After machining a fair number of parts with threads, I’ve tweaked my thread milling feeds and speeds to both go a little bit faster, give a more reasonable fit, and remove the last bit of niggling interference with the M2.5 recipe.
I’ll list the changes here, and have updated the original recipe
|M3 Pitch Diameter Offset||0.538mm||0.568mm|
|M3 Repeat Passes||NO||YES|
|M3 Lead To Center||NO||YES|
|M2.5 Pitch Diameter Offset||0.430mm||0.480mm|
|M2.5 Stock to Leave||0.0mm||-0.02mm|
|M2.5 Repeat Passes||NO||YES|
|M2.5 Lead To Center||NO||YES|
Notably, the “Lead To Center” option found on the linking tab is what prevents the M2.5 threads from rubbing when inserting in later passes. Thanks to Quincy Jones from Implemented Robotics for that tip over in the mjbots discord!
3 thoughts on “Update on Pocket NC v2-50 Threadmilling”
Very good info. I’m always having to dial in that PDO with a few trial runs in scrap material when threadmilling a particular thread size for the first time. A suggestion: It would be helpful to add the minor diameter you are using for the M2.5 and M3 bores. The minor size combined with the PDO will determine the thread fit. Good to list both in your recipies. –thanks, Ed K.
For all of these tables, the threads were created using F360’s thread feature set to M2.5 or M3. The minor diameter is then whatever fusion uses (which is just the nominal for I think a class 2, 6H fit), plus (minus) the “Stock to Leave” from the table.
When I made these tables, I didn’t have any means of measuring the thread fit. I do have some go/no-go gauges now, but haven’t gone back and tried to actually get a thread that meets any particular fit.
Ah, got it. Thanks again for the great write-up. Threadmilling is one of the most useful operations these small machines can perform.
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