# Re: Index and feed problem

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Posted by Bill S on March 23, 2005 at 18:21:35:

In Reply to: Re: Index and feed problem posted by Charley Briggs on March 23, 2005 at 08:28:07:

Hi Charley,
I'm in North Carolina, but I'm sure that together we can solve the mystery. I recommend that you print out this message and take it to the machine.

I'm going to give you a different set of gears to mount on the machine. Follow the directions exactly to determine which gear goes where. Also this will remove the possibility of a mismarked change gear (unlikely but it has happened!).

First, are you sure about the index being 12:1? Don't rely on the change gear cover to tell you - It could have been changed with another machine. If you have cut spur gears before using 12:1 then I'm convinced, so continue on with the directions. If not, then we need to explore the possibility that it is something else by cutting a spur gear. Let me know if you have NOT cut a spur gear on this machine before and I'll show you an index gear set to cut a spur gear.

Next, let's check a few things: First the change gears. These are laid out as:

1st Driver x 2nd Driver
--------------------------
1st Driven x 2nd Driven

47 x 63
INDEX = ----------
43 x 91

26 x 41
FEED = ------------
57 x 61

1st driver is on the shaft that rotates when machine is under power and change gears are not mounted. It meshes with the 1st driven on the idler shaft. 2nd driver is other gear on idler shaft, and it meshes with final, or 2nd driven.

For example, the index set starts from right to left looking at the end of the machine.
The first driver (right side) in the index is 47T.
It meshes with 43T on the idler stud. Next on the idler stud is the 63T gear. The 63T meshes with the 91T which is the final driven gear (far left).

The feed gear train starts with the powered first driver shaft. The first driver is 26T and it meshes with the 57T gear on the idler shaft. Next on the idler shaft is the 41T gear and it meshes with the 61T final gear.

There are only 4 gears in each change gear set. No extra idlers are involved. Table feed is toward the headstock away from the tailstock.

You can swap 1st and 2nd drivers if necessary, or you can swap 1st and 2nd drivens. NEVER swap a driver with a driven.

NON-DIFFERENTIAL MACHINE
The setup was done for a 6-10 without differential. If your machine has another set of 4 change gears (three different change gear sets with swing arm idlers) let me know.

HOB CUTTER
Make sure that the cutter is single start RH. It is RH if it looks like a RH screw. It is single start if its "thread" has only one entry looking at the end.

If the cutter is anything other than RH and single start, the setup I gave you WILL NOT work. Let me know if this is the case, and I'll redo the setup.

TABLE ANGLE
Cutter should have its angle marked on it somewhere. The angle should be small, usually between 1 - 3 degrees.

Since you are cutting a right hand gear, the table is swung CCW (end of cutter arbor swings to the right of 0 degrees) by an angle equal to 16Deg 7Min minus the angle of the cutter. In other words the table angle setting will be less than 16D 7M by the angle of the cutter. The table angle setting is not critical, but should be close. The gear angle is generated by the combination of index and feed change gears, not the table angle setting.

I think you will have found the problem before getting to this point, but if not, then there are some other (unlikely) possibilities.

LAST RESORTS:
If everything agrees with the steps above but the problem remains, then either the index constant is not 12:1 or one of the change gears is wrong, or marked wrong. Count the change gear teeth to be sure (Yep, it happens!).

If the table feed disengages without turning the machine off, that will cut the teeth off. The cutter must pass beyond the blank before the feed drive disengages. In other words, you can't disengage feed before exiting the blank.

Make sure each change gear has its key/keyway in place for positive drive.

There's nothing else to check except feed constant, but I've never seen a 6-10 that wasn't .075 (there's a first time for everything :^).

Let me know what you find out.

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