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Zero off Table or top of Material ?
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10106&t=47301
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Author:  Vinny [ Fri Feb 19, 2016 9:23 am ]
Post subject:  Zero off Table or top of Material ?

Hello everyone, I'm curious to know whether you zero your Z axis to the table or top of the material you're milling and why? I've been setting my cam program and machine to the top of the material from the start, but I believe that I can benefit from changing that to the table spoil board. I've skimmed into my table because of inconsistent sized boards that cause my Mill to take 20 thou's off the spoil bd. If I set my z to the table top using a touch probe and script , then add an additional operation to face the top of the material before milling it I believe I would have more consistent results. I have a Z touch probe coming in the mail so I'm glad to get that added to the mill. I'm using Mach3 and Vetric's Cut2D and Cut3d. I greatly appreciate all advice, Vince

Author:  Chris Pile [ Fri Feb 19, 2016 9:37 am ]
Post subject:  Re: Zero off Table or top of Material ?

As a long time machinist and programmer, I can tell you definitively - depends on the job. There is no hard and fast rule.

Author:  Don Williams [ Fri Feb 19, 2016 1:29 pm ]
Post subject:  Re: Zero off Table or top of Material ?

Chris is correct.
Examples:
1. When surfacing a part to a specific thickness, or when machining a fretboard, you should definitely use the top of your fixture.
2. If you're cutting a pocket in something to a specific depth, then you need to go from the top of the part for more consistent results.

Author:  Allen McFarlen [ Fri Feb 19, 2016 3:26 pm ]
Post subject:  Re: Zero off Table or top of Material ?

What Chis and Don said.

You just have to think about what you are trying to accomplish and where the critical dimension / tolerance is that you are striving to achieve.

Author:  Sheldon Dingwall [ Sat Feb 20, 2016 1:34 pm ]
Post subject:  Re: Zero off Table or top of Material ?

+3 when we machine pickguards we zero off the part for the screw holes and countersinks and then zero off the fixture to machine the edge chamfer

Author:  Chris Pile [ Sat Feb 20, 2016 2:42 pm ]
Post subject:  Re: Zero off Table or top of Material ?

Quote:
+3 when we machine pickguards we zero off the part for the screw holes and countersinks and then zero off the fixture to machine the edge chamfer


PERFECT EXAMPLE.

Author:  demonx [ Sun Feb 21, 2016 12:52 am ]
Post subject:  Re: Zero off Table or top of Material ?

Every job I do is zero'd different, so I'd tend to agree with the previous posts.

Author:  Vinny [ Wed Mar 09, 2016 9:34 pm ]
Post subject:  Re: Zero off Table or top of Material ?

Thanks to everyone for your replies, I can see why you would do it each way with the examples you mentioned. Very very helpful. regards, Vinny

Author:  Stuart Gort [ Thu Mar 10, 2016 12:39 pm ]
Post subject:  Re: Zero off Table or top of Material ?

It's really just a matter of determining what matters and what doesn't matter with regard to precision. Your machine doesn't care where its zeroed at...it's your preference.

I usually (not always) use the bottom of the tooling jig or jaws for everything because, with a tool changer, I can set up the whole job so I just run the first first op, flip the part over, and run the second op, and so on until it's done.

Author:  Bobc [ Sat Mar 12, 2016 7:36 am ]
Post subject:  Re: Zero off Table or top of Material ?

I zero off the spoil board. I don't have to change it so zero is always the same unless I have to re-surface the spoil board. Forgetting to set a new 0 when changing jobs can lead to some scary tool plunges. Ask me how I know. oops_sign

Author:  Ken McKay [ Tue Mar 15, 2016 1:44 am ]
Post subject:  Re: Zero off Table or top of Material ?

I like to zero on top of the part when I can. But when I need to thickness the part it has to be the spoilboard. The reason I like the top of the part is because then I can "go to Zero" where I have marked so I can see if I have missed steps or something has gone wrong. If you go to zero and your z is below the part it is a disaster with the bit routing through your part.

Author:  Ken McKay [ Tue Mar 15, 2016 1:57 am ]
Post subject:  Re: Zero off Table or top of Material ?

oops dp
[uncle]

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