CNC honing is an excellent way to achieve tighter tolerances and better surface finishes on a wide range of precision machined components with a round bore. Here's a simple guide to this sophisticated process.
What Is Honing?
The honing process consists of stroking an abrasive stone within an internal, round bore. This abrasive stone acts as a tool travelling along a controlled path and the action results in the creation of a precision, polished surface.
Ultimately, the goal of honing is to refine a surface. This could involve achieving the desired size and tolerance, improving its geometric form, or changing the characteristics of the surface (for example, by applying cross hatching).
CNC Honing
CNC stands for "computer numerical control", and is a more sophisticated version of the classic honing process. Unlike in standard manual honing where the component is manually stroked along a stationary but rotating tool, in CNC honing, the tool rotates, moving in and out, while the piece of raw material remains stationary. With in-process gauging on some CNC honing machines, the need for continuous monitoring of size whilst machining is also removed.
Because of the difference in process, CNC honing can often achieve better results than classic, manual honing. You can mostly expect a more precise finish, with a far greater degree of accuracy and repeatability. However, there are certain components and finishes which can only be achieved by manual honing as CNC machines simply cannot replicate the amazing feel and sensitivity of the human hand!!! Also, manual honing is also the only option for extremely small batch runs or one-offs to ensure competitiveness for the customer.
The CNC honing process is an extremely specialised area of manufacturing. Although computers are involved, this does not remove the need for a skilled operator. Ultimately, a highly skilled operative must still be at the heart of CNC honing, or you are likely to achieve unsatisfactory results.
When Is CNC Honing Used?
Using a CNC honing machine has a number of advantages over other honing techniques. Set up is often a little longer but the need for manual labour for processing is removed.
CNC honing is used in a variety of industries and works particularly well in situations where close tolerance achievement is essential. Components such as bearings, fuel injectors, valve components and automotive gears are all common targets for the CNC honing process.
CNC honing can achieve high levels of precision, but also consistency. This makes the process ideal for long production runs, where accuracy is essential, and parts must be identical. A CNC honing machine, used correctly, will deliver identical results over and over again - one of the most important factors in the manufacturing process.
Learn More About CNC Honing
At Hone All, we have spent decades perfecting our knowledge and expertise within honing. Although we also specialise in other manufacturing processes such as Deep Hole Boring, Deep Hole Drilling, CNC Turning, Honing remains at the heart of our business, and we are always happy to discuss your needs and help you decide if CNC honing is the right process for you. Get in touch with us on 01525 370666 to talk through your project today!
What is honing? CNC honing machines, the process, operation and definition
What is Honing?
Honing machines are metal abrading tools and the honing process utilizing hard tooling or honing stones and perishable abrasives stones for the correction of
Diameter
Shape
Surface finish
Positional tolerances of bores
The honing process was developed to allow for perfection of bore geometry, size control, final surface finish and surface structuring. Lapmaster can help you learn the honing process that can provid the final sizing and creates the desired finish pattern on the interior of tubing or cylinder bores. Finishing is accomplished by expanding abrasive stones of suitable grit and grade against the work surface. The stones are rotated and reciprocated in the part with hone abrasive under controlled pressure. Combining rotation and reciprocation produces a cross-hatch pattern in the surface of the part being honed.
Why use a Lapmaster honing machine?
Lapmaster can provide a cost effective honing machining method for:
Removing stock
Generating exacting
Bore tolerances
Bore polishing
Finishing bores of almost any material such a: sprayed coatings, CGI, Ceramics, etc.
Define The Honing Process:
The honing process provides the final sizing and creates the desired finish pattern on the interior of tubing or cylinder bores. Finishing is accomplished by expanding abrasive stones of suitable grit and grade against the work surface. The stones are rotated and reciprocated in the part with hone abrasive under controlled pressure. Combining rotation and reciprocation produces a cross-hatch pattern in the surface of the part being honed.
Lapmaster Honing Machines Perform Three Operations
First, it is a stock removal process (vertical honing machine) which takes out ruptured metal and reaches base metal.
Second, a finish pattern is generated to provide the best possible surface for promoting optimum lubricating conditions.
Third, honing stones assures extremely accurate straightness, roundness and size of the cylindrical surface.
What is single pass honing machine?
Single pass honing is done with a diamond abrasive, boring bar type honing tool. This type of honing tool produces a straight, round, and un-tapered bore in one pass of the tool through the part. Single pass honing is ideally suited for honing engine crank and cam bores. Since size is achieved in one pass, there is no crosshatch pattern in the finished part. The adjustable single pass tool expands the hone stones with a cone similar to standard tooling. However, the stones are not expanded and retracted as with conventional honing. The stones are only expanded to achieve size. The other difference is the hone tool is longer than standard tooling and the super abrasive coat the length of the tool. The single pass hone is tapered for about seven inches and has a final size section of 2.5 inches. See the photograph on the next page. The single pass tool has no in-process hone expansion, the machine must be stopped to adjust the tool.
When to Choose Lapmaster Single-Pass Honing Tooling?
Single-Pass honing machines, also called Bore Finishing, is selected for a variety of applications that have special needs involving honed cavities:
Small diameter honing tool machine (normally within 2”)
Honing tools for High-production quantities
Proper honing tools can reduce the cost per part
Reduced down-time for CNC honing tool change-over
Repeatable accuracy for dimensional tolerances such as bore size, roundness, surface finish
Only super-abrasive materials (Diamond and CBN) are used for the Single-Pass processing
A high rate/volume of coolant is needed to constantly remove the chips from the honing area
Oil or water-base coolants may be used for Single Pass honing, though oil is the most common
Single Pass honing process islimited to the types and volumes of material that can be removed. Specifically, the size and volume of chips removed must be no greater than there is clearance between the super-abrasive grits on the tool sleeve. As such, the Single Pass honing process is best suited for honing operations that produce a relatively small amount of chips, such as interrupted or short length bores. It is most successful (but not limited to) in honing cast iron and powdered metals.
Applications that feature a long length of material to be honed, small quantities and/or requiring a lot of material to be removed, are not the best suited parts for Single Pass honing. Rather, they may be best served using conventional Stroke Honing. In many cases, conventional Stroke Honing can also provide excellent dimensional geometry for these types of applications.
Why use Lapmaster Stroke Honing Machines / Systems?
Barnes Stroke Honing Machines & Finishing Systems offers a complete line of products for all honing requirements. We can offer fully integrated systems and machines for high volume production applications and equipment for low volume job shop applications. Lapmaster also offers used honing (rebuilt) and upgrade services for existing machines. We provide our customers with fully engineered complete custom solutions and offer a full line of accessories and consumables in addition to comprehensive training and repair services.
Our extensive line of Stroke honing machine / systems have the ability to hone machine bores with diameters ranging from 0.25 – 30 inches and bore lengths up to 75 feet. We offer systems for both medium to large-scale serial production as well as small batch production; these systems can be made to be manually operated or fully automated. With innovation and customer service as our main objectives, Barnes Stroke Honing & Finishing Systems is continuously researching and developing new technology and machinery. By consistently staying on top of the latest developments on the market, we ensure that our customers are provided with the most state-of-the-art production and control.
Why Single Pass Honing Machines / Systems?
Barnes Single Pass Honing/Finishing machine line is suitable for a variety of single pass honing applications. The flexible machine design can be configured with a single spindle for lower volume production requirements for the smallest of machine shops. It can also be arranged with multiple spindles to satisfy high volume production requirements for the most demanding of companies. Our Single Pass honing machines are designed and manufactured for minimal maintenance requirements and It's accessible configuration also reduces set-up and changeover time from part to part.
Answering 5 Honing FAQs
According to Sunnen, honing is typically required to achieve bore diameter tolerances of ±0.0002 inch or tighter with high quality surface finishes. (All photos: Sunnen)
As one of the most common machining operations, holemaking presents manufacturers with plenty of options. Depending on bore diameter and surface finish tolerance, a shop might choose drilling, milling, electrical discharge machining (EDM) or a combination of those CNC machining processes and achieve quality results. For example, the hole created by a 0.5-inch drill might range from ±0.002 inch or be as much as 0.006-inch oversized, but a subsequent reaming operation can produce a smoother surface finish and a hole diameter within ±0.0002 inch. Reaming or boring milled holes can achieve similar results, while EDM is even more precise, producing a bore diameter within ±0.0005 inch.
However, there are good reasons to turn to honing for applications with the most stringent requirements for surface finish and precision. According to Sunnen, a manufacturer of honing equipment that provided the information for this article, EDMed holes typically require further processing to smooth surfaces. The process is relatively slow as well. Optimized milling processes followed by boring or reaming may produce high-quality results, but not always consistently. Honing achieves all three goals: That is, the process consistently and reliably achieves bore diameter tolerances of ±0.0002 inch or tighter with high-quality surface finishes.
