The drive side threads on a t47 frame that I’m working on just don’t want to start straight.
Steel pmw shell. Park taps and handles.
It feels like just a bad combination with the fine threads of t47 and very sharp taps.
I’m considering using a stone to dull the first couple of leading edges so it will be less likely to dig in. With how expensive the taps are, I want to see if anybody has gone down this route first.
The other solution I’m considering is using a die grinder to create a blunt start. Anybody attacked that before, or have any other bright ideas for making t47 thread chasing a little more user friendly?
Are you able to fully thread the nds tap, then use the guide function of the handles to start the drive side?
I wouldn’t worry too much if you are facing afterwards.
I made a few t47 frames with ovalized bb shells, and had a hard time starting the tap and had to remove a lot of material. I never had a problem afterwards, and definitely wouldn’t alter the tap.
It was stressful, but if you can bury the nds tap, you should be able you should be able to fight past it keeping the tap square with the handles. Make sure to use plenty of cutting fluid.
Yeah the nds side goes in all the way. It feels like you’d expect where there is even pressure all the way through. The pilot lines up nicely so my issue is really just aligning the threads to start. The drive side must be warped just a little more where I can’t quite feel where the two thread starts meet.
So far I’ve mostly been able to avoid t47 but it’d sure be nice to get a method that doesn’t rely on luck.
I wonder as well if other brands of taps have different rake angle of taper on initial threads that makes this better or worse?
Just spit balling here- I might install the LH tap/pilot first, wrap the RH side end of the shell with masking tape so a “collar” of tape extends past the face, take a thread pitch gage and engage it’s first couple of teeth into the shell’s thread, with the portion of the gage sticking out past the face one might be able to transfer the gage teeth tips locations into a piece of something that was stuck to the masking tape collar. This would give you a visual of where the threads are WRT the shell. Or measure from the face to the gage teeth and see if you can duplicate this with the tap on the pilot.
never chased a t47 shell but have done a lot of warped shell clean ups with 68x1.370 shells and every time by just fussing enough was able to pick up on the shell’s entry threads. Sometimes this fussing took way too long… Andy
Thanks Andrew. I was thinking something similar, how it’d be nice to somehow use a thread gauge to project the threads upward toward the tap and that idea quickly evolved into adding a full thread pilot plug on the taps.
I made some undersized 47x1 right and left threaded guides from brass. Bonded each to the face of a tap while aligned together in the threads of a fresh shell. Zero stress or worry of any misalignment now.
If anybody finds this useful then I’d be happy to make a couple more. Learned a few lessons making these!
Really smart!!! I had thought about using a lock ring but that is so old school and I knew of no T47 lockrings, of either thread direction:) I recently watched a vid about using LockTite to bond a work piece to a mandrel for machining. Never thought I’d see it used in the bike world. Andy
