Thread: Rounding key ends

From time to time I mill a blind slot in a shaft and fit a key to it, usually a 1/8" to 5/16" key. My current method of rounding the ends of the key is to do it by hand on the bench grinder but I find it hard to do a neat job plus its fiddly and slow. Does anyone have a quick method or nifty homemade gizmo they use for rounding the ends of key steel?

This blurry photo almost makes my key look respectable.

IMG_2025.jpg

Nope I did mine same as you freehand on bench grinder.

Hi Bob,

Apart from being neat and ease of fitting of whatever has to slide onto the key, there isn't any real need to round the ends.
I know its been done like that for years, and an old time craftsman would cringe and rap my knuckles if I suggested not to bother.

But you did ask and I do the same as you. Grab it with a pair of pliers and grind to shape, though an old timer would file it.

I round them on a linisher and generally get good results.
The hand motions used to round something freehand and unsupported just seems to work better for me than having the key on a grinder rest.
Using a coarser belt tends to remove material quicker and cooler than a grinding wheel too.
Cheers,
Greg.

Originally Posted by kwijibo99

I round them on a linisher and generally get good results.

Same. No need to do any more.

PDW

Rounding stuff works a little better on the unbacked portion of a linisher belt. On my Multitool linisher this is area is small but enough to round things like a key end. on my larger (2m x 150 mm wide) linisher theres ~100mm of unsupported belt and that is pretty handy for larger things.

I also use the linisher.
I color the key ends with a texta and find a flat washer with about the same ID as the width of the key then use the ID of the
washer to scribe the radius on both sides of the key so it can be flipped when linishing.
If I am making the key from scratch I do one end while it is still attached to the stock, then after it is cut off and to hold the key for linishing the cut end I hold it with vise grips, pliers are useless for holding and grinding little things.

happy days, shed

Hi Bob,

Sorry but I would just do it the same as you.

Actually, when it comes to doing the example shown in your photo, the correct method is not to use a milling cutter but a woodruff cutter. The sharp edge created with an endmill is a stress raiser and as such, critical parts should be done with a woodruff cutter. That would also negate the need to radius the end of the keyway.

Of course I don't own a single woodruff cutter and have always done what you have done. None of my parts I make are critical parts.

Simon

A woodruff cutter will also produce sharp corners, unless of course the edges of each tooth are radiused. It is pretty easy to produce a slight radius on the corner of end mill teeth using a diamond file and hand stone and even easier to do it on a 2 tooth slot drill which would be a better choice when cutting a keyway.

Could you use a small manual rotary table on the mill ? It wouldnt have to be as elaborate as this one.

https://www.youtube.com/watch?v=mVRgxBX3Lro

I guess by the time you have secured the table to the mill bed then centred and secured the workpiece you have already finshed the job with your method

leave them square..makes them easier to get out asa well.

Buy keys with rounded ends

Originally Posted by Pete F

Buy keys with rounded ends

Are they available in sizes required for Keyway lengths or are you taking the urine?

Originally Posted by pipeclay

Are they available in sizes required for Keyway lengths or are you taking the urine?

I guess that would depend on the length you want, but I have about 50 or so keys in 3/5/6 mm of various lengths and they all have rounded ends. Indeed generally that's how they're supplied if you buy keys vs key stock (which I have in larger sizes) and rolling your own.

https://www.machineryhouse.com.au/K72310

Originally Posted by pipeclay

Are they available in sizes required for Keyway lengths or are you taking the urine?

Yes you can buy them with already rounded ends !
But they come in fixed sizes and are expensive when compared to a length of key steel. The other thing is that you can rarely buy just one, usually a box of ten or twelve.

A 13" inch length of 0.250" square key steel costs 0.90p plus vat, say £1.20p, a box of 12 X 1" inch costs anything from 3.95p + vat.
It also comes in useful for other things !