Pressure angle for a spline?

[nmeyers]

I'm working on sending a drawing of a spline to a gear manufacturing company in my area. However, they need to know the pressure angle of said spline. The size is standard (5/8" 36) but I can't seem to find any literature which gives the pressure angle of such a spline. Any suggestions for where to look? I know that a lot of places sell  5/8" 36 shafts, but it's cheaper for me to buy 5/8" round stock and send it to this manufacturer (I'm on a racing team and we have a sponsorship with them), so I would like to know the exact angle.

[Guest]

Have you tried the gear chook to see if you have enough to get a layout....

ALT + C  pick gear.dll

[mkd]

Machinery handbook?

[Allan Brown]

I believe the steering shaft splines are 60 deg included so a 30 deg pressure angle.

You should be able to check quick with a 60 deg fish tail thread gauge on a standard spline shaft.

 

Allan

[huskermcdoogle]

On 10/28/2017 at 6:17 PM, nmeyers said:

I'm on a racing team and we have a sponsorship with them

I am guessing you are on an SAE team?  What university or school?  I cut my teeth on baja.

Anyway, I wouldn't say its a 60 degree included, that's just too simple.  They are likely involute and therefore that would only be a quick visual check but with the shallow depth, could be inconclusive.  A somewhat easy way to figure out what the pressure angle is, or to reverse the size of a spline is to check a gear span, this is measured from involute to involute across as many teeth as required to contact the face of the teeth.  Typically on small shafts this is easily done with standard 0-1" Mics.  You will need a nominal gear calculator, or some good charts to figure out what it needs to be, but it should be doable.  Your gear shop should be able to help you with this, in fact I am sure they would love to work with you quickly to educated you on how this is done so you can be self sufficient in the future.

[Allan Brown]

I would bet that the chances of hobbing this spline is slim anyway; it is only .625 dia

These things would be rolled in production likely never cut.

Good read and the basis for my therory

 

The pressure angle of a spline is the angle between where the pitch diameter meets the involute curve and a tangent point on the base diameter (fig. 4). There are three major pressure angles used in the spline rolling industry today. These angles are 30, 37.5 and 45 degrees.

The 30 degree pressure angle is most often used when the two members are allowed to slide. Another common application for 30 degrees is when one of the two members has a thin walled section on or about the spline area. The 30 degree pressure angle will normally roll a straighter lead with less fall-off on the ends of the spline. Tool life is prone to be shorter than the same spline of a higher pressure angle.

The 45 degree pressure angle is most often used for axles and other torque delivering members which are not subjected to bursting forces. The 45 degree pressure angle is the most economical in terms of tool life. However, it does not roll the nice straight leads that the 30 degree pressure angle splines do. These 45 degree splines are prone to larger o.d. fall-off and the lead charts will usually have a crowned look to them.

The 37.5 degree pressure angle is a compromise between the other two pressure angles. It is often used when the shaft material is harder than normal and the application will not allow a 45 degree spline.

The pressure angle of a spline cannot be checked. The involute form of a given spline can be checked. The involute curve is controlled by the base diameter which is a product of the pressure angle and the pitch diameter (B.D. = P.D. x cos. P.A.). The most common method of checking the involute form is with an involute checking machine. This machine uses a stylus which touches the spline tooth. The part is then rotated about a simulated base diameter. While the part is being rotated, the stylus follows the form of one side of the tooth. An electronic signal is sent to a recording unit and a chart of the form is recorded. If the involute form is correct, a straight line will be recorded on the chart paper. Another method of checking the involute form is with measurement over pins. A series of calculations would permit several different sized pins to be used to check the tooth thickness of the spline at several different diameters. The pin method of checking forms is time consuming and somewhat inaccurate.

 

[crazy^millman]

Allan I know this recently this one thing was a big issue with a customer from that link.

Quote

Spacing error or index error, as it is sometimes referred to, is the maximum radial misslocation of the spline teeth. In other words, if we have a spline with 36 teeth we should have the centerline of a tooth every 10 degrees around the pitch diameter (360 degrees divided by 36 or the number of teeth). Spacing error is the maximum error of this radial location in opposite directions. If a given spline has a min. actual tooth thickness of 0.096″, and 0.003″ of spacing error it can be said to have a effective thickness of 0.099″ (assuming there is no detectable lead, involute, or other form error). If the same spline had 0.003″ of spacing and, 0.0015″ of plus condition on the involute forms, the effective thickness of this spline would be 0.1005″ (0.096″ + 0.003″ + 0.0015″ = 0.1005″, same assumptions).

Math is not always a constant and where understanding the results of the computation is important to get the correct results needed to hit the form, fit and function of the spline.