Collet inserts for square stock

[mklotz]

Soon after getting a lathe I built a 5C collet chuck for it. Early on, I bought only round collets, planning on adding other types as needed. Before I could get a set of square collets, an engine I was building required turning on some small square stock.

So I made these two split collets to hold 3/16 and 1/4" stock in a 1/2" round 5C collet.

While these look pretty simple, care is required in making them. There are undoubtedly numerous ways to make them but I'll describe what I did.

1/2" stock was held in a round collet in a square collet block in the mill vise and exactly half the diameter was milled away for a length a bit more than twice the finished collet length. The collet block was then held in a V-block so the milled section was 45 degrees to the horizontal. A conventional end mill then milled out the V-groove in the collets. The resulting piece was then split into two collets and the ends finished.

As can be seen from the picture, the two halves fit together nicely into a cylinder with a neatly centered square hole in the middle.

Bonus hint:

This is also a nice way to produce a square hole for a wrench or similar. Simply make the collets as described and silver braze the two pieces together.

[ncollar]

Marv
Very nice, I always like your idea and the best way to proceed.
Thank you.
Nelson

[old_toolmaker]

mklotz,

That is a very neat idea and there are times when one needs just such an adapter and they can be made quite accurately as well.

[DIYer]

Thanks mklotz! We've added your Collet Inserts for Square Stock to our Machining category,
as well as to your builder page: mklotz's Homemade Tools. Your receipt:

Collet Inserts for Square Stock by mklotz

tags: collet

[Toolmaker51]

So I made these two split collets to hold 3/16 and 1/4" stock in a 1/2" round 5C collet.
1/2" stock was held in a round collet in a square collet block in the mill vise and exactly half the diameter was milled away for a length a bit more than twice the finished collet length. The collet block was then held in a V-block so the milled section was 45 degrees to the horizontal. A conventional end mill then milled out the V-groove in the collets. The resulting piece was then split into two collets and the ends finished.

This infallible technique used to be Top Secret! No intent to high jack a new thread, I can add only one helpful detail.
What ever diameter bar stock and collet combination, grip on material will improve by milling slightly beyond one half of the diameter. .005-.010 per side will do. The collet will continue to locate central, when radius of the bar and collet coincide. It might be helpful milling recess first, aiding setup and measurement.

These also work on material larger than you may have a collet; in 3, 4, or 6 jaw chucks and machine vises. [With material in place, skim cut a reference band that will indicate [clock up] round on first occasion to use.

The suggestion to make square sockets this way is a perfect substitute for broaching too. As some import machines retain square headed lock bolts, their wrenches are poorly made castings; with cored holes, not machined. Draft angles, clearance, and un-square recesses are worsened by cast iron, whereas steel used in the past. Crappy handles that don't transmit movement in tactile manner, or fall off with a little vibration are nuisances.

[Gundrx]

Not to be a party pooper, but for mounting square and octagonal stock in a collet, I take a deep well, 12 point socket, cut off the base and make a 0.060"+/- slit along one point with a hacksaw, cut-off wheel or (Gawd forbid) a Dremel tool. The body of the socket fits neatly into a collet and you have the means of centering stock in a flash +/- 0.010". It is accurate enough to face off or center drill non-critical parts. Gundrx

[Gundrx]

Also, I made a '9/16" square-drive' handle for my milling machine table by using a 12-point socket, 10-32 set screw and piece of 3/16"x 1"x10" CRS and a Lutz #2 file handle. (If I knew how to upload a pic, I would.) Gundrx

[Gundrx]

Clever idea for accuracy, but I try to employ the K.I.S.S. principle whenever possible for non-critical applications. Also, the split, 12-point socket works in a three jaw chuck for large parts. i.e. 3/4" and above where extreme accuracy is not critical, but dang close is good enough.

[Frank S]

Clever idea for accuracy, but I try to employ the K.I.S.S. principle whenever possible for non-critical applications. Also, the split, 12-point socket works in a three jaw chuck for large parts. i.e. 3/4" and above where extreme accuracy is not critical, but dang close is good enough.

Using a deep well socket that is cut all the way to the bottom offers better gripping

[Gundrx]

Yes, the socket is cut/slit from end to end. (Forgot to mention that.) Basically it is a 12-point tube with a 0.060+" slit end to end, to allow it to compress the stock in a collet or three jaw chuck. I use this method for facing and drilling the breeches in muzzleloading gun barrels. Its close enough for Gov't work. If I need super accuracy, then I go to a four-jaw and indicate it. Gundrx