Taper turning. (offset attachment)

[Nick_GParticipant @nick_g]

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Has anybody here got any knowledge of these. **LINK**

Are they any good.?

Nick

[Nick_GParticipant @nick_g]

[JasonBModerator @jasonb]

You could save yourself some money and use your boring head which will do a similar job and save offsetting the tailstock. Or just offset the tailstock.

Never mind all this tooling have you decided what the postman is going to deliver next?

Edited By JasonB on 05/02/2016 12:10:52

[Nick_GParticipant @nick_g]

Posted by JasonB on 05/02/2016 12:09:34:

and use your boring head which will do a similar job and save offsetting the tailstock. Or just offset the tailstock.

.

Good point Jason.

Except that I don't have a boring head. ……….. But you are right.! I would get far more 'bang for buck' by purchasing one. Especially if I purchased 2 arbours to fit it. One INT 30 to fit my mill and one MT3 to fit the lathe tailstock.

But is the principle OK providing I did not get too eager with the depth of cuts.?

I do realise the same is possible by offsetting the tailstock. But it's always a time consuming pain to set it right again.

Next project. – Not totally decided but I do keep thinking. "Uc-itt, grow a pair" and jump into a Corliss.

Cheers, Nick

[JasonBModerator @jasonb]

Principal is fine. My only niggle with one like you have shown is that it is quite wide and could get in the way of the tool post more than a boring head would and you could make a half centre for that if needed. As you say you can have a lot more fun with a boring head as that attachment can't really do anything else.

[Swarf, Mostly!Participant @swarfmostly]

Hi there, Nick,

From my armchair, it looks as though the device would work better with a female centre and a ball-bearing. Ditto at the head-stock end.

Best regards,

Swarf, Mostly!

[JasonBModerator @jasonb]

Or use a bell type centre drill, no jokes about the ends

[Gray62Participant @gray62]

I made one of these years ago from one of the Hemingway kits, less than a quarter of the price of one of those and more satisfying than buying one.

[Jon GibbsParticipant @jongibbs59756]

+1 for the Hemingway kits version which has a half-centre (dead of course).

I used mine, instead of setting over the tailstock, in order to be able to screwcut a taper between centres for a pigtail mandrel (that I could have bought for a few quid but I thought it'd be more fun to make one) which doesn't need a precise taper.

Even though I have it I don't use it for conventional tapers as it's quite tricky to set up precisely and the arms then need to stay horizontal and not move after the set-up. All my other tapers have been short enough to stay within the capabilities of the top-slide.

HTH

Jon

[Simon Williams 3Participant @simonwilliams3]

Comments above bear out my own experience, and it cheers me up immensely that my experience in using this style of taper gismo has been that of others. I made a scratch one out of curiosity, but was completely unable to get it set to turn the same taper twice over. I suppose it depends on the reason for wanting to make something tapered – if it's to make a precision fit then this isnt going to cut the mustard, but if you just want to make a tapered end on something then this (and a big bag of patience) might be enough. Whether you use a boring head to achievethe same outcome probably doesn't matter in terms of results, but it is a.more cost effective thing to buy for sure. My parsimonious nature likes the idea of buying one accessory and getting two results, but if you want an accurate taper buy or make a taper turning attachment.

I know resetting the tailstock true is a pain in the vernaculars, but so is not being able to make two parts that fit together. For me, failing a TTA I'd take my chance with the tailstock every time!

[Russell EberhardtParticipant @russelleberhardt48058]

I don't know what is so difficult about resetting the tailstock. I just adjust mine so that a razor blade held between the centre points sits at right angles to the bed.

Russell.

[mechman48Participant @mechman48]

Here's one I made earlier ( many years ago )…

… only used it in anger once, did the job nicely

George.

[Raymond AndersonParticipant @raymondanderson34407]

I agree with Russel, Re- setting the tail stock is quick and straight forward. [ for me anyway ] I always use a between centers bar, which I had specially made for the purpose. It is 350 mm long, 30mm Ø and is is hardened and ground BETWEEN centers. I specified straightness , parallelism , and roundness to 0.004mm. It was quite pricey, but worth it.

For anyone wanting to know who made the bar, it was "Strongbar " in Norwich.

[Clive FosterParticipant @clivefoster55965]

To my mind the major weakness of such devices is their being held in a simple taper without drawbar or other restraint making them vulnerable to twisting under cutting loads. I have seen variants with support devices down onto the bed to prevent this but that does add rather more complication.

Don't really see the difficulty in getting repeatability. Obviously the taper per unit set-over varies according to the length of the component which can be tricky to determine accurately. Geo.H Thomas has written at some length on this very problem and gives what appear to be efficient methods to determine the effective length of the component taking into account the centre drilling depth which should be used in calculating the set-over. To me that all has an air of picking up a soldering iron by the hot end. Generally taper turning set-up methods seek to substitute relatively easily made linear measurements for hard to do really accurately angular ones. My practice is to convert any taper to inches / thous / mm per some linear distance for which I have an adequately accurate block, set the component up roughly by eye then use the block and bedstop to determine exactly what the taper is enabling appropriate corrections to be made iteratively.

OK I have proper taper turning attachments on my lathes which makes the process easier but it will work just fine with offset devices or even tailstock set-over. I reduced a gash set of gauge blocks for this sort of "rough" spacing. They may not wring together any more but they are still as accurate as I can determine using my equipment. Even easier with DRO systems.

Clive.

[Michael Cox 1Participant @michaelcox1]

Posted by Clive Foster on 05/02/2016 21:28:32:

To my mind the major weakness of such devices is their being held in a simple taper without drawbar or other restraint making them vulnerable to twisting under cutting loads. I have seen variants with support devices down onto the bed to prevent this but that does add rather more complication.

One way round this is to clamp the offset to the tailstock quill rather than inserting it into the taper, see:

http://mikesworkshop.weebly.com/tailstock-offset.html

Mike

[Bob Unitt 1Participant @bobunitt1]

I made this one a few years ago, primarily to turn the tapered columns on a 'Lady Stephanie', but it's done a few other things (e.g. morse #1 for my wood lathe tools) as well over the years. The arbor was a commercial blank, force-fitted into the rest of the tool (which is mainly bar-stock). The moving slide carrying the centre is dovetailed into the fixed part. The rotation problem Clive refers to is prevented by the piece sticking out of the back besides the taper, which slots into the anti-rotation slot on the outside of the tailstock barrel.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Russell Eberhardt on 05/02/2016 16:19:17:

I don't know what is so difficult about resetting the tailstock. I just adjust mine so that a razor blade held between the centre points sits at right angles to the bed.

Russell.

Hi Russell,

Much depends on the lathe I think. It was easy enough to get the razor blade right on my old mini-lathe until the adjusters were tightened to fix the setting. At the last moment the tail-stock would describe a small figure of eight around the headstock axis. Getting it spot on could be quite a fiddle!

As to cause, the innards of my tail-stock were a bit rough from new and I suspect more expensive lathes might develop similar symptoms if damaged or worn.

Dave

[Clive FosterParticipant @clivefoster55965]

Mike

Clamping the offset device to the tailstock barrel rather than relying on a simple push in taper seems to be a much more engineeringly valid solution. Which rather begs the question why all the published designs I've seen in magazines and books, probably 5 or 6 maybe more over the past 40 odd years, use a simple taper mount. Most especially as such articles usually include instructions on how to make a taper to match your tailstock without the offset device. Invariably stressing the importance of accurate work and covering the inevitably tricky set-up process in some detail. A simple bore, with some appropriate clamping device, to match the tailstock barrel is clearly much easier to do and, so far as I can see, at least as effective. So why did so many published designs do it the hard way?

A minor refinement to setting up is to ensure there is a large enough flat area on top to sit an adequately sensitive bubble, or electronic if you are into newfangled things, level to ensure the axis of shift is pretty much aligned with the late bed. Any significant tilt will affect things enough to upset accurate jobs such as morse and Jacobs tapers.

There are published references to adding fixed, pre-set, offset capability for things like morse tapers. Which sounds a good idea until the difficulty of getting repeatable effective lengths for the blank stock from which the taper is to be made. I suppose a collar could be affixed to the centre drill accurately controlling the depth to which the centres are drilled. If a radius type centre drill or ball in female type centres are used there will be no skewing effects so the results ought to be both reliable and computable. As Geo.H Thomas pointed out the effective length can be determined by calculation from a measurement taken over two balls seated, one at each end, in the drilled centres. Probably something its wise to do as a check on things before setting out to make an accurate taper by means of measured offset.

I wonder how variable centre drills are in terms of depth from the point to a suitable diameter of cone? If there is any significant variation and you expect to be doing a few tapers over the years it might be as well to dedicate a centre drill, or two if one size doesn't fit all, with a depth setting collar permanently fitted to the job.

Every time I think I'm going a bit OTT faffing about making sure that things should go well before starting a job I remind myself that a do over after producing a bad part is much more work in the end. My workshop Gremlin colony keeps me well supplied with do-overs anyway without a helping hand from me.

Clive.

[Sam Longley 1Participant @samlongley1]

Posted by Michael Cox 1 on 05/02/2016 22:46:08:

Posted by Clive Foster on 05/02/2016 21:28:32:

To my mind the major weakness of such devices is their being held in a simple taper without drawbar or other restraint making them vulnerable to twisting under cutting loads. I have seen variants with support devices down onto the bed to prevent this but that does add rather more complication.

One way round this is to clamp the offset to the tailstock quill rather than inserting it into the taper, see:

http://mikesworkshop.weebly.com/tailstock-offset.html

Mike

Interesting clamping system

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