Where Can I Get Thread Grinding Wheels?

[Tony Wells]

As mentioned, thread grinding id a specialty on par with, or possibly above helical gear generation. It is normally reserved for thread gages and such precision threads as in ball screws or precision lead screws. In an industrial setting, a dedicated machine is used for this, not a hobby lathe.

May I ask your intention or goals (motivation) for this endeavor?

 

[Wreck™Wreck]

Are these unobtainium for the hobbyist? I can't find them for sale anywhere.

Not unobtainable merely a very small market with many variables, any such tool will be made for your particular application, no one would stock such a thing.
I can think of very few applications for thread grinding other then precision lead screws used in every industry from semi-conductor manufacturing, thin film metallic deposition equipment, very high end optical devices, metrology and I suspect microscopic surgical devices. Why a hobbyist would want to grind threads is interesting.

 

[strantor]

May I ask your intention or goals (motivation) for this endeavor?

For threading all the way to a shoulder. Imagine threading something with a really coarse thread, like this:



Maybe you have the lightning fast reflexes to disengage the half nut and back out the cutter before it crashes into the shoulder, but I don't have the confidence to try it. I'd much rather set my spindle on the lowest speed possible and engage the backgear, so the spindle rotates super slow while another tool (tool post grinder) does all the work.

 

[Tony Wells]

I don't normally have a problem threading up close to a shoulder like that, but I understand how it can be difficult for some. The reality of it though is that the mating female thread likely has a counterbore a little larger than the major diameter, so the thread isn't "perfect" as close to the shoulder as it may appear.

 

[Wreck™Wreck]

For threading all the way to a shoulder. Imagine threading something with a really coarse thread, like this:



Maybe you have the lightning fast reflexes to disengage the half nut and back out the cutter before it crashes into the shoulder, but I don't have the confidence to try it. I'd much rather set my spindle on the lowest speed possible and engage the backgear, so the spindle rotates super slow while another tool (tool post grinder) does all the work.

I believe that you underestimate your own abilities here, turn a relief groove 1 or more thread pitches wide at just below the minimum minor diameter at the shoulder, run the spindle very slowly and even insert tooling will produce a decent finish depending on the material of course.

Before doing so use a piece of plastic material or if that is unavailable wood, run the same spindle speed and thread lead as a test, I suspect that you will be surprised at how quickly and accurately you can open the 1/2 nuts, do not be shy as these are machine tools not delicate flowers and the worst that can happen on a small part is that you will ruin the part, break the tool and knock the toolpost out of index.

Have at it, you will never learn what you can do until you actually do it, any older manual machinist that insists that they have never crashed a threading tool into a shoulder either did not do much thread work or has a poor memory.

Good Luck

 

[dave_r_1]

...the tool crashed into the piece then broke so the tip embedded in your chest, meanwhile, the part got out of balance, causing the lathe to shake violently and tip over onto you, then when your wife heard your screams and came to help, just as she reaches you, the motor shorts 220V to the frame, killing both you and your wife. a week later, the dog is dead because it hasn't been fed.

 

[mksj]

It is also possible to use an electronic stop or limit switch that interfaces with your controls to stop the machine. Problem with non-VFD machines is the lack of electronic braking, so hard to figure the stopping point based on the momentum in the system and the cutter drag. With an electronic stop and braking, the stopping point is repeatable to better than 0.001", often it is the same exact point that the cutter stops on repeat passes. I would think at a hobbyist level it would be difficult to implement an accurate, thread grinding system. I am wondering if the thread could be partially cut on a lathe and finished to the shoulder with a die. I routinely do some threads this way (usually up to 1/2"), I reverse the die on the final cut to get a full thread up to the flange or stopping point.

 

[strantor]

I believe that you underestimate your own abilities here, turn a relief groove 1 or more thread pitches wide at just below the minimum minor diameter at the shoulder, run the spindle very slowly and even insert tooling will produce a decent finish depending on the material of course.

Before doing so use a piece of plastic material or if that is unavailable wood, run the same spindle speed and thread lead as a test, I suspect that you will be surprised at how quickly and accurately you can open the 1/2 nuts, do not be shy as these are machine tools not delicate flowers and the worst that can happen on a small part is that you will ruin the part, break the tool and knock the toolpost out of index.

Have at it, you will never learn what you can do until you actually do it, any older manual machinist that insists that they have never crashed a threading tool into a shoulder either did not do much thread work or has a poor memory.

Good Luck

Ok, I'll try that on some PVC. Hopefully I surprise myself.

 

[JimDawson]

Just turn the tool upside down, run the spindle backwards, away from the shoulder.

 

[strantor]

Just turn the tool upside down, run the spindle backwards, away from the shoulder.

Genius! Why didn't I think of that?



Why isn't this the normal mode of operation? I'm guessing there will be some tradeoff, and I'm guessing it will come about from the tool being pulled up instead of pushed down... is that right? Will it be less rigid, more prone to chatter and bad finish? Should I take really light cuts?