SDS-plus vs SDS-max: shank sizes and which bit fits

The fitting comparison

Bosch's SDS-plus guidance explicitly distinguishes the two shank sizes and says the bits are not interchangeable. Hilti's UK explanation also distinguishes the diameter and shape of the connection end. The letters after SDS matter: a listing described only as an SDS drill bit is not enough to establish the fitting.

Shank diameter and hole diameter are separate

The connection goes into the tool holder; the cutting head determines the advertised drilling diameter. An 18 mm SDS-max shank does not mean every SDS-max bit makes an 18 mm hole. Read the separate diameter field on the exact product rather than selecting by the connection size.

For example, Bosch's UK EXPERT SDS max-8X listing identifies part 2 608 900 214 as a 16 mm drill bit with 200 mm working length and 340 mm total length. Those are three different measurements. The 340 mm overall length is not a claim of 340 mm usable drilling depth. This example explains the labels; it is not a recommendation for an unspecified hammer or fixing.

Choose by the exact hammer and application

Hilti describes SDS-plus as suited to everyday anchor-hole work and SDS-max as serving heavier, larger-diameter or deeper-hole applications. Treat that as a broad distinction between systems. It does not replace the permitted drilling range, operating mode or accessory requirements of an individual tool.

Start with the model label and manual, then identify the material and the hole dimensions specified for the job. For a fixing, use its manufacturer's drilling requirements. Do not assume that a physically matching shank makes every cutting diameter, length or material application suitable for your hammer.

Read the complete listing before buying

Keep the system name, cutting diameter and working length together in your shortlist. Check total length as a separate access and handling dimension, and confirm the selected variant and pack quantity. Search results can mix lengths and fitting systems even when their titles share the same drilling diameter.

An adapter is a separate compatibility question. Do not infer permission to use one from the SDS names or a retailer photograph; any adapter, accessory and operating mode must be permitted for the exact tool. This directory's SDS-plus shopping page is a product-type buying reference, not a database of verified SDS hammer models.