# Need Keway Broached



## lesrhorer (Aug 21, 2021)

Since no one wants to lend their broaches, and I can't find anyone locally who can handle metric broaching, I wonder if someone out there can broach a timing pulley for me?  It needs a 4mm keyway.  The hole diameter is 45mm.


----------



## Suzuki4evr (Aug 21, 2021)

Would have helped with pleasure, but we have a distance problem


----------



## Karl_T (Aug 21, 2021)

Do you own a mill or lathe?  if so, there is a fairly simple way to cut that keyway with an HSS tool bit. I'll share more if you are interested.


----------



## Suzuki4evr (Aug 21, 2021)

Karl_T said:


> Do you own a lathe?  if so, there is a fairly simple way to cut that keyway with an HSS tool bit. I'll share more if you are interested.


I was just about to suggest what you are about to propose. But you go for it.


----------



## tjb (Aug 21, 2021)

Karl_T said:


> Do you own a mill or lathe?  if so, there is a fairly simple way to cut that keyway with an HSS tool bit. I'll share more if you are interested.


Not my post, but I'm interested.


----------



## Karl_T (Aug 21, 2021)

Thought sure there was a tutorial on how to do this. My google foo is poor right now, best i found was this









						CUTTING KEYWAYS IN A PULLEY!!!
					

Has anyone cut a keyway in a steel pulley without a broach? I was thinking about ways to do it, like using a blank cutter from a lathe and using a press taking small cuts or maybe a drill press in off position as a press taking small cuts. I have done one where the center of my tractor rear...




					www.hobby-machinist.com
				




Basically, you got to get creative, somehow grind a piece of HSS to form of the slot, then use the carriage or quill to manually go back and forth as a poor man's slotter. Advance table or cross slide to depth.


----------



## Jubil (Aug 21, 2021)

There are videos on you tube broaching on a lathe or mill.
Mr Pete, and Kieth Appleton to name a couple.
What machines do you have or access to? What material is pulley?
What does this pulley do? Pics would help too.
Chuck


----------



## ErichKeane (Aug 21, 2021)

I'd have to build a tool for it, but I could do it on my shaper depending on the shape/vice-hold-ability of the pulley.


----------



## Bi11Hudson (Aug 22, 2021)

Then there's always a couple or three hacksaw blades and a 3 square (triangular) file and a little elbow grease.

.


----------



## Zack (Aug 23, 2021)

Yep, that's the way I broach.  Tightly tape 3 good 32 tpi hacksaw blades together for an 1/8" broach in a pulley  then dress it up/tweak it  with a small triangle file.    For a wider keyway just tape together more hacksaw blades.    I've tried never tried to do a timing pulley though.    That would complicate things.


----------



## lesrhorer (Aug 23, 2021)

Jubil said:


> There are videos on you tube broaching on a lathe or mill.
> Mr Pete, and Kieth Appleton to name a couple.
> What machines do you have or access to? What material is pulley?
> What does this pulley do? Pics would help too.
> Chuck


I should have mentioned from the outset it is Aluminum.  It's for my mini-lathe.  I am replacing the stock 750W brushed motor with a 1200W brushless motor.  The tiny V-belts that currently drive the spindle are too frail.  I've owned it less than a month and one of the V-belts shredded itself.  They are also quite expensive and hard to find, being something of a specialty item.  I am replacing the 2-step V-belt pulley system with a single flat timing belt.

I already had a friend broach one of the pulleys with a 5mm HSS bar using his lathe.  The results were not very good.


----------



## lesrhorer (Aug 23, 2021)

Zack said:


> Yep, that's the way I broach.  Tightly tape 3 good 32 tpi hacksaw blades together for an 1/8" broach in a pulley  then dress it up/tweak it  with a small triangle file.    For a wider keyway just tape together more hacksaw blades.    I've tried never tried to do a timing pulley though.    That would complicate things.


You mean because of the thin lips?  Well, maybe.  Certainly the thin lips can't be held very tightly in a vice.  A shim on each side a little deeper than the depth of the lips will protect them from the holding force, no matter what sort of clamping method is used.  That, or one can clamp the pulley along the spin axis, rather than on its edge.


----------



## ErichKeane (Aug 23, 2021)

lesrhorer said:


> I should have mentioned from the outset it is Aluminum.  It's for my mini-lathe.  I am replacing the stock 750W brushed motor with a 1200W brushless motor.  The tiny V-belts that currently drive the spindle are too frail.  I've owned it less than a month and one of the V-belts shredded itself.  They are also quite expensive and hard to find, being something of a specialty item.  I am replacing the 2-step V-belt pulley system with a single flat timing belt.
> 
> I already had a friend broach one of the pulleys with a 5mm HSS bar using his lathe.  The results were not very good.


So the one thing people don't really mention with the lathe method: you're basically making it a shaper, and need to use shaper tools. So it comes down to the grind!

Even on a large machine, a 5mm wide cut would turn out awful chatter wise. You basically should have a RH and a LH shaper tool plus a rougher (or a flat face tool thst is narrow to do all 3).

This becomes tougher on a large, since I think you don't have enough axes to do it Right.


----------



## lesrhorer (Aug 23, 2021)

Zack said:


> Yep, that's the way I broach.  Tightly tape 3 good 32 tpi hacksaw blades together for an 1/8" broach in a pulley  then dress it up/tweak it  with a small triangle file.    For a wider keyway just tape together more hacksaw blades.    I've tried never tried to do a timing pulley though.    That would complicate things.


Interesting.  If I can find the right thickness blades, this could be done pretty easily on the lathe.  I am a bit leery of a purely hand based approach.  Since this pulley will be under significant loads and spinning in both directions, the keyway needs to be pretty accurate.

Right now, I am leaning towards using a 3mm end mill and moving the mill bed 1/2mm each direction.  Getting rid of the 3mm radius on both sides won't be difficult using a file.  I can pretty easily clamp the pulley flat on a pair of parallel bars.


----------



## ErichKeane (Aug 23, 2021)

lesrhorer said:


> Interesting.  If I can find the right thickness blades, this could be done pretty easily on the lathe.  I am a bit leery of a purely hand based approach.  Since this pulley will be under significant loads and spinning in both directions, the keyway needs to be pretty accurate.
> 
> Right now, I am leaning towards using a 3mm end mill and moving the mill bed 1/2mm each direction.  Getting rid of the 3mm radius on both sides won't be difficult using a file.  I can pretty easily clamp the pulley flat on a pair of parallel bars.


If you rough it out with the mill, the lathe shaper thing should go way easier for pulling out the corners too, in car you wanted to indicate it in/get it quite accurate.


----------



## lesrhorer (Aug 24, 2021)

ErichKeane said:


> If you rough it out with the mill, the lathe shaper thing should go way easier for pulling out the corners too, in car you wanted to indicate it in/get it quite accurate.


That's a great idea.  I think I will try that.


----------



## lesrhorer (Aug 24, 2021)

I have been thinking about how to locate the bar in the lathe so it is dead center off the pulley axis.  I have a QCTP, which makes things easier, but how to measure dead center?  There are a number of easy ways to determine when the top of a tool is dead center, but for this application, the center of the bar needs to be dead center on the part.   I am going to bore out a piece of round stock to the same diameter as the diagonal of the tool bar.   (5.66mm 7.07mm, respectively for the 4mm and 5mm keyways.)   I can then tweak the height of the bar until it slides perfectly  into the hole bored in the round stock.  The center of the bar will then be dead center on the spindle axis.  Replace the round stock with the pulley in the chuck, rotate the tool holder a few degrees to give it some clearance, and viola!  A poor man's keyway broach.  I just hope I have better results than my friend did.  I think with a preliminary 3mm rough cut on the mill it will do just fine.  'Fingers crossed.

Now I just need to figure out a good way to lock the lathe spindle so the part doesn't accidentally rotate.


----------



## lesrhorer (Aug 24, 2021)

ErichKeane said:


> I'd have to build a tool for it, but I could do it on my shaper depending on the shape/vice-hold-ability of the pulley.


That sounds rather expensive, not to mention a bit of work for you.  Of course, a shaper would work quite well, as long as one has a good way to center the pulley on the shaper's thrust axis.


----------



## ErichKeane (Aug 24, 2021)

lesrhorer said:


> That sounds rather expensive, not to mention a bit of work for you.  Of course, a shaper would work quite well, as long as one has a good way to center the pulley on the shaper's thrust axis.


I've actually got most of the parts around... I am going to use a spare 5c collet block and weld it to barstock to hold in the tool holder, just never got around to it (and may have re-used my bar for something....)!  As far as centering the pulley on the shaper's axis, thats a pretty common task.  You set the pulley so it sits 'straight up' in the vise, then run a square bottom tool so it touches on both corners, thus you are reasonably well centered.

Either way, total is about an afternoon to get it setup and cut.


----------



## lesrhorer (Aug 24, 2021)

ErichKeane said:


> I've actually got most of the parts around... I am going to use a spare 5c collet block and weld it to barstock to hold in the tool holder, just never got around to it (and may have re-used my bar for something....)!  As far as centering the pulley on the shaper's axis, thats a pretty common task.  You set the pulley so it sits 'straight up' in the vise, then run a square bottom tool so it touches on both corners, thus you are reasonably well centered.
> 
> Either way, total is about an afternoon to get it setup and cut.


Well, OK.  How much do you want to do two pulleys, one with a 4mm keyway, and one with a 5mm keyway?


----------



## ErichKeane (Aug 24, 2021)

lesrhorer said:


> Well, OK.  How much do you want to do two pulleys, one with a 4mm keyway, and one with a 5mm keyway?



Cover shipping and a 12 pack (plus include some blueprints), and I can get to it next time I'm in the shop.  PM me and I'll send you my address.


----------



## lesrhorer (Aug 24, 2021)

Well, as long as we are talking domestic - not one of those high-falutin' import beers, you've got a deal!  PM on its way.


----------



## ErichKeane (Aug 31, 2021)

Well, whew! Spent most of the afternoon getting the first one setup. 

I made a plate of aluminum into a holder to put in the vise as a poor-mans angle plate.

I ended up turning a close-fit bar that I could put down the bore, use paper off each side to touch off and use a dial indicator and math to center the tool. I figure the keyway is sub-3 thou centered wise.

I only ground 1 tool for both keys, so it is only .130 wide, which means a bit of back and forth with the dial indicator to cut the whole thing. I fed only 2-3 thou per cut so it got a pretty smooth side.

Then I did a cut across the bottom to clean that up. I got a touch of chatter for some reason at the bottom in 1 spot, but didn't notice until it was off the machine.

Depth and width were cut to exact book-spec, though the key I was given ended up not fitting cleanly. I spent a few moments with a file, and it fits just right.


----------



## lesrhorer (Aug 31, 2021)

That is some fine looking work.  I would feel bad if it were not for the fact (I hope) you will be able to make good use of the fixtures and tools in the future.


----------



## ErichKeane (Aug 31, 2021)

lesrhorer said:


> That is some fine looking work.  I would feel bad if it were not for the fact (I hope) you will be able to make good use of the fixtures and tools in the future.


 I like using the shaper, and wanted an excuse to make an internal shaping tool, so this was a good excuse!

Additionally, the mill work for the fixture plate lead to me discovering my mill was miswired! I had a separate thread about that one a few days ago. So multiple good things coming out of this project.


----------



## lesrhorer (Sep 1, 2021)

In that case, I'm glad I could help.


----------



## lesrhorer (Sep 5, 2021)

I got the pulleys in the mail yesterday and spent the night installing them and machining the idler pulley bracket.  Everything works great!  The lathe spins up to 3000 RPM quiet as a mouse with almost no vibration.

I want to give a shout-out to Erich for his excellent work on the pulleys.  The 45mm bore was perfect.  The 19mm bore was just a tenth or so under, which isn't surprising since he did not  have the actual shaft to use as a measure.  It was close enough I could have pressed it on or heated the pulley, but I want to be able to easily change it in the future if needed.  Two minutes with a Dremel sanding drum and it slides on and off with ease.  The keys fit easily and smoothly.

It was a real joy working with Erich.


----------



## ErichKeane (Sep 5, 2021)

Ah shucks! I really thought it was going to be the opposite! I hit the 19mm shaft dimension within about 2 tenths, and was almost 2 thou over on the 45mm bore!

I wonder if the shafts are a little oversized? (Or maybe just my metric to 'Merica conversion was off a touch!).

Either way, glad it worked out for you! I had fun getting the shaper set up for internal keys, it was a fun experience to do on this new shaper. I'd only done it before on a small one.


----------



## lesrhorer (Sep 6, 2021)

Well, the 45mm fits on a threaded shaft, so if it is .002 or so oversized, it's not at all obvious.  I did not measure the run-out, but visually I don't see any.  The gear next to it has a lot of axial wobble, so that it touches the pulley on every revolution, so it is far better than the lead screw gears on this lathe.  (I will have to do something about that, some day.)  I seem to recall the motor shaft was indeed about 0.2 thousandths over when I measured it a few weeks ago.


----------



## lesrhorer (Sep 6, 2021)

Any of you who are interested can take a look at the results here. (See Phase II.)


----------

