Cutting keyways in a lathe

[HacksawParticipant @hacksaw]

Evening gents, I need to cut a keyway in a pulley , just like Tubal Cain on youtube..

**LINK**

At 12.30 there's a critical bit about setting the correct height of the tool … how do you do this ? By eye ?

And once i've cut this keyway, do i tap a hole in the pulley to fit a grub screw ONTO the key … or opposite the keyway ? ( Pulley is going on a Honda GX engine to drive a compressor ) Ta !

[HacksawParticipant @hacksaw]

[Neil WyattModerator @neilwyatt]

Onto the key is best IMHO, less likely to burr the shaft and stops the key from dropping out.

Neil

[HacksawParticipant @hacksaw]

I've just remembered from karting days , you drilled a dimple in the back axle ,opposite the keyway and used a sharp pointed grub to keep the hubs in place ..And one on the key too !  And they still moved ! So how do i set the tool height  any ideas , is it obvious and i'm i being thick ? 

Edited By Hacksaw on 14/10/2015 23:12:19

[AjohnwParticipant @ajohnw51620]

That method needs a warning – a great way of breaking a tooth or two off the rack feed wheel. tt's probably ok with light cuts and narrow keys on soft materials.

I made something like this years ago and have even used it to gash silver steel. Not needed all that often but very useful when it is. The one I made went with a myford but the boxford came with one at the correct shaft height.

**LINK**

It was based on a casting but not this one just similar with simpler lighter linkages and a flat lever.

**LINK**

Too late to post a photo.

The hole for the slotting head is drilled and reamed with the casting or block of metal etc fixed to the cross slide so that is always on centre. Some one on here made one that fitted onto the toolpost recently to produce some straight knurled knobs.

Your right to wonder about setting the slotting tool height. If it's going on a commercially made spindle the key on that will be dead central. If you cut one on a pulley and go for a precise fit and it's off centre they wont fit together and out comes a file to correct it.

The best bet is to turn up a bush, slot that and check that it fits on the spindle then do the pulley when your sure it's ok. That's probably what he did.

Oh – it's also possible to slot a shaft but care has to be taken to make sure it doesn't get bent.

John

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Edited By John W1 on 14/10/2015 23:38:54

Edited By John W1 on 14/10/2015 23:41:24

[JasonBModerator @jasonb]

I just use a height gauge resting on the cross slide, I know the ctr height of my lathe is 3.387" and just add half the width of the tool, set the gauge to the total and then set the top edge of the tool to tough the gauge.

These 3/6" wide x 1" long keyways were just done by winding teh carrage back and forth, I'm not one for making tools if I don't have to

[David Clark 13Participant @davidclark13]

Say it is a 1/4" slot, turn a bar in the chuck to 1/4" and set tool so it is in line withe the diameter. Should be in line when the slot is cut. I cut a load of key ways using a Colchester Triumph 2000 lathe. The rack was not powerful enough so I used the tailstock to force the carriage along. Knackered the tailstock which had to have a new nut and knackered me as each key way took at least 20 minutes to cut and I had about 20 of them to do.

[AjohnwParticipant @ajohnw51620]

I broke a tooth of a Raglan doing it Jason. It can happen. Mild steel and cutting a key in one of the variable speed pulleys. When I bought the lathe I found one of them was cracked. Lathe still worked ok so made another.

John

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Edited By John W1 on 15/10/2015 09:27:36

[John PParticipant @johnp77052]

The photo in the album shows this keyway slotting tool
that was published in the Model engineer in the early
nineties issue 3980 page 541 ,is available in the My
Hobby store plans list as "Slotting attachment for the
Myford super 7 lathe " plan no WE 68.
Uses the topslide as a guide and as such can be rotated to
cut keyways in tapered bores ,simple to make as it only
consists of a holding block ,lever and pivot.
Centre height the tool block is bored directly from the chuck
when the tool is made .
John

[AjohnwParticipant @ajohnw51620]

One mod I intended to make but haven't is to angle the tool bit holder, say about 15 degrees. Only problem is that if some one happens to have a drill pad for the tail stock it's more difficult to get the bit hole for the bit on centre in the holder.

The holder could be set up in the tool post and drilled. Say in a qctp boring bar holder.

The one I use now has a rod end as one bearing. Home made. May as well buy one less the usual spherical bearing no time to think if using a spherical one would cause problem. I'm off out.

John

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[Ady1Participant @ady1]

Alternatively, drill/cut a hole with a slot drill and finish off with a file of the correct size

[HacksawParticipant @hacksaw]

David Clarke wins for simplicity …. Jeez fella, you're sooo mechanically sympathetic ! Just like me ! My once tight Smart&Brown model M, is now like the old Myfords we used at school

The tool is great, but that'll take me too long to make for the one job .

[Author]

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