09-01-2013, 01:54 PM
Hello Greg and Anthony,
The strange feel of slight side force dislodging the "fit" is typical of an "Hourglass taper"
The reason that the blued/chalked fit indicates well is from over rotation of the two parts, you see any more than 1/4 turn and the marking can seem like it is all around when in reality the marking is from the wobble of taking a second bite while turning the pieces, so stick to 1/6th of a turn max, the less the better.
So the process is;
1, stick it in with no side force at all till it just touches,
2, turn it in one direction no more than 1/6th of a turn,
3, pull it out and inspect,
Never re check or do a full revolution or apply side pressure.
Regards Rick
Hour glass tapers are equally caused by incorrect tool centre height and worn or badly adjusted compound slide, not locking the saddle slide or compound slide, inconsistent feeding of the compound slide during final cutting of the taper, over extended compound slides and a few other factors.
The reason an hour glass taper causes the funny feel is that at least one point usually the first 1/3rd of the hole the tapers fit well then with just a thou of axial distance outward they "fit" again so a wobble between two good fits.
The strange feel of slight side force dislodging the "fit" is typical of an "Hourglass taper"
The reason that the blued/chalked fit indicates well is from over rotation of the two parts, you see any more than 1/4 turn and the marking can seem like it is all around when in reality the marking is from the wobble of taking a second bite while turning the pieces, so stick to 1/6th of a turn max, the less the better.
So the process is;
1, stick it in with no side force at all till it just touches,
2, turn it in one direction no more than 1/6th of a turn,
3, pull it out and inspect,
Never re check or do a full revolution or apply side pressure.
Regards Rick
Hour glass tapers are equally caused by incorrect tool centre height and worn or badly adjusted compound slide, not locking the saddle slide or compound slide, inconsistent feeding of the compound slide during final cutting of the taper, over extended compound slides and a few other factors.
The reason an hour glass taper causes the funny feel is that at least one point usually the first 1/3rd of the hole the tapers fit well then with just a thou of axial distance outward they "fit" again so a wobble between two good fits.
Whatever it is, do it today, Tomorrow may not be an option and regret outlasts fatigue.