RE: [CAD_CAM_EDM_DRO] Re: small spindle ?

Should have been ‘below 0.001”…



Jeff



From: CAD_CAM_EDM_DRO@yahoogroups.com [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Jeffrey T. Birt
Sent: Friday, June 08, 2012 6:36 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: RE: [CAD_CAM_EDM_DRO] Re: small spindle ?





Any decent ER11 chuck/collet will have run-out well below 0.0001”. The construction of the spindle in question looks to be a smallish DC motor, about the size of a battery powered drill, with a modified ER11 collet chuck attached to the motor’s shaft. This type of motor is not deigned to handle a side load like that. By comparison a spindle or spindle/motor (such as used in commercial routers) has much larger bearings that are designed for that type of work.

The PreciseBits collets for the Colt come in two flavors, of which the lowest grade provides a run-out of less than 0.0006”, the PG grade collets are less than 0.0004”. When you move up to the larger router motors the UP grade collets can provide a run-out of less than 0.0002”. These collets/closing nuts fit right in place of the stock collets and closing nut; there is no ‘mounting’ of anything.

Jeff Birt

Soigeneris.com

From: CAD_CAM_EDM_DRO@yahoogroups.com <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com> ] On Behalf Of Larry Guthrie
Sent: Friday, June 08, 2012 4:46 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
Subject: Re: [CAD_CAM_EDM_DRO] Re: small spindle ?

Jeff,

I don't believe the motor used in those spindles is the same type as a battery powered drill. Why would they be? The bearings in any high speed spindle, small trim router motor, or a rotary tool such as the Proxxon are going to be radial bearings. Radial bearings are specifically called for when side loads are high. I suspect the bearings in the spindle in question (in the link) will last as long as the quality of the bearings used not the type of motor.

However .0015 runout is pretty high for a spindle. It would have to be made pretty poorly to have that much runout. I can tune a drill press with a hammer and get runout that good (or poor). It's probably good enough for a hobby machine since it's too small to measure with most calipers. I suspect the poor runout specified is the result of the chuck used, not the motor bearings.

Any idea what the runout of a trim router would be? Probably pretty low until the chuck is added. I would think that even a collet like the PreciseBits would be fairly difficult to mount to a router without increasing the runout. Seems to me that the only way to get precision for cheap would be a belt driven spindle. That would take the runout of the motor out of the equation.

ljg

Larry Guthrie
yrralguthrie@... <mailto:yrralguthrie%40yahoo.com> <mailto:yrralguthrie%40yahoo.com>
larry.guthrie@... <mailto:larry.guthrie%40yahoo.com> <mailto:larry.guthrie%40yahoo.com>

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