The Boley Leinen collets have been a controversial issue. Sometimes difficult to find in a good condition but available time to time. There are no public Boley Leinen information about the right collets to be used. This poses some questions that owners are solving as the time goes. This post shows what collets are and features the most interesting information about them.

I Got Them

Time ago, I acquired an almost complete set of collets for the Leinen lathe. It was achieved through a rather unusual offer in german ebay. After an year following ebay and other forums looking for Leinen collets the last week I found an almost complete set in good condition and including the draw bar. It was really an incredible discovery. I found no traces of leinen collets during a year and suddenly it appeared an entire set of them.

What Are Collets For?

(After some questions of my nephews Martí and Bernat)

The collets are devices designed to precisely hold work in a lathe. Usually every size and profile of work require a specific collet and thus it is an expensive system. However it has a number of advantages that makes the system preferred in some conditions. This advantages include:

• Quick changeover time
• Great accuracy
• Low mass and thus better conditioned to high speeds
• No marks left on the turned part

This is a draw-in collet:

The collet is fitted in an accurate lathe nose as shown in this picture:

The collet is draw from behind using a draw-bar as this one:

The draw bar is tightened and it presses the frontal cone of the collet against the lathe nose:

A perfectly round part can be hold in the collet as shown here:

Here you can see the headstock with the draw bar and a collet holding a milling cutter:

The collet can be a very accurate holding device. In this picture woy can see the maximum deviation of this collet. It is near 0.01mm of excenticity.

The nose can held other tools in addition to collets. Here, for instance, it holds a dead center that have the same shape that the collets.

The Set of Collets

The set is composed by:

1. A set of 363E draw-in round collets from 1mm to 22mm in 0.5mm steps but the 20mm collet that was missing. The collets in the set are probably manufactured by three firms. Appoximately a half of them are marked «boley-leinen». Collets are used but in a very good condition.
2. A dead center. It is an original boley-leinen center, a standard accessory of the Leinen LZ4SB.
3. A special driver. Although it has no mark it was probably made by boley-leinen too. This kind of driver appears in the leinen catalog and it is used to drive taps an dies, Remember that this kind of collets can also be used in some turret lathe special attachments that were sold for the Leinen LZ4.
4. A draw bar that fits in the Leinen LZ4SB spindle.

Below there are some pictures of the complete set and the special driver:

The Boley Leinen Collets Standard

Which is the standard of Boley Leinen collets? In Boley Leinen catalogs the LZ4xx lathes collets are always referenced as s25 collets. It is an in-company reference but it is not clear if corresponds to a known standard. Many colleagues in the past thought that draw-in collets match the numbered series 363E . These collets have these characteristics:

• Body diameter 25mm
• Length 89mm
• Collet taper 32 degrees
• Round bore till 22mm
• Max pass-through bore 17mm
• Thread M23x1

However, in this post, Iron-rage notes that the thread profile is not metric but a 55 degrees one, maybe Whitworth. The thread, then, do not corresponds to the 363E type. The conclusion is that s25 is a non-standard type of collets with thread Z23x1.

It is known that 363E collets feel a bit tight when threading into Leinen drawbar. This should be the reason.