Cutting Tolerances

SomethingMetal · Post by **SomethingMetal** » Sun Sep 09, 2012 8:28 pm

What kind of tolerances are you guys comfortable cutting? +- .015" or what? I cut some pieces for a company that did not supply me with tolerances and I assumed being what it was, it really wasn't that critical. I am a machinist my trade and I am use to dealing with tight tolerances but they are asking for a +- .005" and some only a +.005" on some aluminum switch panels. My sample pieces I gave to them were all within a .015" tolerance and most of them being within .008". I thought this was extremely good considering its not being but with an CNC milling machine. This pieces are also being cut from .090" 3000 series aluminum. What do you guys think? We are either going to come to an agreement on some tolerances or I am going to send back their deposit check minus parts and labor thus far. Maybe I am crazy but a tolerance like that could get me into alot of trouble and alot of money out of my pocket.

Largemouthlou · Post by **Largemouthlou** » Mon Sep 10, 2012 7:36 am

They are looking for water jet or lazer quality!! I don't even think HD plasma can get that close..

SomethingMetal · Post by **SomethingMetal** » Mon Sep 10, 2012 9:27 am

that is what I was thinking. +-.005" is just silly considering it is just a switch panel for rocker switches.

Post by **jimcolt** » Mon Sep 10, 2012 9:41 am

The tolerances are too tight for production with an air plasma. You could likely pull it off with a high definition plasma....but I would say it is better suited for a laser (although the .005" is tight for that as well) or water jet. Probably would be best done on a cnc mill.

Many engineers today spec tolerances that are unneccesary...and end up making the product more costly. I have worked with a few companies to change specs that were too tight. One example was a company that was bidding on a military contract for spare tire mountin brackets for a military vehicle. It was made from 1/4" steel...and had about 10 holes that were to make the part lighter in weight...no other function. The holes had a plus or minus .001" tolerance.....we got it changed to plus or minus .015 (took a few months)...and it became a plasma part with much lower cost!

Jim Colt

SomethingMetal wrote:What kind of tolerances are you guys comfortable cutting? +- .015" or what? I cut some pieces for a company that did not supply me with tolerances and I assumed being what it was, it really wasn't that critical. I am a machinist my trade and I am use to dealing with tight tolerances but they are asking for a +- .005" and some only a +.005" on some aluminum switch panels. My sample pieces I gave to them were all within a .015" tolerance and most of them being within .008". I thought this was extremely good considering its not being but with an CNC milling machine. This pieces are also being cut from .090" 3000 series aluminum. What do you guys think? We are either going to come to an agreement on some tolerances or I am going to send back their deposit check minus parts and labor thus far. Maybe I am crazy but a tolerance like that could get me into alot of trouble and alot of money out of my pocket.

sodfarmer · Post by **sodfarmer** » Mon Sep 10, 2012 6:19 pm

I have a story like Jim's. I was managing a shop with a laser and a guy comes in wanting to make header flanges. They were being cut out of 3/8" thick steel. He speced the bolt holes @.500. I recommended going with a .525 hole. He said stay with the .500 holes, guess what he had us make them the next time, .525. Just my 2 cents.

SomethingMetal · Post by **SomethingMetal** » Mon Sep 10, 2012 9:09 pm

Had a nice talk with the guy I have been dealing with within this company and his exact response was send me the rest of the 120 parts because the sample of 5 worked great. Told me he would change the tolerance spec on the prints to better suit what I am capable of doing. The quality guy was going directly on what was on the print and it was +-.005". Man I thought I was going to have to get ugly because he told me the sample 5 were good to and go ahead and cut the remaining 120 and they were already at the powder coater.

All is good again........ until next time

brandon350 · Post by **brandon350** » Wed Sep 12, 2012 7:32 pm

I would recommend +/- .030 on plasma cut parts, the shop I work at we have both laser and plasma i spec all laser parts at +/- .010 and all plasma cut parts at .030 (high definition). What you have to think about is a production setting, sure your machine may be able to hold a tighter tolerance but you got to expect consumable wear different types of material etc. You are better off having a slightly bigger tolerance rather than beating your head against a wall and going through a boat load of consumables to hold a tight tolerance. Just my two cents

SomethingMetal · Post by **SomethingMetal** » Wed Sep 12, 2012 9:47 pm

Thanks Brandon I will keep that in mind.

Cutting Tolerances

Cutting Tolerances

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