# Adding Vernier Caliper to indicate lathe saddle travel



## Brian Rupnow (May 26, 2015)

I have never been able to depend on the accuracy of the travel indicator dial on my lathe saddle. It always gets me close, but only close. If I build my "oscillating engine", I have to bore the cylinder to a very precise depth. The travel on my tailstock spindle is only 1 3/8" which is not enough. The cylinder will have to be bored with a boring tool held in the toolpost on my compound rest. For many years now I have thought about adding a Vernier caliper to my lathe to act as a poor man's DRO.----But----I didn't want to disassemble the cross slide to start drilling and tapping attachment points to it. This morning I studied on it for a while, and decided the tapped holes which hold the way-wipers would work for what I want to do, and still be able to hold the way wiper. So----First a hand sketch and some head scratching.


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## Brian Rupnow (May 26, 2015)

And then some quick modelling of the area in question to see if it seems reasonable.


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## Brian Rupnow (May 26, 2015)

Which quickly morphs into a drawing---


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## Brian Rupnow (May 26, 2015)

And then into a "to scale" printed off profile, glued to a cardboard backing and tried on for size to see if it is what I want--


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## Brian Rupnow (May 26, 2015)

So far, so good. That seems to hold the Vernier in a very stable manner. Now to figure out a mount for the other end.


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## aircraftmech (May 26, 2015)

Love it! Nice and simple..


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## purpleknif (May 26, 2015)

Uhhh... not to be a smart ass but why not just a carriage stop and gage blocks ?


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## goldstar31 (May 26, 2015)

purpleknif said:


> Uhhh... not to be a smart ass but why not just a carriage stop and gage blocks ?


 
More accurate! Cheap verniers are- cheap.


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## Swifty (May 26, 2015)

I will have to soon make the radiator for my Howell V4, there are literally hundreds of fins on the 1/2" square brass core to cut. I was wondering what method I should use for spacing them out. The hand wheel on the saddle isn't good enough, so Brian's method is one idea, but I may still consider buying a dial gauge with a long travel. I recall, years ago, seeing a turner that had a dial gauge type of thing that had a wheel that ran along the ways on the lathe, just had to be aware of the revolutions that it did.

Paul.


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## goldstar31 (May 26, 2015)

One way is to use a setting gauge utilising a scrap mike. I have( somewhere) the remains of Martin Cleeve depth gauge fitted to his ML7.

Part of it is barely visible in one of the photos in his Screwcutting in the Lathe. However, a full write up is in ME- somewhere in the 50's. I have it- somewhere.

I saved it on an external drive. 

Norman

Actually it is October 1956 but in my search, there is a more sophisticated one by a D.H.Downie- possibility a Canadian but my memory is ancient


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## Brian Rupnow (May 26, 2015)

Finished!! It works very well, I can reset it to zero at any point in it's 6" travel, I didn't have to drill any new holes in the lathe, and all it cost was $3 for a battery to revive the old Electronic Vernier caliper. I quit using electronic calipers a year ago and went back to a dial type mechanical Vernier because I like it better. It took me four years to realize that Verniers are good for marking out and rough measuring, but micrometers are for measuring anything that really matters. I modified my rear carriage stop to hold the other part of the Vernier. It takes me about 15 seconds to remove the caliper from the brackets or to re-install it. The Vernier will only be mounted for specific tasks, otherwise it will get all gunked up and not work.


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## Brian Rupnow (May 26, 2015)

purpleknif said:


> Uhhh... not to be a smart ass but why not just a carriage stop and gage blocks ?



Well, ummm---I don't have any gage blocks. I did have the caliper.


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## tornitore45 (May 26, 2015)

Even if you had gauge blocks... figure the stack for a 0.885" travel, clean them up, assemble, pinch the stack while positioned at the start point, remove the stack; do the cut until the carriage stop against the stop.  No notion of how close you are to the end other than eyeball the gap to the stop.

I had four electronic calipers stop working in a 3 years period, the dial calipers never failed me when used for the intended accuracy.


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## gus (May 26, 2015)

Hi Brian,

Good Idea. Gus copycatting this idea. Been racking my brains to DIY Poor Man's DRO for the mini lathe. I did one for the vertical mill to cut cams last year. Cost peanuts to buy a MIC Digital Caliper v/s $''arm n leg'' for a good DRO. Recalled the Heidenhahn DRO cost me US$2000 back in 1992. 

DRO for the lathe will have spring loaded return. Here's my DIY DRO for the vertical mill.


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## bazmak (May 26, 2015)

Like it very much Brian.Nice and simple.May try it on my C4.The saddle/rack is a calibrated dial but each mark is 0.5mm.Is it easy to set accurately
using the coarse feed.If its simple to unclip you still have the caliper
for normal use.Can still be used with the carriage stop if you make another


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## Cogsy (May 26, 2015)

I made some carriage stops a while back, and I use them reasonably often, but I don't consider them overly accurate. An un-noticed piece of swarf between the stop and the carriage is all it takes to be out at least a few thou.

I like this idea and I'll be stealing it as well! Thanks Brian.


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## bmac2 (May 26, 2015)

Hi Brian
I knocked tougher something similar a couple of years ago to fit my ML7 when Princess Auto hade some 12 calipers on cheap (around $10.00). It just clamps to the saddle and the ways with brass shims. Like you said its on and off in a minute when you need it and out of the way when you dont. One of the hidden benefits I have found with it is the odd time when I have to work in metric. You may be surprised just how often you use it.


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## goldstar31 (May 27, 2015)

Bob, Brilliant,  I have an equally grubby Myford but an old Mk1 Super7B. But what I like is that I also have a fabricated Stent tool and cutter grinder that has dials galore but none on the x-y travel.

Thank you- twice

Norman


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## Gordon (May 27, 2015)

http://start-model-engineering.co.uk/machines-and-tooling/minilathe/micro-dro/

I made one of these a few weeks ago and it is fast, accurate and cheap. I also made a mount for a linear scale a couple of years ago and it works well but takes quite a while to mount on the lathe. The tire gauge is less than $10 and is easily moved and used at other locations. I have even used it on the drill press.


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## digiex-chris (May 27, 2015)

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.


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## Brian Rupnow (May 27, 2015)

digiex-chris said:


> 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


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## digiex-chris (May 27, 2015)

Brian Rupnow said:


> 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?


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## Jyman (May 27, 2015)

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


Sent from my iPhone using Model Engines


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## digiex-chris (May 27, 2015)

Jyman said:


> 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
> 
> ...



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.


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## purpleknif (May 27, 2015)

goldstar31 said:


> More accurate! Cheap verniers are- cheap.



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


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## digiex-chris (May 27, 2015)

purpleknif said:


> 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...


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## goldstar31 (May 31, 2015)

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.


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## Brian Rupnow (May 31, 2015)

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


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## Gordon (Jun 1, 2015)

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.


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## digiex-chris (Jun 1, 2015)

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.


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## Howder1951 (Dec 16, 2016)

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.


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