How to cut an inside keyway

I need some advise: I'm trying to figure out how to cut a 1/4 x 1/4
keyway inside a 1 5/16" ID x 3 1/2" long Hub, it's cast iron. Short
of buying a new broach I can't figure out how to get it cut. I've got
available a Claussing knee mill, a 9" South Bend lathe, a Ammco 7"
shaper. However, based on reading about cutting keyways, all of these
machines have limitations that make cutting an inside keyway difficult
if not impossible. I've tried using the lathe with a milling
attachment on the cross feed and using a boring bar in the tailstock.
That process was marginal at best and I finally gave up (only had 2
1/2" travel on the tailstock).
Any suggestions?
Reply to
Bob Julian
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Why..the shaper of course!!
You do have Errols Shaper CD, dont you? If you dont..GET IT!!
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Reply to
The Ammco shaper will do it just fine. One of the major uses for a shaper is cutting internal keyways.
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Reply to
Since you don't know how to use your shaper for that job, the other path is a keyway cutter tool which can be done by hand or on a press.
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Reply to
Bob May
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Grant Erw>Not difficult at all, Bob. I just did an inside keyway on a 4-step
That will do it -- but I think that you missed that he has a 7" shaper. The trick with that is to mount your boring bar setup so it is parallel to the ram, and use that to cut the keyway. That automates a lot of the work you're doing manually on the lathe.
I'm a bit late on this, because my news feed was out starting Friday evening.
Enjoy, DoN.
Reply to
DoN. Nichols
First, Thanks to all you guys for the valuable comments, I've learned a lot. I've set up the hub on a milling attachment on the lathe crossfeed and used a 3/4" boring bar with a 1/4" tool for the 1/4x1/4 keyway. I abandoned the process due to: 1) the extension on the tailstock required that I reverse the hub to finish the back side (not easy due to geometry), 2) the tool in the cast iron didn't "cut", but more like scraped, really crummy cutting action (perhaps due to my grinding the shape of the cutting tool, though that's not too likely). I also found that there was a bit of rotational "slop" in the tailstock, resulting in the boring bar turning slightly (perhaps approx 5-10 mils). This process seem more like chewing a keyway than cutting a keyway. Thus, I'm leaning towards buying a 1/4" broach on Ebay ($10) and making a collar to fit the hub depth. Broaching the keyway seems to be the more appropriate way of cutting this slot.
However, I'm still puzzled why some of you suggest that I can cut the keyway on the shaper. Since I am an admitted dunce about shapers I have several questions: 1) I assume that I need to buy / make a tool holder that will accept a boring bar. I don't see how the standard tool holder would work. 2) Then, there's the ram throw distance when the ram is fully retracted and the vise. The vise is fixed on the horizontal table, so I can't move it to gain more clearance between the fully retracted ram position. I don't see how I could possibly get sufficient ram travel - particularly with a boring bar mounted. To make this work it appears to me that I would need to get at least 7" clearance between tool with the ram fully retracted and the back side of the keyway.
Here's the reason I'm interested in answers to the above questions: It appears to me that with a lathe and mill in my shop, that the shaper is of marginal use and mostly redundant. Can any of you provide reasons why a shop with a lathe and mill needs a shaper? (OK... perhaps this is one of those quesitons that if I have to ask the question, I shouldn't have the machine... but, I'm still trying to figure out the shaper's purpose). Depending on your commnents I may be leaning towards selling the shaper.
Again, thanks to all of you for providing advise, I'm very impressed that you'all take time to offer advise to novice machine shop guys like me.
Reply to
Bob Julian
I don't have Errols Shaper CD. Tried to find it through a Google search. What is it, where do I get it?
Thanks Bob
Reply to
Bob Julian
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go to the metalworking drop box, and search the archives for "volz". The gentleman was kind enough to post some prints of some easily made shaper tooling, including an inside keyway/spline cutter.
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Reply to
Hold the hub in the chuck. Lock the chuck by engaging the back gear. Fix the boring bar in the carriage tool holder with the cutting edge facing you. Move the carriage to do the cut, using the cross slide to advance the cutter after each stroke. This lets you use the full carriage travel to cut the slot. That should be far more than enough to cut a 4 inch long slot.
Remember that you're cutting the inside of a curved surface. Make sure you ground enough clearance into the cutter to allow for that or it *will* scrape rather than cut. Cast iron makes a crumbly chip anyway. That's normal. But you should be able to achieve a clean cut with a sharp cutter of the proper shape.
That's correct. Just bore a block to accept the boring bar, and hold it in place with a setscrew. Fix the block to the clapper with a bolt the same way the normal tool post would be mounted. If this isn't clear, imagine a rectangular block. Near one end you drill a hole to accept the toolpost bolt. Near the other end, you drill a hole parallel with the first which will hold the end of the boring bar. Drill and tap a cross hole for a setscrew. Now mount it to the clapper so that the boring bar hole is below the ram. (Note, keep the block short as possible to maintain rigidity.)
First, remove the vise. Now take a heavy plate and bolt it to the *front* of the table (note the T slots there for this purpose). It should stick up above the table enough that you can clamp the hub to the plate with strap clamps. The plate should have a hole in it matching the bore of the hub so the cutter can pass through at the end of the stroke.
Note that as with the lathe, you'll be cutting on the inside *side* of the hub, ie horizontally, so orient the boring bar cutter accordingly. The table advance will increase depth of cut with each stroke until you've reached the desired slot depth.
Perhaps 90% of machining is figuring out how to set up the work on the machine. You often have to be a bit creative. Shapers excel at cutting slots, and at producing flat surfaces. Many times the vise is just in the way. Mounting the work directly to the table, or with an angle plate or flat plate fixture, is just part of setting up the job.
See, you knew there was a reason to keep all those pieces of scrap metal around. :-)
Reply to
Gary Coffman
you kids have me interested in cutting keyways with my lathe now. you've all gone and done it.
what shape tool do i need? i've got plenty of HSS squares. is it essentially going to look like a chisel?
thanks -tony
Reply to
Went al the way back to 1997. No Volz. ergards, Jim
Reply to
I use a boring bar that holds a square tool at 90 degrees to the tool. I use a square piece of HSS as the tool, shimmed to the center of the holder if necessary, lots of back relief and a groove in the face so the tool will have a lot of positive rake. I mount the boring bar in a holder on center and cut on the 'pull' stroke, usually taking .001 to .002 at a time.
Reply to
Russ Kepler
There was an excellent article in a HSM a few years back. It showed the exact way to grind a square toolbit to use when stroking a keyway with the lathe. I followed this article exactly recently and got a perfect 3/16" keyway in a 2-7/8" thick pulley.
Enco has their square-holed boring bars on sale right now. I bought one of these to do my keyway cutting job. They are made in India but I can say the one I got was machined accurately and worked perfectly. I just ordered the set of 5 (under $30, can you believe it).
I didn't do anything fancy to stop my spindle from turning. I did set the vertical height of the toolbit by using a depth mic from the top of my pulley. That worked very well.
I had a lot of fear the first time. Now I'm confident and would do this again in a minute.
Grant Erwin Kirkland, Washington
Russ Kepler wrote:
Reply to
Grant Erwin
what if i were to use a straight piece of square HSS? that is, no boring bar.. just a, say, 1/4" x 1/4" x 6" piece of HSS, running about 5deg or so to the spindle axis? with some relief cut, of course.
do you feel by hand? or powerfeed? i can't figure how i'd get my lathe to powerfeed without having the chuck spin. especially if something like the brake is engaged.
should i just shut the power off?
'night, -tony
ps.. think one could cut a 1/2" keyway 4" long this way?
Reply to
Do you have a part #, or catalog page, or more specific name than "boring bar". A search on that returned a list of 100's. TIA, Bob
Reply to
Bob Engelhardt

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