Feb 27, 2017
Hennig Gasket has been in business close to a century, and there’s still a Hennig at the helm. The business was started by Otto Hennig in 1920 before passing to James Hennig. He ran it for forty years until his retirement in 1987, and now it’s run by third and fourth generations of the family.
A lot has changed in that time. When Otto Hennig started the business the automobile was in its ascendancy, electricity was spreading across the country, and demand for gaskets for heating systems and manufacturing operations was growing. Of course, Chicago endured a few challenges in that period, but who knows, maybe cork or fiber gaskets made by Hennig found their way in to some of the bootlegger’s stills!
Some things haven’t changed though. We still make traditional cork and fiber gaskets, die cutting them from sheet, or if we don’t have the tooling, using an oscillating knife or even just hand cutting. If you’re maintaining or restoring aging equipment that used gaskets like these we can supply replicas of the originals. Alternatively, you may prefer upgrading to one of the many modern gasket materials that manufacturers have developed.
One example of material changes is the rise and fall of asbestos gaskets. Once essential in high temperature applications like boilers, (and perhaps stills,) these have been replaced by a range of non-asbestos gasket materials like Garlock BLUE GARD®. (This incorporates aramid fibers in a nitrile, neoprene or SBR binder.)
Neoprene and SBR gasket materials have themselves been around a long time, (just like Hennig Gasket & Seals!) but today there many newer alternatives. Elastomers like EPDM and FKM are proving valuable in many applications, especially for sealing against corrosive and high temperature fluids.
The best way of learning about gasket material properties is by speaking with an expert. At Hennig we’ve accumulated a wealth of knowledge and experience. And if you’re in the Lower West Side neighborhood of Chicago, call in. Just look for the brick mill-style building at 2350 West Cullerton.
Feb 13, 2017
Like everything manufactured, gaskets have tolerances on their key features. These are dictated by a combination of material characteristics and manufacturing process. It’s important to understand these tolerances if your new gasket is going to fit.
Unless a gasket goes in a channel the outer dimensions aren’t usually critical. What does matter though are the bolt hole positions, bolt hole diameter, and the inner shape, (because the gasket should not intrude into the flow.)
Gasket Material Thickness
Tolerances are dependant on the type of material and industry standards. RMA commercial gauge sheet rubber tolerance chart shows typical tolerances.
Manufacturing Process Tolerances
Here at Hennig, gasket material is cut in four ways: die cutting, oscillating knife (flash cutting,) water jet and by hand. Die cutting, used for quantity orders, is probably the least accurate yet also the most repeatable. The oscillating knife and water jet machines provide excellent accuracy, and as they cut one gasket at time repeatability is about the same. Hand cutting is the least accurate.
Here’s some more detail on each process:
- Die cutting. Accuracy, defined as conformance to design, is set by the precision to which the steel rule is set into the mounting block. A laser-cut block can usually hold +/- 0.015” (+/-0.381mm) although this tolerance increases with the size of the tool. Larger tools are less precise. Softer, thicker material deforms more during cutting and a convex edge profile may result. Die-cut gaskets are very consistent, with the first piece identical to the last, (until the blade starts to wear.)
- Water jet cutting. Accuracy is set by the precision of the gantry and table motion. In general, this is around +/-0.007”.
- Oscillating knife. Machine repeatability is claimed as 0.010mm but in practice +/-0.003” (+/-0.076mm) is more typical. Softer and thicker materials can show greater variation.
Consider Tolerances When Ordering
Critical gasket dimensions influence the choice of cutting methods. In such cases, it’s important to let us know about these at the quotation stage.