Adding Vernier Caliper to indicate lathe saddle travel

[Brian Rupnow]

Brian, Craftex B2227L? If so, you can turn off the lead screw with the handle to the left of the apron, engage the leadscrew with the apron leadscrew engagement, and move the carriage with the crank at the right hand side of the tail end for much finer feed and dial graduations.

I imagine you won't ever use it now that you've got a DRO though.

Let me know if that's the machine and if you'd like some details on my tailstock cam lock or reversing the leadscrew for cutting left hand threads.

Yes, that is my lathe. I only EVER use the crank on the right hand end to turn the leadscrew. I have built my own tailstock cam lock. I buggered up my auto-feed for the lead-screw about 3 weeks after I bought the lathe 5 years ago, and really, I have never missed it.---Brian

 

[digiex-chris]

Yes, that is my lathe. I only EVER use the crank on the right hand end to turn the leadscrew. I have built my own tailstock cam lock. I buggered up my auto-feed for the lead-screw about 3 weeks after I bought the lathe 5 years ago, and really, I have never missed it.---Brian

Indeed, I rarely use the autofeed myself unless I'm doing something really long. I'm pretty happy about the machine, except for the odd graduations on the tailstock ram. I can never get my head around how much advance is happening per 5 or 10 ticks. I've been thinking about how to add a caliper to the tailstock for that reason, but given how little travel it has, and that I have to fully withdraw the ram into the tailstock in order to release one of my centers, I'm having trouble thinking my way through that one. Any ideas?

 

[Jyman]

Nice job Brian, I will definitely have to copy that one for my self as I have the same lathe as you,

Digiex-Chris I would love to find out how you cut left hand threads with yours


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[digiex-chris]

Nice job Brian, I will definitely have to copy that one for my self as I have the same lathe as you,

Digiex-Chris I would love to find out how you cut left hand threads with yours


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Pretty simple.



It's just a plate with a pivot that holds any gear in mesh with the gear train as an idler. I even put a key, so that all of the wear is on the pivot, instead of the gear. It just swings to adjust for different gear ratios. Just use any gear there to reverse it. The top and bottom bolts on the bracket are tapped into the edge of the casting. Looks like there was about 5/16" to work with.

Another thing I discovered with this lathe is that confused me for a bit is that there is a reduction of 4:1 between the spindle and the first threading gear shaft. It also has a 7tpi leadscrew. That means if you need to calculate a gear ratio that's not on the threading chart, just pretend you have a 28 tpi leadscrew in your calculations. Also because of that 4:1 reduction, the error in lead when cutting metric threads is very small. So small that I don't usually pay any attention to it and proceed like it was a metric lathe.

 

[purpleknif]

More accurate! Cheap verniers are- cheap.

Not hardly. You're leaving yourself open to sine error.

 

[digiex-chris]

Not hardly. You're leaving yourself open to sine error.

Cheap calipers tend to be lacking in the temperature compensation and low battery protection as well. As long as you're familiar with those effects it's fine though. Even taking cosine error into account, it's still significantly more accurate than trying to split the 0.01" (the smallest division on this particular lathe) lines on the carriage wheel. It makes it even worse that it's 0.55" per revolution, giving you 2.something turns per inch...

 

[goldstar31]

Perhaps a workman should not be over critical of work that is produced on cheap jack equipment.
I don't think that John Ruskin was wrong about price and whatever. They did name a British University after him. Not a good one but one that was within three standard deviations of the mean.

 

[Brian Rupnow]

I'm not making parts for the space program on my lathe. I don't believe that anything I've built so far suffers from lack of temperature compensation, sine error, or polar shift.----Brian

 

[Gordon]

I am with Brian with this. Most of what we do does not require super precision. Usually it is a case of knowing when to be precise and when it is not important. For example a 6" flywheel at +/- 1/16 is probably not important but a cylinder bore of +/- .001 is probably important. Most of us compensate by making parts selective assembly. A cylinder which is .005 oversize can still be usable by making the piston .004 oversize and fit by trial and error. This is a hobby and for our own enjoyment and the fact that you cannot take a piece from my engine and make it work on Brian's engine is not important even though they may be the same design and we were both shooting for the same size. Some folks have the skill and equipment to hold tolerances to .000001 but most of us are working with cheap and/or used equipment. I would rather see someone enjoying making engines on a cheap Harbor Freight lathe than not making engines at all because they cannot afford or justify a $10,000 lathe. The same is true for much of the tooling and measuring equipment we use. It may be nice to buy $15 drill bits and $30 end mills but for most of us the cheaper stuff does the job and just requires a little more care in use and an understanding of the limitations.

I am not trying to put anyone down here. If you can afford and justify the expensive stuff, good for you. Most of us enjoy just getting out there and building something. If your enjoyment comes from making super precision parts that is good.

 

[digiex-chris]

agreed. It's the man, not the machine. Just take a look at the watchmaking trade to see what's possible with hand held tooling. Incredible precision.

 

[Howder1951]

Love that caliper, is it true that "power fist" is just a re-branded "Pittsburgh" brand? haha.
That is a great addition to your lathe, one of those"why didn't I do this long ago" things.