How to gently increasing pulley bore size

[RainbowsParticipant @rainbows]

I recently had a spindle made from my Wizard lathe by a well known Stevenson (thanks again). My old spindle would slip into the pulley with no friction and needed a grubscrew to keep it roating on the shaft. The new spindle is a fairly tight intereference fit with the pulley where to get the spindle to go in by any amount requires a medium hammer. After some time considering the options I decided I would want a looser fit and to modify the pulley rather than the spindle.

Anyone got a method for enlarging the hole by a tiny amount to get a slip fit while keeping everything concentric?

[RainbowsParticipant @rainbows]

[John HaineParticipant @johnhaine32865]

Wet'n dry paper, and patience.

[Ian PParticipant @ianp]

I think you need to think again about the problem before removing any metal. Firstly what are the diameters involved (and can you measure them accurately). From your description the spindle may have been manufactured oversize (reject it as out of specification, 'not fit for purpose' etc )

An adjustable reamer would probably be the best way of opening the pulley bore. As long as you have some way of keeping it square and concentric the bore could be enlarged in minute increments to get the fit you want.

Ian P

[Ian PParticipant @ianp]

If the pulley has a machined flat face, sit it on the drilling machine with reamer in chuck at slow speed (or turn by hand). The reamer will keep pretty concentric and if you turn the pulley a quarter of a turn every few revs of the reamer it will compensate for any tilt of the table.

Ian P

[duncan webster 1Participant @duncanwebster1]

Make up a soft lap and use te driling machine to drive it, assuming drill is something like square to table

[John Stevenson 1Participant @johnstevenson1]

Posted by Ian Phillips on 10/02/2016 23:37:33:

I think you need to think again about the problem before removing any metal. Firstly what are the diameters involved (and can you measure them accurately). From your description the spindle may have been manufactured oversize (reject it as out of specification, 'not fit for purpose' etc )

Ian P

.

You just can't get the staff can you ?

[Ady1Participant @ady1]

Wet'n dry paper, and patience.

If anything goes into a hole, it's on a stick, not on your finger.

And wrap the W&D around a bar, don't grab it with your fingers

Takes a while but gives good results

[oldveloParticipant @oldvelo]

Hi

A 50 plus years old pulley bore may no longer be in good condition with burrs and other damage.

If there is no keyway in the pulley you may be able to use a "Brake Cylinder Hone" on the bore.

Or a light linishing on the spindle would be my preference.

Eric

[JasonBModerator @jasonb]

Expanding reamer

[HopperParticipant @hopper]

If the pulley already goes on the shaft with a medium hammering, it only needs about half a thou taking out of the bore to make it a neat sliding fit.

Bit of emery paper and two minutes should do you.

[Chris Evans 6Participant @chrisevans6]

Or two minutes with a heat gun. Just like fitting a gudgeon pin to a piston.

[Michael GilliganParticipant @michaelgilligan61133]

Given that the Pulley has a grubscrew … I would carefully check the bore for bruising [and bell-mouthing] before deciding on the best approach.

MichaelG.

 

Edited By Michael Gilligan on 11/02/2016 08:53:11

[HOWARDTParticipant @howardt]

Use a Flexhone, not cheap but is easy and gives a very gradual increase in diameter.

[John Stevenson 1Participant @johnstevenson1]

Problem with flex hones in a case like this is the pulley is only 1/2" diameter bore and probably the same depth and those hones just want to expand at both ends and you finish up with a trumpet shaped bore.

Bit of wet and dry or even emery on a split dowel will have done this in less time than it took to write this.

[HOWARDTParticipant @howardt]

Flex Hones design will not produce a cone as the constant movement through the hole and the design of the hone prevents it. Any diameter/length ratios are permissible.

[AjohnwParticipant @ajohnw51620]

I would probably use an expanding reamer remembering that they usually have a bit of a mind of their own.

In some ways it might be best to expand in the bore well past any lead in the reamer may have for a rather light interference fit rather than trying to open up until a light cut is taken.

John

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Edited By Ajohnw on 12/02/2016 16:19:29

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