Yosemite Steve
New member
Thanks cw308.
RCBS PRecission Mic
- Thread starter Yosemite Steve
- Start date
according to everyone in the reloading world a press with a eccentric linkage is a cam over press. Rock Chuckers have eccentric linkages
CAM-OVER: DON’T DO IT. JUST DON’T.
CAM-OVER: DON’T DO IT. JUST DON’T.
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Yosemite Steve
New member
I am in half agreement with this blog. In the case of my press the cam over puts the shell holder the the top of the travel it can reach and a bit past. I think that this is good because it assures me that I have gone to the maximum reach of the stroke, particularly when my die and shell holder are not making contact. In the instance where a reloader puts the die in contact with the shell holder I think it is still ok to let it cam over but with moderation. When the shell holder meets the die with enough pressure to fully contact the surfaces resizing is done. The cam over can be adjusted so that it does not put an egregious amount of pressure on things. Here is an instance where a precision mic would be useful in measuring how much contact is enough and how much does nothing more. The instructions for my Rock Chucker are a little "over the top" with regards to how much further to screw in the die. I think that 1/8 turn past contact is enough to cam over but not enough to wear things out.
I also size with the Rock Chucker , I screw the die down to the shellholder not to cam over but to remove any slack in the threads . I full length size my brass and never had to cam over or would want to , Once the die bottoms out on the shellholder what good is a cam over doing ? It would seem to me only harming the press or am I missing something ? It is the same with the PM as it screws down to the shoulder or the bullet ogive , you can feel the contact point . With cam over for some reason the case can not be sized down enough, better to have a custom die made . I'm lucky I guess , never had that problem.
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I have 12 Herter presses, all of my Herter presses are cam over presses. Again, there are two members on this forum that have instructions for presses from RCBS. One of their last cam over presses was the A2. RCBS identified the press as a cam over press and they identified the A2 as a bump press because it was a cam over press.
And then one day a reloader walked into a Cabela's store with a video camera and starting videoing the ram going up and down while he was operating the handle on a Rock Chucker. He then decided the press was made in China because the ram came to the top and then kicked forward. The press did not have a die, shell holder or case installed. And then the bashing started; I tried to get ahead of it by explaining I have (at the time) 4 Rock Chuckers and all 4 had this problem of locking up, jamming up and getting tangled when the ram came up with no case in the shell holder.
I could not get a reloader to crawl under the table to examine the linkage, I could not get a reloader to push himself away from the keyboard long enough to stand up and look thorough the hole in the top of the Rock Chucker to determine if the ram kicked forward or if it cam-ed over. I could not get anyone to do the research but there is a company that makes Vise grip plyers. In one of their patents they claim they invented 'the leaver lock'.
I can measure the amount of cam over in thousandths on all of my cam over presses. The last A2 I operated had .017", in my opinion that is too much.
I have never been able to get the ram on the Rock Chucker to change directions with one exception. I modified one Rock Chucker by grinding the contact points between the toggle and linkage. I do not have to worry about that happening again because a reloader would have to get up and look under the table to find the toggle.
I believe they should take Red Green's advise, reloaders have a choice; they can be handy or they can be cute.
F. Guffey
Just Looked at the linkage on my RCBS Rockchucker and when I raise the ram the linkage first moves back then forwards in an elliptical motion. The ram itself is bushed so that it moves only vertically. If that ram starts moving in the x and z planes I would think it is time to rebush it and if that isn't a cam over press I just think I will be wrong with the rest of the world
We used to have a saying in the Navy...there is a right way, a wrong way and the Navy way. I think that could be adapted to this forum
We used to have a saying in the Navy...there is a right way, a wrong way and the Navy way. I think that could be adapted to this forum
RCBS will give you another press before they would install bushings. I would knurl the hole through the press before I would exchange one of my presses. RCBS sent me a new ram with the instillation kit.
And one more time, I have never seen a Rock Chucker that cams over, I know a lot of reloaders that believe their Rock Chucker cams over and they believe their cam over presses bump. If it bumps it has to do it twice, once on the way up and again on the way down. The two reloaders that have RCBS press instructions know the cam over press is adjusted differently than the non cam over press.
Again: The Rock Chucker is aligned with a case, if there is no case in the shell holder the ram is kicked back at the bottom and forward at the die,, it is nothing personal, that is the way it is.
F. Guffey
Mr. Guffey is correct. Camming over does not depend on the linkage type or the shape of its travel path. I think elliptical cam lobes on crankshafts are confusing people trying to define camming over by the shape of the motion. But as the dictionary says, even a cylinder turning on a shaft eccentrically (round, not elliptical cross-section) can impart linear motion to a connecting rod in a machine, so it is also called a cam.
In the case of a press, all camming-over depends on is the handle having enough range of movement to drive the press ram to the top of the stroke (camming up) and past the top of the stroke to start dropping the ram back down again (camming down). The transition from camming up over to camming down is called camming-over. This transition happens when the maximum extreme position of the linearly moving part (the ram) is reached and passed without reversing the motion of the handle. This is analogous, but upside-down from a valve cam turning past the point the valve is maximally depressed and starting to let it come back up again. That is camming over from linear motion of the valve stem in one direction to linear motion in the other direction.
The reason camming-over matters, whether the linkage is compound or a simple pivoting handle design, is that either mechanism approaches theoretical (in an ideal, infinitely rigid, zero friction machine) infinite mechanical advantage as the ram passes through the top of the linear ram stroke. That much mechanical advantage can break the press, damage tooling, etc. That's the reason to avoid it.
Most presses these days have overtravel stops to halt the handle just before mechanical advantage gets dangerously high. Usually, it works to protect the equipment, though we had one fellow on another forum, who was an admittedly ham-handed linebacker size fellow, who broke two Rockchucker castings trying to turn his resizing die in further and further because it wasn't making his cases as short as he wanted it. Sometimes the Armstrong method is not best.
In the case of a press, all camming-over depends on is the handle having enough range of movement to drive the press ram to the top of the stroke (camming up) and past the top of the stroke to start dropping the ram back down again (camming down). The transition from camming up over to camming down is called camming-over. This transition happens when the maximum extreme position of the linearly moving part (the ram) is reached and passed without reversing the motion of the handle. This is analogous, but upside-down from a valve cam turning past the point the valve is maximally depressed and starting to let it come back up again. That is camming over from linear motion of the valve stem in one direction to linear motion in the other direction.
The reason camming-over matters, whether the linkage is compound or a simple pivoting handle design, is that either mechanism approaches theoretical (in an ideal, infinitely rigid, zero friction machine) infinite mechanical advantage as the ram passes through the top of the linear ram stroke. That much mechanical advantage can break the press, damage tooling, etc. That's the reason to avoid it.
Most presses these days have overtravel stops to halt the handle just before mechanical advantage gets dangerously high. Usually, it works to protect the equipment, though we had one fellow on another forum, who was an admittedly ham-handed linebacker size fellow, who broke two Rockchucker castings trying to turn his resizing die in further and further because it wasn't making his cases as short as he wanted it. Sometimes the Armstrong method is not best.
Yosemite Steve
New member
I think I understand now. I think that Hounddawg and I have the same rig.
Whatever the definition is, I have a 40 year old Rock Chucker Part #14881 and in the instructions for the dies it says:
I even used all the capital letters like the instructions. As I wrote this I thought of something. I misunderstood the instructions to say 1/8 to 1/4 turn further down. It says 1/8" to 1/4" turn... Ooops.
There is no stop on my linkage system so it most certainly does cam over. The ram goes up and then down just a bit at the end of the stroke of the handle. It then goes back up again and then down all the way as the handle is brought back up. I think that as long as the die is not turned too far down this is a good way to regulate the contact pressure on the die or the travel of the ram is the case such as mine where I do not touch the die at all. I agree that too much will most certainly be wear on the press. The fact that there is no stop for my handle allows the ram to go to it's top and then back down a tad at the end of the stroke. For me to build a stop would require some very hard and thick steel that would not give in relation to my press. It cams over. Yes it does!
Mine does as Guffey said in that with it not having a case to guide it, at the top of the stroke it moves laterally about .010".
Whatever the definition is, I have a 40 year old Rock Chucker Part #14881 and in the instructions for the dies it says:
I even used all the capital letters like the instructions. As I wrote this I thought of something. I misunderstood the instructions to say 1/8 to 1/4 turn further down. It says 1/8" to 1/4" turn... Ooops.
There is no stop on my linkage system so it most certainly does cam over. The ram goes up and then down just a bit at the end of the stroke of the handle. It then goes back up again and then down all the way as the handle is brought back up. I think that as long as the die is not turned too far down this is a good way to regulate the contact pressure on the die or the travel of the ram is the case such as mine where I do not touch the die at all. I agree that too much will most certainly be wear on the press. The fact that there is no stop for my handle allows the ram to go to it's top and then back down a tad at the end of the stroke. For me to build a stop would require some very hard and thick steel that would not give in relation to my press. It cams over. Yes it does!
Mine does as Guffey said in that with it not having a case to guide it, at the top of the stroke it moves laterally about .010".
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And if I could get a reloader to crawl under the press and watch all of the parts move I believe a few of them could find the stop. The toggle hits the linkage when that happens the ram has no other way to go but back, to cam over the linkage would have to change directions. And then there is 'by how much? If my Rock Chuckers were cam over presses I could measure the amount of cam over; my rock Chuckers go into a bind, lock up, jam up etc.
And now we are back to the floating bolt face; the face of the bolt does not align the case, the case aligns the floating bolt face. Again, years ago I removed metal from the stops on a Rock Chucker, after removing metal from the two contact points travel was increased and the jam up, lock up no longer kecked the ram back at the bottom
I have no trouble accepting the fact my ram is kicked back at the bottom and forward at the top. It does seem to me anyone that has been working on equipment for 50 years would realize that is a good way to create an hour glass looking hole in the press.
F. Guffey
Yosemite Steve
New member
Guffey, my press handle stops when it hits the wood it is mounted to or it would go further. It has never jammed. I understand what you were saying about the bolt face. Yes it is aligned by the case. But the bolt face was not square to the bore when seated agaist the reciever so the heads of my cases were also not square to the bore after firing. I resolved that problem by filing down the high lug. I now have .0005" more space from my bolt face to datum/shoulder.
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Guffy I believe you are mistaking slop in the linkage to thinking it is the ram moving laterally. Using a quality dial indicator and magnetic base I just measured the lateral movement of my ram and it measured at a Class III medium fit tolerance as per ANSI 4.1. Less than .0027
I do agree with your assessment of the floating bolt head however
I do agree with your assessment of the floating bolt head however
I think Steve got the bolt face/locking lug idea right. The bolt locking lugs will (hopefully) both rest on receiver steel under chamber pressure.If one lug bears heavy,yes,bolt head float may gaing you locking lug contact,at the expense of bolt face squareness. It just might be Steve got it right dressing off the high lug.
As far as the ram floating on a Rock Chucker,I think RCBS sends them out the door with a pretty good fit. I had a boss that would say "Indicators don't lie,and liars don't indicate"
I believe Hounddawg got .0027 . Presses loosen up with wear.IMO,its not a big deal to have some ram float. One of the best presses for loading straight ammo is the Bonanza Co-Ax. It does not have 7/8 14 threads. The die lock ring floats in a slot.
IMO,the Rock Chucker and many other presses were intended to toggle over past top dead center A LITTLE BIT. Maybe just enough to keep the handle fromdropping via gravity and pinching fingers.
I set up a lot of $40,000 plus German made Arburge molding presses.They are a lot like a loading press. The press is closed and locked via toggles. I received formal training on setting them up.Toggling over top dead center a bit is what holds the press closed. Actually,toggle over activates a microswitch that shuts of the hydraulic pressure to the clamping cylinder. You can power down the machine and it will hold 40 tons of clamp.A pair of tie bars ,hardened steel approx 2 1/2 in dia,were supposed to stretch a bit .We actually would sometimes use an indicator to measure the stretch per Arburg specs to get max clamp.
The most accurate,consistent way to control the top of the ram stroke is passing top dead center.
But,Unclenick is right. Mechanical advantage goe sway up.Its a touchy/feely thing .Be gentle!
More serious than diameter wear/clearance on the ram,over stressing the press will wear/gall the toggles and pins. The Rockchucker has dual toggle bars.Thats a lot like having dual locking lugs,if one is bearing heavy.That causes a number of problems.
Lube your toggles. I suggest something that has "EP" in the description.Love the smell of 90 wt!. Each toggle on that Arburg had a grease zerk.I had to rebuild the toggles on one of those machines. I used the grease gn regularly.
As far as the ram floating on a Rock Chucker,I think RCBS sends them out the door with a pretty good fit. I had a boss that would say "Indicators don't lie,and liars don't indicate"
I believe Hounddawg got .0027 . Presses loosen up with wear.IMO,its not a big deal to have some ram float. One of the best presses for loading straight ammo is the Bonanza Co-Ax. It does not have 7/8 14 threads. The die lock ring floats in a slot.
IMO,the Rock Chucker and many other presses were intended to toggle over past top dead center A LITTLE BIT. Maybe just enough to keep the handle fromdropping via gravity and pinching fingers.
I set up a lot of $40,000 plus German made Arburge molding presses.They are a lot like a loading press. The press is closed and locked via toggles. I received formal training on setting them up.Toggling over top dead center a bit is what holds the press closed. Actually,toggle over activates a microswitch that shuts of the hydraulic pressure to the clamping cylinder. You can power down the machine and it will hold 40 tons of clamp.A pair of tie bars ,hardened steel approx 2 1/2 in dia,were supposed to stretch a bit .We actually would sometimes use an indicator to measure the stretch per Arburg specs to get max clamp.
The most accurate,consistent way to control the top of the ram stroke is passing top dead center.
But,Unclenick is right. Mechanical advantage goe sway up.Its a touchy/feely thing .Be gentle!
More serious than diameter wear/clearance on the ram,over stressing the press will wear/gall the toggles and pins. The Rockchucker has dual toggle bars.Thats a lot like having dual locking lugs,if one is bearing heavy.That causes a number of problems.
Lube your toggles. I suggest something that has "EP" in the description.Love the smell of 90 wt!. Each toggle on that Arburg had a grease zerk.I had to rebuild the toggles on one of those machines. I used the grease gn regularly.
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If someone is really motivated to do so the proper way to check the ram fit is to remove and mike it and mike the hole. I just attached a dial indicator to th epress with a magnetic base and "wiggled"the ram. I am guessing though that it is a RC1 or RC2 fit
ANSI Standard Fits
ANSI Standard Fits
Yosemite Steve
New member
The original instructions for my press, when followed as written, does not create a terrible amount of stress on the linkage. If a person turns the die down 1/4 turn past contact the stress is outstanding. It will no doubt wear the linkage out too fast.
Yosemite Steve
New member
In looking at Rock Chucker presses I see they have changed considerably over time. If mine was mounted on a thinner bench the handle would drop to near vertical before the linkage stopped it. I have enough wood chiseled out behind the linkage end of the handle to let it cam over just a little. The wood it is mounted to is the stop.
The RV is a Winibego with a 362. It goes up hills great with no pinging and there is enough compression with this cam to keep the engine from overspeeding in 3rd gear. I like big butts and I cannot lie.
The RV is a Winibego with a 362. It goes up hills great with no pinging and there is enough compression with this cam to keep the engine from overspeeding in 3rd gear. I like big butts and I cannot lie.
Bumpers/reloaders believe adjusting the die 1/4 additional turn lowers the die .017"+; the problem comes with the limited ability of the rleoader to keep up with a lot of information. If the ram cam-es over the cam over has to be added to the .017".
I said the last A2 I used had .017" cam over; if the reloader lowers the die .017" after the ram is raised the top of the press will have a total of .35" travel if it was possible to spread the bottom of the press from the top of the press.
When necessary I am the fan of increasing the presses' ability to overcome the cases' ability to resistance sizing; It is possible other reloaders do not understand the concept.
F. Guffey