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10-11 inch lathes -- Precision Matthews, Modern Tool
- Thread starter trlvn
- Start date
Rauce
Ultra Member
Here’s a picture of the die holder. Some machinist or tool maker made it ages ago and passed it on it on to someone who then sold it to me… like all the best tools in my experience.
I lock the tailstock quill but leave the tailstock unlocked to the ways and put the machine in its lowest speed (~50rpm). I size the part about .005” under the nominal thread diameter. Once the die gets close to the end of the thread I turn the machine off and turn the chuck by hand to the shoulder then I put it in reverse to back it out.
The part in question is an axle for converting a certain bicycle wheel for use on the velodrome. The wheel manufacturer no longer offers this particular conversion axle for sale. I made one for a friend, posted about it on a forum and have ended up making about 30 over the past 3 years.
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Nice part. Good for you for filling a niche. I hope it brings in a few shekels & helps buy more tools.
What is the material of bike part?
If you find that certain alloys or (larger) thread size don't play nice with full threading on the the tailstock, another quasi-production method is to single point it to say 0.005" undersize of finished thread depth & then use the die to finish it off. That makes for clean consistent finished threads, easier on the die & minimizes thread measuring to final dimension.
What is the material of bike part?
If you find that certain alloys or (larger) thread size don't play nice with full threading on the the tailstock, another quasi-production method is to single point it to say 0.005" undersize of finished thread depth & then use the die to finish it off. That makes for clean consistent finished threads, easier on the die & minimizes thread measuring to final dimension.
Rauce
Ultra Member
I make them from 303 stainless which machines really nice. I’ve done single point followed by a die before as well. I can’t remember what it was for but I had to do a 1.75mm thread recently and that’s one metric pitch my lathe won’t do without a change gear I don’t have. I single point cut a 14tpi thread a bit oversize and then ran a 1.75 die over it.
Very cool. Good on you for coming up with that solution. How did it turn out in the end?
Rauce
Ultra Member
I remember what it was for now! I made a dummy axle for MTB frames that use a thru axle with M12x1.75 thread for installing the rear wheel.
It came out good enough for the application.
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Looks GREAT to me!
Do you remember approximately how complete the original thread was? Just a rough guess will do for my understanding. Eg 1/4,1/2, 3/4, 90%???
Rauce
Ultra Member
I would guess about 80%. The material was 304 stainless and the 12x1.75 die I have is just a cheap one from a set so I wanted it to do as little work as possible.
Thinking about this approach more, I think it would only work on a shorter section of thread. Eventually the difference between the pitch of the single point cut and the die (in this case 14tpi vs. 14.514tpi) would result in an incomplete thread form.
I agree completely.
I once had a debate on this subject over the difference between 16tpi and metric 1.6.
The difference is indeed small.
Some people even claim that 1.6 is not a valid thread size. I argue that it is because I have thread gauges for it, it shows up as an option on my lathe setup, and I have at least one piece of equipment that has that thread in it.
The debate stems from how close the two are. But as you point out, they are only close for short threaded sections. That closeness slowly disappears as the thread length grows.
The issue is more serious though. Much more serious than most realize. If you put the two different threads together, they appear to fit, but as the joint is tightened, the threads begin to deform (as they should) that's all part of the torque equation that prevents joints from becoming loose and/or overstressed. In your case, this doesn't matter because you are actually cutting the proper thread to create the right stress/strain geometry. But for completed threads, it's a recipe for a future problem.
I have a cheap digital caliper. It loves to reset its zero at random times. Yes, I should throw it out. I never had this problem with a vernier.
The only digital caliper I own (and yes, I do own several) that has not lied to me (yet or that I know of) is my Mitutoyo Absolute Digimatic.
But it has its own problems. It has no auto-off. If I accidentally leave it on, it will be dead by the next time I go to use it.
@Dabbler has pointed out that it really never turns off anyway. The on/off button only turns off the display. But even that is significant.
They are pricy and there are many fakes out there. If you do buy one, I'd recommend buying from an authorized dealer (eg KBC Tools) and I'd also recommend buying a bulk package of batteries for it.
That all said, a vernier caliper NEVER lies and NEVER needs batteries.
Dabbler
ersatz engineer
I started with a Mitutoyo vernier caliper for all my 'approximator' measurements.
I now use digital exclusively, as I am very long sighted, and reading the fine lines needs a loupe or magnifying glass. I can easily read my digital calipers. However, if I want accuracy, it is mechanical micrometers all the way.
I now use digital exclusively, as I am very long sighted, and reading the fine lines needs a loupe or magnifying glass. I can easily read my digital calipers. However, if I want accuracy, it is mechanical micrometers all the way.
Sorry @6.5 Fan , I don't agree with @David_R8.
Jigs are not warranted until it arrives at your farm.
At that point, you are required to dance all around it in a perfect circle both ways. Please have the driver take a video and post it here so we can all laugh at you...... er, I mean help you celebrate!
Me practising:
Craig
So...... Does your bride know you have been faking the knee injury all this time?
