wobbley faceplate

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wobbley faceplate

This topic has 9 replies, 5 voices, and was last updated 17 December 2013 at 08:31 by Paul Barter.

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16 December 2013 at 19:57 #138052
Paul Barter
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@paulbarter66156
Hello all,

I have what I hope is a straight forward query regarding a wood lathe, so no tenths accuracy required, but! when fitting a large diameter face plate there is a distinct wobble at low to medium speeds visible at the edge. upon setting up a clock the error is about 40 thou axial total and the maxima and minima are at 180 degrees.The spindle runs true to within a couple thou tir the face plate is a good quality Harrison original albeit made of aluminium.I am going in circles trying to discover what is "out". I would most appreciate any suggestions as to where to start looking. With a big lump of wood swinging round at 1000rpm or so the out of balance forces will be large and I do not want shorten the life of the very expensive imperial taper roller bearings.Thanks in advance to all who offer advice.
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16 December 2013 at 19:57 #6978
Paul Barter
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@paulbarter66156
where do I look for error?
16 December 2013 at 20:08 #138055
Ady1
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@ady1
large diameter face plate

Maybe the plate itself is a bit wonky
16 December 2013 at 20:17 #138056
Paul Barter
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@paulbarter66156
Hi Ady Thats what I thought, but the error is so regular, the error goes from zero to max at 180 degrees and seems to be linear .It seems that a simple buckle would show a wavy,irregular, error not a smooth transition up and down, or would it?my brain hurts trying to visualise the process at work. where do I hit with lead hammer?

Edited By Paul Barter on 16/12/2013 20:18:35
16 December 2013 at 20:47 #138062
jason udall
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@jasonudall57142
My guess..foreign matter on the register

Mark ( say) max away from headstock point..probably stuff between face plate and register at that position. ..
If not foreign matter then maybe burrs

.doesn’t take much with large diameter face plate.
16 December 2013 at 21:10 #138063
Paul Barter
Participant
@paulbarter66156
Hi Jason Thanks for that, the murk is beginning to clear! I have cleaned all the mating surfaces and there do not appear to be any burrs however if the plane of the face plate is not at a right angle to the spindle axis although fixed in one angular position, would this produce the regular runout?
16 December 2013 at 21:44 #138068
Ian P
Participant
@ianp
I see four possibilities. one the faceplate is buckled/distorted. Two the spindle register is not square to the axis. Three, the faceplate register face is not parallel to the face. Four, axial play in the spindle combined with cyclic spindle movement.

None of them are common problems. Normally one would skim the faceplate on its own lathe but that's not easy on a wood lathe, (although you could lash up a temporary cross slide).

If the spindle register is true, (check again), then check it again!

When you clock the flywheel face run-out is it always the same position?

If you can get a micrometer through the central hole and measure the thickness between register and face and you have no errors than the faceplate it self must be buckled. If you are lucky and the two faces are not parallel (but the main face is true and flat) you could just carefully true up the register face by very careful filing. Using blue combined with frequent clocking you will have it dead true in minutes.

Oh, Bearings are tougher than you think!

Ian P
16 December 2013 at 22:18 #138071
jason udall
Participant
@jasonudall57142
As said above.

Most faceplate are held on by screw thread and fit up to a register ( even if bolted on there is still a register)

The two mating faces must have no high spots..

If your faceplate is say 150 mm in diameter and the register is say 30 mm

.you see 40 thou wobble min to max ( I am going to call that 1 mm) thus a half mm at 150 mm dia means 0.5 @ 75 and equals
0.01 mm on the register

So
Try bluing the mating face ..use permament marker if you don’t have blue . Mount faceplate. And disassemble. .lool at contact..un even mating will show up.

Also the face plate might not be true in any case ( generally assumed not to be if not trued in place)..sorry but seems?to be face of life..

But with low density stock like wood does it matter? …I mean just how true will it be mounted onto plate when you start. ..often see square stock trued in place on lathe…

to
16 December 2013 at 22:20 #138072
Robbo
Participant
@robbo
A simpler thought from a simpler person – is the face plate a good tight fit on the register and the thread which pulls it onto the register? Just letting it run on may not be tight enough.
17 December 2013 at 08:31 #138093
Paul Barter
Participant
@paulbarter66156
Thank you all very much for the wealth of suggestions, I am very grateful for your time and attention. I shall be investigating all of them but I may be trying to feed a pig a strawberry. Wood lathes are not exactly precision tools, but the wobble seems so wrong!

Best regards to all

Paul Barter
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