7x10 lathe

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i try to build a small rotary (4th axis) for my router...
already i got the materials for tailstock... but my little lathe crossed my imaginations...

the first issue was the gears... for feed and thread cutting... when i tried to change gears, i discovered theres no 127... the reason lack of room for...
getting on the net i find a few website about this nifty machinery... they talking about the 21 teethed gear

so first looked for the whole problem what can be done on simple way...
on the first picture you can see the original part, made of 3.5 mm hotrolled sheetmetal...
you can see the design ""ignored"" the necessity for gears and modified to the available room for...
so first i cutted a testpart, which one worked better...

some more study on this, and find out the part has more room on the front... new design, and it is close what i would like...

next issue was the gear...
the inch-mm require the 127/120 ratio... even i moved the part to the front, still the room is not enough for... (due to the maximal teethnumber can be applied)

the first test of this was a 51 teeth gear... actually it would require about 0.8 mm dia endmill, but i had only 1.23 dia... so toothroot has a little undercut, but it doesnt reach the main circle..

127/120= 1.0583 the necessary
21/20=1.05 error 0.0083
51/48=1.0625 error 0.0042

might be next week i will get from ebay the right endmill.. already ordered, just it takes time...

thank you