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Spur Gears, 20 Teeth: Cut One Space at a Time on a Dividing Head
Without a hobbing machine, a spur gear is cut one tooth space at a time: a formed involute cutter on a milling machine, the blank turned by a dividing head between cuts. On a 40:1 head, a 20-tooth gear is two full turns of the crank per tooth. Eight involute cutters cover every gear from 12 teeth to a rack.
The picture: cutting a spur gear with the spiral (dividing) head, from "A Practical Treatise on Milling and Milling Machines".
Advanced
A day for a pair
Instructions
1
1
Turn the blanks
Turn the blanks
Saw two slices of round bar and turn each to the outside diameter the cutter's data gives for your module and 20 teeth. Bore the centre to fit the mandrel and face both sides.
Materials for this step:
Mild Steel Round Bar1 pieceTools needed:
Hacksaw
Metal Lathe
Turning Tool Set HSS
Cutting Oil
Vernier Caliper2
2
Set up the head
Set up the head
Press a blank onto the mandrel and mount it between the dividing head and its tailstock on the milling table. Fit the involute cutter for 20 teeth of that module and centre it over the blank.
Tools needed:
Milling Machine
Dividing Head
Mandrel Rod
Involute Gear Cutter3
3
Cut, index, cut
Cut, index, cut
Set the depth from the cutter's data, cut the first space with oil, back off, give the crank two full turns, and cut the next. Repeat until all 20 spaces are cut and you are back at the first.
Tools needed:
Milling Machine
Dividing Head
Involute Gear Cutter
Cutting Oil
Safety Glasses4
4
Second gear and deburr
Second gear and deburr
Cut the second blank the same way. Deburr the tooth edges and check that the pair mesh smoothly at their centre distance (the sum of the two pitch radii).
Tools needed:
Deburring Tool
Vernier Caliper5
5
Indexing 20 teeth
Indexing 20 teeth
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Materials
1- 1 piecePlaceholder
Tools Required
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