Gary's Sabot sparks an idea

[Double D]

       


 

Couldn't something like this be used to make a round ball mould.

Make the the cutting blade for heavy tool steel to the radius needed.  Chuck up a mould block in the 4 jaw, incremental machine out most of the steel that is in way, then plunge this tool to depth to finish?

[KABAR2]

While a two bladed tool works well in wood you need to be going to three blades for metals,

you need the odd number to dampen vibration, the more cutters the better 5 would be better then three......

ask Mike and see what he says.


Allen <><

[Double D]

Allen,

Isn't this design little more than just a short shank spade drill?

A friend who use to work in aircraft manufacturing has sent me a pictures of a similar tool he built for making arcraft parts.  He hasn't given me permission to post the pictures yet.  As soon as he does, I'll put them up.

[dominick]

       


 

Couldn't something like this be used to make a round ball mould.

Make the the cutting blade for heavy tool steel to the radius needed.  Chuck up a mould block in the 4 jaw, incremental machine out most of the steel that is in way, then plunge this tool to depth to finish?

I don't see why it wouldn't work.  I use a rounded spade bit for cutting the breech face on the barrel plugs.  The difficulty would be in making a perfectly round mold.  Modeling clay can be used to check the shape

[Double D]

This would not be used as a roughing tool but a finish tool and built like a spade drill. 

I wonder if you could get a tool and cutter grinder to make you a radius tool bit to fit your spade drill.

[KABAR2]

Part of the problem is keeping the chatter down, the idea is the more blades touching the surface
the better finish and more likely to stay on center, especially if you are using a drill press, 
on a milling machine this would work better, I would not use it on brass, Aluminum ok.

[Double D]

I'm thinking cutting steel and the blade constructed thicker, and a holder built like a spade drill bit.  End mills and drill bits work with two cutting flutes, why wouldn't this especially as a finisher after the form is roughed out?

[KABAR2]

Are you using a mill or a drill press? I have seen the chuck drop out of a drill press when used for this type of operation from chatter,
a mill is the way to go, and I think the slower the better, as long as you can keep the chatter down it will stay fairly well centered,
also with a mill you can lock your work piece down far better than on a drill press.

where is M&T on this? I thought by now they would join in on the conversation.....

[Double D]

Lathe...making a steel ball mould for casting zinc round ball.

I don't think  the standard run of the mill driil press would give the accuracy or be rigid enough to work.

[GGaskill]

Speaking of lathes, is the new one in yet?

[seacoastartillery]

    Thanks for your concern, Kabar2.  Think about how easy a half reamer would be to make and then use on this type of job.  Any of you use one before??  We ahve made several for custom loading dies.  They work slick and don't cost hardly anything.  O-1 is pretty cheap and easy to harden, too.  That's our suggestion.  Sorry, got a contest to run, BYE!

T&M

[Double D]

Speaking of lathes, is the new one in yet?

No, still waiting  the for the correct size machine mounts to come in with $100 refund for the oversize ones sent.

[Victor3]

 It would work, but as Allen noted, you may have some serious chatter with this type of tool. One way to work around this is to bore close to your finish depth, then feed in the last few thou into the work while rotating the lathe chuck by hand. This allows you to scrape the last bit of material off of the cut surface. If all goes well, the chatter will be removed and the diameter will be fairly true.

 The key here is rigidity of the machine, setup, tool and workpiece. Also, the tailstock has to be lined up carefully with the spindle, and the cutting tool has to be made so that the diameter formed by the cutting edges is concentric with the shank.

 For the tool, it would be better to make it out of an old cut off large diameter Morse taper drill shank to fit directly into your tailstock. It would probably be too flimsy (more prone to chatter) if you held it in a chuck in the tailstock.

 Also, a less chatter prone tool design would be one with four, rather than two cutting edges. This could be made similar to the one you show, but with a 2nd slot cut through at 90 degrees to the 1st. Two more cutting inserts, ~1/4 of a circle each could be added perpendicular to the 1/2 circle one. Silver solder the parts together and then finish grind the cutting edges.

 One caveat here; there will be a large web area that will have to be relieved so that the tool will cut in the center. One workaround for this is to make the two extra inserts with a flat ground at the nose so only the main (1/2 circle) insert is doing the cutting at the very center of the tool.

 I have a tool like the above somewhere around here.

[Double D]

So what you guys are saying spade drills won't work because they chatter?

[Victor3]

 No, it's just that they're not ideal, especially in harder/tougher materials.

 With two cutting edges, the tendancy is for the tool to walk off C/L of the workpiece. This can be controlled somewhat, but there are more variables to deal with than when using multi-edged cutters.

 When the C/L of the tool wanders, one of the two cutting edges ends up doing the cutting. This is where chatter starts, and your spherical diameter goes oversize.

 With three or more cutting edges, when the tool wants to wander, the other cutting edge(s) tend to nudge the tool back toward center because there are multiple points of pressure opposing it deviating from its original path.

 This wandering tendency is worse with a spherical boring tool. With a pointy one, the angle on the tool creates a well-defined cone (center) for the tool to follow.

[Double D]

So you missed the part where I said hog most of the metal out of the way and use as a form or finish tool?

Couldn't something like this be used to make a round ball mould.

Make the the cutting blade for heavy tool steel to the radius needed.  Chuck up a mould block in the 4 jaw, incremental machine out most of the steel that is in way, then plunge this tool to depth to finish?

[Victor3]

 Nope, I read it the 1st time. 

 Your problem is going to be as much (if not more) at the end of the cut as the start, as that's the point where most of the cutting edge length is contacting the workpiece.

[RocklockI]

Not sure how big a ball you are looking for , but couldnt you plunge a ball end mill to get it close ...or even as a 'cherry' to make the mold with ?

[seacoastartillery]

     Considering the cost of decent quality ball end mills of 1" dia. or larger, I'm guessing that you already have begun negotiations with Royalty in Denmark.  Sorry, couldn't resist!  He, he.

T.

[RocklockI]

Away With You . Be Gone .

thats two pink feathers for you .

(waves pinky finger only) and nods to gaurds .......

[dan610324]

you could find some really decent quality ball endmills in china for good money if you search a little
but be sure to only deal directly with factories
if its agents they have added at least 100% to the price