Coupling taper angle û relating to locational accuracy
Coupling taper angle û relating to locational accuracy
(OP)
I am trying to find quantify the locational accuracy of two parts coming together, i.e. a wheel onto a shaft. A coupling with no taper (slip coupling) has concentric precision but no rotational precision. While two parts butted together, have no concentric locating but have rotational precision. Some where in between these two extremes should be an optimal taper angle. Machine collets have a taper angle of 15 deg with a large L/D contact surface. The taper angle of 15 deg seems to be common choice, I am wondering what mechanical theories are behind this choice or did this angle come about from trial and error?
I appreciate any info or guidance on where to find a source.
R
I appreciate any info or guidance on where to find a source.
R





RE: Coupling taper angle û relating to locational accuracy
(1) my disk brake rotors on my VW are located onto the hub concentrically by a boss on the hub slipping into a hole on the rotor. The rotational location is taken care of by a M8 FHCS that has a countersink in the rotor. The torque is handled by four lugs through the rotor to the hub. Finally, parallelism is handled by flat face to flat face.
(2) many robot manufacturers have a similar arrangement for their tool flanges for hanging end effectors. Boss-thru-hole for concentricity, dowel pin into a hole for rotation, & flat-to-flat.
(3) I designed some equipment once that used some of those 3-lobed couplings you've probably seen some where (imagine a tapered arrangement, but with three or more lobes for torque carrying). Those things were manufactured with a certain "pitch" where the two parts mated along the length of the male & female coupling parts. Pretty cool method of locating round stuff accurately, but expensive to manufacture.
TygerDawg
RE: Coupling taper angle û relating to locational accuracy
The collet you mention is probably an 'International' sized collet of which there are a few depending in the size of the tool being used.
The International taper series does not self lock and requires a draw bolt to hold the male half in position to get the concentric accuracy. The non locking feature is useful in the autochange mechanism of CNC machine tools.
A Morse series taper(commonly used on taper shank drills/reamers in the UK), on the other hand has a much smaller taper angle and is self locking i.e. the female part grips the male part!!. A drift is required to separate them.
There are various other tapers used in the machine tool industry:
e.g. Jacobs (used to hold 3 jaw chucks to drill spindles) - self locking. R8 taper is used on Bridgeport turret mills - semi self locking - needs a draw bolt but is easy to unlock.
Machinerys Handbook lists most types and their taper details. All these tapers have a reference dimension so that axial location of the two mating can be specified (subject to wear of course.
I guess they all developed in an ad hoc sort of way. I suppose the same applies to taper dowels etc.
RE: Coupling taper angle û relating to locational accuracy
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Coupling taper angle û relating to locational accuracy
RE: Coupling taper angle û relating to locational accuracy
Am I missing something as machining centres run using a taper and they run true within microns?
RE: Coupling taper angle û relating to locational accuracy
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Coupling taper angle û relating to locational accuracy
I mentioned the machine collets only as an example of a 15 deg taper. I am specifically interested in the theories used choose taper angles such as those listed in the Machinery Handbook.
R