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Grinding an ER40 Taper

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ddickey

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#1
I thought I'd try out my tool post grinder I made last summer as I've never used it.
I bought an MT5-ER40 collet chuck that is showing almost .003"TIR so thought I'd try to grind it in.
My question is, does my indicator have to be perfectly on center to align the compound w/the ER taper?
 

benmychree

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#2
Yes, it does, and you may have to do come "cut and try" using layout dye or felt pen inside the hole to see if the taper matches, and the grinding spindle needs to be accurately on center also or the taper will be distorted into a convex shape.
 

T Bredehoft

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#3
the grinding spindle needs to be accurately on center also or the taper will be distorted into a convex shape.
Absolutely. .005 off will make a bad taper, either bell mouthed, or fat in the middle.
 

Alexander McGilton

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#4
If I'm understanding correctly you are setting the compound by duplicating the the existing tapper. Since the taper is so short as opposed to a Morse taper, I would recommend setting it by sine bar. The er collet is an 8 deg tapper per side.

https://www.sommatool.com/images/rd.jpg
 
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