I need help with cherries!

[44man]

I have made a lot of cherries and have differing results. Some cut good and others rub and scrape, even wearing the cherry. I can only cut the cutters with end mills, I have no grinder. Are there any machinests out there that can detail the making of the cutting edges? Number of cutters, if I should mill below center, how much rub area is OK and the best way to take the cutters to the nose since I have to file these.
I can't tell in advance if one will work.

[fido]

I have been pondering the same thing. I am a hobby machinist. Are you using a dividing head? I have an older reloading book illustrating a few pieces. The cherry was a two flute.
I have blocks ready to be cherried, but haven’t had time to build a cherry. I have a good friend that runs a machine shop I did talk to him and from what I can remember he said to cut to center. I think the back side would have to be relieved or like you say you will get a lot of rubbing.


My effort so far.

http://img.photobucket.com/albums/v510/sdeering/P9100029.jpg

I hope someone chimes in hear I am interested too.
Stephen

[Texasflyboy]

The following article (in .pdf format) may be of help:


Hensley & Gibbs Article on Mold Making (http://users2.ev1.net/~eastus1/Casting/Hensley_Gibbs_AR_1968.pdf)

[dragonrider]

Cherries like endmills need to be relieved behind the cutting edge on the circumference to prevent rubbing. It's best if this can be done with some kind of a profile grinder. But it can be done carefully with a dremel tool by hand. Or done before hardening and polished afterwards. It is much easier to make a two flute cherrie than any other, although 4 is just as easy just takes twice as long. Haveing a dividing head is a plus but not absolutely needed, one can use a collet block of 4 or six sides. These blocks hold a 5C collet and can be held in a vise and rotated in said vise keeping your cherrie on a central axis.

[Four Fingers of Death]

Cheeries are just coming into bloom here in Australia :-) No help I know, but I thought that I'd share that with you anyway, Mick :-)

[Bent Ramrod]

44Man,

I've read over and over the "theory of cutting" in various toolmaking books, and I'm not sure I get it even now. (And my cutters do a lot of rubbing, too.) Once you have gashed the flutes on your cherry, reamer or cutter, you still have a circular diameter curve remaining between the right angle of the first gash and the acute angle ahead of the second. You have to reduce this arc in "eccentric relief" almost up to the leading edge at the top of the vertical first gash.

You can do this by painting the diameter surfaces with Magic Marker and by grinding, back to front, with a small cylindrical or circular stone. Ideally this would be on a toolpost grinder with the reamer back between centers, using the same settings you had when you turned the shape in the first place. In practice, I find the smallest difference on my compound rest will leave the edge of different widths, and in any case, the ogive of the bullet cherry has to more or less be done by hand anyway. I should learn to use a bevel protractor, but... Some sort of fixture which would allow you to run a Dremel back and forth but keep you from pushing it fore and aft might be a help.

Finally, when you have just the tiniest remainders of the original circular surfaces left at the top of the flutes, you stone the backs of them up to the fronts, giving a tiny little bit more relief at a shallower angle than the eccentric relief. If everything is done right, there is enough metal behind the cutting edge so it doesn't crumble, but enough relief for chips to break away without rubbing.

Commercial chambering reamers are all made on CNC machinery, but it is my understanding they make a couple of them every time they get an order for one, just to make sure. I would imagine bullet cherries, with their even more complex surfaces, would be that much more complicated.

I find it instructive to make a dummy chamber in clear plastic with my homemade tools. A couple blocks of this plastic could be used to make a dummy bullet mold as well. Bad spots on the cutting edges will melt the plastic, rather than cutting it, leaving rings you can see from the outside. Laying the tool along the dummy cut will help locate any burrs or unstoned spots.

One of Lucian Cary's stories had his barrelmaker J. M. Pyne saying "They used to say it took 20 years to make a toolmaker out of a good mechanic." I think that's as true as ever, even now.

[44man]

I read one article that says to cut .010" left of center, or when in the vise, below center. I don't have a dividing head, too expensive! I rigged my vise to index at either 60 or 90 degrees. I have been making six cutting edges so I don't get chatter. I file three to the nose. Four cutters would work but I can't picture the ogive shape with all four edges meeting at the nose. Maybe two meeting would be OK.
There is a LOT of hand work that needs to be done, filing and stoning. Even every grease groove needs relieved and it is hard to see how much is filed out.
When I look at the side cutters on an end mill. the cutter side is ground out round making a sharp edge, plus the back side is relieved. I don't like the flat front cutting edge I get from the end mill. All I am making is a scraping edge. I have no way to grind this surface.
Texas, I could not open the link on mould making!

[Bent Ramrod]

44Man,

I think the variance of the flutes by a few thou front or back is done to keep the tool from chattering, which it supposedly is prone to do if all the flutes are cut right on the centerline. I would guess this would be less important with non-production tools, as you won't be running at maximum speeds and feeds for the sake of cost-effectiveness.

I used a dividing head in the shop class when I was trying to make such things, but I would think a hex nut on threads cut on the shank of the tool would be close enough, if you wanted to do six flutes. Six is definitely more work than 4. I still have a six-flute cherry in .38 caliber that I gashed and heat-treated and have done nothing further on. All those burrs on all those grooves, not to mention the relief, is a lot of tedious hand work. Some of the books on toolmaking reprinted by Lindsay Publications should have a drawing of how the various reliefs should be ground and stoned.

[BABore]

44Man,

I've done 6-8 cherries so far with really good sucess. I should say my machinist has done most of the work in making it a cutting tool.

After I've lathe cut the intended bullet shape onto a piece od 5/8 diameter O-1 tool steel, he takes over. He sets it up in the mill in a 5C rotary index. We have been cutting 4 flutes in the cherries so far. With the edge of the end mill at 12 o'clock, four flutes are cut at 90 degrees apart. Once they're done the cherry is rotated 5 degrees CCW when looking at the nose. The flutes are recut to give each cutting edge a 5 degree rake angle. The cutter is moved toward the cherry's cutting edge, slowly, until it just barely touches. Once all the rake angles are cut, the cherry is indexed 10 degrees CW from its last cut, to cut a relief angle of 5 degrees. The relief is cut to within 0.005" of the cutting edge. Finally a end mill is used to cut four flutes in the nose to resemble a typical end mill profile. Of course you only have to do this for a FP sytle bullet. From here out everything is hand work. I'm sure your aware of the tedious deburring task. You also need to hand grind relief on the nose ojive to match the cutters straight profile. Everything gets stoned to perfection and then hardened with a torch and oil quenched. The cherry is spun during heating to reduce warpage. We then sharpen the cutting edges with a diamond hone and recheck for burrs. The final check is to set up the cherry in the mill collet, check and adjust for runout, then cut it into the side of a squared up piece of 6061. We run it in a bit past the full diameter point so we can check the cutting diameter with a caliper or gauge block. The cavity is inspected for proper profile and any galling. Nine times out of ten galling is caused by lack of cutter relief. Any left over burrs will show up too.

We have had to reduce the cutting diameter of a couple of hardened cherry's using a lathe. We lack the proper surface grinder. My machinist made up a mount for his straight shaft air grinder that attaches to the lathe's tool post. It has a swing arm to engage and hold the valve lever. Using a hard stone in the air motor, the unit is mount and squared up to the turning axis. A diamond dressing stone is locked in the chuck and the stone is dressed square. The cherry is chucked up and indicated in, then cut to the desired size. The cherry is turned opposite its cutting direction. Finish it up with a diamond stone to sharpen.

Hope this helps. I'm still pretty green on mold cutting, but this has worked well, so far.

[Bass Ackward]

Just because you work with metal or are a machinist doesn't mean you will always get a handle on the art. Machinists that know how to shape and sharpen sometimes toy with those that .... have difficulty. We have gotten reamers sharpened that come back destroyed for the cartridge that they were supposed to be from the company that MADE the reamer in the first place. I guess they are in the business of selling new reamers, not sharpening old ones. :grin:

I can't tell you how many times dad would tell me, "If God had wanted everyone to know how to sharpen, he wouldn't have made catalogs." Turn to page so and so.

Then after I flubbed it up enough times, he'd go do it. Just to enforce that superiority edge. So I learned early to play dummy and flub everything up quick, then he'd get frustrated and not ask me.

Everyone's always looking for an edge!

[44man]

Babore, that is the best info so far. My only problem will be getting the 5 degree difference since I don't have anything but the vise. I like the idea of the undercut edges. Looks like I have to order more drill rod!

[andrew375]

When I made cherries, I started with high carbon steel bar. Turned the profile and shank then cut the flutes on a milling machine using a dividing head, setting the cut roughly ten tho' over centre. On large cherries I also hacked out the majority of the back edge on the miller too. Tilting the dividing head up allows me to cut the flutes and back edges up to the nose, I usually only have every alternate flute continue right to the nose in order to make them thick enough not to break down.

All the crearences I put on with a file, clearences do not need to be precision; just so long as there is some there. Remember to file clearances on the sides of features like grooves as well as the bottom.

After deburring I test my cherry against a piece of wood, anywhere the wood is burnt or torn indicates a problem to be cured with the file. If all is ok I harden and temper the cutter and give the major diameter cutting edges a rub over with a stone to give a smooth finish. I do not have access to a grinder, but I wouldn't attempt this without a dividing head it makes things so much simpler.

[44man]

A dividing head sounds like a good Christmas present!

[andrew375]

A dividing head sounds like a good Christmas present!

After cogitating on the problem I came up with the solution to achieving good angular precision for cutting six flutes. This came to me just on the edge of sleep last night, as these usually do.

Set your cherry blank into a short piece of hexagonal bar. Clamp in place with set screws. If you drill through the hex bar into the cherry shank so one set screw locks into the cherry all the better. Now you can hold the job in a normal machine vice and precisely rotate it in 60 degree steps. Also you can take the piece out of the vice or tilted as often as you like and you will precisely maintain location of the flutes in relation to the cutting edge.

But honestly, if you intend doing this regularly then a dividing head will change your life.

[44man]

That hex bar is a good idea! I happen to have a long piece of it too. Thank you, I never thought of that.

[Greg5278]

44man, do you have a lathe? I was going to try lathe boring myself, but sent my molds out instead. You could use some presicion ground M-2 or D-2 stock and make a profile tool.You could have the decarb ground off at a machine shop on a bunch for a few bucks. Then you can use the same tool for different calibers.
You could make one long tool, and use it to cut differenr weights, and grease grooves.
Greg

[Willbird]

Hmmmm......out of the blue, have you tried a ONE flute cherry ???? Sure would be a LOT less work....and you have TIME to run it longer to get the job done :-) or multiple flutes, but each flute only cutting ONE area of the mold ??

Bill

[44man]

One flute is no good as you need a rub area on the other side, chatter would also be bad. The forming tool works different because you start with a hole and feed it slowly into the cavity. There is a difference between turning the cutting tool and closing blocks on it and turning the work with the blocks closed.
I have a cheap Smithy lathe that I can't trust the dials on and backlash is huge even shimmed almost tight.

[Buckshot]

...............44Man, you can buy an import spin indexer that takes 5C collets for less then $35. It will index to 1 degree, which should be fine for what you're wanting done. ENCO has one on sale this month for $28. Go to www.useenco.com and click on 'Hot Deals'. Go to page 43 in the upper right hand corner is the spin indexer.

Andrew375 had a good idea too, except that screws against a shank will offset the shank to whatever clearance is available in the toolholder. A .500" diameter tool in a .502" hole will be offset .002" to one side. A collet on the other hand, holding with equal pressure on the fingers all the way around will help to better center whatever you're cutting or grinding on.

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

[Willbird]

On the chatter issue, I sharpened tools for a couple years...and MOST reamers and a lot of similar tools have the flutes "thrown off"..this means that they are not evenly indexed expressly to avoid chatter...... The book "The Modern Gunsmith" by Howe...explains this, if you don't have it mr 44 man you NEED it :-).

I single flute cutter would work I am sure, however, it would be far slower...however what I was getting at was dividing up the work done by the cutter over the 3,5,7 flutes ( I have always found odd numbers to work better) so that each flute cuts a section of the profile will give you some tool presure in both diections, but will avoid you having to detail relieve the same feature 3,5,7 times...if I was to do it I would turn the blank, flute it, then mill off the sections on each flute that didnt belong there.

Cutters with a lot of bearing area chatter....if you have ever used a corncob style endmill you will notice that you can just walk it into the work and not have it vibrate...while a normal endmill with the same number of flutes would shriek like a banshee if you tried that, that is because each flute is hitting a bit differant...so it breaks up the resonance......they use chip breakers in broaches and other tools for somewhat the same reason

Also I'm wondering if you rough the cavity first ?? being you do a lot of the same dia bullets, or pretty close, a rougher wouldnt be hard to make,(I'd just use the aforementined corncob endmill) and it would do the heavy lifting, leaving your work of art finisher with just the last .05" to .100 of dia to skin out into a purty cavity.

Bill