Tapered thread

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dmbgo
Posts: 342
Joined: Sat Aug 15, 2020 9:21 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: 0035FF8A7F34-0730203594
Location: Bendigo Vic Australia
Contact:

Tapered thread

Post by dmbgo »

I made a mistake. It is with some chagrin that I now need to remove a "blind" bearing shell from a blind hole. The hole is in the magneto body that I pressed it into.
I don't have the option for removal of by, tapping or pressing the bearing shell from the outside, so I thought I'd make a special puller. The puller would lock under the bearing shell, using an expanding lip, which would be expanded after the puller is inserted into the bearing shell from the rear.
After thinking about the problem, my puller design is as follows....
Similar to a lathe or mill collet, the puller body would be able to expand or contract. When a threaded tapered mandrel is screwed into the puller, this would cause the "lip" on the end of the puller to become larger and to be forced under the bottom of the bearing shell, thus gripping the bearing shell and allowing me to pull or press it out.
A tapered bolt with the same thread as the puller body, would screw into the puller body, causing the puller body to expand and force the lip under the edge of the bearing shell.
Once that happens the bearing shell can be removed.
All of this requires that I am able to cut a tapered thread onto my tapered mandrel and screw it into the puller, thus forcing the puller jaws apart.
Is this possible? I have thought of an alternative method, where I just use a straight thread on the end of a tapered mandrel, but....
Here is a photo of the magneto body with the recalcitrant shell inside.
Magneto bearing shell in Magneto.jpg
cncsnw
Posts: 2796
Joined: Wed Mar 24, 2010 5:48 pm

Re: Tapered thread

Post by cncsnw »

Yes, you can cut tapered threads, using Intercon or G code. In Intercon, just enter your desired diameters, taper, and lead on the F7/Details page.

For a typical external tapered thread, cutting in the Z- direction (so the start is at a smaller diameter than the end) you use a negative taper amount or negative angle.

For a typical internal tapered thread, cutting in the Z- direction (so the start is at a larger diameter than the end) you use a positive taper amount or angle.

The programmed thread diameter (minor diameter of external thread, or major diameter of internal thread) is at the end of the threading cut. The starting diameter will be that programmed diameter, plus the taper amount.
dmbgo
Posts: 342
Joined: Sat Aug 15, 2020 9:21 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: 0035FF8A7F34-0730203594
Location: Bendigo Vic Australia
Contact:

Re: Tapered thread

Post by dmbgo »

Thank you, I'll give it a go once I get the slots cut in my puller.
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