Broaching Keyways with the Lathe

I have watched several videos on YouTube for broaching internal keyway slots using the lathe carriage while holding the part in the lathe chuck with the lathe totally powered off. In this example I cut a 5mm wide by 2.51mm deep slot in a 40 tooth gear bored to 18mm ID. The gears are for a replacement change gears to a 12” swing geared-head lathe (see Homemade Change Gears).

Using the 90 degree end of a 0.500” boring bar with a 3/16” square HSS tool blank ground with 10 degree relief angles, I cut the 5mm wide keyway slot. Grinding the cutting faces on the HSS is done with the longer tool blank. The shorter HSS cutting tool is cut from the larger piece of HSS stock using a Dremel tool with a reinforced abrasive wheel and before completely cutting all the way through, the shorter section of HSS is snapped-off in a vise.

The boring bar set-up uses another longer piece of 3/16” square HSS tool blank to align the boring bar horizontally using a test dial indicator. Also, the QCTP is adjusted to a height to center the cutting tool with the keyway slot (and knowing the distance from the cross slide top to the lathe center). I used a digital height gage to set the HSS tool height.

Broaching began after replacing the longer HSS blank with the newly ground broaching tool. Make sure the lathe chuck is locked in the lowest spindle gear to prevent it from moving. I also used a soft jaw ratchet bar clamp to ensure the chuck could not move. Each broaching pass was feed in increments of 0.001” to 0.002” with the lathe cross slide in order to prevent the cutting tool from hogging into the ID wall. Use plenty of cutting oil. Originally I had planned to use a 0.625” diameter boring bar that holds ¼” square HSS cutters so I could grind the larger HSS tool down to 5mm (0.197”) wide. However, in this case, the 18mm (0.709”) ID hole provided too little clearance for both the boring bar and cutting tool. I used the 3/16” (0.1875”) square HSS set to two different vertical heights to cut the keyway slot to the final 5mm width and checking the slot width using a gage pin before removing from the chuck.

Thanks Paul! I've added your Keyway Broaching Technique to our Machining category, as well as to your builder page: Paul Jones' Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="/keyway-broaching-technique"><img src="/uploads/114142/keyway-broaching-technique.jpeg" alt="Keyway Broaching Technique" /></a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="/keyway-broaching-technique">Keyway Broaching Technique</a> <span> by <a href="/builder/Paul+Jones">Paul Jones</a></span> </div> <div class="tags"> tags: <a href="/tag/lathe">lathe</a>, <a href="/tag/keyway">keyway</a>, <a href="/tag/broach">broach</a> </div> </div> </div> </div>

Very informative post, Paul Jones. It's always nice to learn something new. :)

Hi Paul
Nice work and presentation as ever.
I have in the past used the topslide with the feed screw removed with a hand linkage.
At the moment I am trying to design a motorised version with a 1 inch stroke working on the saddle to machine some small gears integral with a cam.
I look forward to posting it if it works.

olderdan,

I think you will have a winner with the motorized version. I found that grinding the correct angles on the cutting tool for the material being broached was extremely important and more so when motorized. The boring bar and cutter can hog into the inner wall with too much feed and potentially ruin the part. It is not a big deal when driving the cutting manually but will be a problem with motorized. You might want to consider adding some type of mechanical clutch on the driving mechanism to stop the stroke.

Thank you for the comments and looking forward to seeing your broaching system.

Paul

Thanks for your observations, you are right about needing some sort of friction clutch in the drive and it is something of a stumbling block at the moment but I am still chewing on it.
Any thoughts.

olderdan,

How about a simple miniaturized clutch assembly with two small rotating plates and an adjustment nut with a compression spring that put pressure from behind on one plate and the friction between the two causes the clutch to slip when too much resistance occurs on the output shaft due to the tool jam.

Attachment 13648

I don't have access to my CAD so I quickly (and very crudely) drew the clutch cross section in Excel to help with my explanation. Sorry about the drawing.

Paul

Your clutch design looks sound and thanks for that, the problem I have is lack of space to fit an intermediate clutch to the gearbox I have, this an old but very powerfull mobility scooter 24v drive but it will have to have an overhung eccentric so no room for an outrigger bearing.
Your drawing started me thinking that I could maybe make an adjustable spring loaded conrod.
Anyway thanks for your help, I think I need to think about something else for a while and have a fresh start.
Regards

Attachment 13656Attachment 13657

Paul
I am working on a stroker right now. I have done it using a boring bar and manually back and forth, not fun at all and time consuming. I am using a gear head motor with a pivot point like an old locomotive wheel. The mount bolts onto the compound on my South Bend and can use the compound or the saddle screw to move sideways. I am concerned about the size of my gear head motor but that will dictate the amount of cut. It will be better than using the carriage and wear on the bed. I'll be posting soon.
Nelson

Quote:

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Originally Posted by Paul Jones

olderdan,

I think you will have a winner with the motorized version. I found that grinding the correct angles on the cutting tool for the material being broached was extremely important and more so when motorized. The boring bar and cutter can hog into the inner wall with too much feed and potentially ruin the part. It is not a big deal when driving the cutting manually but will be a problem with motorized. You might want to consider adding some type of mechanical clutch on the driving mechanism to stop the stroke.

Thank you for the comments and looking forward to seeing your broaching system.

Paul

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I use a pneumatic cylinder to drive a slotter. There is no need for a clutch because the force can be limited by the set pressure. Just like electrics, pneumatics offer a lot of options for control. You could simply have a manual valve with powered or spring return. If you wanted to be more sophisticated you could set it up to automatically oscillate.
I have such a device for my mill for making clutch baskets and hubs.

Pneumatics is a more logical approach, I did not pursue my original idea as for my limited use it was not worth the effort.
Would still be interested in seeing your set up some time as I am sure it would make a good post.

Quote:

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Originally Posted by olderdan

Pneumatics is a more logical approach, I did not pursue my original idea as for my limited use it was not worth the effort.
Would still be interested in seeing your set up some time as I am sure it would make a good post.

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Alan, It is on my list to make a post, but my list is very long and seems to be growing faster than I can find the time to write them up.
Next time that I set the slotter up I'll take some pix and maybe make a video.

That would not be too hard. Just make a slide valve to change the direction at the end of stroke. I kind of like the air idea.
Nelson

that gives me an idea for air stroker on my sunnen rod hone to make a power stroker for my air cooled cylinders. thanks as always guys!!! different perspectives and ideas are what drives evolution forward.

Quote:

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Originally Posted by marksbug

that gives me an idea for air stroker on my sunnen rod hone to make a power stroker for my air cooled cylinders. thanks as always guys!!! different perspectives and ideas are what drives evolution forward.

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If you put an adjustable needle valve or similar in the air line you'll be able to change the stroke velocity and hence the helix angle of the honing marks.

yes I already was thinking that when I was reading the other post.basically a regulator.and of corse a foot operated switch so it runs as the hone/machine does, so there is no over speed of the stroke when load is removed/eazed up...possiably even a 2 stage air supply.one to stroke at the right speed with no load and another to keep the same speed with the hone loaded...that shouldent be hard at all. And the direction change valve can be moved to vary the stroke length. i had already ordered some linner bearing's&shaft&mount's for this, but had more thinking to do..as always. dont know when Ill get to doing it, Im working on selling all the racecar stuff now for a lot more room in the shop.and as always, more stuff in my head that I have time to do...it's a curse.Ill be working 50 years after Im dead.

Have seen this "conecting rod" one on facebook
https://www.facebook.com/merv.harris...5967129784510/

Paul
Very nice work and love your set up. The thing that bothers me the most is the number of strokes and the wear on the saddle and bed.
In a pinch it works.
Nelson

my new lathe ( new 2 years ago when I got it) enco 9x20. well the gear train was so noisey I skeered me...and I dont get skeered eazely. I got to checken it out and the gear bushings with built in protruding woodruf key to drive the gear so it could be swaped to positions where it could either be idler or drive a shaft. well the bushings had .014" run out....yup thats a lot. there also pretty thin.so i put them in my smaller lathe and machined the center out in the center .030 biger,I then used a thinwall phosphor bronze guide liner(Kline, for relining valve guides in engines). that worked great on all execpt for the one that was rivoted to a shaft:headscratch:.. so I disambled the lathe put the shaft in the chuck of my small lathe( remember it has a built in key) so I could not just turn it true...so...I used the lathe as a broach!!! and just moved the carrage back& forth and let the carbide take some shaves off ,I left some very thin strips inbetween. I then made some shim material brass stock, and shimed the low side and pressed on the gear and checked the run out...the thin uncut strips were pushed over/down so it would shape right and hold tight... it was less than .0015 run out!!!! I guess my calculating was almost dead on.I wasent about to pull it off and try to better my self and eff it up. I put the enco pos lathe all back togeather and hit the switch....holy crap!!!! it was oh so quiet!!!!! so yes lathe can also be a broach!!! most all machines cam do many more jobs than there made for, it's all in your head, just do it!! butt first.....be sure it's safe. sometimes when you strive for perfection you need to stop just short..or you may end up with a lot more work. been there done that tomany tymes:smash: so everybody keep up the great work and post some more!!!!:hattip:


I have since added real ball bearings to the cross slide&compound slide screws.oh somuch better than a sloppey pos cast bracket& wobbly shafts. I tend to rework everything I buy as soon as I get it, especialy the new stuff.

The problem I see what a pneumatic cylinder to power a cylinder hone, is the lag you get at the end of each stroke. When a pneumatic cylinder changes direction in mid stroke, there is a lag with no movement. The pressure from one side has to vent, as the pressure from the other side builds enough to change direction. If this happens mid-stroke, where the cylinder has not reached a hard stop, the lag may be shorter, but cylinder travel limit is difficult to control as it is totally dependent on the loads involved. If there are are hard stops at each end of the stroke to control travel, as I imagine you would want when honing a cylinder, the lag would be longer as the pressure changes would be greater, thus the time for air to vent one side, and pressurize the opposite side will be longer.

This lag would not be a problem with a broach, but would need to be dealt with if used for a hone.

I do not want to hijack this thread, but would like to have a dialog with Tonyfoale and Marksbug, in regard to cylinder re-sleeving and honing/sizing.

Quote:

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Originally Posted by hemmjo

I do not want to hijack this thread, but would like to have a dialog with Tonyfoale and Marksbug, in regard to cylinder re-sleeving and honing/sizing.

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Well you could continue here, start a new thread or use email. If you keep it on this forum then you will get the advantage or maybe disadvantage of more people's input.

hemmjo,

Don't worry about hijacking this thread because sharing experiences and information is the basic mission of HomemadeTools.net (HMT). We all learn from the comments, posts and mistakes because it is a learning experience. Take this thread where you want to go with your experiences.

Regards,

Paul

This thread caught my attention, as I have done some broaching on my lathe. I have cut keyways in gears and pulleys and cut splines to make a "wrench" to remove the sprocket from a 10-speed bike wheel.

Then Tony and Mark chimed in talking about honing. Currently I am in the process of rebuilding the engine from a little jet boat. Same call them Jet Ski, but this is a sit down style. !998 TigersShark, 770. I have two of these that I bought with non running engines. I got one running by swapping good parts from the second engine. None of the shops around here do this kind of work anymore. It is time for me to get set up to do it myself.

The jug is 2 cylinder, it is too big for me to mount in my lathe and bore as I could on a single cylinder engine. I do not have a mill to use. I have been thinking about mounting the cylinder on carriage, and mounting my Lisle 15000 hone in the chuck to work on these cylinders. I would need to make a second universal so the hone is free to find its place in the cylinder. I can remove the gear and hand wheel from the carriage so I can slide it easily, perhaps making a lever set up to slide it between stops to hone the cylinder. My lathe has a pan with drain etc so I can recirculate honing oil. The question is.... should I try it? All of the hones I see are set up to operate vertical. Will gravity make the cylinders out of round?

The second question is in regard to sleeving. I now have two of these engine to rebuild since I bought a 3rd engine to get more parts. It is actually in pretty good shape, so I hope to end up with 3 engines for 2 boats. I have put sleeves in an old Ford farm tractor those sleeves pressed out and back in. I have been reading about sleeving 2 cycle engines some show boring the old sleeve out, others show heating the cylinder then pressing the sleeves out. I am not sure how to tell how these are removed.

That is what I am thinking about now....

even a sunnen ck 10/cv 616 are soft at the end, not much but not a jerk to the other direction. they also have a dwell lever so you can stop the stroke where you need it to stop to either straighten a wonkey bore or keep bores straight. I dont forsee a issue using air cylinders. many hones already do ( cheeper kinda knock offs of the sunnen hones) and a dwell valve could also be incorprated. Ive not run a air operated hone, but have seen some in shops,Ive a few thousand hone jobs on sunnen hones ck&cv& rod hones/bushing grinder&valve guide hones. there is no better equipment than sunnen.and they aint cheep, thus lots of knock offs.I knew the man& his sons who desinged the ck hone and sold it to sunnen way back when.it was a 2x8 wood frame, most of it was wood and had been used since it was made up untill a few years after the dad died about 15 years ago.I wonder where it is now I havent seen any of them in a few years.
there are many aspects to honing cylinders correctly. most shops dont.

hemmjo,

You might find this previous post of mine to be of interest.
http://www.homemadetools.net/forum/c...5286#post81520
In fact that might be a better place to continue this theme, maybe be easier for people to find as the subjects are more related.

As you are only ever likely to have a limited number of cylinders to hone I would suggest that you didn't bother too much about making some form of powered stroker. It is not unusual to drive the hone vertically with a hand drill or similar power source, stroked manually. When using a heavy drill it is quite common to support it with a long spring. A commercial setup using such a setup is likely to have a recirculating and filtered lubricant flow to wash away the junk. I only need to hone cylinders occasionally and I simply put the cylinder in a tall bucket and fill it above the cylinder with fluid. The cylinder sits in the bucket on a screen which allows the particles to sink below. It has a pump, filter and some hose to keep things clean.
With a bit of testing you can adjust your hone speed and stroking rate to get the helix angle that you want.

You might also find this of interest.
http://www.homemadetools.net/forum/i...769#post102422

Topslide keyway slotter
I have never liked the idea of racking the lathe saddle back and forth to cut keyways, it puts undue wear on bed ways and over strains the rack feed parts.
Much better to use the top slide as a ram with the saddle locked down, this is not my idea as I saw it in the Model Engineer years ago and at least one manufacturer offered this as an attachment. With a 4:1 ratio on the lever it makes light work of a keyway with the added possibility of tapered bores being keyed. I have seen gear teeth internal and external cut by this planing method but have not tried it myself.
Parts are simple to make, all it takes is to remove the feed screw and fit a suitable forked adapter and a lever of your choice, I clean and oil the slides before and after and have noticed the slide is much smoother after having had a good workout, it does not move much in general use apart from taper turning.

olderdan,

I agree with your assessment of not liking to use the lathe saddle for broaching keyways with the metal lathe. My example was for performing a 5mm keyway broaching for two my missing change gears. The method was just to get started with single point threading for Imperial threads (the missing 40T gears). Using the lathe for keyway broaching is only a temporary solution and not a long term production method. After my initial HMT article about using my 12" swing lathe for broaching the missing/replacement change gears, I now have several arbor presses and lots of various Imperial and metric broaches for doing this type of work. I plan to add a several ton hydraulic press to my set of tools to make the keyway broaching even easier and much faster.

Regards,
Paul Jones

To hyjack this thread just a little, a method I have used with some success, is to spin up a plug to suit the bore, then for square keys, drill down the "joint" line. half of the diameter of the drill will drill the job, the other half will drill the plug. maximum diameter is at the joint so all you have to do is square up the bottom, instead of having to "broach" all of the material out.
With respect to the removal of old liners, what I have done before is to weld straight down the barrel in three or four places round the bore, when the weld cools it shrinks the liner just enough to press it out easily.