Cutting matching inside and outside tapers

[JamesFParticipant @jamesf]

Following on from my thread about David Fenner's headstock dividing tool…

I'm about to cut the inside taper on the arbor. No major problems there — set the top slide over eight degrees and get on with it.

But, to avoid inaccuracy due to moving the top slide it would seem sensible to cut the outside taper on the plug with the top slide in the same position. This would appear to mean cutting the taper so it is narrowest near the chuck which looks tricky.

Would that be the right way to do it, or should I set the top slide eight degrees over in the opposite direction and cut the taper so it is widest at the chuck end, accepting that there may be not be a perfect match between the arbor and plug?

Or is there another way to skin this particular cat?

James

[JamesFParticipant @jamesf]

[David JuppParticipant @davidjupp51506]

If cross slide travel allows, turn the tool over and cut at the back of the part. At existing top-slide setting.

Better still, if your lathe is suitable to run backwards, have tool normal way up (but has to face forwards)  and cut at the back of the part with lathe in reverse – forces on tool / carriage are then in usual direction.

Edited By David Jupp on 19/04/2013 13:41:55

Edited By David Jupp on 19/04/2013 13:43:20

[JamesFParticipant @jamesf]

Ah, of course! The lathe will run in reverse so there should be no problem with that. I should have thought of it myself…

James

[NJHParticipant @njh]

James

Take care – I don't recall what lathe you have but if it a screw on chuck then cutting with the lathe running backwards may unscrew the chuck ( You can imagine the possible consequences of this!)

N

[JamesFParticipant @jamesf]

That could cause some embarrassment

It's a Conquest Super, so it just has a switch to run the motor in the opposite direction. The chuck is bolted to a plate on the end of the spindle, but I'm not sure how the plate fixes to the spindle. I shall check before I try anything.

James

[David JuppParticipant @davidjupp51506]

Yes – perhaps should have been more explicit! I carefully wrote 'suitable to run in reverse' rather than 'can run in reverse'.

[wheeltapperParticipant @wheeltapper]

Posted by JamesF on 19/04/2013 16:02:16:

That could cause some embarrassment

It's a Conquest Super, so it just has a switch to run the motor in the opposite direction. The chuck is bolted to a plate on the end of the spindle, but I'm not sure how the plate fixes to the spindle. I shall check before I try anything.

James

If it's the same as my Comet variable speed the spindle and plate are one lump.

I've run mine backwards stacks of times and nothings fallen off..

Roy.

[Sub MandrelParticipant @submandrel]

I would definitely cut both tapers at the same setting. You may have trouble moving the tool to the right place running in reverse, but it may not be hard to bore the outer part, and then turn the outside of the inner with it the 'wrong way round'.

Neil

[Gordon WParticipant @gordonw]

I would always cut both tapers at the same setting, and think about cutting extra male tapers as well. I cut the big end of the taper away from the chuck and a run out groove towards the chuck. Must admit I never thought about it before.

[John McNamaraParticipant @johnmcnamara74883]

Hi James F

A while back I posted a method of making a taper to a very good match for the machine it is going to be used in. You do not need a chuck or face plate to hold the piece. It simply slides into the spindle as it is turned end for end and each adjusting cut is made until it is perfect. (When the bluing transfers completely and evenly along the contact area)

**LINK**

Maybe you could cut your arbour using this method? instead of cutting the piece in half, Just cut away the second taper and turn it parallel etc, to fit the business end of your arbour.

Cheers

John

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

In the real world a taper is just something to be made as specified on a drawing – given the dimensions and tolerances you just set the machine up , cut the taper and get the required result .

In production work parts with mating tapers were often made by different people , on different machines and at different times . Random samples would be checked against each other but the expectation would be for a perfect match each time .

( Odd exceptions for super precision work and for ' make and mend ' jobs where male and female tapers have to be matched on a one to one basis &nbsp

So for the simple taper needed for the Fenner device just decide what the taper actually should be , set up for inside or outside turning as appropriate using either a parallel bit of the work or a test bar and a dial gauge and cut the taper .

On some other day set up for the mating taper – doesn't matter if its ten years later – if both mating tapers are to required dimensions and tolerance they will fit properly .

Easiest way to specify a taper for home workshop machining is simply as one reference diameter ( typically large end or small end – but needn't be ) and taper given as difference in radius (optionally diameter) per inch travel .

Tolerances for Morse tapers are biased opposite ways round for male and female tapers so that worst – worst case still gives satisfactory matching . This is a good principle to follow but you could use simple tolerancing for the actual job in hand .

Nobody will believe this but a perfectly fitting no2 Morse taper can be cut perfectly first time on a rattly old ML7R just by setting up as described above .

Michael Williams .

PS: Be aware that male and female tapers which are cut at the same setting are not nescessarily going to be exactly matching – all those factors which cause so many people problems of erratic and non parallel turning will be acting twice over and possibly in opposite directions when cutting tapers this way .

[John McNamaraParticipant @johnmcnamara74883]

In our owner driven workshops we are able to fit our tapers perfectly, hand fitting to each machine we have. It does not matter if the machine is worn? or it may have been out of spec in the first place. We can turn grind or scrape the piece until it is perfect. A (thin) coat of Bearing blue does not lie, once the coating is smeared evenly all over the surface of when we insert it gently and give it a quarter turn, we can be pretty sure it is "spot on".

If the tool has to be used across several machines then it will have to be checked it against each machine separately. Hopefully it will be a good fit in all of them! Good luck on that…….

Cheers

John

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