GB2338441A

GB2338441A - Mandrel

Info

Publication number: GB2338441A
Application number: GB9813010A
Authority: GB
Inventors: Stuart Hyson
Original assignee: TEDDINGTON CENTRELESS GRINDING
Current assignee: TEDDINGTON CENTRELESS GRINDING
Priority date: 1998-06-16
Filing date: 1998-06-16
Publication date: 1999-12-22
Also published as: DE19927510A1; GB9813010D0

Abstract

A mandrel for use in adjusting the interior diameter of metal tube passed along the mandrel, comprising an elongate shaft having attached lobe elements 5 made of hard enduring material such as tungsten carbide, preferably bonded to the shaft by adhesive.

Description

Agent's Ref: P02074GB 2338441 MANDREL The invention relates to a mandrel,

and more particularly a mandrel for use in the manufacture of fine tolerance tubing i.e. having a wall thickness within narrow limits.

It is known to pull metal tubing over a mandrel in order to dimension its internal diameter. One mandrel comprises a shank made from an elongate steel shaft with a U-shaped bend at one end, the other end being welded to a first lobe section. The first lobe section is made from a single piece of steel comprising a first cylindrical portion, a barrel-shaped portion known in the art as a lobe and a second cylindrical portion. One end of the first lobe section is welded to a second lobe section, comprising the same three parts as the first lobe section, the only difference being that the maximum circumference of the second lobe is slightly larger than that of the first lobe. In use, metal tubing is drawn over the shank and then the first and second lobes respectively. The first lobe serves to enlarge the internal diameter of the tube slightly less than that required in preparation for final dimensioning by the second lobe. The lobes of such mandrels are subject to considerable stress, and while their useful life can be extended by hard chrome plating, the entire mandrel will normally require replacement after about 10,000 hours of use.

It is an object of this invention to provide a mandrel having an improved life.

2 In one aspect the invention provides a mandrel for use in adjusting the interior diameter of metal tubing passed along the mandrel, comprising an elongate shaft having a separate lobe element which is made of a hard enduring material and which is mounted on and secured to the shaft.

Preferably the lobe element is present between the ends of the shaft and comprises a body having a through bore, which receives extensions of the shaft from opposite ends of the bore, the extensions being secured therein by set adhesive. The parts may however by engaged in any other suitable way.

Claims

Other features of the invention are set out in the defendant Claims.

Preferably, the shaft is made of silver steel and the lobe is made of tungsten carbide or M2 HSS hardened to 62 R.C.

The lobe may be plated with hard chrome, nickelIPTFIE or titanium nitride.

In order that the invention may be well understood one embodiment will now be described by way of reference only to the accompanying diagrammatic drawings in which:

Figure 1 is a longitudinal section of a mandrel of the invention having two lobe elements, and Figure 2 is an enlarged section through one lobe element.

3 The mandrel of Figure 1 comprises an elongate metal shaft 1, having a Ushaped bend 2 at one end. The other end of shaft 1 is welded at joint 3 to one flat end of a first elongate shaft 4 having at its other end a smaller diameter coaxial extension 4b. A first lobe element 5 comprises a barrel shaped member 5a having a coaxial through bore 5b. The first lobe 5 is connected to the first shaft, the extension 4b being received in the bore 5b to slightly less than half way along the bore 5b and being bonded to it by adhesive 6. The end faces of the element and the shaft are flat and are abutted against each other. A spacer shaft 7 comprises a central portion 7a having smaller diameter and extensions 7b and 7c. End extension 7b is received and bonded in the bore 5b by an adhesive 6 from the opposite side.

The mandrel has a second lobe element 8 and second cylindrical shaft 10 connected to it in the same way as the first shaft 4 and first olive 5, the only difference in these members being that the maximum circumference of the second olive 8 is marginally greater than that of the first olive 5. The second olive 8 is attached to end 7c of the spacer shaft 7 using an arrangement identical to that to bond connecting end 7b to the first olive 5.

The first and second olives can be made from various enduring materials such as tungsten carbide and M2 HSS hardened to 62 R.C. ^are plated with materials such ad hard chrome, nickelIPTFE or titanium nitride. The shaft 1, shafts 4 and 10 and spacer %Nft 7 can be made from silver steel and an 1 ', 4 adhesive such as AXIOM 100 SA Tm is used to bond the elements to the shafts.

In use, metal tubing is first drawn over the shank and then the first and second lobes successively. The first lobe serves- to enlarge the internal diameter of the tube slightly in preparation for final dimensioning by the secondlobe.

The mandrel is of conventional appearance and hoge long useful Nfe.

CLAIMS A mandrel for use in adjusting the interior diameter of metal tubing passed along the mandrel, comprising an elongate shaft having a separate lobe element which is made of a hard enduring material and which is mounted on and secured to the shaft.
2.

A mandrel according to Claim 1, wherein the lobe element is present between the ends of the shaft and comprises a body having a through bore, which receives extensions of the shaft from opposite ends of the bore, the extensions being secured therein by set adhesive.
3. A mandrel according to Claim 2, where in the body has straight end faces which abut the opposite faces of the shafts.
4. A mandrel according to any preceding Claim including two lobe elements on a common axis, the elements being bridged by an intermediate shaft length having two end extensions.
5. A mandrel according to any preceding Claim, where an acrylic adhesive is used to secure the lobe element and shaft.

6. A mandrel according to any preceding Claim wherein the shaft is made of silver steel.
6
7. A mandrel according to any preceding Claim wherein the lobe is made from hardened steel or tungsten carbide.
8. A mandrel according to any preceding Claim, wherein the lobe has a plated exterior surface.
9. A method of assembling or replacing a mandrel according to any of Claims 1 to 8, comprising forming a lobe element having shaft engaging means and optionally hardening the exterior surface thereof, and then mounting and securing the lobe element to the shaft between the ends of the shaft.
10. A method of manufacturing pipes with a precisely controlled interior diameter comprising drawing g length of pipe of slightly smaller diameter than required over a mi having an elongate shaft and a separate lobe element e of hard endud% -material; the mandrel being secured to the shaft.

LSINSWM.C.98