WO1984004896A1

WO1984004896A1 - Coldworking method and lubrication system for coldworking of holes

Info

Publication number: WO1984004896A1
Application number: PCT/US1983/000910
Authority: WO
Inventors: Louis Zeno Micai; Val Kent Starkey
Original assignee: Boeing Co
Priority date: 1983-06-09
Filing date: 1983-06-09
Publication date: 1984-12-20
Also published as: EP0146546A1; IT8412509A0; IT1221435B

Abstract

A lubricant forced through a hollow needle (42) saturates an encircling felt pad (40), a hole through parts to be joined is uniformly roughened (54) throughout its length to impart about 10 to about 175 micro inches of roughness to the surface. The roughened surface has lubricant applied by the activated pad and a mandrel (60) pulled through to cold work the treated hole.

Description

COLDWORKING METHOD AND LUBRICATION SYSTEM FOR COLDWORKING OF HOLES

BACKGROUND OF THE INVENTION

Cold orking is a process which, when applied to holes, increases fatigue life of the resultant structure when subjected to stress. One of the better known methods of coldworking holes is set out in Patent No. 3,566,662. In that patent a pre-lubricated disposable sleeve is placed on a mandrel, the sleeve positioned in the hole and the mandrel pulled through to coldwork the hole. The sleeve is discarded after use. Numerous attempts have been made to cold work holes without the use of a sleeve, but those attempts have not been successful. It was found that holes can be coldworked without using a sleeve.

_ OMPI SUMMARY OF THE INVENTION

Roughness is imparted to the surface of a hole, a lubricant applied to the roughened surface, and a mandrel drawn through the roughened lubricated hole to enlarge and coldwork the hole. The lubricant is dispensed through a hollow needle onto an encircling felt pad and the pad inserted into the hole to apply the lubricant.

DESCRIPTION OF THE DRAWINGS

Figure 1 shows a side elevational view in cross- section of the lubricant apparatus of this invention applying lubricant to a hole to be cold worked.

Figure 2 shows a side elevational view in cross- section of a mandrel with puller mounted for coldworking a hole prepared according to this invention.

Figure 3 shows a fragmented side elevational cross- sectional view showing a hole in parts to be joined.

Figure 4 shows a means of roughening the hole in the parts of Figure 3.

DETAILED DESCRIPTION

Lubricant dispensing apparatus 10, has a housing 12, and a spout 14. A piston 16, is shown for being pressed against the lubricant located inside the housing at 18, for dispensing that lubricant through the spout. The method of actuating the piston is not shown as it may be actuated by any known means such as, but not limited to, trigger operated ratchet or pneumatic means. The spout has a radially inward extending projection 20 with an axial opening 22, and internal threads at 24, A hollow, adapter 26 is threaded at 28, to mesh with the threads in the spout and press a gasket 30, against the projec¬ tion. The adapter is threaded on the opposite end at 32, to mate with the threads 34, on a sleeve 36 for securing a shaped inner seal 38, A felt pad 40, having an axially located hollow needle 42, is secured to the end of the sleeve by threads 44, and a nut 46. The needle extends, from near the outer end of the felt pad, into and becomes sealingly joined inside the inner seal. Other types of lubricant dispensers may be used to dispense the lubricant into the felt pad. The lubricant dispenser 10 is used to lubricate holes 48 in parts 50 and 52. This application of lubri¬ cant is in preparation for cold working of the hole to obtain greatly enhanced fatigue life. The preferred lubricant is applied once the surface 54, of the hole 48, has been properly roughened.

In order to successfully cold work a hole the roughened hole should be relatively uniform through the length of the hole, and have from about 10 to about 175 micro inches of roughness with about 50 to 150 micro inches of roughness preferred. These roughness figures cover the range required to coldwork various size holes from small size holes, requiring a low degree of roughness, up through large size holes, which require a high degree of roughness. The degree of roughness may be obtained in many ways with a preferred means being as is shown in Figure 4. In that Figure a wire brush 56, sized to an interference fit in hole 48, is mounted to e drive unit 58, and the brush is driven at a low speed rota¬ tion. This roughens the surface 54 as is best s.. n in Figures 1, 2 and 4. Small size holes, which requi. a a low degree of roughness, in some cases may obtain the required degree of roughness by the type and method of drilling and not require post drilling treatment, as long as the roughness obtained falls within the range shown, In operation the surface 54, of hole 48, is first properly roughened. Piston 16 of lubricating dispenser 10 is then depressed to force lubricant through hollow needle 42 and saturate the shaped felt pad 40. The pad is inserted into the hole and removed to deposit lubri- cant along the surface of the hole, A tapered mandrel 60, preferably sized to impart about a 3 to 4 percent increase to tile hole size, is then pulled through by puller unit 62, to cold work the hole.

OMPI

Claims

WE CLAIM:

1. A method of coldworking holes, with steps com¬ prising: roughening a hole for coldworking by imparting from about 10 to about 175 micro inches of roughness, applying a lubricant to the hole, and coldworking by drawing a mandrel through the hole.

2. A method of coldworking holes as in Claim 1 wherein the step of roughening the hole further comprises utilizing a rotary brush of metal wires.

3. A method of coldworking the holes as in Claim 2 further comprising utilizing a long-chain alcohol as the lubricant.

4. A method of coldworking the holes as in Claim 3 wherein the method of applying the lubricant comprises: dispensing the lubricant through a hollow needle and into a felt pad, and pressing the felt pad against the side of the hole.

5. A method of coldworking holes, with steps com¬ prising: imparting about 50 to 150 micro inches of roughness to a surface of a hole, coating the surface of the hole with a long-chain alcohol lubricant, and moving a mandrel through for expanding and thereby coldworking the hole.

6. A method of coldworking holes as in Claim 5 further comprising sizing the mandrel for imparting a

3 to 4 percent diameter increase to the coldworked hole.

7. A method of coldworking holes as in Claim 5 wherein coating the surface of the hole with lubricant comprises: dispensing lubricant through a hollow needle into a surrounding felt pad, and pressing the lubricated pad against the side of the hole for trans¬ ferring the lubricant to the surface of the hole,

8, An apparatus for applying lubricant to a hole to be coldworked comprising; a lubricant dispenser having a spout, a hollow needle to extend from the end of the spout, a felt pad around the needle and extending beyond the tip, a lubricant inside the dispenser, and means for moving the lubricant out the end of the needle and onto the pad.

9. An apparatus for applying lubricant to a hole to be coldworked as in Claim 8 wherein the lubricant used is a long-chain alcohol,

10. An apparatus for applying lubricant to a hole to be coldworked as in Claim 8 wherein the felt pad is sized for an interference fit in the hole to be lubricated.