Curious about spline manufacture
Spline recognition and how to make them
Recently I went to a largish swap meet in search of engineering gear and purchased a small box of assorted HSS milling cutters and at another vendors shop I bought a pair of what looked like new HSS spline cutters. The only marking on the spline cutters was Maxwell, no further details to advise what they were meant to cut was provided. In the bottom of the box of assorted used milling cutters was a modified 4” x 3/8” x 1” side and face cutter which had chamfers ground on either side and a concave face approximately 6mm wide with a radius of approx. 12.5mm ground into the face of the cutter. This also appeared to be intended for cutting splines into shafts.
Thus I started on investigating what these cutters were designed to cut. The only useful source I have found so far was Machinery’s Handbook which mainly focused on involute splines but also mentioned SAE straight-sided splines and British Standard straight-sided splines. Tables for the SAE splines only were provided and I think it was stated that the British standard was the same as the SAE.
I did an internet search and found Maxwell tools were mentioned as an Indian manufacturing source of cutters. Although the cutters appeared to be the same, one was 11.2mm wide and the other was 12.8mm wide. The formed faces seem identical.
The first concept that needed to be assimilated was that the shape of the form cutter was the negative to the positive machined into a shaft and so I could not immediately see the splined shaft being created by the cutters.
The cutters have a concave recess ground centrally into the face with a radius of approx. 12.5mm. Either side of the concave recess are angled sides tapering out from the recess which measures approx. 6mm across and terminates with a change of angle at a width of approx.8.3mm. The formed face of the cutters then has a different straight angular edge to the final width of the cutters. On examination under a magnifying glass both angles are symmetrical on either side of the central curved recess and are not shaped to the side of an involute form.
It was apparent to me that the 12.5mm radius was near enough to half inch and therefore the cutter was likely to produce a minor diameter of 1” approximately on a splined shaft. I was aware that an agricultural 6 splined shaft of 1 3/8” was a common size and Machinery’s Handbook indicated that this was nearly exactly right, (1” minor diameter), for the standard shaft fit.
As a practical measure to identify their use I cleaned up an old input shaft for a slasher gearbox which has a 6 spline shaft and half of a universal joint coupler also with a 6 spline female fitting which will mate with the spline on the input shaft. Using these devices and attempting to mate the recess on the slasher input shaft I found that the modified 4” side and face cutter was virtually identical to the cut in the shaft which forms the spline (major diameter) out of the unmachined shaft after it was turned from the raw stock to a circular shape of 35mm diameter. I found that the Maxwell cutters were too narrow in the concaved area to reproduce the spline and although deep enough down to the change of angle the second angle appeared meant for a much bigger shaft because there was clearance between this angular feature and the finished spline.
As mentioned in Machinery’s Handbook the female spline fitting is the defining shape of the spline and most commonly formed in a one pass operation of an appropriately shaped broach. The clearance as required is machined into the mating shaft.
Since Machinery’s Handbook only describes the dimensions required and not the procedures required to achieve the serviceable article I am seeking the details of how to achieve an acceptable product. I am curious as to how the cutter is developed. Should every tradesman be expected to manufacture and maintain his own cutter?
I expect that this area is specialised and mainly limited to the automotive field. I am aware that the 4 spline shaft is utilized in my Pollard pedestal drill and my TOS milling machine. Therefore I would expect that machine restorers might have encountered this topic before. Also does the part get subjected to heat treatment to harden the spline surfaces after machining? I am thinking of the hard wearing spline surfaces in a truck’s drive shaft where a relatively fine spline is provided in the final centre bearing assembly where the final section of the drive shaft connects to the differential. During the course of the day differing loads on the truck compress the spring suspension to different positions and the spline is needed to lengthen and shorten the last section of the drive shaft to accommodate this movement.
I realize that this story would benefit greatly from some pictures and although my cheap digital camera might not be able to get very close to the cutters etc. I shall attempt to post some pictures in due course.
Any contributions on this topic to expand my limited understanding would be appreciated. We have a couple of firms in Brisbane which specialise in driveline component manufacture and repair and I hope to have the time to annoy them for information when next in their vicinity. Thanks to all.
P.S I did a search on this topic but because of dial-up access limitations was thrown off the internet before browsing could commence. So my apologies if this is a repeat of tired old questions.
Splined joints are widely used across all sorts of industries, not only in automotive applications.
The three common methods of making splined shafts are milling, hobbing and rolling. They each have their place. Cost, application, material, strength, production numbers are some of the considerations for selecting a particular spline design and production method.
Milling is the slowest, it's suitable for only very low or one-off numbers such as prototype, very low production or repair work situations.
It's not unusual to heat treat the splined portion of a shaft. Induction hardening is a frequent choice.
I'm not sure what your specific question(s) is. Perhaps it's a wide ranging quest for an overview.
Don't forget that male splines are often broached as well, including things like spur gears...
Are you talking about gear shaping type operations and describing that as a broaching type process?
Dave E I still remember how worn the spline was on the drive shaft of my old Inter ACCO and yet it still functioned OK. Although I accept your opinion on the widespread use of splines for coupling of shafts and the transmission of power, the broaching of female splined components I regard as the norm. If this is the case there should be many more businesses engaged in maintenance and an essential part of their equipment I would expect would be a hydraulic broaching machine. So far in my limited experience I have only seen one horizontal pull type broaching machine in a manufacturing environment. Maybe I need to get around more? And yes, the circumstances I described have generated the interest and I hope I will always see a component and wonder how it was made.
It's fascinating to me that there are ingenious tradesmen out there who know how to modify standard cutters to do special jobs.
Thanks for your kind offer, Richard. I've already got the manual and parts catalogue direct from Jones and Shipman at enormous expense needless to say. But when I can get access long enough to download that pdf document I'll have a go. Thanks. I still have a lot of parts that I want to order but shipping costs are a major issue.
I saw a video on youtube sometime in the past on it...Instead if of the broach cutting teeth being on the outside of the broach, the broach is hollow and the teeth are on the inside..
Originally Posted by Damien W
Another broaching is rotary broaching, where both part and broach spin at the same speed and the broach is given a slight wobble to make it cut as shown here YouTube - Slater Tools Rotary Broaching Demo Video