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Selecting Boring and Honing Equipment for Your Shop

Today’s boring and honing equipment is much more automated and precise than machines from the past, however not all shops want or need this much automation. For those who like the manual variety there are some manufacturers that specialize in this equipment, which can be a very viable option for some small shops.

By Brendan Baker
The engine building market has changed dramatically due to advancements in engine technology without a doubt. Equipment needs have changed and continue to change along with the needs of the market, note equipment experts. The technology has had to keep up with the sophistication of today’s engines, as production engines are now on par with high-end race engines of just a few years ago, and in some cases those engines were not as precise as almost every production engine built today. To keep up with the technology, engine builders must have boring and honing equipment that meets the machining demands these engines require, or risk quality problems, which can put you out of business in a hurry.

Today’s boring and honing equipment is much more automated and precise than machines from the past, however not all shops want or need this much automation. For those who like the manual variety there are some manufacturers that specialize in this equipment, which can be a very viable option for some small shops. On the other end of the spectrum for shops that wish to be on the cutting edge (no pun intended), there are a number of higher performance computer controlled machines, with higher price tags to match, but the demand for these machines is growing.

Experts say, there’s no margin for error these days when it comes to honing. Surface finish specifications have changed dramatically in the last 15 years. New ring and piston technology has shops fitting pistons with no clearance so you had better have a good handle on surface finish parameters and what they mean, along with being able to measure them. Additionally, new coatings for cylinders have changed the way cylinders are machined. Some of the new coatings can only be honed with diamonds.

Because cylinder boring and honing is such a big part of the machining operations engine builders do on a daily basis, the equipment you use will have a lasting effect on the quality of the product your shop sends out the door. There is a wide variety of equipment from manufacturer to manufacturer that can fit almost any shop’s needs for a specific type of machine. So if your shop is cramped for space and you can barely find a lane to walk, let alone fit a large single-purpose boring machine, you may find a multi-purpose machine that combines several operations best fits your needs.

Boring, Not So
Boring out a block to accept oversize pistons or to salvage an old core or even to increase displacement is a regular operation in most engine building facilities. In performance applications, boring a block to fit hardened cylinder sleeves is opening up many new opportunities for shops capable of doing this work. Sport compact engines have been utilizing sleeves for years to better handle the high loads created by forced induction systems such as turbochargers, superchargers and nitrous oxide.

Although the principals of boring technique have stayed the same for years, the equipment has evolved to keep pace with both OEM advancements as well as the demands of racing. Compared to the equipment of years past, the new equipment uses air-float boring bars that float across the ways and can center itself over the cylinders, whereas older boring bars were portable and bolted down to the deck of the block. The new bars use indexable cutter bits instead of brazed-on cutter bits. Some machines use coated carbide bits that are not as expensive as CBN or diamond bits but also don't have as long of tool-life or cut as fast.

Older machines were designed to use brazed-on carbide bits, therefore the speeds and feeds were slower than they are now. Boring equipment today uses indexable carbides and have coatings on them can that allows for faster feed speeds and higher rpms to get the job done fast. Older machines just aren't capable of that, and on older machines that are worn out it will be much harder to hold these tight tolerances.

Experts say, gone are the days when you fit a piston into a cylinder bore with clearances from .0025˝ to .004˝. Today, piston-to-wall clearances are much tighter and in some cases are even “zero-fit,” so you have much less room for than in the past.

Technology advancements now allow for higher spindle speeds and feed speeds to get the job done faster, say the experts. The other part of that equation is that machines are designed better, with better materials, so they generally outperform older machines quite substantially.

For some small shops just entering the market, they may find that a portable boring bar is the most economical route.

There are a few limitations to your capabilities when using a portable bar, say equipment experts, but they do offer a way to get into the business for less financial investment. If you are interested in the portable bar, spend a little more money and purchase a complete machine with a stand and an air-float system. The stand will prove to be an invaluable part of a portable boring bar system, especially when used on newer engines. Experts say it is not recommended to mount the bar on the deck of a new-style thin-wall engine block because it could cause bore distortion.

One option for some smaller, custom shops may be a multi-purpose boring/milling machine. Multi-purpose machines take up much less space in the shop and, for the price of one piece of equipment, you get virtually two machines. Because smaller shops typically don’t do as much volume as larger shops, they tend to focus on precision work rather sheer speed and volume.

For the Production Engine Remanufacturer (PER) and those shops looking for speed and automation, there are several options to choose from. Since engines come in many shapes and sizes you need to know what type of work you do most, whether it’s heavy-duty diesel engines with larger bore capacity or small motorcycle or karting engines. If you primarily build smaller automotive engines then a machine capable of boring a large diesel engine may not be the best choice for you.

Many of the automated boring machines have programmable boring cycles and automated centering, which optimizes your workflow.

Honing In
Most engine builders now use some type of honing process to finish cylinders. But there are several levels of honing equipment, so it depends on what a shop can afford. Some machines are fully automated and require almost no operator attention, while other machines are almost completely manual. Again, the honing machine you ultimately choose will come down to the level of your needs and budget.

One of the biggest changes in honing in the last few years has been the switch to diamond abrasives. Conventional vitrified abrasives are still effective for finishing cylinders but they wear almost as much as the metal you are finishing. You have to monitor the wear and dress the stones often to avoid cylinder taper. With diamond abrasives, they last longer and bore more consistently for the life of the tool. The coolant that is used when honing helps keep the cutting action cool therefore it doesn’t transfer heat into the cylinder.

Most of the automated machines on the market have on screen readouts to show exactly where you are in the honing process and will automatically dwell if necessary. When the machine identifies a high spot or cylinder taper, dwelling occurs. The hone head will hold in place on the high spot and rotate for a certain length of time to straighten the cylinder. While the automated machines are much more sophisticated, there are several basic honing machines available which have many of the same features as high-end machines minus most of the automation.

The Equipment
Sunnen’s new SV-10 Automatic Cylinder Hone utilizes two motors, one for the spindle and one for the stroker, the SV-10 has the capability to run standard Sunnen tools as well as Sunnen’s new DH-series diamond hone head. Sunnen’s expertise, with multiple-diamond honing on its top-of-the-line machine, is now available on its competitively priced SV-10. The DH-series diamond hone has 16 points of cutting action and produces truly round cylinder bores. The mechanical stroke allows for a precision surface finish with a consistent crosshatch angle in each cylinder no matter what tool is used.

Sunnen’s SV-310 Vertical Honing Machine combines power, precision, durability and technology to deliver mid- to high-volume manufacturers the lowest cost per honed part.

The SV-310 incorporates an all new stroking system (patent pending) that produces a true vertical stroke and can dwell in any part of the hole, end-to-end, selectively removing stock for the straightest, roundest bore possible. In addition, its innovative stroking system delivers precise control and a consistent crosshatch pattern throughout the entire length of the cylinder, which Sunnen says was nearly impossible until now. And to make setup a easy, the SV-310 incorporates a 2-axis hand wheel that allows you to fine-tune the vertical stroke and honing tool feed positions. Multiple position scans be programmed for in-line bore honing.

Sunnen says its SV-310 makes vertical honing faster, easier, more accurate, more economical and more productive than ever.

Rottler’s F8A cylinder boring machine uses a precision ground ball screw to control feed rate and cutter position. This allows machine to repeat cutter position accuracy to .0002˝. The boring depth can be programmed to .0001˝. And the machine has programmable boring cycles and automatic centering cycles. It can also store up to 100 different boring programs. Press cycle start and “walk away,” machine will center and bore to exact depth. The F8A has a draw bar system for quick changing of cutter heads.

The Rottler F68A CNC block machining center uses Rottler’s exclusive touch screen programming that allows you to program for any style or make of block without having to rely on someone to write a new “G” code program each time a different make or style of block comes through your door. The F68A can store up to 100 programs. With Rottler’s software you don’t need to know how to write G code or have experience operating CNC machines. If you have to bore a block with a standard boring bar or surface a block with standard style surfacing machine the F68A CNC block machining center can do both with one machine. The software allows you to choose between blueprinting, probing, or dial indicating for positioning of cylinder or lifter bores. Rottler also offers cam locators for centering the block while machining lifter bores for even more accuracy. Rottler says it is the only machine on market that offers .0002˝ accuracy when line boring main bores.
 
Rottler’s HP6A honing machine was designed and built to run diamond abrasives. The stone feed up system (exclusive to Rottler) allows operator to set machine and walk away. This machine will hone each cylinder within .0002˝ straight and round and to size without operator assistance. Water based coolants keep parts cool and eliminate the need to touch hone after cylinder cools when using oils.

Rottler’s controls offer the operator the ability to change feed load on cylinder during the honing cycle. The automatic cycle senses taper and automatically dwells or short strokes to correct the tight area. Two-stage roughing and finishing cycle allows for fast stock removal for roughing and light loads for finishing. These controls also offer plateau program for plateau honing of cylinders. Set parameters start machine. The machine begins honing process reaches percent of load specified and counts down given strokes per cycle ensuring a consistent plateau finish.

Winona Van Norman’s CB1X Boring Machine is designed to handle a wide range of work pieces. The CBX1X has a boring range of 2.2˝ to 4.6˝ to handle everything from single cylinder to passenger car blocks. The air-float system centers cylinders quickly and easily with its Tri-Radial centering fingers that expand through the full boring range for one step centering accuracy. The direct-reading micrometer prevents mistakes, and tool holders have a spring pin that sets for size to ensure accurate and consistent boring. The base has been newly designed for the CB X-series for more rigidity.

 Winona’s LHC3500 Combination Hone bills itself as “twice the machine in half the space.” It’s actually a line hone as well as a vertical cylinder hone designed to handle automotive V8s and V6s, as well as line bore blocks up to 42˝ long.

The friction feed hone head allows you to remove stock quickly, while the Ammeter allows the operator to maintain straight round cylinders without stopping to gauge.

Additionally, the stroke speed control knob and air/oil stroke system gives you a smooth, consistent crosshatch angle that is infinitely variable. The positive bottom stop is adjustable and prevents the hone head from hitting the main webs. It also features a carriage traverse handle mounted up front, which allows the operator to quickly and easily position hone head over cylinder.

Peterson’s HC1DP honing machine allows the machinist to rough hone and finish hone twice as fast as other methods, according to Peterson, while maintaining excellent bore finish, straightness and concentricity. It features on the fly dwell control at the touch of a button, and stroke length corrections can be made without stopping.
RMC-V30 CNC Machining Center has unmatched repeatability in all 4 axes and uses one of the most powerful CNC Control. It features fully automated, menu driven programming, and support and training are included at no extra charge on new machine purchases.

RMC-200PSH Cylinder Honing Machine automatically centers the engine block and will stroke or dwell in any position. The machine features a bi-directional hone (feed/retract), and comes with an Ammeter for identifying taper in the cylinder.

T&S Machine’s TS-1000 multi-purpose boring/milling machine center features a remote joy stick pendant control of the X and Z axis. The optional Boring Kit includes, boring head with ISO 30 taper, indexable carbide tool holder, centering indicator assembly and CBN insert.

If you haven’t purchased new boring or honing equipment in the last several years, now may be a good time to get acquainted with what’s available and how it can improve your workflow and quality.

Whether you lease or buy depends a great deal on your shop’s individual circumstances. Your ability to take advantage of tax incentives available by leasing, or your ability to pay cash and save thousands of dollars in finance charges and interest both need to be considered.

Whatever option you consider, equipment suppliers say you shouldn’t jump blindly into a major equipment purchase. The key to purchasing equipment is to do your homework, and make sure your boring and honing equipment will be supported by its income producing capabilities.