Pressure foot for machine tool

In combination with a machine tool having a spindle, a cutting tool rotatable by said spindle, a worktable means beneath said cutting tool for supporting a workpiece, said worktable means being movable laterally relative to said cutting tool for causing said cutting tool to produce in said workpiece a cut along a predetermined line which cut upon completion thereof will produce a cutout part from the portion of said workpiece within said line, said cutting tool exerting a relative lateral force on said workpiece such that when said cutting tool has reached a predetermined point on said line and prior to completion of said cut, said cutting tool will cause lateral motion of said portion of said workpiece relative to said worktable means unless said portion is restrained, a device for selectively holding said portion of said workpiece within said cut line comprising

• a body adjacent said spindle and fixed against lateral movement relative to said spindle,
• a workpiece-engaging means carried by said body and movable laterally relative to said body, and
• force means operable when a substantial portion of said cut has been made for forcing said workpiece-engaging means against said portion of said workpiece for clamping said portion of said workpiece against said worktable means and preventing lateral movement of said portion of said workpiece relative to said worktable means,
• whereby upon said relative movement of said worktable means and said cutting tool during the completion of said cut said workpiece-engaging means is stationary relative to said worktable means and moves laterally relative to said body.

In combination with a router having a spindle assembly including a spindle, a collet and a router bit, a worktable beneath said router bit for supporting a workpiece, said worktable being movable laterally relative to said router bit for causing said router bit to produce in said workpiece a cut along a predetermined line, which cut upon completion thereof will produce a cutout part from the portion of said workpiece within said line, said router bit exerting a relative lateral force on said workpiece such that when said router bit has reached a predetermined point on said line and prior to completion of said cut, said router bit will cause lateral motion of said portion of said workpiece relative to said worktable unless said portion is restrained, a device for selectively holding said workpiece comprising

• a housing carried by said spindle assembly,
• said housing defining a chamber around said spindle assembly,
• a slide member in said chamber,
• said slide member being substantially parallel to said worktable and having an opening receiving said router bit,
• a first annular member of relatively high coefficient of friction carried by said slide member,
• said first annular member circumscribing said router bit and having a projecting face adjacent said worktable,
• a second annular member of relatively low coefficient of friction,
• a support member carrying said second annular member so that said second annular member circumscribes said router bit, and has a projecting face adjacent said worktable,
• a first spring means biasing said support member to an outer position where said second annular member projects beyond said first annular member for engaging a workpiece on said worktable,
• a second spring means biasing said slide member to a normal centered position within said chamber,
• lock means holding said slide member in said centered position,
• means for pressing said housing toward said worktable with a first force sufficient to cause said second annular member to bear against such a workpiece and hold said workpiece flat on said table while said router bit produces such a cut in said workpiece,
• means for pressing said housing toward said worktable with a second and larger force sufficient to cause said support member to be pushed inwardly in opposition to said first spring means to a retracted position and to bring said first annular member into engagement with said workpiece around said router bit for holding said workpiece, including the portion thereof within said cut line, against movement relative to said worktable during the final increment of said cut for thereby preventing motion of said cutout portion of said workpiece relative to the remainder of said workpiece, and means for releasing said lock means and permitting said slide member to move within said chamber relative to said housing during said final increment of said cut, said last-mentioned means being operable substantially simultaneously with said means for pressing said housing toward said workpiece with a second and larger force.

The method of producing a cutout part from a workpiece of larger lateral dimension than that of said cutout part comprising the steps of

• positioning said workpiece on a supporting surface,
• holding said workpiece against lateral movement relative to said supporting surface by engaging a first portion of said workpiece,
• engaging a second portion of said workpiece remote from said first portion thereof by a rotating cutting tool,
• producing relative lateral movement between said cutting tool and said workpiece in a predetermined pattern so as to cut said workpiece along a predetermined line,
• such that at a first predetermined position along said line a cutout part remote from said first portion of said workpiece and unrestrained by said engagement of said first portion of said workpiece will be produced from said workpiece,
• and such that at a second predetermined position along said line immediately adjacent said first predetermined position said cutting tool will produce a lateral force on the portion of said workpiece interconnecting said cutout part and the adjacent portions of said workpiece sufficient to cause movement of said cutout part laterally relative to said supporting surface if said cutout part is unrestrained against such movement,
• biasing a means against said workpiece for biasing said workpiece against said supporting surface during said relative lateral movement between said workpiece and said cutting tool while holding said means substantially laterally fixed relative to said cutting tool, and then releasing said means so that said means is laterally movable relative to said cutting tool,
• and engaging said cutout part by said means adjacent said cutting tool before said cutting tool reaches said second predetermined position and forcing said cutout part against said supporting surface such that said cutout part is held against movement relative to said supporting surface as said cutting tool reaches said second and said first predetermined positions.

The method of producing a cutout part from a workpiece of larger lateral dimension than that of said cutout part comprising the steps of

• providing a rotatable cutting tool and a worktable adjacent said cutting tool,
• positioning a workpiece on said worktable,
• engaging said workpiece at a first location and restraining said workpiece at said first location against lateral movement thereof relative to said worktable, rotating said cutting tool and simultaneously causing relative movement of said cutting tool and said worktable such that said cutting tool engages said workpiece and produces a cut therein along a predetermined line remote from said first location such that upon completion of said cut a cutout part will be produced which is unrestrained by said engaging of said workpiece at said first location,
• engaging said workpiece adjacent said cutting tool by a means and pressing said workpiece against said worktable while holding said means substantially fixed laterally relative to said cutting tool so that said means slides over said workpiece during said relative movement of said cutting tool and said worktable from the beginning of said cut until said cut is nearly completed,
• then releasing said means so that said means is laterally movable relative to said cutting tool when said cut is nearly complete and throughout the last increment thereof and causing said means to engage said cutout part and hold the same laterally fixed relative to said worktable during said last increment of said cut, and then releasing said cutout part for removal from said worktable.