Taper cutting

[Hilton MillarParticipant @hiltonmillar81014]

Started a new piece for the previously posted  thread on dovetails. This piece involves making an MT4 taper to fit in the boring bar I am constructing. Here lies my problem. Having turned the diameter on a piece of EN4 bar stock and received a wow finish it was time time to tackle the taper part. All calculations were made and the tail stock set over exactly as specified by thos who know. Time for turning. No matter what I do, with any cutter, set dead on centre, all I get is the most awful chatter with hardly any cut. Please help where to now?

[Hilton MillarParticipant @hiltonmillar81014]

Set Over Method

[George ShoneParticipant @georgeshone63264]

Hi Hilton, kinda hard to tell what you problem is from your description, I gotta assume that you have a fair to big size lathe (MT4 aint no miget taper !) because thats a whole lot of set over ya got there. ?what kind of tailstock center are you using, ? have you got the driving dog wired to the drive pin, ? RPM’s  ? feed speed………come on back good buddy and I’ll think some more.

George.

[david greggParticipant @davidgregg87136]

 I dont know what size of lathe you are using  ,but one of my lathes is a  Harrision 300 and to m/c a morse taper 4 I would set the compound slide to the correct angle . In my opinion you should  not ofset the tailstock by the amount needed to m/c this taper ,the tailstock should only be used for very slow tapers . When you ofset the tailstock by this amount the tailstoct centre and the headstock centre do not locate properly in the cenre hole in the workpiece hence your problem with chatter . If you project aline through the headstock and another through the ofset tailstock  and then draw a line through the centre line of the workpiece you should see what I mean .  I hope this makes sense  if not come back  and and I will try again .

[CirclipParticipant @circlip]

Try making some ball end locators instead of pointy end locators for turning between centres Hilton, much smoother.

 

   Regards  Ian.  

Edited By Circlip on 05/07/2009 12:16:19

[Hilton MillarParticipant @hiltonmillar81014]

Thanks for the feedback all. I have a chinese 9×20 and the the taper is for my mill/drill. My compound cannot be set over to the correct taper as the topslide travel is short by half. I am using a live centre on the tailstock and dead centre and driving dog on the headstock. I have tried from 100 RPM to over 600 RPM. No Joy. I think maybe it is the steel I am using as I remember reading somewhere that HRS with low carbon tends to work harden. Am I right in this? Seeing that I can hardly make a cut at all. Thanks for the ball end advise. I have never seen these anywhere. Are they easy enough to make or does someone have a drawing that I could follow?

 

[CirclipParticipant @circlip]

Use a ball bearing silver soldered onto the end of a cup drilled piece of bar of smaller dia. than the ball, PS, do it twice.

 

     Regards  Ian.

[Geoffreh HarrisonParticipant @geoffrehharrison]

In MEW No 157 on Page 55 in References 2 , Harold Hall refers to “Turning a Morse Taper” article in MEW issue 6, Page 28.  Please would someone advise me how to get a copy of this article.  Hopefully this will help Hilton as well as me    Regards – Geoff

[JasonBModerator @jasonb]

e-bay or go to the Myhobbystore link on the right and see if they have back issues available.

 

Here

 

Jason

Edited By JasonB on 10/11/2009 07:26:52

[Tony Pratt 1Participant @tonypratt1]

Hello Hilton, when you say you are getting hardly any cut do you mean the tool or top slide  is pushing away or the tool is wearing as it tries to cut the job? Also what is the cutting tool mtl?

 

Regards,

Tony

[CirclipParticipant @circlip]

Check yer P/M Geoff.

[Hilton MillarParticipant @hiltonmillar81014]

Hello Tony. I am unsure how to describe the action. I have tried HSS and Indexed insert cutters. The tool IS in contact with the work piece but I am getting no swarf. It is as if the cutter is rubbing the steel instead of cutting. Obviously all the expected alignements have been checked. Centre height, backlash on crossslide, etc, etc.

[mgjParticipant @mgj]

Are you CERTAIN CERTAIN that the tool is not too high. If so, then the angle of the front clearance will bear and will do an excellent job of polishing the workpiece.Try lowering it in stages and it might start to cut.

 

Is the tool actually sharp?

 

[Tony Pratt 1Participant @tonypratt1]

Hi Hilton, it is certainly strange that neither HSS or carbide will cut this material if they are sharp and on centre line, carbide will certainly cut hardened steel to some degree depending on the grade you are using.

Another check you can do is to get a decent file and try to mark the corner of your workpiece when it is nor revolving, this rough and ready method should at least tell you if the steel is soft or not. Let us know how you get on.

 

Tony

[Ian S CParticipant @iansc]

Tony,he has put in center holes!Of course he could be using an old half shaft-nitrided 5-6mm on the out side.IAN S C

[mgjParticipant @mgj]

Well if he has, he can always get the special tips for cutting super hard materials!! Sandvik list them.

 

If chatter is the problem the likelihood is that some slideway adjustment is out,- the job is not being held tightly, hes not feeding fast enough, hes got too high a speed selected or the job is springing, the tool is blunt or cutting over too long a face or has a large nose radius.

 

It may help to understand the physics of chatter. It’s a high frequency vibration, so the action is that the tool is applied, starts to cut – the job flexes or its mountings flex – and the job pushes away, decreasing the cut – the job springs back  – tool starts to cut etc etc. the point is that movements are small, so bigger cuts and faster feeds can sometimes solve as much as extra rigidity.

 

Edited By meyrick griffith-jones on 14/11/2009 10:32:29

[Tony Pratt 1Participant @tonypratt1]

Hi Ian, yes that’s true about the centre holes etc, but he does seem concerned about work hardening on the O/D etc.

 

Tony

[chris stephensParticipant @chrisstephens63393]

Hi Guys,

Seems a bit late to join in now but….  

The centre holes, were they cut with a standard Slocombe drill? If they were it might be a better bet to use one of the centre drills that produce a curved seating for the drive and tail centres, these are much better for offset turning, in fact they are made for it.

chris stephens

[Ian S CParticipant @iansc]

Hi Chris,I was just explaining belled centers to a friend today in conjunction withthis question,but my oppinion is that the taper being attempted is too great.The material could be something like Nickel alloy steel,or stainless,but I think it more likely that the angle of the centers in their holes means that the work is just being pushed away from the tool,might get away with ball ended centers,but I would use the top slide set over,even if it needed two or three moves sideways to get the full taper cut.I think the “awfull chatter” indicates the lack of support.IAN S C

[CirclipParticipant @circlip]

MT 4 Taper Ian S C ??  The ball ended centres can have a barn dance on that one.

 

  Regards  Ian.

[Ian S CParticipant @iansc]

Hi Circlip,I’v never personally tryed the ballend centers,and with that angle and that weight of metal I wouldn’t try it in this case.IAN S C

[mgjParticipant @mgj]

There is of course another way.

 

Set all dead straight.

 

Off set the topslide. to the right angle.

 

Measure accurately  the thick dia and the thin end.

 

Turn two short tapered  collars to size and take a groove out between the collars.

 

Its going to be difficult to get it dead right, so some adjusting with emery, oil and engineers blue is going to be necessary, but it will do it without all this chatter bit, and use of bell -ends.  (I have a couple – lucky me!. Arc Eurotrade do them)

 

You can always test by taking the whole chuck off – don’t loose true centre.

 

Last alternative.  – Hemingway – taper turning attachment.  Make – fit  – use. Recommended – gets over all these problems. You can extend it too, so its long enough to do loco rods and traction engine con rods etc. (I wasn’t going to pay for a Myford one)

[John Stevenson 1Participant @johnstevenson1]

It’s not a problem even with large chunks of metal, you just need bigger balls.

 

To give an idea of size that’s a 6″ centre hight lathe. Ironically it is equipped with a taper turning attachment built in but I use the old boring head method most of the time for tapers that can’t be handled by the topslide.

 

Main reason is it’s a lot easier to adjust to get the correct taper. I NEVER move any of my tailstocks over, can’t see the point of upsetting something that took ages to achieve when there are other methods.

 

John S.

 

[John Stevenson 1Participant @johnstevenson1]

Can’t edit these post but i meant to say that this arrangement will fit any lathe whether it has taper turning or not.

So you can swap between machines if needed, Bonus is that you can always use it as a boring head as well.

 

John S.

[chris stephensParticipant @chrisstephens63393]

Hi Hilton,

Just a thought but do you need a full length Morse taper, if it is a bit short in most cases it will still work, well enough. Then you could just use the top slide.

Another thought, (must have had fish for breakfast, eh Jeeves?) Beg, borrow, or scan a copy of MEW27 on pages 51-54, where  Mr. Ron. Bentley explains how to make a “Tangential Skiving Tool” for cutting Morse tapers, well worth a read.

chriStephens

[Author]

Posts