Gauge Length

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06 Sep 2010 13:14 #4006 by BigJohnT
Gauge Length was created by BigJohnT
On BT30 tool holders there is a "gauge length" spec. What does that mean?

Thanks
John

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07 Sep 2010 04:12 #4023 by jmelson
Replied by jmelson on topic Re:Gauge Length
BigJohnT wrote:

On BT30 tool holders there is a "gauge length" spec. What does that mean?

Thanks
John

Gauge length is some Z distance that is used as a reference for the depth of the taper.
I believe on a BT30 and similar tapers with a flat, that the gauge length starts at the
flat of the spindle nose, where the drive dogs almost seat against.

Jon

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07 Sep 2010 12:02 #4031 by BigJohnT
Replied by BigJohnT on topic Re:Gauge Length
I noticed that different holders have different gauge lengths. Is this something you can use when presetting the tools?

John

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07 Sep 2010 14:44 #4032 by andypugh
Replied by andypugh on topic Re:Gauge Length
I think it is more a matter of how much "reach" the holder has.
The gauge-line is where the face of the spindle reaches on the taper with the tool fully home (and that in itself is very likely to vary from machine to machine and holder to holder).
At a guess the "gauge length" is the distance from that line to the bottom face of the holder. As you can then put in any tool you please, at any protrusion, I doubt that the number is any practical use for tool setting.

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09 Sep 2010 09:16 #4070 by robh
Replied by robh on topic Re:Gauge Length
Gauge length should always be taken from spindle Flat face (ie if u had no tool in the spindle, where dogs and tool would sit and meet each other) to the end of the holder where the tool goes in ie. the nut or other part of holder.

Then if u have offline tool measuring u can measure this length with a hight measuring device, set the Z distance correct and just enter in the overall gauge length & tool length measured into the tool table.
making it easy to replace a broken tool or the likes..

when you buy holder, most will say ER16120L, the 120 means from gauge length to the nut part. so as jmelson pointed out, how fare you can reach with the holder with no tool sticking out.

so yes andy and jmelson where correct, just wanted to confirm for others..

like andy said every machine is different, due to how much the tool will sit in the taper etc..
some new machines now make the flat of the holder meet the spindle flat, and it pulls up onto this part, giving a more deal lenght, so as the spindle warms up the tool holder can not grow or shrink in length, after few hours of machining

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10 Sep 2010 11:39 #4090 by BigJohnT
Replied by BigJohnT on topic Re:Gauge Length
Thanks for the explanation, it makes sense to me now.

John

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