Posted by: chikky ® 04/27/2006, 02:05:25 Author Profile eMail author Edit

We manufacture alu sand cast parts in A356 alloy. We machine these parts with standard NPSM and NPT (1/2" thru 2") HSS taps. WE have regular problem of material built-up on the taps and the poor finish of the threads. I need help in finding the solution to resolve these issues. Can different tap other than the standard ones can help? Or using some specific cutting oil??

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Re: Aluminum machining
Re: Aluminum machining -- chikky	Post Reply	Top of thread	Forum

Posted by: rjbeng ® 04/27/2006, 09:27:16 Author Profile eMail author Edit

There are a couple of ways to address this problem. 1) Use coated taps to reduce the galling. See article in Cutting Tool Engineering https://www.ctemag.com/pdf/0301-slipperywhenblue.pdf. There are other coatings that address this same issue, you may want to test drive different types to get the best results. 2) Thread mill in lieu of tapping. This will dramatically reduce the friction and spinal loading associated with tapping. Your threads will be cleaner and more consistent. This will also remove any material damage caused by galling.

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Re: Re: Aluminum machining
Re: Re: Aluminum machining -- rjbeng	Post Reply	Top of thread	Forum

Posted by: randykimball ® 04/27/2006, 15:10:35 Author Profile eMail author Edit

We used a product called TapMagic for aluminum.. I'm sure there are several brands out there that are about the same thing. AND.. on sand castings, I remember good results using Crisco mixed with kerosine, brushed on with an acid brush. Use just enough kersoine to make the Crisco turn into a gravy when mixed. If you purchase the acid brushes by the peck (144) you can get them pennies each. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

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