All gear hobbing machines have an Index Constant. This constant, along with the number of teeth to cut and the number of starts in the hob cutter determine the index gear ratio and the index change gears. Some typical Index Constants are: 36, 30, 24, 15, 12, 10, etc. Let's take an example using a single start hob cutter.

The concept is simple. Let's say the gear to cut is 100 teeth. If it were to be a spur gear (helix angle = 0) then the index gear ratio would be Index Constant divided by teeth. For an index constant = 30, the gear ratio should be 30/100 as shown in the prior topic. Using 30/100 would synchronize the hob to the workpiece so that when the workpiece completes each revolution, the hob would be meshed precisely in the same tooth.

A hobbing machine in its simplest form has no differential, yet it is versatile and productive. A basic non-differential gear hob can serve well for break-down and production work over a wide variety of toothed members. The type of work generated is determined by the hob cutter tooling. Hob cutters are readily available to cut nearly any external tooth member: spur or helical gearing, splines, timing belt pulleys, roller chain or silent chain sprockets, and throated worm gears.

There are sources listed in FAQ "Manuals for my Gear Cutting Machinery" that may have the operator's manual you need. Also, the Gear Forum is a good place to ask for this kind of help. If you can't find a source for the differential formula then you can determine the formula for yourself using the following procedure, but you must have a way to measure a gear's lead.

you probably already know, prime spur gears on most gear cutting equipment require a change gear with the same prime number of teeth. For small prime numbers (less than or slightly larger than 100 teeth), you likely have a change gear. If you have such a change gear for your hob machine, then the index change gears are in the ratio INDEX / PRIME NO. OF TEETH.

If manual or automatic "step" shifting is used, the normal setup is unaffected. Shifting of the hob in this case occurs during the non-cutting part of the work cycle. If continuous tangential hob shift is used, then an adjustment must be made in the lead change gear ratio. In other words, a spur gear could not be cut without a differential action equal and opposite to the continuous hob shift.

If the gear faces are parallel, the Helix Angle is the same for both gears. This means the machine is Type A. Just for information, the gear lead in this case is different for both gears but the helix angles are the same.)

Feed formulas are found in the machine's manual or on the machine itself. Table Feed as discussed here is the cutter table feed in a direction parallel to the workpiece centerline. It should not be confused with infeed or tangential feed. While some hobbing machines may be equipped with infeed or tangential feed, all hobbing machines are equipped with Table Feed. Some hobbing machines mark the machine with a whole number indicating feed (let's call it K).

Some differential hobbing machines do not use feed change gears. These machines use a hydraulic control to advance the cutter through the workpiece. A "dial" is used by the operator to control the amount of feed per revolution of the workpiece.

All hobbing machines use an Index Constant that synchronizes rotation of the workpiece with the cutter. For example, a 30:1 index constant means that the index change gear ratio is equal to 30/Teeth for a single start cutter cutting a spur gear. With the correct index change gears, a single start cutter will rotate a number of revolutions equal to the teeth on the workpiece while the workpiece makes one complete revolution.

The spur gear should not be glued on in any way. Remove the nut, 2 washers, spring, black plastic cap, shaft pin, slipper plate and slipper pad. You should now be able to slide the damaged gear off.

Primarily, when you need to recut helical gears. The differential allows you to keep the workpiece and hob cutter in sync while you back the cutter up for another cut. This is particularly handy for "getting it right" the first time, larger pitches, and some harder materials. Also, with a little trickery you can cut prime spur gears with large tooth numbers. See How to cut a large spur gear with a prime number of teeth? for a description of a method for large prime gears.

This is a sequence of diagnostic tests for setups on new or unfamiliar hobbing machines. The main purpose is to isolate individual error sources in a setup and to diagnose a problem. The procedure is designed for any experience level. When setting up a machine for the first time, use an inexpensive blank. These tests will cause some damage to the blank's OD.

Mechanically driven Shapers require change gears to sync the rotations of cutter and gear. Therefore shapers have the same problem with large prime numbers as most hobs, specifically requiring large prime number change gears. There are ways of cutting large prime gears on differential hobs (see answer above). There is a way to use a shaper also, but not the hob way. Unlike the hob, the shaper completes a gear in one rotation of the workpiece (the finishing cut).

When the US defence department developed the GPS satellite system, it was meant for military applications - to help pinpoint the exact position of a soldier in the field, for example. That system is extremely accurate, within something like 50 feet. The DoD didn't want to give that capability to the enemy, so they scrambled that signal. The signal that's available to the public has been deliberately tweaked to provide a position within about 200 feet.

To do this you must add certain lines to your Linux startup files to add a pseudo slip port to talk to TNOS. First I shall give details of the necessary lines that must be added to your startup files, and then the lines which will need to be added to your TNOS startup file (autoexec.nos). NOTE: You must also have IP_FORWARDING enabled in your Linux kernel. This is set in the make config part of building a kernel. Usually these lines can be put in one of the rc.* files found in # # the /etc/rc.

I can find preprinted fusible interfacing with 1, 1 1/2, or 2 inch squares but not 1 1/4. Is there such a thing. I have decided to work my photo quilt with 1 1/4 inch blocks. I am not sure how critical this part is. I hope you can guide me. The book "Simply Amazing Quilted Photography" has a whole chapter on this subject. I don't use the preprinted fusible interfacing, I use plain fusible tricot. This chapter also tells you why I think 1 1/4" squares are best.

Yes and no. AlNiCo magnets are very easy to machine in any way you wish. NdFeB magnets are by nature very hard and brittle. Although they can be cut, drilled and machined, it should ONLY be done by folks who are experienced with ceramics. If the magnets get over about 300 deg F, they will lose their magnetism permanently. They are flammable, and it is not difficult while grinding or machining to get them (or the chips and dusts from cutting) so hot hot they ignite.

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