unknown taper on lathe centre

This centre fits the tailstock of my vintage Pittler lathe c.1895, the shaft is just 32mm long and tapers from 14 to 12mm.

It's not any taper that I can recognise so has anyone got any suggestions as to what it might be and if so any other lathes that use this taper?

I would be tempted to first convert your measurements into all known ‘systems’ and then browse through this lot:

**LINK** http://www.tools-n-gizmos.com/specs/Tapers.html

MichaelG.

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For example, the taper could be expressed as a half-angle slope of 1:32

Edited By Michael Gilligan on 05/10/2022 09:53:23

Doing your own stuff from established systems may be what it is

I extend my MT1 taper system for fatter bigger requirements

As Michael says, it may be a descriptive type

Modding your tailstock is pretty easy for an artisan (even bodgers can do it)

Edited By Ady1 on 05/10/2022 10:09:43

If the rest of the lathe uses Imperial fittings, threads, etc, using Metric units may be counterproductive and confusing.

measure major and minor diameters, a carefully measured distance apart..

Convert your dimensions to Imperial and use those, to calculate in various formats..

The taper can be expressed in a variety of ways, Angle, Half Angle, Inches per Foot, Inches per inch.

the "Tool-n-Gizmos" website lists many tapers and their dimensions.

You may find what you require there.

Nothing on Lathes UK that helps?

Howard

Edited By Howard Lewis on 05/10/2022 10:39:09

That's something that is not as simply done as said.

Measuring the diameter of a taper at any specific point is rather difficult, let alone two specific points a known distance apart.

Maybe it could be done by setting up in a lathe, zeroing an indicator on something of known diameter, then taking comparative readings on the taper, along with tracking the distance apart.

That will find the taper angle or rate but length dimensions on a taper are more nominal/indicative than definitive.

B-tapers are just the small or large end of a Morse taper, so confirming the taper angle will allow you to see if they remain a possibility.

Vic [with apologies for the inevitable repetition in what follows]:

Is there a centre in the back-end of that centre ?

… if so; set it up between male and female centres and, with a DTI mounted at centre-height in the tool-post, traverse with a convenient number of turns of your your 8tpi lead-screw and check the distance moved by the plunger.

If you choose to use 8 full turns, there is room to take several measurements and average them.

Measurement job done

MichaelG.

Edited By Michael Gilligan on 05/10/2022 17:13:50

From Vic's dimensions I get the 'Angle from Centre' of his taper to be 1.7899°

From the tables at LittleMachineShop I can say it's not Morse, Jarno, or Brown and Sharpe. The only potential match is Jacobs #33 which is 1.8184°

Given the difficulty of measuring tapers accurately, 1.7899 might be 1.8184, but I'm not convinced a 19th Century German lathe would have a Jacobs taper.

I think one of my books lists a few more tapers: I'll see if I can find it.   They are:

Sellers Taper - 0.75 in per foot, with a keyway throughout

Reed Taper -  1:20, similar to Jarno

Standard Tool Company Taper - between 0.6 and 0.63 inches per foot

Dave

Edited By SillyOldDuffer on 05/10/2022 18:01:14

Edited By vic newey on 06/10/2022 10:24:09

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Because you are replying within the message that you are quoting

… if that message has been edited, then the text which states that fact is in a small font

… that font is then carried forward to what you are typing.

MichaelG.

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Edit. ___ When you replied to Dave’s post, you first deleted a lot of it,  and your reply is therefore in the standard font because that is what was lurking there ! 

Q.E..D.

Edited By Michael Gilligan on 06/10/2022 11:12:15

Easily done - every time I measure tapers I get them wrong! The corrected half angle is 1.5482° - still doesn't match any of the tapers I now of. The different ways tapers are expressed is a right pain: Ratio, Angle, Half Angle, Inches per Foot, Inches per inch etc. make some tables hard to compare.

Why is nothing ever easy?

Dave

For something that short, set it up to run true in a four jaw chuck. You can use a micrometer on the parallel part to verify your dial gauge and hence obtain both diameter and length measurements at the same time.

The historical context is important in putting any of them forward as possible candidates. If a particular taper was invented or standardised after the machine was made, it can be eliminated. You also have to use common sense: an obscure taper used by a single US manufacturer has to be very low on the list of options.

I am not going to find a USB port on my CNC Bridgeport no matter how carefully I measure it.

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Some later versions of my Pittler lathe have the tailstock fitted for 15mm collets with a drawbar, ones such as mine do not have the quill bored through.

von Pittler was a brilliant inventor and patented hundreds of machines in his lifetime inc his revolver capstan lathes which still exist today. I guess the taper for this didn't catch on although I need to find other C3 owners and see what they have for the tailstock

I have been playing-around with a tiny spreadsheet, which I think is on the way towards being useful.

The layout can be tidied-up easily enough.

It does nothing that we couldn’t do in a minute or two with a calculator, but as the results are near-instantaneous and presented automatically I think it may have some merit.

I’ve done it in Apple’s iOS App ‘Numbers’ but it should easily convert to Excel, etc.

Constructive criticism would be welcome.

Note: for my sample input, I have doubled-up Vic’s measurements … this allows us to easily see the difference between the vulgar and normalised presentation of Slope.

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If you want to fire some numbers at me, so that we can check the results … please do

If you want a copy of the file, to develop it yourself … please send me your eMail address by PM

MichaelG.

Not criticism but just to draw your attention to a possible bug lurkiing within. I suspect that if you play with it for a while it will be possible to get something vulgar in the normalised part.

The spreadsheet will do its maths with base 10 (decimal) and takes care internally about rounding without you needing to do anything.

When you do maths base 60, you have to deal with that issue very carefully and explicitly.

There is a good chance that there will be some combination of input that will display x:60 in the normalised part.

You can get a situation where the minutes are 59.999, so a strict mathematical check means the degrees do not roll over (and the minutes reset), but then when you display/format those minutes as an integer (zero decimal places) so a human can read them they turn into 60.

.

Thanks for that, but [entirely my fault for not describing it in detail] … the two versions of ‘Slope’ are not showing degrees and minutes.

The colon is purely text, and there to show a ratio

60 [or indeed any larger number] would be entirely reasonable

MichaelG.

Thank you guys for carrying on trying to sort this out for me, I'm afraid it's got a bit too technical for me to make sense of though, I'm really just a vintage lathe enthusiast who likes to potter around making minor repairs and adjustments rather than make any models or anything like that.

As you might gather I have no engineering background whatsoever but spent years as an effects painter for TV & film and before I retired I spent years as an architectural modelmaker working in wood and making models for museums and collectors worldwide. Doing all those models I never used any drawn out plans either!

I was rather hoping the taper might be a recognisable standard so I could seek out a drill chuck but it's looking rather unlikely at present