ER collets vs. R8

If you already own a decent set of R8 collets, there isn't a compelling reason to switch. Personally, I use an ER40 chuck on my Bridgeport because I possess a larger collection of high-quality ER40 collets. The cost of the chuck was comparable to completing my R8 set with premium collets.

I have some end mills that don't match my R8 sizes, so I usually keep the ER40 chuck installed and utilize those collets. Additionally, I already own ER40 collets and a chuck for the lathe, which sees significant use. My collet blocks also utilize ER40s, benefiting from their through-hole capability.

Advantages and Disadvantages

Some individuals prefer changing collets with a spanner on the ER chuck instead of using the drawbar, though it's a minor difference for me. I'm tall, so reaching the drawbar nut isn't an issue, but it could be for shorter users. One downside to ER collets is the greater torque needed compared to R8 collets.

While the chuck may introduce some runout, it's minimal in my experience and acceptable for my work. If necessary, I would purchase additional R8 collets. Although I haven't noticed significant differences in rigidity, ER collets do cause a slight reduction in Z-axis space.

Considerations for ER Collets

If you choose to use ER collets, you'll need to buy both the ER collets and an ER to R8 adapter chuck. This investment might only be justified if you already have ER collets for another purpose, such as for use with a lathe or collet blocks. Otherwise, sticking with R8 might be more cost-effective.

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Post by toastydeath » Fri Jun 12, 2009 12:09 am

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I acknowledge the debate might be over, but I use ER-40 collets in my work setting. ER-40 shines in its intended use, particularly with a CAT-50 collet chuck. The setup minimizes overhang due to the robust locknut holding the collet.

The CAT-50 setup is far superior compared to a smaller R8 system. For instance, a CAT-50 chuck weighs 15-20 lbs, vastly heavier than a 5 lbs CAT-40 or the mere ounces of an R8. ER-40 collets handle large tools well and offer excellent grip, suitable for high-power machinery, unlike a 5 hp Bridgeport.

Using ER-40 collets on an R8 shank is overkill. R8 systems aren't designed for such large tooling, and the overhang is considerable. While ER-16 or ER-25 collets might be acceptable for certain applications, R8 collets are generally more practical for mills with an R8 taper.

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