parting off with a drill?


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Thread: parting off with a drill?

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    Default parting off with a drill?

    Attached is a pic of a linkage ball that i need to make hundreds of. Very small, ball diameter is 5.25mm, through hole is 2mm, diameter at base is 4mm. My machine does not have a sub spindle so im trying to come up with a parting strategy that will leave the part finished without a burr. I havent ran any yet, so the first thing ill try is just parting it off with a very thin sharp carbide parting insert that is biased to one side, front edge of parting insert has 7 degree angle so the point of it breaks through the part side first. This may still leave a ring of material around the 2mm through hole. Another idea i had was to run the parting op before the 2mm through hole. Parting op will run to a depth just a few thou beyond the edge of where the 2mm bore will be. After that i will drill the 2mm hole that will meet up with the parting feature and separate the part. At this point the part will be sitting on the drill, which can feed over to a fork, drop down over it, and back up to push the part off of the drill into a container.

    so im wondering if this could possibly leave a cleaner part off line vs just doing the parting op last. When the drill breaks the part free, there will most likely be a ring of material there at the back corner, but the drill will continue to feed through into the bar stock behind the part. I would think the little ring of material left on the part would get sandwiched between the drill and bar stock, effectively removing it and leaving a nice clean part off. Has anyone tried using a drill for parting off like this?

    parting off with a drill?-ball-2-jpg

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    Default Re: parting off with a drill?

    I think you would be best off doing the parting operation last. If you make sure the the 2mm drilling operation drills the hole to it's absolute minimum depth, then there should be no ring of material left on the part.



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    Member Jim Dawson's Avatar
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    Default Re: parting off with a drill?

    My best guess is that the part will pop off of the stock and move down the drill slightly and leave a small burr. Exactly how it reacts will depend on the exact OD of the nub left by the parting tool relative to the drilled hole diameter. I will be very interested to see if I'm correct.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: parting off with a drill?

    Ok, thanks guys. Ill experiment and see what works best. Jim, you might be right. Also i think another possible scenario with the drill parting is the ring of material causing the drill to break since the link ball along with the bur is going to immediately stop spinning on the drill when breaking through, so the drill is just gonna be pushing into that stationary material as the bar stock is rubbing on the back side of it. Kinda like a drill trying to recut a chip. 2mm carbide drill is pretty fragile. We'll see what happens. Looks like i might need to order another tool for holding vbmt style insert to get at all the geometry.



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    Default Re: parting off with a drill?

    Interesting way to do a Setup. would be a fun one to watch run for sure with Vending Machine Fork ejector....luv it. But, why add the extra op.... unless you need the finished sharp edge outward as opposed to inward on the 2mm dia. One more thing maybe to think about is 2mm (.0787) diameter would bend or break with any sideways force.

    my2cents,
    DJ



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    Default Re: parting off with a drill?

    Hmmmmm….personally I wouldn't bother making parts like that, parts that are too hard to make and have problems don't pay well anyway......I learned that a long time ago, I would think you could put your time to better use on another job......time is money after all.....just my opinion.
    Ian.



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    Quote Originally Posted by handlewanker View Post
    Hmmmmm….personally I wouldn't bother making parts like that, parts that are too hard to make and have problems don't pay well anyway......I learned that a long time ago, I would think you could put your time to better use on another job......time is money after all.....just my opinion.
    Ian.
    This isn't really a job shop thing. Its part of a much larger project. A product I designed from the ground up. I could probably outsource a large amount from China for pretty cheap, but I'm still in the prototyping stage which means I need the ability to make them myself and be capableb of making small adjustments. Once im that far and have the tooling needed, I might as well manufacture them myself if it can be done efficiently. Material is about 3 cents a piece and I'm guessing easily under a minute each running continuously, so pretty efficient part to make, but that's assuming I can get it to part off with a minimal burr. If it needs a second op, then yeah, no way I can do them efficiently.



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    Default Re: parting off with a drill?

    I did not catch the type of material. I used run a similar repeat job out of 303 stainless. With a 24 degree angled .030 wide parting tool feeding at .0005 IPR @ 2500 rpm, I could drop them with a very mininimal burr in the bore that you could easily clean up with a cordless drill and a chamfer tool or tumbling in small tacks and media. Even if you did not deburr them you could pass a gauge pin through that was only .001 under hole size.



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    Quote Originally Posted by Dualkit View Post
    I did not catch the type of material. I used run a similar repeat job out of 303 stainless. With a 24 degree angled .030 wide parting tool feeding at .0005 IPR @ 2500 rpm, I could drop them with a very mininimal burr in the bore that you could easily clean up with a cordless drill and a chamfer tool or tumbling in small tacks and media. Even if you did not deburr them you could pass a gauge pin through that was only .001 under hole size.
    303 here as well. The through hole is not crucial, just needs an m2 cap screw to pass through so there's a few thou of room. Also the parts that these bolt onto will have a chamfered tapped hole, so even if a the burr ends up slightly on the face, that's probably ok as well. Sounds like a regular part off might be ok.



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    Default Re: parting off with a drill?

    Quote Originally Posted by QuinnSjoblom View Post
    303 here as well. The through hole is not crucial, just needs an m2 cap screw to pass through so there's a few thou of room. Also the parts that these bolt onto will have a chamfered tapped hole, so even if a the burr ends up slightly on the face, that's probably ok as well. Sounds like a regular part off might be ok.
    The smaller the stock the skinnier the part off tool must be.



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    Quote Originally Posted by Dualkit View Post
    The smaller the stock the skinnier the part off tool must be.
    Yep, I'm gonna get a really tiny one. My Kaiser thinbit holder has been super handy for various odd applications. Thousands of insert options



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    Default Re: parting off with a drill?

    When you're making a prototype the cost factor of a second op would not be something to think about, it's when you then go on to a production mode that the time becomes a critical cost factor, and in this case you're going to source your production parts from a better labour cost source like China etc...…..why are you stressing out on a prototype problem?
    Ian.



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    Default Re: parting off with a drill?

    Quote Originally Posted by QuinnSjoblom View Post
    Yep, I'm gonna get a really tiny one. My Kaiser thinbit holder has been super handy for various odd applications. Thousands of insert options
    I will have to look into that. I have an Iscar holder. I just use Thinbit for skinny grooves. Not sure what machine you have but I have a small overhead gang tooled Swiss that has very limited clearance between tool positions and the gap between the guide bushing and gang assembly. That eliminates a lot of insert tools.



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    Quote Originally Posted by handlewanker View Post
    When you're making a prototype the cost factor of a second op would not be something to think about, it's when you then go on to a production mode that the time becomes a critical cost factor, and in this case you're going to source your production parts from a better labour cost source like China etc...…..why are you stressing out on a prototype problem?
    Ian.
    I don't plan on outsourcing any of my unique parts to China. I'm still in the prototyping stage and part of that is developing the manufacturing methods I'll be using. Only parts that will be outsourced are centerless ground shafting, bearings, timing belts.
    The product is a large performance RC helicopter. These models are commonly crashed and rebuilt so all replacement parts need to be available at all times. 2 of the common things that kill these helicopter brands are QC issues and delays in spare parts availability. If just 1 of the 50 or so unique parts gets delayed at any point, people are grounded.
    My particular model is a higher priced unique design with higher quality materials, also limited quantity which makes the China outsourcing even more of an issue to keep up with because of MOQ and lead times. Manufactured in the US is something else that's pretty much non existent in this hobby and something that many people appreciate. Its an expensive hobby and there's plenty of people willing to pay a premium for something unique. Sounds like a hard sell, but with just the few prototypes I have out there now, there's already people trying to throw money at me just to get in line for one.
    Went through the cam last night and as long as the parting op works out, I can crank these out continuous at 40 seconds each and 3 cents material, so I really don't see a need to put QC and timing in the hands of an overseas manufacturer.



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    Quote Originally Posted by Dualkit View Post
    I will have to look into that. I have an Iscar holder. I just use Thinbit for skinny grooves. Not sure what machine you have but I have a small overhead gang tooled Swiss that has very limited clearance between tool positions and the gap between the guide bushing and gang assembly. That eliminates a lot of insert tools.
    My machine is a completely custom mill turn with no sub spindle, gang tools next to milling head for turning. If i was grabbing with a sub during part off, I'm assuming there would be clearance issues with the thinbit, but since I'm just parting off the main with nothing in front of it, there's plenty of room. Insert edge is about flush with the edge of the thinbit holder, so it can get right up against the collet. I suppose if I was trying to part between 2 spindles with something tiny like this, I would orient the holder with the body of it towards main, grab with the sub, pull the part out and bar with it a ways to gain some clearance for the holder, then part off. If pulling the bar out the distance needed to give just enough stock for next part wasn't enough clearance for the holder, I would pull out further, part off, then push the bar back in before starting next part. Not sure how all that works out in a swiss, I know how crowded they are.



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    Default Re: parting off with a drill?

    Quote Originally Posted by QuinnSjoblom View Post
    The product is a large performance RC helicopter. These models are commonly crashed and rebuilt so all replacement parts need to be available at all times..
    Great business to be in. I had a friend who had a strange unjustified amount of confidence in his abilities yet he pretty much failed at any new task he tried. He had never even tried to use a remote control car or even a boat, yet he said he was going to buy a remote control helicopter. I told him to buy something easier and work his way up. He insisted it would be no problem. I swear that thing never got more than two feet off the ground before he crashed it. There was a hobby shop in town that sold parts for it, my friend who was on disability leave paid that shop daily visits. I think after about crash #50 he tossed that thing in the trash. I blame You Tube for his troubles. Too many people watch highly skilled people with a lot of experience do something and think "That looks easy, I can do that." They don't realize it is the operator's skill that makes it look easy, not that the task is easy.



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    Quote Originally Posted by Dualkit View Post
    Great business to be in. I had a friend who had a strange unjustified amount of confidence in his abilities yet he pretty much failed at any new task he tried. He had never even tried to use a remote control car or even a boat, yet he said he was going to buy a remote control helicopter. I told him to buy something easier and work his way up. He insisted it would be no problem. I swear that thing never got more than two feet off the ground before he crashed it. There was a hobby shop in town that sold parts for it, my friend who was on disability leave paid that shop daily visits. I think after about crash #50 he tossed that thing in the trash. I blame You Tube for his troubles. Too many people watch highly skilled people with a lot of experience do something and think "That looks easy, I can do that." They don't realize it is the operator's skill that makes it look easy, not that the task is easy.
    Ha! Yes it can be a very addictive hobby and a total money pit. Helicopters are by far the most challenging and the story of your friend is pretty much how it goes for all heli pilots, but some persevere and finally get the hang of it. Very rewarding feeling when you can finally fly a helicopter proficiently. I've been doing it about 5 years now and was flying on a team for a while.
    Designing my own model was originally just for fun. I had no intention of producing it, but after a couple of really skilled pro pilots tried it out, they said there was something very special about the way it flies. Very lightweight design with specific weight distribution. So now I'm gonna try manufacturing it in small quantities. Even best case scenario, it will never be a big money maker, but possibly some side income and a way to grow a cnc business. I have a day job with no intention of quitting. Thus us a side project that I really enjoy doing.



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    Default Re: parting off with a drill?

    We also don't have subspindles on our lathes so sometimes the cut off can be tricky especially on small parts.
    We will program the cut off to almost cut it off then turn off the coolant for the last .010 or so and reduce the feed and the part will drop into the parts catcher. Almost always.
    Like others have said, angled sharp thin cut off blade.



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