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Warning: This post contains metalworking content - Deburring "Finished" Parts

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  • Warning: This post contains metalworking content - Deburring "Finished" Parts

    I make a lot of parts that are generally a rectangular solid. Typically they have a lot of details machined into one surface making it a mold. About the most efficient way to finish and deburr that surface is either to go over it gently with a very fine grit sanding block, or to make a minimal (or zero) surfacing pass to cut off or fold over the burrs. Both work pretty well.

    Surfacing depending on the part and the machine the part is on can take upto a few minutes.

    Sanding runs the risk of some minor edge erosion of the cavities and dulling the flat machined face, but is very fast. Usually far less than a minute. It does require hands on time though.

    I prefer the look of a dull sanded surface, and it flattens slightly any irregularity from tool marks, but some customers judge that as a negative. They like that bright shiny look even if tool marks are visible. Polishing is not an option in most cases due to both time, and possible additional edge erosion.

    I've gone to a surfaced finish rather than a sanded one, because its easier than explaining to people the difference and I don't have to do more than swap the tool. While it is often slower (on that primary face) than sanding I do not have to stand there sanding it. The part effectively gets surfaced twice. Once at the beginning at normal speed, feed, DOC, WOC, to remove enough material to get a good reasonably flat face, and a second time very fast with wide WOC and almost zero DOC to remove burrs from features.

    You can pick through that and look for something to bash if you like, but I've spent a lot of time and have a fair amount of experience that lead me to that process.

    At this point I have a part that is technically functional, but it still has upto 10 primary edges with what can be much more serious burrs depending conditions. Four of those might be able to be debured on machine with a chamfer tool, but as you may be aware unless the tool is brand new measuring its tool height in a tool holder can be tricky. It also requires that each piece of stock be precisely pre-sized in both X and Y before being loaded in the machine. That adds another step that is not necessary for the part to be functional. Typically unless the mold is being used in an automated machine and needs to have parallel faces I do not even machine 3 of the 6 faces on the part. Time saved is time saved. Two of the faces often only need to be machined to remove the obnoxiously ugly saw cut end and allow for re-indexing if multiple setups are required or minor recuts need to be done.

    Anyway, I have upto 10 edges that still need to be deburred. Even if I did chamfer that top I would still have 6. If both ends of the part happen to hang out of the vise or fixture it might be possible to chamfer 4 more of those with an end mill. If those ends hang out an under cut tool, back chamfer tool or even a single point thread milling tool could cut a chamfer on the two remaining edges.

    AGAIN: You can pick through that and look for something to bash if you like, but I've spent a lot of time thinking about all of these things and have my reasons for why that is not always efficient. In fact its rarely efficient. I routinely cut parts that are smaller than the vise width when I use a vise, but more often I am using fixture plates to maximize the part density on the machine. This saves crazy amounts of time to produce parts. Sure I could make more complex fixture plates with clearances for all of those things, but then part indexing time and part density starts to suffer. If I can run 2 parts instead of one I halved the tool changes. If I can run 4 parts instead of 1 I have 1/4 of the number of tool changes. That is a crazy amount of time savings on a small production run. No I do not have big fancy high end production machines with automatic tool changers and chip to chip times measured in seconds, if I did machine time efficiency might be more important and seconds be more important as well in order to pay for the machines.

    Anyway, all of that has two purposes. The primary one is to provide background and explanation for my quandary about removing the burrs from those last ten edges when all else is done. The other absolutely not intended and not wanted purpose was to give nitpickers and judgmentalists something to peruse looking for a minor part to attack so they can feel better about themselves.

    What I do now is one of three things depending on the part and how I feel at the moment. I'll knock the burrs off those ten edges with a sanding block or with a file. I'll walk back and hit the edges on the little 1x30 belt grinder. I'll worry the edges away with a stainless steel wire bush on the bench grinder. File tends to require coarse and then fine faces to be used at two angles. Sanding block tends to leave the nicest most consistent edge. Belt grinder is by far the fastest. Wire wheel is the slowest and often does not remove the burr. It just rounds it over unless I go back and forth from both sides of the edge. A harder wire wheel might do a better job, but it also leaves open the potential for more damage.

    Some of the things I am exploring are:

    A carbide tool chamfering machine that basically runs like a router table. I think dialing it in to remove just enough material to debur (yes I know it may leave its own much smaller burr) on most of the sides of the nearly finished part it will be tricky, but once adjusted will work for many parts. Probably longer than the life of a belt on the belt grinder. Then it can probably be adjusted to use another section of the cutter edge. I think it would work adequately on all of the longer edges, but on many parts it would still leave 4 short edges that may not be safe to debur on this machine. Maybe a moving t-slot T-tool/gage and a clamp could make this safer.

    The other is a better quality belt grinder and surface conditioning belts. The thing is I can't run surface conditioning belts on my current belt grinder. It doesn't have the power. I have never used a surface conditioning belt so I don't know if its worth the time to build or cost to buy a machine that will run them.

    I could build either machine in a day. My ego says a few hours, but my experience tells me a long day. Maybe two. Or I could buy something that may or may not address the the potential issues I already see with either.

    The chamfering machine might be marginally better if for every part that really is just a rectangular solid, but I do make a fair number that have boss features along one end for making a hinge. There is no way I know of to use a chamfering machine to clean up the burrs on those edges.

    Time is the most valuable and most finite commodity in my shop. If I spend some time today working on this I want to make sure it will save me a little time everyday hereafter.

    For many who would sincerely try to help I apologize for my writing style. I hope to prevent or atleast reduce those comments that would force me to go back and defend or justify processes I have already decided upon based on experience and what I believe to be good reason. If you are one of those who would choose anyway to attack or pick at one of those things instead of focusing on the core quandary, please take the time to explain in detail and defend your choice as well as including a superior solution along with your explanation and defense of it as opposed to other solutions.

    Yes, I am aware there are still dawn of time explanations necessary to "defend" some of my premise process and conclusions. "How can you machine the saw cut ends off if they do not stick out of the vise?" is one such. I have a solution for that which does not leave fully open the bottom and corners for alternative chamfering and burr removal. One part (or class of part) I make routinely has blanks roughed out nine at a time on one machine, and finished four at a time on either of two other machines. All are done in fixture plates to maximize part density. Time saved is dramatic over using a single piece in a vise or even one each in two vises.

    Yes I have a carbide swivel type deburring tool. (Three of them actually. Each with a different blade for different applications.)

    Yes, the methods I am already using do work. Maybe not as well/quickly/easily as I would like but they work.
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.