By David P. Monyhan, ASE-Certified Cylinder Head Specialist
As seen in Engine Builder, January 2004
So, you finally decided it’s time for a new cylinder head machining center? Congratulations! You’ve made a great decision that will increase the profitability of your shop.
In the old days (last year) they were called seat & guide machines. They originally started out as simple drill presses modified to do two basic machining operations, hence the name Seat & Guide machine. Now they are designed to not only perform the most basic of seat and guide repair but to perform very intricate seat angle cutting, bowl enhancing, spring seat pad work and a host of other very involved machining operations. There a few that also do fly cutting of cylinder heads surfaces, or machine the intake or exhaust manifold. There are even a few that do align boring on a block. The features incorporated into these late model machines provide the operator with the most accurate set up available.
These machines are not what your father used to drive. They are state of the art machining centers and they’re a lot faster than their older brothers.
Let’s face it, when you went out and invested in this new state of the art equipment, some or a great deal of that investment is in the tooling. That tooling needs proper care – especially if you want your new machine to perform according to the manufacturer’s specs. These newer machines don’t have a clue that your tooling is dull, bent, nicked, burred, or not the correct size. They do exactly what you direct them to do, and if your tooling is not up to spec you’ll trash a work piece in record time.
Most of these newer style machines incorporate the latest in tooling for three-angle seat cutting. This consists of very special cutter blades, carbide pilots, extremely sensitive leveling systems and an upgraded mounting fixture. Most feature a tool board to store and make ready the necessary tooling. This tool board organizes the tooling and provides some protection for the tools when not in use. However, the operator has a huge responsibility to insure the tooling is in tip-top condition at all times.
Let’s start with the tooling made from carbide
Carbide tooling comes in a variety of forms. You have carbide counter-bore cutters, valve guide pilots, core drills, core reamers, ID reamers and single or multi angle cutters. Carbide is the most affordable material that provides long life, holds size and can be formed into a variety of shapes and is readily available. However, it needs tender loving care. Carbide by its very nature is more brittle than high-speed steel.
Due to engine manufacturers putting as many five valves into each cylinder, some with stem diameters as small as 4.5mm the only way to have any chance of seat centricity is to use a solid carbide pilot. Let’s face it; with all three angles being machined simultaneously the weak link in the equation is the pilot. The high-speed steel pilot is actually bent over by the cutting pressure. It can flex by as much as .002″. To hold centricity the automotive aftermarket started making pilots out of solid carbide. While carbide is very stable, it is also very brittle. If you drop a carbide pilot onto a concrete floor you will have many smaller, unusable carbide pilots. Since carbide pilots can cost a pretty good chunk of change, it’s in your best interests to treat them with the utmost care!
At the very least you should put a fatigue mat in front of the work area for two reasons:
- It makes it more comfortable for your operator.
- It provides a somewhat soft landing for your tooling.
Store your pilots away from each other during when not in use. That’s what all the little vertical holes in your tool board are for. Don’t let them bang away at each other in a drawer. Organize them according to size; mark your tool board so you know when one is missing. Always wipe the pilots down when done, which cleans the machining dust off and prevents that dust from transmitting into the next job. Periodically check the top and bottom size to insure they are still accurate. They will wear over time. Replace as necessary.
Three angle cutter tips
These little guys are the real worker when it comes to cutting the seats on multi-valve overhead cam type cylinder heads as well as performance and diesel cylinder heads. Although they are readily affordable they are not free. Take a magnifying glass and inspect the cutting edge, look for nicks, burrs and burn marks. If you find damage, you can sharpen the cutting edge. It won’t reshape the degree of angle it just sharpens the cutting edge.
Keep the tips in a protected environment to prevent them from banging against each other. Be sure to keep the little plastic sleeves that your supplier always ships them in. When you acquire enough of them, take the time to mark the out side of the box and then only store that blade in that box. Over time you will have a complete and well-organized inventory of tips. In a perfect world you would have your most popular tips installed in holders and ready to go for the next job.
Another tip to prolong the life and improve the cutting action of your tips is to use a cutting fluid. I found some stuff that really works well.
Seat counter-bore cutters
Counter-bore cutters are generally fixed in size and the carbide tips are either indexable and replaceable, or they are brazed. They are available in a variety of sizes and some manufacturers offer a fully adjustable type of counter bore cutter. Again don’t let them come in contact with each other and periodically inspect for chips or burrs. They can be resharpened or rebuilt by a quality supplier. Always test bore or measure them prior to using them on a customer’s cylinder head to insure the counter bore size is correct.
Core Drills and Reamers
The core drill is the tool for cutting out integral-type valve guides. Core drills are made mostly from high-speed steel, but you can get them in carbide as well. Your core reamers are made from the same material and again you can’t just toss them into a drawer. Organize them according to size on your tool board. Periodically inspect the cutting flutes for nicks and burrs. Also look for overheating, this will create a blue color change in the flute area. Core drills and reamers can be resharpend by a quality supply house or take them to a professional sharpening service close to your shop.
Finish reamers are used to size the ID of the valve guide. This sets the amount of oil clearance you choose for that application. They can be made from carbide or coated with Titanium Nitride. You will probably have one for each guide size known to man and have them .001 increments. If you run out of room on your tool board, I saw a clever idea in a shop a few years back. Take a 2×4 and drill 5/16″holes about 1″to 2″apart and bolt that 2×4 to your workstation. Then you can mark the board and organize them according to size.
Most bronze guide liners being installed today are finished on the inside diameter by a carbide sizing ball. The neat thing about a carbide-sizing ball is, its carbide, it rotates as it is being used and by rotating it wears evenly and its life is greatly extended. Drop one of these little guys and you will spend a while looking everywhere for it. I suggest you put a tray (even a cookie tray) and (be sure to ask the wife first) under the cylinder head stands. I would even go so far as to line the tray with a rubber cushion so that when you send the carbide ball through the valve guide it will stay in the tray and the rubber cushion will prevent it from being damaged and keep it from bouncing onto the shop floor.
Rotary files are used mostly for machining the ports on high performance cylinder heads. They are also used to chamfer the oil holes in crankshafts or cylinder heads and blocks. Again arrange them according to size and protect them from each other by proper storage. Inspect them for nicks and burrs; also make sure the shanks are not bent! If you put a bent rotary file into a high-speed die grinder, it will shake so hard you will probably drop the whole assembly on the floor. Always work in a deliberate cut. And don’t let the carbide bounce, it will chip. For light material removal, use a stone or abrasive roll.Boring tools
Boring tips or brazed cutters are brittle and need periodic inspection as well as in house resharpening. Always store away from other boring tools and keep them sharp to maintain fast and efficient boring cycles.
Brake lathe cutters
These types of tools are generally throwaway types of carbide. They are readily available and can be dressed to keep the edge sharp. Also the super heavy duty can be resharpen when they become dull.Tools that can be resharpened
Core drill, core reamers, finish reamers, three angle seat cutters, brazed counter bore cutters, brake lathe tips, boring tools and rotary files can all be resharpened. When resharpened properly they will reduce your over-all cost in tooling. Make sure they are resharpened by a qualified sharpening service, and always measure to insure the size is correct before you use them
Remember your tools are your machine’s best friends. Take care of them! They will take care of you! If you don’t, that job you need to get out on Friday will be compromised due to the fact your tooling was not up to the challenge. Remember – be true to your tools and they’ll be true to you.
Remember, if you have more questions, contact the Goodson Tech Department at 1-800-533-8010 (customers outside the US & Canada, please call 507-452-1830).