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Haas BT40 taper contact area

baldhead

Aluminum
Joined
Mar 31, 2007
Location
USA
I have a new Haas with a bt40 taper spindle. I noticed that the witness/contact area for the tool holder taper was 1/2" less than the contact area on my older taiwan machine. The contact area for the haas machine stops about 5/8" before the end of the tool and on the taiwan machine it stops 1/8" before the end of the tool. I was curious about this?
 
Many builders have different bore sizes for the drawbar to fit. If the diameter is bigger it will make the contact area a little less. I wouldn't worry about it too much. Your main concern should be drawbar force and the condition of the inside taper. Keep it nice and clean. Also the small end of the tool holder doesn't take as much as the cutting forces like the big end. My machines are the same way. about 1/2 or maybe more isnt touched when clamped.
 
I had read or heard something about overtightening pull studs and slightly deforming the tail end of the tool holder. I wonder if this could be possible? I think the drawbar force is OK because the dimple on the pull stud look good but I don't have a way to check for sure.
 
Do not overtighten the pull stud. I would recommend 50-65 ft-lbs. No oil or locktight. At least that is what I do in my shop and I have over 300 holders in production with no issues. Make sure you use quality pull studs. Don't try to save money on pull studs. It can me bad for your health, and your spindle.
 








 
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