Taper attachment

I’ve a taper to cut with the lathe for an ER 32 collet, 8 degrees is the angle, I’ve never used the taper attachment before but I’ve that bit sorted out so ok there, it’s the angle I’m struggling with, can I convert 8 degrees in to taper per foot, I found some info on the net that gave me a number per inch of 1458 thou, I haven’t the piece of paper with me I wrote it on but think that’s what it was, the taper attachment set tool on center but the tapers wrong, I’m doing something wrong but not sure what , can any one help.

Regards Alan.

You want 1.68649" per foot to get 8deg

Or looking at it the other way 0.140541" per inch (1.68649/12)

Or 1 in 7.11536

Edited By JasonB on 11/05/2019 13:30:24

I knew I could rely on you Jason thank you very much, it’s makes sense as the trial taper I cut is slightly to much, is there a conversion calculator from degrees to taper per foot I’ve looked but to know avail, me and maths aren’t very good friends, 🙄

Thanks Alan.

Alan

Tangent tables are your friend when it comes to tapers.

Unfortunately funny numbers, whether degrees, distance per foot or both (eek) go together like ham and eggs when it comes to tapers.

Best way I've found to set things is to run a dial gauge against a bar in chuck or collet truly aligned to the bed using the bed-stop and an accurately measured distance piece to set the baseline. My parallels are 6" long so one makes a great distance piece when working in taper per foot. Setting up a second bed-stop on the other side of the saddle makes life even easier.

It helps to set your measurement baseline central, or at least close to it, on the taper turning device. That way you can get very close by simple measurement at one end of the travel set by the distance piece. So long as your set-up distance centre and taper turner pivot centres are decently close simply splitting the differences between indicator readings will bring you close enough for most jobs. Hafta work a little harder for Morse tapers tho'.

Once set-up you can cut your taper anywhere along the device but some lathes with telescopic cross slide screws have only limited travel and can run out of movement towards the end of the taper slide on larger angles. Found that out the hard way on my SouthBend Heavy 10.

Clive

Well this afternoon I’ve had another go at the taper, but I’ve still got something wrong,the taper is to great, I set an indicator on the ways to zero and another one on the rear of the top side, with one inch of travel I get 140 thou of inward travel so I thought happy days but no, tool is dead on center hight I’ve made sure I come back far enough to account for the backlash on the taper turning attachment, the info I found on the angle for the ER 32 collet taper says 16 degrees included so I’ve worked it on 8 degrees, am I right ?

Alan.

Yes you need to set to 8 degrees.

Easiest way to check is put a bit of silver steel in the chuck and slip a collet of the same nominal size over that, the larger the better. Now set your dti to run on the outside of the collet and adjust the taper attachment until there is no movement on the DTI.

The final check would be to stop boring a bit before reaching finished size and blue up a collet to see how it contacts the bore, make any adjustments and then work upto finished size at that setting

Alan,

On an 8 deg right angled triangle with a base of 1", the height upright will be .14" & the hypotenuse will be 1.01", is that what you have?

Tony

An ER collet? Why use a taper attachment? Does you top slide not have sufficient travel?

The usual way to copy a taper is to mount a master copy in the lathe and adjust the top slide movement (or taper turning attachment) such that an indicator does not deviate as the top slide (or carriage) is traversed along the taper. It is important to set the indicator at cutting (centre) height).

Yes, I think so. All the maths and previous advice looks right to me. 0.140" over 1" is about right for 8 degrees (correct for ER).

Can you measure the angle? If it's nearly right, you may have an measurement/set-up error. Strictly atan(0.140) is nearly 7.97° That's pretty close to 8, but perhaps DTI error has made it worse. 141 thou over 1" would be 8.026°

Working with angles is tricky: I'd print or draw a big triangle on A4 and cut it to use as a template. You can use it to see if the taper attachment is tracking as expected.

I don't have a taper attachment, but even if I did, I wouldn't use it on a short ER depth taper. I'd adjust the top-slide to the correct angle using the 0.140 to 1 ratio and cut the taper with that. Harder to describe than do!

Dave

Once again chaps you’ve all come up trumps with some great advise as normal, it’s realy good to know you can get some good advise when your struggling a bit, Tony your question about the right triangle may as well have been written in German as I’ve know idea what your asking me, but I’m great full you took the time to try and help me out , as I said preaviously maths and me are not good friends, Jason, the thing I was going to try tomorrow is the same as you’ve suggested, still stumped on why it’s so far out though, Clive, great explanation of how you go about this type of thing, food for thought in the future, Not Done It Yet, I’ve not used the taper attachment yet so I thought it would be a bit of practice I’ve cut these before using the top slide but thought I would give the taper attachment a go, glad I did as I’ve leant a bit today playing with it, Dave thanks mate, as I said above I just wanted to try it, tomorrow’s another day I’ll let you all know how I get on.

Thanks Chaps, Alan.

If you are running a clock along the face of the topslide (as it says in your post above), are you sure this face is parallel to the lathe axis. If not all bets are off. Never used a taper turning attachment, but how about fastening the DTI to the cross slide running against the taper turning thing and adjusting that to get the 0.1405" per inch

Alan, can you post a photo of the setup and what you are setting the taper attachment to.

You say is is "far out" so I wonder if your TT may be callibrated in something else, maybe even included angle

Alan's query made me realise I don't know how taper attachments work. There's a picture of one in this book, not quite what I expected:

Fig 29 shows the attachment is graduated in ⅛ inch over 1 foot, which is unfriendly!

What I was expecting (having glanced at one at an exhibition) was a rod connected between two scales behind the saddle and fixed to the bed such that traversing the saddle moved the cross-slide. Memory very untrustworthy but I think the scales were in degrees, total or included I know not.

Conclusion: more than one type of taper attachment, and setting them up could be in degrees or as a length ratio, other than the obvious tangent. Be good to see a photo of Alan's attachment, I'd learn something!

Dave

You have it right, your description matches the pic you posted. Guide bar A is adjustable to the angle as marked on the end scale. Small saddle D traverses up and down it as the main lathe carriage moves along the main bed. Link F transfers the angular motion to the cross slide, which is free to move because the cross feed screw has been disconnected from the feed nut.

The whole taper unit in your pic is a bit more complex than on say a Myford as it has the ability to be slid up and and down the main bed and clamped in position to turn tapers at different distances from the headstock, but principal remains the same.

It would help to know what kind of lathe is in the OP and pics of teh set up would help. Some use degrees, others taper per foot on the end scale. And some refer to total included angle of the resulting turned taper, others to half that amount, ie the actual angle or offset of the guide bar itself. Varies from make to make.

ONe thing common to all is that the end scale is just a starting point guide, Final setting is almost always arrived at by trial and error cutting and measuring, or setting a known parallel bar between centres and reading off a dial indicator to get desired amount of infeed per inch or number or inches. Final fit can be by using a master taper - eg morse adaptor sleeve etc -- and light bearing blue or even lead pencil marks to get a reading how they match up.

Edited By Hopper on 12/05/2019 13:05:58

A further variation concerns the cross slide feed. On smaller, cheaper, lathes the cross slide screw is disconnected and the slide driven by the taper attachment. Feed is put on using the top slide set parallel, or close to parallel, to the cross slide. On larger, mostly industrial lathes, the cross slide screw is telescopic so feed can be applied with the cross slide handle as normal while still allowing the cross slide to move in sympathy with the taper attachment.

Apparently the taper attachment for my lathe (Harrison M300) is of the latter type. I don't have a taper attachment; if one came up at an advantageous price I'd buy it, but I'm not desperate to buy at any price. If I need to cut long taper I use the hydraulic copy unit. if the taper really needs to be accurate I'll use the cylindrical grinder. The swivel table on the cylindrical grinder is marked in degrees.

Andrew

I managed to have another go today so here’s what happened, first I did not alter anything, I did as Andrew suggested and turned a piece of bar to 20 mm then fitted a collet on the bar, set up a DTI and ran it along the collet, using the taper attachment it stayed perfectly at zero, Was not expecting that, turned the chuck 180 and did the same this time with .0015 of runout turned another 180 and zero runout again, I put this down to the collets as there cheap ones, so the set up was fine, so the issue I thought must be when I’m turning so I adjusted the cross slide gib and the top slide, gave everthing a good clean at the same time, cut a new taper and it worked out really well, cut some threads on it fitted the collet and nut inserted a 16mm carbide end mill init and checked the runout, .001 out so happy days, the taper attachment on my Colchester Master 2500 is the type where you just clamp the fixed bar on the lathe bed and away you go, no need to remove the cross slide nut, I’ll include some photos so you can have a look.

Once again chaps thank you very much for your help, ps still hate maths.

Regards Alan.

Edited By JasonB on 13/05/2019 06:59:03

Sorry for the mitiple pictures, this site has a mind of its own sometimes.

Alan.