Centring Spindle

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Centring Spindle

This topic has 7 replies, 4 voices, and was last updated 30 September 2011 at 13:44 by Paul Scholey.

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29 September 2011 at 20:39 #21940
Paul Scholey
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@paulscholey17560
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29 September 2011 at 20:39 #75559
Paul Scholey
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@paulscholey17560
I need to position the spindle on my miller in the centre of a bearing on a small petrol engine, its about 15mm inner race, the plan is then to remove this bearing so that I can bore down in-line to another bearing housing so that it will take a roller bearing instead of a brass bush.

I have never used wigglers before but am wondering if this is something that they can be used for?

Thanks in advance

Paul.
29 September 2011 at 21:43 #75563
Les Jones 1
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@lesjones1
Hi Paul,

I have not used wigglers but I know they are used to position the spindle axis with reference to an edge. If you have a DRO on the X and Y axis of your mill you can use the wiggler. Position the wiggler approximately in the centre of the bearing. Move the X axis so that the wiggler is indicating it is aligned with say the left hand side of the hole. set the X axis zero at this point. Now move the x axis so the wiggler is aligned on the right hand side of the hole. Note the X axis reading. Divide this reading by 2. Now move the table so the X axis displays this value. You are now centred on the X axis. Repeat this on the Y axis. You do not need to know the diameter of the end of the wiggler for this to work. Some DRO’s have a centre function which removes the need to divide the reading by 2. If a finger type DTI you could mount it on the spindle and turn the spindle by hand positioning one axis at a time so the reading is the same on both sides of the hole. Another way would be to make a piece of metal that one end fits in the collet chuck of the mill and the other fits the hole you are trying to align to. before the crank case is clamped down have the end of this piece of metal in the hole to position the crank case. Now clamp the crankcase down to the table. Raise the Z axis so that the piece of metal is withdrawn from the hole. now lower the Z axis to confirm the piece of metal enters the hole to confirm the crankcase did not move when clamped down. I think the DTI method would be the most accurate.

Les.
29 September 2011 at 21:51 #75564
Phil P
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@philp
Les

You just beat me to it.

I would just add that it might be better to remove the bearing and set up from the bore in the casting itself.

I would personally forget the wiggler and stick with a finger type DTI gauge (if you have one)

Also make certain that you have “trammed” the mill, to be sure the head is square to the table.

Phil
29 September 2011 at 22:38 #75568
Paul Scholey
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@paulscholey17560
Thanks for replies. I don’t have DRO, I did think about the second method but was unsure how accurate it would be. I understand what you mean about the mill head not being square but I am able to lower and lift the table so avoiding that. I did think about putting a dti gauge in a collet ect and turning the spindle by hand but it must be very difficult following the gauge round?
29 September 2011 at 22:57 #75569
Les Jones 1
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@lesjones1
Hi Paul,

You only need to compare two readings at a a time with the DTI method. I also agree with Phil about setting up to the bearing housing. Also I think I would set up to the brass bush housing rather than the ball bearing housing. Whichever method you use you need to have a face that you are sure is perpendicular to the crankshaft axis that sits on the mill table.

Les.
30 September 2011 at 11:30 #75579
David Littlewood
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@davidlittlewood51847
Paul,

If you try to use Les’s first method on a mill without a DRO, relying on the feedscrew dials, you will almost certainly get an unacceptable error because of backlash in the feedscrews.

David
30 September 2011 at 13:44 #75587
Paul Scholey
Participant
@paulscholey17560
Thanks for replies again, I have a good machined face that I have clamped the engine down on, but I am not able to set up from the housing that I want to machine because the brass bearing has broken up and damaged the aluminium in the housing.
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