular press has been claimed to be a cam over press by reloaders. It is used with an attachment that includes a one way clutch. If the press was a cam over press it would be tuff on the one way clutch.

    I measure, if the ram goes to the top and starts back down before the handle goes into a bind the press is a cam over press.
    If the ram goes to the top and stops before beginning the return trip, the press is not a cam over press, if is a jam up, cram over, lock up press, the linkage goes into a bind and limits travel. I have modified rock Chuckers to cam over.

    The RCBS A2 is a cam over press. Without a die in the Rock Chucker the ram kicks forward when the linkage is jammed together at the toggle.

    All of my Herter presses are cam over presses. I have instructions that include directions for adjusting a cam over press and a non cam over press.

    The cam over press is also a bump press. It is possible to measure the amount of cam over/bump.

    F. Guffey
  3. higgite

    higgite Well-Known Member

    Depends on your definition of cam over. If you mean can they be made to "bump" or toggle over at the end of the stroke, yes they can, by manipulating how far the die is turned in. It "locks" the mechanism at the top of the ram stroke by putting the press mechanism in a bind.

    If you mean does the ram go past top dead center and start back down at the end of the stroke, so do, some don't. My Lee Classic Cast and Classic Turret both have stops built into the mechanism to keep them from doing that, but I can set the sizing die to make them toggle over. My CH4D press has no built in stop and it cams over in the sense that the ram goes past TDC and starts back down at the end of its stroke IF its travel isn't restricted by a die.

    I can make my progressive press toggle over at the end of its stroke by manipulating how far the dies are turned in. Some call that camming over, some don't. ymmv
    Last edited: Jul 11, 2014
  4. ironworkerwill

    ironworkerwill Well-Known Member

    Right! I see how that would indicate "CAM"

    Understood. I'd always call'd it cam over.
  5. Potatohead

    Potatohead Well-Known Member

    Ive read the Lee Classic turret doesnt "cam over" but Im not sure. If anyone could enlighten me to exactly what "cam over" is, I could tell you. Well, I see Higgite is kind of getting at what it means exactly.
  6. ironworkerwill

    ironworkerwill Well-Known Member

    Cam is the ram sligltly lowering after the ram has reached its highest point. On the up stroke of the ram that is.

    I suppose most progressive presses have stops on the linkage to prevent cam over?
    Last edited: Jul 11, 2014
  7. 918v

    918v Well-Known Member

    You don't need it to actually cam over. You need to be able to bottom out the die against the shell holder.
  8. Catpop

    Catpop Well-Known Member

    Won,t any press cam over? I like mine to flat out bottom out. That way I know where I am. IMHO catpop
  9. Potatohead

    Potatohead Well-Known Member

    Thanks IWW
  10. savagelover

    savagelover Active Member

    i have often wondered about this cam over thing....If the ram is at the end of travel why does it have to cam over ?It makes no since to me what so ever...If at the end,then it's at the end..:banghead:
  11. ironworkerwill

    ironworkerwill Well-Known Member

    Take my Challenger for example: Being made of aluminium, the frame will flex more than a cast frame of a similar design.

    If I was to bottom out the die on the shell holder and go 1/8 more turn on the Challenger press- I'll see "day light" between the holder and the bottom of the die while sizing.

    If I turn the die in 1/2 turn in after contact, then the shell holder will flush up with the bottom of the die.
  12. gamestalker

    gamestalker member

    I have an old RCBS "O" frame press I bought some years back at a garage sale that doesn't cam over. I'll have to dig it out to see what model it is, but it's a tank, very heavy cast iron press. My RC and my RS 2 both cam over.

    As for whether it matters or not, I don't know. I need to dig that big boy out and give it some loading time really.

  13. horseman1

    horseman1 Well-Known Member

    As far as I can tell, my Redding Boss press has stops for the linkage and stops with the ram at the top of the stroke. There is no going back down, unless I were to remove the steel stop pins, and then the linkage would probably hit the bench after going much further. I certainly hope this is of no concern. The press has worked brilliantly for me so far with no detectable slop that I can tell.
  14. rsrocket1

    rsrocket1 Well-Known Member

    A cam over press is difficult to adjust for bump. Since you are trying to stop the upstroke of the brass into the die, a cam over press will stop its upward motion and go back down based on force rather than stop at a certain point regardless of force. If you are neck sizing with the Lee collet neck sizing die, you can crank the die way down and the press will stop even if it is a cam over press and it will never get to the cam over spot.

    If you are trying to bump with a full length die, you may never know whether you bump to the right spot because the press will cam over based on force rather than length. If all your brass is of equal softness, you probably will never have a problem, but if the brass hardness is all over the board, you may have big variation.s
  15. tightgroup tiger

    tightgroup tiger Well-Known Member

    Ok, you all have me confused also. The ram on my press doesn't cam over but my linkage does right at the end of the stroke. I know this because when I preload one of my rifle dies I can feel it when it goes over. I don't see the ram starting back down. How do you define that?

    This is a RCBS Rock Chucker Supreme I bought about 25- 30 yrs ago( I think). Does this mean my linkage is worn out or is it the way the press was supposed to work?

    Either way, I will continue to use it because it still works beautifully for me.
  16. tightgroup tiger

    tightgroup tiger Well-Known Member

    Look at the linkage at the bottom of the ram, if it cams over then it's a cam over press. My Rockchucker definitely cams over even though the ram doesn't start back down. The cam over is greatly exaggerated at the linkage compared to watching the ram. My ram doesn't appear to move back down but the linkage clocks at say 1:00 o:clock, when it hits the stop. I can't see it in the ram but I can definitely feel it.

    That, to me, is definitely a cam over press.
  17. ironworkerwill

    ironworkerwill Well-Known Member

    From what I understand from this is if the ram lowers after top dead center it is a "cam over".

    And if it is just past a die kiss on the shell holder on a non camover press, then it's a toggle.

    Though I've called them both cam over forever.
  18. 918v

    918v Well-Known Member

    If you bottom out the die against the shell holder with a case in there, frame flex becomes irrelevant.
  19. ironworkerwill

    ironworkerwill Well-Known Member

    Yeah! That's why I have got to go past 1/8 to get a full length size.
    So in the Challenger press that equates to 1/2 turn past. Or was I unclear?

    The cast iron press is much less flexible. 1/8 is ok for most applications.
  20. fguffey

    fguffey Well-Known Member


Share This Page