2 keyways, tolerating the angle?
2 keyways, tolerating the angle?
(OP)
Hello,
Does anyone knows the tolerance of the angle? My keys are at 120°. I've nothing found in the DIN 6885 .Everyone keeps saying "the angle must be as good as possible", but this is no way to go in the shop.
Kind regards.
Jurgen
Does anyone knows the tolerance of the angle? My keys are at 120°. I've nothing found in the DIN 6885 .Everyone keeps saying "the angle must be as good as possible", but this is no way to go in the shop.
Kind regards.
Jurgen





RE: 2 keyways, tolerating the angle?
You have to look at how the 2 keyways are going to be placed in the part. If they are broached in a single pass then you +/-110% of the broach tolerance. If they are made on a mill/turn machine, what can you hold there. If they are made in 2 passes on a broach, will it be fixtured each time, locating the 2nd keyway off the first? There are a lot of variables to look at when tolerancing... you have to know the capabilities of your shop.
With more information, more help may be available.
HTH,
Alan M. Etzkorn

Product Engineer
Nixon Tool Co.
www.nixontool.com
RE: 2 keyways, tolerating the angle?
RE: 2 keyways, tolerating the angle?
Are the keyways internal or external? Are you using 2 keyways to share torsional load between 2 parts or is this a simpler case where you only use the keys to establish angular relationship between 3 parts?
More information about the assembly and its components would be nice. The correct tolerance is the largest tolerance that still assures function. Why does everyone keep saying "the angle must be as good as possible"?
RE: 2 keyways, tolerating the angle?
and the angle would have to be very
accurate to have them work properly.
You have not indicated at all how
accurate you are machining these.
RE: 2 keyways, tolerating the angle?
Thx for the replies, this is the situation (try to explain
I have redesigned an old (+70 years) transmition. I had to start from an existing shaft,with 2 keyways at 120°. No one knows the accuracy of the angle. We can't measure the angle until we start building the new transmition (with hollow shaft) around it...
So I'm building an calibre to measure the angle over there. Once the angle is measured I can make a special home made key according to the difference of the angle between new/old. The Torque is alway in the same direction, so back clearance of the key is not so important (i guess)
I think, this is going to happen.... After everthing is installed, firt time torque is applied. So the hollow shaft can rotate a bit until one of the 2 keys hit the flange of the keyway. At this time the first key takes all the torque, so it deforms a bit. Due the deformation of the first key, the hollow shaft rotates again a bit, until the cealerance between the other second key is gone. But when the clearance is too big, the first key will deform too much...So what's the max clearance (between keyway flange an key). I thought there were some standards for the angle. with the angle i could maybe calculate the clearance....?
Hope you guys understand the problem
Kind regards
Jurgen
RE: 2 keyways, tolerating the angle?
If the keyways are or can be through keyways (not blind), then I would wire them in with EDM after a very careful measurement of the shaft. This is your most accurate means of generating the 2 keyways IMO for a prototype.
The good news is that even if you have to resort to shaping or broaching the keyways, you can still fit the keys to give a good sharing of the loads. This is where the prototype quantity works for you.
RE: 2 keyways, tolerating the angle?
The bad news is that the keyways are blind en we can't disassemble the input shaft over there
So it will be measuring over and over again...but I have to now some allowable clearance between 2nd key/keyflange
RE: 2 keyways, tolerating the angle?
If the hub does not have to be removed often, use Locktite Quick Metal to take up any extra clearance and lock the hub to the shaft. Be sure to load the keys before the Quick Metal sets up. This will insure that one key will have metal to metal contact. Quick metal has a load capacity of about 6,000 psi minimum, so a quick area check in relation to the torque will help determine if this method will work.
RE: 2 keyways, tolerating the angle?
Kind regards.
RE: 2 keyways, tolerating the angle?
Key Width, and other particulars? Also the
T and S dimensions that you are considering.
A good vendor would have made the
key very accurate as far as angle
is cut on the shaft unless you have reason
to believe otherwise. Is it an inch series
or metric? Much is based on size of parts.