High Performance reaming is a great way to improve your manufacturing processes. It can be used to replace single point boring along with other methods of hole finishing. The benefits include higher feed rates, improved surface finishes and less scraped parts because of accuracy. For more information on how reaming can improve efficiency check out this article. There are a few different styles of high-performance reamers and deciding which one will depend on your unique application.

Monaghan Tooling Group offers two types of Diatool reamers, expandable & non-expandable or solid type. So, which should you use? Well it all depends on the type of parts you are making and what the bore tolerances are for the application. For parts such as connecting rods, transmission carriers and other high precision parts you should use the expandable type. For parts like truck suspension components like axle beams, or automotive steering knuckles or agricultural gear cases you can use the non-expandable or solid type. Each diameter will have a specific tolerance range, to see what tolerance ranges are best for each type see our Solid vs Expandable Reamer Tolerance Chart.


The reamer diameter for a new expandable reamer is targeted to the mean of the bore and for the solid type reamers the size is targeted to 2/3 of the total tolerance. This means the expandable reamers start right on the proper size (usually the mean) and can be expanded to maintain that mean size as the reamer wears. On the other hand, the solid reamers are targeted to be slightly larger than the mean. This means as the tool wears it will get closer to the mean giving you longer reamer life compared to if it started right on the mean (it would get too small too soon). We can of course target the reamer size to whatever you need to run at.

Before we go further, an explanation about what expandable means is in order. As parts are reamed the tool will start to wear down, causing the size to get smaller. For high precision parts like connecting rods it is super important to have a consistent size. Parts like this usually require SPC (statistical process control) charting to make sure the process is stable. So as the reamer wears, we can compensate for the wear by expanding the reamer slightly. Typically, expansions can range from 0.0002” (0.006 mm) to 0.0004” (0.012 mm). A reamer tool can be expanded between 2-4 times before the reamer needs to be re-tipped back to new condition. The reamers however are not “adjustable”, some would say this is semantics here, but it is an important distinction, the reamer only has a very narrow range of expansion. If your bore size is off by a 0.002”-0.003” (0.050-0.076 mm) you need to get it re-tipped larger then. You will not be able to expand a reamer by 0.001”-0.003” (0.025-0.076 mm).  Another rule is that the reamers can only be expanded, you cannot reduce the bore size by backing off the screw. The cutting edges need to be under tension at all times.

Monaghan offers two types of expandable tools, our monoblock series and our cutting ring series. The monoblock reamers are available from Ø0.22”-2.38” (Ø5.6-60.6 mm) as standards and up to Ø5.91” (Ø150 mm) as specials. The rings are available from Ø1.99”-8.09” (Ø50.6-205.6 mm).


The solid reamers are available in the same ranges as the expandable types. For non-expandable reamers Monaghan offers the following: monoblocks, reaming heads, and TSR (Top Speed Rings).

The reaming head is similar to the monoblock reamer tools, but the head is removable. It has a size range of Ø0.377”-2.38” (Ø9.6-60.6 mm).

The Top Speed Ring is similar to the expandable rings except they have more reaming teeth which increases the feed rate and thus reduces the cycle time. They use a different holder than the expandable rings, but they have the same size range.

Contact us or fill out our RFQ form and we will create a reaming solution for just for your needs.