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klemchuk
05-12-2010, 11:13 PM
I need to make a 3/16 keyway in a 1 1/2 bore approximately 5 inches long.
What would be the easiest way to do it. I have nothing at present that I think is capable. Would a broach & arbour press work?

Mcgyver
05-12-2010, 11:18 PM
I need to make a 3/16 keyway in a 1 1/2 bore approximately 5 inches long.
What would be the easiest way to do it. I have nothing at present that I think is capable. Would a broach & arbour press work?

possibly with some special bushings and shims. The different sizes max out at different lengths buts a lot less than 5, maybe 1.5". The problem is because its a progressive cut when things get too long, your taking to much DOC. However, you can make a bushing and engineer a set of shims such that only the last tooth or two cuts on each pass it should work.

Dr Stan
05-12-2010, 11:21 PM
I need to make a 3/16 keyway in a 1 1/2 bore approximately 5 inches long.
What would be the easiest way to do it. I have nothing at present that I think is capable. Would a broach & arbour press work?

The short answer is yes. You will need to make a special guide for the broach.

BTW, 3/16 is quite narrow for a 1 1/2" bore or shaft.

You may want to consider using a lathe or a vertical mill to cut the keyway. You would want to use as large of a boring bar as possible and manually cut the keyway with the carriage or the quill as appropriate.

tyrone shewlaces
05-12-2010, 11:26 PM
Step one - Get some 3/16 square HSS tool steel. You might already have some.

Step two - make a bar.
Get some 1" round bar stock long enough to be clamped in your lathe and reach the end of your 1-1/2" bore with some extra.
Drill a hole through one end of the bar just large enough for some 3/16 square cutter bit to fit through.
Drill and tap a hole (at 90 degrees to the previous one - either in the end or from the diameter side - doesn't matter much) that intersects the first hole. This will be for a set screw to hold the tool bit in place.
Slip the 3/16 bit through the hole so it sticks out a bit more than the depth you want it to cut and tighten it in place with your set screw. Probably want to cut any excess off the back side (if you have any) so it's flush with your bar.

Step three - mount your piece in the lathe chuck and the bar into your tool holder in the lathe, pretty much just like you'd use a boring bar except you want the tool bit centered in the middle rather than the upper edge of the bit.

Step four - lock the chuck in place or put it into your lowest gear. Maybe even unplug the lathe in case you think you might turn it on accidentally.

Then just use your carriage to feed it through the bore. Feed it into the material in the bore a thou or so per pass. Left-right-feed out-left-right-feed out-left-right, etc.....until it's to the desired depth.
Prolly want a few spring passes (no feed) when you get close.

Congrats! You just made your lathe into a shaper. And got a bit of exercise at the same time.

p.s. Don't have the exact stuff I described in the steps? No big deal - just improvise. Obviously need to grind the tool bit to a workable geometry, and can grind a larger bit down to 3/16" if you need to, etc. etc. etc.

Carld
05-12-2010, 11:47 PM
Yes, you can do it with a push type broach. You will have to make or buy a bushing that is 5" long, buy a 3/16" broach if you don't have one and make several thin shims longer than 5".

It would be a good idea to make the slot in the bushing a little deeper than stock so it don't take a heavy cut on the first pass. Then with several .020" shims adding up to get the correct depth of keyway you can start. You will have to use a bar to finish pushing the broach through the bore. You should also broach it from both sides on every other pass.

I have even used two standard bushings in a bore rather than make a long one. You have to have three or four hands at times doing this so you may need a helper.

Bazz
05-13-2010, 06:57 AM
I need to make a 3/16 keyway in a 1 1/2 bore approximately 5 inches long.
What would be the easiest way to do it.

I would cut it with a end mill ,plug it with a key and weld it and turn the OD.

Not for high precision but i done it that way many time

MuellerNick
05-13-2010, 07:26 AM
Not a very clever idea to make it with a standard keyway broach (like the ones from DuMont). They only can take a cut of a certain length. Even if you do make your own bushings and take more passes.
The reason is, there isn't enough room for the chips. A longer cut makes a longer chip. It will fill the room between the teeth and then the tooth will break.
Only a quick way to ruin you expensive broaches.

A single toothed broach is a different storry, a slotter is the solution. You could do that on a shaper too.


Nick

Michael Edwards
05-13-2010, 08:55 AM
You could do that on a shaper too.



Slip across the border and I will sell you a 16" G&E shaper. :D


ME

MuellerNick
05-13-2010, 09:03 AM
... and I will sell you a 16" G&E shaper.

Nice toy! :p
My big shaper has 650mm (25" for the metrical challenged ones).


Nick

Michael Edwards
05-13-2010, 09:28 AM
I am starting to run out of room. I have 4 shapers, 14, 16, 24 and 28" I just picked up a Reid 6x18 surface grinder recently and a kiln that I will add better controlls to make a heat treat oven. So, something has to go cause I don't want my shop to be as crowded as Mcgyver's. :D

shapers (http://farm3.static.flickr.com/2326/1558017808_d4fce82cee_b.jpg)

ME

Mcgyver
05-13-2010, 09:31 AM
Not a very clever idea to make it with a standard keyway broach (like the ones from DuMont). They only can take a cut of a certain length. Even if you do make your own bushings and take more passes.
The reason is, there isn't enough room for the chips. A longer cut makes a longer chip. It will fill the room between the teeth and then the tooth will break.
Only a quick way to ruin you expensive broaches.


whether its clever or not will be determined by whether it works and no one loses an eye (or broach). It's doable and i've done them longer than they broach is supposedly capable of (although i haven't done 5")

You just have to plan the shims so that your not overloading things. A broach is taper and is normally designed to take a bit off on each tooth per pass, the shim gets changed a second pass is taken. The idea for this job is to create much small steps using a lot of different shims - you engineer it such that the its not taking off more than it can handle, load or clearance, in once pass. If that means 5 thou a pass on one tooth or retracting the tool to clear the chip half way, whatever...its still doable...essentially turning the the broach into a one or tooth slotting tool. For that matter, make your own cutting tool and avoid buying the broach if there's only 1 to do - if its only a single tooth broach, easy enough to do.

A pita with all those shims? maybe. less than dragging a 16" shaper across the border or acquiring a vertical slotter :)

snowman
05-13-2010, 10:20 AM
Do it like you are line boring in the lathe, only have the tool bit locked into position parallel with the travel of the saddle. Now mount your work to the saddle, with tool bit in bar that is between chuck and center. Moving carriage back and forth, advance part into tool bit.

Carld
05-13-2010, 11:30 AM
As I said I have made keyways longer than what is considered standard with the Dumont broaches and the critical thing is chip size. For that reason you can't use more than a .010" to .020" shim AND you have to deepen the slot for the broach so the first cut will not be excessive.

Yes, it takes a lot of time but if your only doing one or a few it is cost/time effective.

I agree Nick, if you have a shaper or a single point keyway cutter it's better but home shops and small machine shops have to take the best and cheapest way for them.

strokersix
05-13-2010, 11:54 AM
How about making a long bushing with a tapered slot. Taper magnitude 1/2 the broach taper. Set the broach into the tapered slot then push broach and bushing through together. Shim and repeat. This will reduce each tooth DOC by half.

To reduce chance of bore damage from galling select bushing material accordingly and use plenty of lubricant.

Note that I have not actually done this but seems like it might work.

MuellerNick
05-13-2010, 02:40 PM
You just have to plan the shims so that your not overloading things.

Load is one thing. But length of cut is what makes the volume of every chip.
Just a quick check on a Hassay 4mm broach:
Height difference between one tooth to the next is 0.07mm. If you want to reduce chip volume, you have to shim in smaller steps than 0.07mm. So you wanted to suggest to shim in 0.02mm steps? Would require about 100 cuts for a 4mm keyway.

You may do as you want.

Nick

John Stevenson
05-13-2010, 02:54 PM
I have to do some rotors from time to time 40mm bore [ 1 - 1/2" ] and 120mm deep so 5" and these are 8mm keys [ 5/16" ]

I have a bushing that's cut slightly deeper to give the first cutting pass a gentler time.
The bushing is full length and D shaped in that I have flatted it off where the teeth are, every couple of inch or so I blast it in the D section with the air line to blow the part chips out and down.

This means I only need to use shims of half thickness so I get the keyway done in 7 or 8 passes instead of the standard 3.

Been doing them this way for years. Still quicker than setting the slotter up given that when broaching you only have to support on the base, when slotting you have to hold the job, not easy with a laminated rotor with cooling fins on.

bborr01
05-13-2010, 08:55 PM
I just went out to my shop and did some measuring on a DuMont 3/16 broach.

It is about 6.5 inches long. That means a push rod of some sort to go through 5 inches.

Chip load is also a problem. Each tooth is approx. .004" larger than the one below it. Unless you plan to use shims in increments of .002 or so, the last tooth/teeth will still see the same chip load.

I have broached literally hundreds of keyways, as well as cut some up to an inch wide on a vertical slotter.

The only time I have ever seen problems is with trying to broach a keyway that is too long, like this one.

Once you get the broach in until the chip has filled the tooth clearance in the broach, it is not likely to go back any easier than it is going to go forward.

The previous posts about cutting it on a lathe are right on.

That is what I would do.

Brian

Carld
05-13-2010, 09:31 PM
What is interesting is those that have not done it are telling those that have done it that it can't be done.

Think about that for a while.

If you ever get a broach stuck in while cutting with heavy chips or any other reason and try pushing it out backwards you will probably be buying a new broach. I know this first hand BUT you can press the bushing out and then remove the locked up broach and maybe save it. I also know this first hand.

I like John's idea of having clearance to blow the chips out.

I haven't tried pushing the bushing and broach through at the same time to cut a keyway so try it and let me know if it works.

Oh, and don't try to broach a long keyway in SS with the normal shims. Broaches hate SS.

beckley23
05-13-2010, 09:34 PM
I don't have any idea how these cost, but;
http://www.keyseaters.com/
Harry

jack3140
05-13-2010, 09:44 PM
would this not be hard on the carriage drive?
Step one - Get some 3/16 square HSS tool steel. You might already have some.

Step two - make a bar.
Get some 1" round bar stock long enough to be clamped in your lathe and reach the end of your 1-1/2" bore with some extra.
Drill a hole through one end of the bar just large enough for some 3/16 square cutter bit to fit through.
Drill and tap a hole (at 90 degrees to the previous one - either in the end or from the diameter side - doesn't matter much) that intersects the first hole. This will be for a set screw to hold the tool bit in place.
Slip the 3/16 bit through the hole so it sticks out a bit more than the depth you want it to cut and tighten it in place with your set screw. Probably want to cut any excess off the back side (if you have any) so it's flush with your bar.

Step three - mount your piece in the lathe chuck and the bar into your tool holder in the lathe, pretty much just like you'd use a boring bar except you want the tool bit centered in the middle rather than the upper edge of the bit.

Step four - lock the chuck in place or put it into your lowest gear. Maybe even unplug the lathe in case you think you might turn it on accidentally.

Then just use your carriage to feed it through the bore. Feed it into the material in the bore a thou or so per pass. Left-right-feed out-left-right-feed out-left-right, etc.....until it's to the desired depth.
Prolly want a few spring passes (no feed) when you get close.

Congrats! You just made your lathe into a shaper. And got a bit of exercise at the same time.

p.s. Don't have the exact stuff I described in the steps? No big deal - just improvise. Obviously need to grind the tool bit to a workable geometry, and can grind a larger bit down to 3/16" if you need to, etc. etc. etc.

Carld
05-13-2010, 09:46 PM
They are expensive Harry but they work like magic, especially for a blind hole. I have used them and really like them. They are not fast but they do a good job.

Dr Stan
05-13-2010, 10:20 PM
would this not be hard on the carriage drive?

Not really. In fact this is how I learned to first cut a keyway at the Navy's Machinery Repairman's School.

bborr01
05-13-2010, 10:21 PM
I just went out to my shop and did some measuring on a DuMont 3/16 broach.

It is about 6.5 inches long. That means a push rod of some sort to go through 5 inches.

Chip load is also a problem. Each tooth is approx. .004" larger than the one below it. Unless you plan to use shims in increments of .002 or so, the last tooth/teeth will still see the same chip load.

I have broached literally hundreds of keyways, as well as cut some up to an inch wide on a vertical slotter.

The only time I have ever seen problems is with trying to broach a keyway that is too long, like this one.

Once you get the broach in until the chip has filled the tooth clearance in the broach, it is not likely to go back any easier than it is going to go forward.

The previous posts about cutting it on a lathe are right on.

That is what I would do.

Brian

I should probably add to this that a shaper or slotter would be preferable to a lathe even if just to save the elbow grease.

Brian

Dr Stan
05-13-2010, 10:25 PM
I should probably add to this that a shaper or slotter would be preferable to a lathe even if just to save the elbow grease.

Brian

I agree, but the machine shop on most destroyers at the time consisted of a lathe and a drill press. It's a bit different today, and that's a good thing.

klemchuk
05-13-2010, 11:14 PM
Thanks for all the great ideas. It looks like I'll be doing this job on a lathe. I am going to have to do 13 of these now and another 14 sometime soon. I don't think that volume would warrant me buying any more equipment.

tyrone shewlaces
05-14-2010, 12:19 AM
would this not be hard on the carriage drive?

Yes it is. Eventually it will wear it out. BUT it's no harder on the lathe than normal operation either, which is what eventually wears them out :D
So your arm will wear out waaay before the lathe will.

Not a dumb question. It's a different kind of operation than you normally do on a lathe so thinking about whether it's bad for the machine is appropriate. Consider this though - hand-feeding the carriage for a roughing cut at say .014" per revolution would offer some pretty good resistance you can feel in your arm. That's why we normally power feed (besides being able to stand back and duck flying chips). Just shaving a thou or two away while the lathe isn't spinning is no harder on the carriage or rack than it is with the spindle rotating. (I wouldn't try to take .010" or even .005" per pass. That's too hard on your arm)

So no. It won't hurt the lathe any at all.

p.s you can also do this with the quill in a milling machine. Who needs a shaper? :)

jack3140
05-14-2010, 07:58 PM
my thanks to dr stan and tyrone for taking the time to answer my question i will give it a try jack

darryl
05-14-2010, 08:48 PM
If that job was mine, and I didn't have a broach set or anything already made up, I'd do it this way- (bear in mind that I haven't done this, so I don't have the proof of it as personal experience) Your bore is 1.5 inches, so find a rod 1.5 inches diameter and maybe 8 inches long. Turn it or otherwise machine it so it will slide through the bore without binding. Cut into the side about an inch from one end, and cut halfway through, then cut into the end to release that chunk. Drill a cross hole in the remaining tab using a 3/16 bit, keeping the bit up against the side cut, and centered on the tab. Then rotate the piece and drill out that hole to a size that allows a 3/16 hss cutter bit to slide through without being sloppy. The size of that hole also has to be 'thread friendly' for a setscrew to go in. Tap it through from the outside of the rod to as far as it can go without binding up on the side cut.

Start a setscrew until it just passes being flush with the outside of the rod. Grind the end of the 3/16 hss cutting stick flat, then insert it across the side cut and up against the setscrew. You'll have to cut this off pretty much flush with the other side of the rod so it doesn't stick out- what does stick out is the depth of the first cut it will take. You'll have to grind some relief on that end anyway, but it should become obvious what the profile should be on this 'business' end. Just ground flat across with some back relief.

The part of the hss stick that's laying across the side cut in the rod will have to be kept in line, so whatever way you want to do that- I'd probably drill and tap a hole either side of it, near the edge of the rod, then use a short socket head screw in each hole. Make a short piece of material with two holes in it which can be screwed over the hss stick under the heads of these two bolts. Tighten enough to be snug, but not enough that the setscrew can't advance the hss stick.

If you've cleaned up the burrs, this tool should press through the bore pretty much without incident. There's lots of room for the swarf to go, and the only thing that might be a problem is the burr that's raised during the first pass or two. For those first passes, it might be good to use the tailstock to keep the tool from rotating as it is pressed through the bore. Once the track is started, the rest of the job could be done on a press, or you could continue to use the tailstock ram. I suspect you won't have the travel to do a full continuous pass without readjusting the position of the tailstock on the bed, so this could be considered just the start of the keyway groove so it goes straight and doesn't spiral.

Some lube to help the whole thing slide through relatively easily, and off you go to finish the job on the press. The tool falls through the bore and you start it off again from the top, readjusting the setscrew for depth of cut each time, and before you know it you're done.