Dale,

We have been using these taps for years. You should check in Machinerys Handbook or with the manufacturer for the tap drill size. I always ask for a tap with a air/lube relief groove. Hand tapping can be tough with the roll tap as these are called.

Bill Jepson 


-----Original Message-----
From: Dale Rogers <dale.r@cox.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Wed, 22 Aug 2007 12:09 pm
Subject: [FlyRotary] Re: Tap 'em holes was [FlyRotary] Throttle Body Nut Ideas

This machinist says:  "Why would you want to *do* that?

Strictly speaking, cut threads - what you get from conventional taps -
are weaker than swaged threads, such as the rolled threads one usually
finds on AN class fastener. 

So ... if one wants threads in alumin(i)um, one needs a tool that
displaces the metal, rather than cutting it.  Eureka! Such a tool does
exist - the "fluteless thread forming tap"   E.g.:

http://www.shoprutlandtool.com/webapp/wcs/stores/servlet/ProductDisplay;jsessionid=0000aUcDvp-FmIJrmRkZmUaWieP:-1?productId=27670&langId=-1&storeId=10001&catalogId=10001&parent_category_rn=

Rutland Tool # 21238428

Good hunting,
Dale R.
COZY MkIV #1254



Ernest Christley wrote:

Ed Anderson wrote:

Scott,  I think the best answer is to simply tap those bolt holes for the thread size of your bolts.  This does a number of things.

I've been told by a machinist that tapped holes in aluminum are weak.  Any truth to that?

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