Honing tapered bar or bore

[Martin DowingParticipant @martindowing58466]

It is well known that lapping of tapered features does not work but what about honing?

Lets say that we want to hone a bore (or an arbor) using 3-legged hone applicable in motor industry. For honing an arbor of course spring would be rearranged in such a way that honing stones are grabbing tapered bar rather than springing out.

With steep tapers there would be a problem with rapidly changing force of contact because of changes of spring tension along a taper and that would cause slight changes of taper angle (not acceptable).

But what about mild tapers, say one of 1:50 or even a taper like MK4?

Did anyone try that and what was a result?

Edited By Martin Dowing on 19/02/2021 20:49:16

[Martin DowingParticipant @martindowing58466]

[David George 1Participant @davidgeorge1]

Do you mean making a tapered pin match a tapered hole if so I would just make both yo same angle and lap together with lapping paste.

David

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin Dowing on 19/02/2021 20:42:32:

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It is well known that lapping of tapered features does not work […]

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Forgive me if I am being dim, Martin

I thought that lapping of tapers was not uncommon:

At opposite ends of the taper spectrum we have ground glass stoppers, and IC engine valve seats.

Please educate me

MichaelG.

[Martin DowingParticipant @martindowing58466]

@Michael.

Reciprocal linear movement of tapered mating parts while maintaining full contact is impossible, so abrasive cannot be distribued like in lapping of cylindrical parts and it will tend to accumulate forming groves etc.

[Paul LousickParticipant @paullousick59116]

The tapers on the stem and body of the plug valves on my steam engine have all been lapped together to achieve a water/steam tight seal.

A possible problem doing this on a lathe spindle with a tapered plug is that the plug and spindle surfaces are both worn away to achieve a common taper between them and this taper angle may not be exactly tha same as the other tooling that you insert into the spindle. On a valve, the 2 are a matched set.

Paul

[Ramon WilsonParticipant @ramonwilson3]

Hi Martin

To my mind the only way a taper, either external or internal, can be 'lapped' is with a 'lap' of the exact same taper – usually the matching component.

As Michael says in his example's – a glass stopper, a valve seat – another is a plug or drain cock.

To hone something externally or internally would not be impossible but unlikely – the hone would need to be manufactured to exact standards for as you comment any slight wear would result in minute changes of taper which would defeat the object.

A floating three leg hone as used in the motor industry will not take out a taper nor ovality – it just follows such irregularities. If used incorrectly though it can produce a barrell mouthed internal taper.

The IC engines I have made do have 'tapered' liners in as much as the lower liner portion is lapped more than that of the top. It is not measured dimensionally to any degree but done more by feel – the piston lapped parallel to just enter the liner at the botom then slowly hand lapped to fit the bore. I know that some do but there is no way I would attempt to do this as two individual components without the use of some very sophisticated measuring kit. Unfortunately, despite it's desirability, I don't possess such kit.

Hope that helps some

Ramon (Tug)

[HopperParticipant @hopper]

Common practice over the past 100 years or more for motorbicyclists to lap tapered holes in engine sprockets to the tapered end of the crankshaft using a bit of valve grinding paste. It works. And transmits 50 horsepower or so very commonly. I've done the same on tapered crankpins where they fit into tapered holes in motorcycle flywheels. Still running 40 years later.

If making tapered MT4 etc shanks and sockets in the lathe, the usual method is to test for fit by twisting together with some lead pencil lines (these days marker pen) along the male taper. Lines rub off on the high points. Final adjustment can be made to topslide angle then surface finished with emery cloth etc. Use a wooden dowel for internal tapers to hold the emery, not your finger which can tend to shear off if it catches in there. No need for lapping if you take care.

I would expect those cheap hones to wander all over the place and as soon as you have used them, the stones are no longer dead flat and straight so adds more error. And they are a surface finishing tool so just follow the existing surface so no great advantage over emery paper etc. that I can think of.

There's a Workshop Practice Series book on Grinding, Lapping and Honing by Stan Bray if you wanted to look into it in more depth from a reliable source.

 

Edited By Hopper on 19/02/2021 22:21:32

[Martin DowingParticipant @martindowing58466]

Thank's all of you for comments. So after all there are ways to lap tapered parts.

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