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IndustryArena Forum > MetalWorking > MetalWork Discussion > How much offset on waterjet cuts to clean up with milling?
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  1. #1
    Join Date
    Aug 2012
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    278

    How much offset on waterjet cuts to clean up with milling?

    How much offset do I need to put in my cad/cam (Fusion 360 btw) for waterjet for rough outlines which I will be doing finish milling on? First time setting up a waterjet project. Will need dowel holes so I suppose it would be worth having them water jet at the same time? How wide is the cut?

  2. #2
    Join Date
    Dec 2013
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    5717

    Re: How much offset on waterjet cuts to clean up with milling?

    The water jet guys will do the kerf offset in their setup. If milling cleanup is required, I would leave about 0.040'' per side or so. The waterjet work I have had done is pretty accurate, normally better than 0.010''.
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
    Join Date
    Aug 2012
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    278

    Re: How much offset on waterjet cuts to clean up with milling?

    Thanks. I can ask the waterjet shop what the kerf is. I was thinking I would provide a dxf file and would like to set the kerf so there are usable parts on both sides. But that may not be how they usually do it. Also wondering about the kerf amount so I can nest parts.

  4. #4
    Join Date
    Dec 2013
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    5717

    Re: How much offset on waterjet cuts to clean up with milling?

    They probably don't want you to nest the parts. They normally like to do that. Ask them about how they want the drawings.
    Jim Dawson
    Sandy, Oregon, USA

  5. #5
    Join Date
    Jul 2018
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    6248

    Re: How much offset on waterjet cuts to clean up with milling?

    Hi Jim27- Usually a manufacturing dwg is done to final size and there will be a note to the shop to add a machining allowance (eg 1mm as per jimD) If they are profiling with a 6mm cutter then 1mm or 3mm does not matter but if the operator has to fiddle around to set the part up then you chew up labour $$$ quick stiks... On thin parts the kerf is nearly non existent. (Thin and thick are relative to the machinery they have) On thick parts it can be wide depending on how you spec the edge finish. If the edge is non functional then leave it as water cut. The re-machining of an edge on a CNC will cost many more $$$ then the water jet cutting. If it requires a machined functional edge then allow a lot of extra material so the set up of the blank is easy and non critical. Often its cheapest just to use the jetting to create rectangular blanks or quite "rough shape blanks" with some fixturing holes vs shaping if the part edge is to be finish machined (costing is based on cutting length of material so a rectangular blank is often cheaper then a shapely part. Plus often the costing is based on the bounding box material not the actual shape so you have paid for more material then you use... Do your manufacturing drawing, specify all functional requirements & tolerances then work through the issues with the cutters and machinists. Often its actually much cheaper to have the machinist do the lot then double handle it eg the machinist I use has billet pre-blanked from the material supplier and this is way cheaper then a water jet contractor can do... . Just depends on what you actually are doing.... Peter

  6. #6
    Join Date
    Aug 2012
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    278

    Re: How much offset on waterjet cuts to clean up with milling?

    Thanks Peter but I will be doing the milling myself. Can't justify the cost of sending out all the work as it's for a hobby business and it's a challenging project I want to do. Was just looking at waterjet to cut some larger plate into manageable sizes. As long as I am doing that it was suggested to do some of the profiles. Have a shop near work that does some side jobs for good price and need to put together enough information on the job to talk to them about it. If it's too much I have access to equipment to bandsaw or plasma cut them although the bandsaw is much more limited on overall size. And I have found a local steel supplier that has a good sized list of drops for a good price that will work for material.

  7. #7
    Join Date
    Jul 2018
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    6248

    Re: How much offset on waterjet cuts to clean up with milling?

    Hi Jim - That makes sense. Talk to your material supplier, they often have billetting facilities using shears or big bandsaws that are cheaper then jetting. Having a shop that does side jobs is a good thing. I used to use a shop that did this and they ran night jobs to keep the machine tenders busy while the big machines ran large moulds 24/7. Was very economical just sometimes they were slow but for 50% off usual cost was worth it. Peter

  8. #8
    Join Date
    Aug 2012
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    278

    Re: How much offset on waterjet cuts to clean up with milling?

    Not familiar with what a "billeting facility" is. I asked about getting the drops cut - they do cutting but said the drops are only available as is - no cuts. They also have a 100 lb minimum but that's not an issue. If the jetting is too expensive I will find another way.

  9. #9
    Join Date
    Jul 2018
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    6248

    Re: How much offset on waterjet cuts to clean up with milling?

    Hi J27 - Some metal suppliers have bandsaw, shears and plasma facilities to provide billet to customers. You spec the size billet you want and they cut it for you. Cheers Peter

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