#### Re: Cutting a SB Change Gear with a Straight HOB!

G K

The process is also reference here:

The calculations refereed in creating the HOB is the depth of cut:

Depth = 3.41/DP

For a SB gear, DP=18 with a PA=14.5

Depth = 3.41/18 = 0.189

Tooth Spacing (Circular Pitch) = PI/DP = 3.141/18 = 0.175

However, if I draw a HOB with this information, it results in a cutting tooth that appears too wide for a given DP=18, PA=14.5 gear. (See the attached HOB image)

The cutting tooth is ~0.072 wide whereas the width of the cut on a gear  (not sure of the term) is ~0.071.  No too different, but if the gear is cut with the HOB profile to that depth and thickness, the resulting tooth profile will not mimic that of the SB gear.  It will have straight sides.

Maybe I'm getting too far into the weeds.  That is why I was hoping to hear from someone who has done this specific process before.

On Wednesday, November 10, 2021, 11:09:03 AM CST, G K via groups.io <bug_hunter2000@...> wrote:

My intent is to create a HOB and cut a gear as shown in the following video:

On Wednesday, November 10, 2021, 10:57:17 AM CST, Ondrej Krejci via groups.io <okrejci@...> wrote:

Greetings?

I believe you mean a gear cutter for line milling not a hobbing cutter, which is helical and used in a special hobbing mill.
Anyway, you would have to make a number 2 profile for 55 to 134 teeth, if 100 and 127 tooth gears are intended.
What calculations are problematic?

Good Luck,

OK

On Wednesday, November 10, 2021, 11:17:32 AM EST, G K via groups.io <bug_hunter2000@...> wrote:

Anyone out here who has cut a change gear with a straight hob?  I am undertaking making a HOB on my SB9c to try to make a gear , but am having some issues lining up the calculations with an image of the gear I am going to create.

Some insight would be great.

Thanks!

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