2025-12-22 – Weekly Machinist News : Why is ER32 called 32?

Last week on the forum, machinists were actively discussing the ins and outs of shop-floor training and the best practices for implementing Gantt charts in daily operations. There was also considerable interest in material selection for tooling, with a focus on the differences between S7 and H13 for forming dies. A technical topic that garnered attention involved precise measurement tools and their reliability, particularly in maintaining stable runout.


This Week’s Hot Topics

Advanced GD&T and CMM training recommendations
Members shared resources and personal experiences to elevate skills in geometric dimensioning and tolerancing, crucial for precision engineering.
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S7 or H13 for 304 forming die
A lively debate on the pros and cons of these tool steels for forming dies, factoring in durability and application.
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Stable 0.00005" test indicator for runout
Members explored the best tools for accurate measurements, vital for ensuring part quality.
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0.866 and hex stock
A technical discussion unraveling the math behind hex stock dimensions, of interest to those working with custom parts.
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Gantt charts and the 6 a.m. whiteboard
A practical look at integrating project management tools with daily shop routines for better workflow.
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Best format for shop-floor training
An engaging exchange on effective training formats, from hands-on sessions to digital modules.
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Taming chatter on a light lathe
Strategies and tips were shared on minimizing chatter, a common issue that affects surface finish and tool life.
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Why ER32 is called 32
A brief history lesson on collet naming conventions, sparking curiosity among newcomers and veterans alike.
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Cleanroom-friendly coolants and cutters
Discussion on materials and techniques suitable for cleanroom environments, important for high-tech manufacturing.
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The last tenth keeps taking lunch breaks
A humorous look at the challenges of achieving that elusive perfect measurement.
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Looking forward to another week of productive discussions. Keep sharing your expertise and questions.

It’s the series’ nominal taper size — “32” is the about 32 mm major diameter per ISO 15488 (quick ref: Collet - Wikipedia). In my shop, if we’re working tight forming-die pockets like in that S7 vs H13 convo, I’ll choose ER25 with a slim nut first because ER32 nuts are chunky and love to kiss walls unless we truly need a 20 mm shank. What shank size do you need to hold?

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For anyone speccing holders, “ER32” labels the taper size, not the shank capacity — max tool shank is about 20 mm (3/4"), so don’t try to stuff a 32 mm in there. @ava73 good call on the ISO bit; one practical gotcha is nut bulk — ER32 uses an M40x1.5 nut and can crash in tight die pockets, so check clearance. Anyone using slim or power nuts to keep forming-die setups out of the danger zone?

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