5C COLLET INDEXING FIXTURE
REVIEW AND USE
Although I own a very good machining vice, "V" blocks and just finished designing and building a fine custom horizontal, non geared simple rotary table, I have always wanted some type of fixture that would allow round, hex and square stock to be held at right angles to the milling spindle. The rotary table can accept chucks, small collets ( Taig ), faceplates as well as holding the work so it is facing the spindle. I couldn't afford a vertical rotary table at the present time, which is why I decided to build a simple horizontal table myself. I suppose I could have built the table as a vertical / horizontal unit but I didn't so that's water under the bridge. Another would take a couple of months of new work so the only immediate solution was to buy a 5C fixture of some sort. Of the versions available, I saw units costing several hundreds of dollars for USA made to as low as twenty eight dollars. I decided on a unit offered by Enco as they offered it on sale at the lowest cost of any other company.
Before one goes ahead with the purchase of a collet fixture, you most own or at least consider the purchase of a few collets in the sizes you think you will need the most. As with anything having to do with tooling now a days, the price and quality range seems to run proportionally. You could purchase collets that will set you back $30 a pop but you can be assured that they are as free of run out as possible and on the other end of the equation, you can pay as little as $5. each for Chinese made collets which may not be as well finished and could possibly impart a few thousands run out to your work pieces. It depends on what is the minimum quality you demand. Sets of collets are available at a substantial savings to individually purchased pieces so I decided on a set of fifteen.
Anyway, back to the fixture. The unit arrived in 4 days and I was very impressed with it as it was very well finished considering it cost only $31 plus shipping. All of the ground surfaces were very smooth, flat, and I could not discern any extraneous scratches other than those imparted during the grinding process. The main housing consists of a 12 pound cylindrical casting through which the rotating, ground 5C spindle is installed. It is finely ground and seems very accurate. The base of the unit is also accurately ground and I could not detect any "daylight" between the base and the edge of my Starret square. When I checked the squareness of the front of the spindle, it was a perfect right angle to the milling table surface, again to level at which I'm able to measure. It features a click stop, lever actuated, 24 stop indexing ring that is rotated within a very heavy split locking ring. To use the unit, you clamp and align it on your milling table and insert the proper size collet into the tapered spindle. A collet closing ring is screwed against the threaded end of the collet as it protrudes out the rear of the spindle. The proper sized work piece is inserted into the collet and the ring is turned to tighten the collet around the work. Now you can begin machining the work and if required, it can be rotated to any of 24 equally spaced positions. As you know, 5C collets can be obtained with round, hex, as well as square bores and can hold work up to 1-1/8" in diameter and larger with special step collets. Custom made square, hex, or octagonally faceted pieces can be easily milled by just indexing every six, four or three holes of the 24 hole indexing ring.. Another similar 5C collet fixture is also offered by Enco which although similar, it features a 36 hole index plate plus a 10 degree vernier to allow a total of 360 single degree divisions. The spindle also slides in and out of the housing to adjust the lateral position of the workpiece even after the unit has been clamped down.This tool would be perfect for cutting spur gears on either the drill or the milling machine. You would need to make mandrels for each diameter of gear bore needed, with the mandrel held on the proper diameter collet. The tail end of the mandrel is turned to a perfect sliding fit through the gear blank bore, stopping about mid way with a square shoulder. The remainder is threaded so a nut can lock the blank tight against the shoulder. The opposite end is center drilled and a simple center point can be built to support that end of the mandrel while the gear blank is indexed and the teeth milled. These things are so cheap to buy that you could just get yourself a second unit to hold a 60 degree ground point acting as a tail stock for your mandrel. The best thing about this fixture is the $31 price tag. I'm glad l did not let this one pass by.