|Robin Graham||08/11/2018 20:19:47|
|631 forum posts|
I need to make a keyed fitting between a 19mm shaft and a steel sprocket wheel. I'm thinking a 5mm square key, looking at the keys on my lathe changewheels. I can mill the way in the shaft OK, but don't have broach for the internal way in the wheel. Or a press for that matter.
I think I've read that this can be done by 'planing' on the lathe. Can anyone advise or point to advice about tool geometry/DOC/feed for this process?
|Ian Childs||08/11/2018 20:30:36|
|15 forum posts|
The way I did this was to make a tight fitting dolly, centre punch the line in the required position and drill through both the edge of the hole and the dolly, remove the dolly and then file the half round hole square to fit the key. This was in a sprocket too although the hole was a bit bigger. Think I did it three times like this.
|David George 1||08/11/2018 20:38:26|
1012 forum posts
Hi robin you can rough out the internal keyway using a slot drill in a mill then transfere it to a lathe and finish it with a tool ground to the correct width taking small slices untill corect depth. I have a piece of silversteel cross drilled with a 6mm hole and a grub screw in the end to clamp the has tool bit ground to suit the key size like a part off tool on its side.
|Andrew Johnston||08/11/2018 20:47:13|
5074 forum posts
You just need a toolbit that looks like a short parting tool. Like these:
These tools and bars are actually intended for use in a slotting head on the vertical mill. But they could just as easily be mounted in the toolpost on the lathe and moved back and forth with the saddle.
|Neil Lickfold||08/11/2018 20:53:34|
|579 forum posts|
If the tool is sharp, you can push through 0.001 inch depth of cut to about 0.002 inch depth of cut, from 0.002 inch diameter to a max of 0.004 inch diameter. Metric 0.05mm to 0.1mm max on diameter. The blade or cutting wants to be around 5 deg or so . If you make it too much like a chisel, it will pull the cross slide in and try to keep making a deeper cut. Having the tool face , the one in line with the bore, if that is set so it is about 1 deg clearance, this will also help to stop the tool digging in. Any material taken out before hand, dramatically reduces the cutting loads. Even if you hand file a rough slot , and then use the tool in the lathe for finishing the key slot works well. HSS works really well for lathe key slot cutters.
277 forum posts
|I have cut keyways in a couple of flywheels using Andrews method, it worked well.|
I pushed it through in small stages with the tailstock.
|Michael Cox 1||08/11/2018 21:59:27|
|521 forum posts|
Here is an easily made adjustable broach:
I would suggest that you remove most of the material by drilling or milling first and then use the adjustable broach to clean up the slot.
|John Rudd||08/11/2018 22:14:33|
|1367 forum posts|
|448 forum posts|
+1 for Andrew's method.
3893 forum posts
I've done a few Myford change gears the abovementioned way, converting early pin-drive gears to the later keyway type. I just used the regular boring bar with toolbit in effect turned sideways. Racked it back and forth with the carriage handwheel, taking one to two thou cuts. Tool geometry was as described above, about 5 degrees back rake, plenty of clearance on the sides and front, and honed razor sharp. It's a rather tedious process but you get there. I would not like to do a full set of change gears like this in one sitting! But fine for a one-off.
|Andy Pugh||09/11/2018 01:31:30|
|47 forum posts|
With a CNC it becomes quite easy.
Edited By Andy Pugh on 09/11/2018 01:32:28
|Danny M2Z||09/11/2018 04:34:22|
770 forum posts
Brilliant Mike, I like the fact that it is adjustable. Maybe that's why I should visit your site more often
* Danny M *
|485 forum posts|
I've never bothered,
I use the mill to slot the shaft and again the mill to slot in the pulley etc.......as for the pulley, as long as the slot is deep enough, at least 1.1/2 times normal keyway depth, I leave the slot with a rounded top......custom make the key from flat stock.......can't justify buying special tools for the odd job and besides the keyway is usually covered with a nut and washer anyway.....
it's not a perfect world.......I'm sure this'll create trouble on the forum but life is to short........
this has been my go to method for years and it has been sucsessfull on high horse power items used on tractors etc.....clogs
|76 forum posts|
I,m with clogs on this one as I said in another thread a few days ago ,if you want it to look pleasing to the eye its easy to make a rounded top key from some flat stock by using an edge rounding milling cutter, so say for a 6mm wide key a pass either side with a 3mm rad cutter forms the round top and a bit of fitting with a file fits it in the keyway , so compared to the lathe method it takes a bit longer to make the key but way less time to do the keyway.
|Trevor Roberts||09/11/2018 09:39:40|
|8 forum posts|
Have a look at this link.
Clickspring is an interesting site. There is a link to him using the cutter, I think t is him making a keyway in a pulley.
Here is the link to the pulley
Edited By Trevor Roberts on 09/11/2018 09:42:47
|Andy Pugh||09/11/2018 10:11:31|
|47 forum posts|
I haven't seen a mention yet of a hand-slotting attachment for this task.
One is mentioned and shown in a photo here:
(That forum, especially the pre-ww2 section, has a number of fascinating 12" to the foot models being built.
|119 forum posts|
I have successfully planed a keyway in an aluminium pulley with a home made bit in a standard boring bar mounted in the toolpost.
I also have fond memories of watching my late father cut a perfect 1/4" keyway in a steel shaft with a cold chisel.
Now, this is probably a silly question but, in my ignorance, I am wondering if/why a key really needs to be square. Taking an earlier suggestion about mounting the pulley on a mandrel ( or perhaps its own shaft ) and drilling on the join line before filing square, what would be wrong with just fitting a cylindrical key? Obviously it would only work on the end of a shaft. The crucial area would seem to be the interface between pulley and shaft, where the shear effect on the key would be concentrated. Is the shape of the body of the key important?
|Andy Pugh||09/11/2018 12:50:33|
|47 forum posts||
They don't. Tangential keys, used in pairs, are (or were) sometimes used:
Of more relevance here, you suggest cylindrical keys. These work well, but why limit yourself to plain cylinders? threaded keys into tapped holes half-and-half drilled can work very well and are very secure.
There were a couple of examples on my Harrison milling machine.
|Mick B1||09/11/2018 13:08:40|
|1277 forum posts|
+another 1 for Andrew's method.
I was actually taught to do it this way at the Government Training Centre where I learned the lathe in '75, and it was one of the exercises. Broaching was for batches of tens to hundreds.
I've used a similar technique to shape out square through-holes in the lathe from round - at some cost in blistered palms!
277 forum posts
|This post spurred me on to put the keyway in my otherwise finished flywheel!|
Using Andrews method, I fitted a length of shaft into the bore secured with a dab of picture on the end, just enough to hold it in position.
I then drilled down through the joint line with a 3/32 drill which was then opened up to 3mm.
Shaft tapped out I adjusted the broach to remove about ten thou per cut. Could almost be tapped through by hand although a hide mallet was used.
Came out well and didn't take long.
If photo doesn't work it is in my photos!
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.