Business of tooling: high-feed milling, tips and tricks

Seco's Turbo 10

High-feed milling has revolutionized milling applications today. High-feed milling works from a chip thinning principle using the lead angle of the cutter.

A 90 degree cutter will produce an average chip thickness of the programmed feed rate. When you program a feed rate of 0.010 inch per tooth the average chip thickness will be 0.010 inch. In a 45 degree lead cutter the average chip thickness is about 70 per cent of the programmed chip per tooth. In high-feed milling the average chip thickness is about 15% of the programmed feed per tooth.

Therefore a programmed feed rate of 0.060 inch per tooth will generate an average chip thickness of only 0.009-inch. The lead angle also has a major effect on the cutting forces. With a 90 degree cutter the cutting forces act perpendicular to the spindle.

The net result is the forces are trying to push the spindle and or part away. This is very hard on the spindle. The tool should extend from the spindle the minimum amount to avoid deflection.

A 45 degree lead cutter will have the cutting forces act at 45 degrees to the spindle and the part. This is an improvement, however care should be taken when machining a thin part as the forces may try to push down on the part and cause “oil canning”.

Oil canning is where the cutter pushes the workpiece down and the material springs back after the cutter passes. With high-feed milling the cutting forces act almost parallel with the spindle. Since the cutting forces are directed back up into the spindle it is easier on the machines spindle and the cutter can be run at extended lengths.

High-feed milling is a very versatile way to remove material. The tool can ramp and interpolate. Unlike many other types of milling, this means the tool never has to leave the part. The tool can simply be ramped down to the

next level while continuing to mill.

Since the tool is never lifted from the part, it reduces the probability of re-cutting a chip and breaking an insert. High-feed milling is now commonly used for hole making. High-feed milling is about six times faster than drilling and one tool is capable of producing numerous size holes, reducing cycle time to index to different drill diameters, reducing the cost of the additional tools and reducing tool inventories.

Care should be taken when selecting the size of the high-feed cutter. Often programs use very short ‘jerky’ motions when creating its tool path. When these short jerky motions occur it is often difficult for the machine to ramp up to the desired feed rate. For example a three diameter cutter may be programmed to run at 300 inches per minute but since the short jerky movements don’t allow enough travel for the machine to reach this speed the cutter may only average forty inches per minute.

Whereas a one inch diameter cutter may reach the 300 inches per minute of feed rate since its tool path is longer. Although the one inch diameter cutter has three times the distance to travel it is doing so seven and a half times faster, making the one-inch cutter much faster than the three-inch cutter.

Many CNC controls today have a safety feature that limits the maximum feed rate. Many shops put in a new high-feed cutter, program the feed rate for 250 inches per minute or more and have the false sense that they are running faster yet are not because the maximum feed rate is set to 150 inches per minute.

A new trend in high-feed milling is the use of rectangular inserts. The benefit of this style of insert is that it does not take up as much space in the cutter body as would a trigon or square type of insert. This means the cutter body can have a higher density of inserts per diameter.

Some cutting tool manufacturers have cutter bodies with five inserts in a one inch diameter or 10 inserts in a two-inch diameter. With a chip per tooth of 0.060-inch, five effective cutting edges and elevated RPM due to the small one inch diameter the tool is easily capable of running at feeds exceeding 600 or 700 inches per minute.

With metal removal rates as high as that the cutting forces produced are tremendous, some cutting tool manufacturers have opted to build a big bulky insert to prevent insert failure.

While this may offer some shock resistance, it limits the amount of effective teeth, thereby slowing the process. Other manufacturers have opted to make their high-feed inserts much more positive and reduces the cutting forces which maintains super high-feed rates, reduces cutting forces and is easier on the machine’s spindle.

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Fixing Common Woodworking Mistakes

Fixing Common Woodworking Mistakes

Fixing Common Woodworking Mistakes

Fixing common woodworking mistakes generally isn’t a big deal. Even though we never make mistakes our self, this is something that alwaysfix woodworking mistakes groove happens to the other guy. Woodworking mistakes to a beginner can be very devastating thinking his project is a write off.

The good news is that 99% of common woodworking mistakes can be repaired leaving them in most cases undetected.

The most common things you will need to repair mistakes in wood are glue and a quality water base color match wood filler. The water base filler will take stain to hide the repair in most cases.

Types Of Common Mistakes

  • Having Tare Out:-  perhaps while using the router, a chip is pulled out of the wood. This is easily repaired if you can find the missing chip and simply glue it back in place. A bit of sanding and the job is done. But if you can’t find the chip, the location of the chip may fixing-mistakes fillerhave to be enlarged and a larger piece of wood glued in place. A bit of planing and some sanding usually corrects the problem.
  • Mortise Misplaced:- mortise in the wrong location, no problem. Cut a piece of color match wood the right size to glue and drive into the mortise. Plane off excess and sand.
  • Wood Dents:- wood dents are nothing more than compressed wood fibers that react well to water and steam. Simply put a little water in the dent, cover with a wet cloth and apply some heat with an iron. This causes the fibers to swell and expand. when dry, simply sand lightly.
  • Deeper Dents:- sometimes a dent is to deep to iron out so a color match water base wood filler is the answer. Fill the void with filler, let dry and sand smooth.

Check out Wilson and Miller for some fine woodworking tools!

How to Fix a Stripped Screw Hole

angled screws - Jim Jurica / Getty Images

One of the most frustrating experiences in woodworking can be when a screw hole becomes stripped out and will no longer support the fixture, accessory or accent that it was designed to hold. In this event, you can learn how to fix a stripped screw hole using a variety of methods, as there really isn’t a “one-size-fits-all” solution to the problem.

The first step is to determine whether a slightly longer or wider-diameter screw will solve the issue. Perhaps just a bit more bite will solve the problem without altering aesthetics. Many times, this isn’t a viable option.

Well, if a larger screw won’t be appropriate, the next best thing is to try and determine precisely what type of wood you’re dealing with. If you’re working with pine, fir or other similar softwoods, you may be able to fill the hole with small strips of the same type of softwood. Simply cut off some thin, but still relatively substantial shavings from a piece of stock of the same species.

Dip the tips of these pieces into some wood glue and tap them into the hole until the hole is filled. Allow the glue to dry for a few hours, then trim off the excess with a sharp knife or chisel and sand the fill if necessary. Tap a slight pilot hole using an awl into the filled wood and then drive the screw home. Your problem should be solved.

You can take the exact same approach if the stock with the stripped out hole is a hardwood, but try and use pieces of the same species to fill the hole. You definitely don’t want to use hardwood filler in softwoods, as the hardwood might split the softwood when the screw is driven in. By the same token, filling with a softwood filler into hardwood may not be durable enough to accept and hold the screw.

Now, if you can’t determine the species of stock, or if you don’t have any of the same stock to use for filler, what do you do?

Well, there are other methods for filling the hole, which may work with some success. My personal favorite, particularly in softwoods is to tap a few wooden match sticks (with the heads cut off) into the hole. You can use a few drops of wood glue in the hole before filling it with match sticks, but the wood glue isn’t absolutely necessary. The match sticks are consistent widths and are thick enough that they shouldn’t snap off when driving them into the hole. Hardwood dowels or toothpicks might be other options (again, based on the stock being repaired).

I’ve heard of woodworkers using epoxy or even “Bondo” to fill such blemishes, but I tend to shy away from these chemical fixes for this problem. The reason is that wood is flexible, and will expand and contract based upon weather conditions. Hardened chemical solutions will not have the pliability of the wood it is filling, and as such, may cause greater problems with cracking or splitting down the line. In cases where the stock expands with the weather, the plug could even fall out. I would have less of a problem using small amounts of epoxy to hold in the wood plugs mentioned in the previous paragraphs, but I’d wait until the epoxy has thoroughly cured before re-seating the screw. If the epoxy grabs the screw before it dries, you may never get the screw out in the event that you need to make other repairs or disassemble the piece later.

One final note: in the stain aisle of your local home center, you’ll find plenty of “wood fillers.” These products are designed to help fill holes before (or after) applying a finish. They are for aesthetic purposes only and are not appropriate for fixing stripped screw holes. If you try to use a wood filler for structural purposes, you’re likely to be sorely disappointed, and be right back to square one relatively quickly.