GL5 Forum

What is a good technique for putting a key-way slot dead centre of an axle?

I intend to do the work on a Mill and have made a block to hold the axle which in turn allows me to flip it over and thereby put the two key ways at 90 degrees for quartering and the same on each of the three axles.

So, just wondered what techniques have been used by others... ??

The easiest way is to use an edge finder to align the spindle with the edge of the shaft and then index in a distance equal to half the dia of the edge finder plus half of the shaft dia.

Alternatively align the slot drill against the shaft using a cigarette paper as a feeler gauge. That is, move the cutter towards the shaft until the paper is just trapped against the shaft. Cigarette papers are about .002" thick which can be allowed for when indexing half the cutter dia plus half the shaft dia to get to the centre of the shaft, if you are very fussy.

Dave T.

Thank you for your two techniques.

Having never done a keyway before I am wondering just how accurate do I need to be. and, in the event I should I end up with a slightly loose key will loctite retaining compound be enough to hold it in place?

If using a standard slot drill the width of the keyway should be correct for standard key steel or propriatory keys. The centering should be satisfactory if you use the methods described previously carefully.

Keys are usually made a light "tap fit" in the shaft and a CLOSE sliding fit in the hub. Best practice puts a small saw cut in one end of the key at shaft surface height to allow the key to be prised out when required.

Stepped keys were often made to accomadate errors betweenn shaft and hub both in alignment and size. A lot of work but it is essential that the key is well fitted to both the shaft and hub for long term reliability. Any small alignment errors you make can be saved by this fiddle with little effect on the finished job, just don't tell anybody!!

Dave T.

Hi Keith while I entirely agree with Davet's method, I have also obtained good results by the simple expedient of putting a sharp accurate centre in the 2MT Quill of my Tom Senior, placing the shaft under it, and while interposing a good true feeler between the point of the centre and the surface of the shaft, gently bear on the quill feed arm, while moving the table so that the feeler is dead horizontal, assuming of course that the m/c table is horizontal.

Thank you Brian and Dave,

I quite like the feeler gauge method, and thought along those lines but vertically against a reference pillar i had made to fit snugly in the Tee slot.

I still didn't like the idea of risking any errors in the maths vs actual, so the idea came to me that all i need do is simply use a small engineers square and slip gauges.

The engineers square is placed on the table and against the axle. The axle i should point out is mounted in a square block bored out to suit and held captive by a 2BA screw. The axle is placed against a pair of reference pillars and the block held down. Now all i did was work out the theoretical distance between cutter and edge of axle, which is the edge of the square. Make this up dimension using slip gauges and trap them between cutter and square. Move the table till the slip gauges drop. Zero table. Place the square on the other side and repeat. My reference point moved 0.04 thou so i tweaked the slips and started again til the same occurred on both sides and the reference point was the same, and thus dead center was reached.

Hope that makes sense. Dead lucky to have a set of slip gauges i must admit.

Keith

Yer pays yer money and takes yer choice.
I hope the job came out satisfactorily.

davet

yes...well That is to say have put a pair of wheels on to the axle and then turned them down between centers on the lathe, ready to receive new tyres.

Two more sets to go (0-6-0) Hope to be ready for Gilling! Next thing is to put the tyres on. See next subject - fitting tyres.