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mickri

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#1
Some of my upcoming projects will require me to turn a taper. So I have been looking into lathe taper attachments. Everyone that I found requires you to make a contraption that hangs off the back side of the lathe except for one which uses a wheel attached to the crossslide turned by a taunt wire. Don't know if it is kosher to include a link to another site so I copied the post that describes this taper attachment.

Here's a simple taper attachment that is easy to make. It uses a taut wire wrapped around a
specified wheel which is attached to the cross-slide lead screw. The wire is attached to the
lathe bed by means of two stand-offs. This, of course, works for inside, outside, long, or
short taper turning.

Plans for this taper attachment were published by the Home shop Machinist:

Title: An Accurate Taper Attachment for Under $5.00.
Author: J.O. Barbour, Jr.
Issue: March-April 1986 Page 20


How it works: A wheel is machined to an exact diameter needed for a certain taper. This
wheel is attached to the cross slide lead screw. Then a taut wire is wrapped once around
this wheel and fastened parallel to the lathe bed by stand-offs (see photo below).

When the carriage moves it will automatically turn the cross slide in proportion to the
machined wheel...thereby giving the correct taper. The wire doesn't have to be very strong
since most of the stresses are on the cross slide lead screw or carriage. The main thing is
that the wire wrapped around the wheel must not slip...which one wrap should accomplish when
wire is drawn taut.

I think this works great, especially for tapers that need to be made over and over again.
Set up time would only involve the time necessary to attach the wheel and pull the wire
taut.

All parts don't need to be made with any particular accuracy with the exception of the
wheel. This wheel needs to machined very accurately (minus one wire diameter less than
calculated diameter). This is very easily accomplished using the lathe and micrometer. Of
course, the stand-offs need to be strong - but that's not a problem!

Here's an example: Lets say a 1/8" taper per foot is desired and the wire being used is
0.020" music wire. Since the taper is being cut on both sides, the cross slide only needs go
1/16" per foot of carriage travel. If the lathe has a 10 TPI lead screw then the wheel needs
to turn 62.5 percent of a revolution in 12". This means that the circumference needs to be
0.625 X 12 = 7.500" then divide by pi to get a diameter of 2.387". So the final diameter of
the wheel will need to be 2.387 - 0.020 = 2.367".

As one can see, this is very handy as it doesn't depend on the length of material the taper
is to be cut on, as it would be on a tailstock offset, just the taper per foot.



One additional note:

For the wire "clamp" on the stand-offs (which is not part of the article) a small drill
chuck was used. This chuck sells for about $8.00 and can be obtained at most hardware
stores. The chuck comes threaded for a standard size and the bolt used is threaded for about
three inches. Flats were also machined on each side of the bolt so one can use a wrench to
hold the chuck from turning when tightening the wire. In addition, the bolt has a small hole
drilled thru its entire length for excess wire to pass. This setup works great to achieve
the proper tautness of the wire so it will not slip on the precision machined wheel.

Have any of you guys used this type of taper attachment? What do you think?
 

cathead

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#2
Personally, I would build up a conventional type taper attachment or use the tail stock offset method. If the wire taper method
was really great, you would see it on commercial machines.
 

dlane

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#3
My lathe has a taper attachment, but a lot of folks use the tailstock offset, or a boring head in the tailstock.
But let us know how that works out , with pics ,:grin:
 

mickri

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#4
I have tried to find pictures with no success so far. The pictures with the post that I copied were no longer visible. There was a thread about it on Practical Machinist. Their main concern was if it would be accurate enough to do morse tapers and the small size of the wheel to do tapers over 1/2" per foot. Again no photos. I'll try to contact the man who was using it to get some photos.
 

Jimsehr

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#5
Here is one I made cutting a taper on my Logan. It swings on a base plate . After I have set it to a taper I drill thru the top and bottom plate and use an 1/8 pin so that
I can return to that taper later if I want to cut it again. For my Logan spindle taper I stamped a letter l Next to that hole. Next to a Morse taper I stamp a M1,M2 or whatever taper it is so that I can return to that taper by pinning with a 1/8 inch pin.
I built it to fit on my production cross slide but you could make it fit any cross slide.

https://photos.app.goo.gl/ObZJGeo67hyuSsbP2
 

mickri

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#6
I like your taper attachment but it would be too short for my projects. The taper on one project needs to be around 6" long and the other projects will require a taper length of around 21".
I have sent an email off the man who posted the wheel taper attachment I referenced above.
 

markba633csi

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#7
I think it's a great idea for those of us who turn tapers very occasionally on machines that never had a taper attachment offered
Mark
 

mickri

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#8
I agree Mark. The tapers that I want to turn just have to look nice. I am not trying to make a morse taper that has to be spot on with little room for error. Still waiting for a response to my email.
My first project is to do what is known as growlerizing the axle shafts on my 1966 Midget. Midget axles have a stress point where the outboard edge of the spider gear in the differential bears on the axle shaft. This stress point causes the axles shafts to snap at this point. Growlerizing the axle relieves the stress point. What you do is measure in 1 inch from the end of the axle and then turn the axle down to the depth of the splines for about 4 inches. You then taper the next 6 inches back to the original diameter. This is what I want a taper attachment for.

spridget axle.jpg

The top axle is a stock axle. The bottom axle is a growlerized axle.
 

markba633csi

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#9
Growlerizing! I love it! I just learned my new thing for the day
Mark
 

mickri

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The name growlerizing came from a midget racer down in OZ whose handle was Growler. This was a known fix in the race circles for quite some time but not known to the masses. Growler spread it far and wide on internet forums devoted to midgets and sprites.
 

mickri

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#11
Was looking at my Craftsman 12x36 lathe this morning and found that I have access on the backside to the end of the cross slide screw. I am going to try to make a mandrel that screws onto the cross slide screw that I can then attach different size wheels to. In stead of using wire I am going to use small diameter line used on boats. These lines are stronger than steel with less stretch and are designed to go around sheaves in blocks. I am going to make the wheels wider and try to create a threaded surface so the lines don't tend to cross over each other. The line will wrap around the wheel two times. With all the other projects and stuff I have going on it is going to be several weeks or longer before I can get this done. I'll take pictures and do a complete report when I get it finished.
 

markba633csi

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#12
I follow you, you are referring to multi-strand stainless steel cable sometimes called "aircraft cable"? That's what I would use too, around 1/16"
 

mickri

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#13
I thought about the small 1x7 or 1x19 SS cables but think that the synthetic lines like dynema and other brands would work better. They are more flexible, have less stretch and are designed to run in small blocks. The small SS cables are flexible and can turn corners but aren't really designed to make complete circles. Especially small circles. Sorry for the boating terms. I have been actively sailing for almost 50 years up and down the coasts of California and Mexico.
1x19 and 1x7 refers to the number of strands in the cable. 1x7 is more flexible than 1x19 but has more stretch. Neither like going around a complete circle, especially small circles which will deform the wire.
 

mickri

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#14
With my spacer project completed I will now concentrate on this. The acme screw on my cross slide appears to be 1/2" x 10 tpi left hand thread. I don't have a acme thread gage and the space on the cross slide is too narrow get an actual measurement on the diameter of the screw. My lathe is a craftsman 12x36 . Can anybody confirm to me that this is a 1/2" x 10 tpi LH?

Here is my plan. I will put a coupler nut on the end of the cross slide screw and screw around a 6" piece of acme threaded rod into the coupler nut. I might have to turn down the coupler nut to fit in the cross slide. The end of the cross slide is open and there are two existing threaded holes on the end of the cross slide. Holes look to be 1/4 x 20 tpi. I will make a plate to cover the end with a hole for the threaded rod to extend through, secured by bolts into the existing holes. I will take another coupler nut and turn it to be a flange nut. This flange nut will act as a bearing to keep everything in alignment and provide a flat surface for the wheel to sit against. I will use a nut to lock the wheel against the flange nut.

In looking at the backside of the lathe there is an existing bolt roughly level with the lathe bed that can be used to anchor one end of the line. The far end of the lathe bed does not have any existing bolts that I can use. I will have to make a stand off to anchor this end of the line. I will do a rough sketch of what I am thinking and take some pictures of the cross slide and the back side of the lathe.

If the cross side screw is 1/2 x 10 tpi McMaster Carr has the nuts and threaded acme rod that I need to make this.

Any and all comments and suggestions are welcome.
 

mickri

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#15
cross slide.jpg
This is a rough sketch of the end of my cross slide. It is not to any particular scale.

cross slide with taper.jpg

Here I have added the taper attachment. The only thing you can't see in this sketch is the flange nut/bearing. It is hidden behind the wheel. Again not to any particular scale. Just representative of what I am thinking would work.
 

magicniner

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#16
"Spider Gear", is that like a splined end on a shaft, but somehow different?
 

jwmelvin

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#17
Why do you want the extension, to which the wheel is secured, to be threaded? Why not just a shaft connected to the leadscrew with a coupler?
 

mickri

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#18
You have to use different diameter wheels for different tapers. Although by adding purchase on the line going around the wheel you would change the taper. For example if you had a wheel that gave a taper of 1/8" per foot with no purchase by adding a 2 to 1 purchase the the taper would increase to 1/4" per foot. 3 to 1 would be 3/8" per foot and 4 to 1 would be 1/2" per foot. Without the mechanical advantage of the purchase the wheel keeps getting smaller and smaller as the taper per foot increases. At some point in time you have to add purchase to the system. Also having the wheels as large as possible decreases any error in the amount of taper due to an error in the diameter of the wheel. When I get to making the wheels I will do the math to determine what wheel size and purchase to use for a given taper. I'll leave that for another day.

The shaft has to be threaded at the wheel end in order to secure the wheel to the shaft and to be able to use different size wheels. You could just thread the end of the shaft where the wheel goes and attach the shaft to the the lead screw with a non-threaded coupler with set screws. The set screws would damage the threads on the end of the lead screw over time and I don't want that to happen.

Your suggestion would be simpler to make. Thinking about it I would still use a threaded coupler to thread onto the lead screw and slip the shaft into the other half of the coupler. The shaft could be secured to the coupler with a set screw. This would eliminate the threaded flange nut which also acts as a bearing. The smooth shaft wouldn't need a bearing and I could thread the end of the shaft to any convenient thread size.

I like your suggestion. Thanks
 

jwmelvin

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#19
Why not attach your various wheels with a key and set screw instead of a threaded nut? Or a dimple and a setscrew (e.g. shallow hole and dog point setscrew)?
 
B

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#20
"Spider Gear", is that like a splined end on a shaft, but somehow different?
The (bevel) gears on the end of the halfshafts, that deliver power from the differential's (bevel) planet gears to them - with the reduction in the diff' and the radius of the wheel/tyre, there's a lot of torque between them and the halfshafts under Firm Acceleration.
I think the sudden change in section where the flange and halfshaft meet is where they snap? so reducing the section of the halfshaft (the taper) lets it act as a torsion spring and relieves some of the stress at the stress-raiser?

Not on Spridgets, but I've seen halfshafts with 3/4 of a turn of twist on them before they've broken - one was from a schoolfriend's Morris Minor with a supercharged 1275 Spridget engine...

Dave H. (the other one)
 

magicniner

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#21
The (bevel) gears on the end of the halfshafts
Half-shafts don't have gears on the ends, they have splines, these fit into sockets in the differential, half-shaft splined ends are not driven directly by any gear.
 
B

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#22
I sit corrected... So power is transferred to the halfshafts from the diff, via a gear carrier with the bevel gear at its inboard end, and the stress raisers are the cuts for the splines, I take it? So the spline effectively goes into a gear...? Wouldn't be a diff' otherwise?

Dave H. (the other one)
 

mickri

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#23
Lots of confusion on the parts in a midget rear axle. Here is a parts diagram.

differential parts diagram.jpg

The axle haft shafts, #29 or #30, have male splines on the inboard end. These splines fit into the gear, #20, which has female splines. Because of flex in the axle housing the upper edge of the outer edge of the gear, #20, bears on the splines of the haft shafts. This creates a stress point on the haft shafts and the half shafts typically break at this point. The haft shafts rarely fail at the flange on the outer end of the haft shaft. When you growlerize the haft shaft as described in a previous post the outboard end of the gear no longer bears on the haft shaft eliminating the stress point.
 

magicniner

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#24
This photo makes it easy to see both the relationship between shaft and gears and also the differential function MidgetDiff.jpg
The author's arrow is pointing at the gear with which the shaft engages.
 

mickri

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#25
I am going to order a coupler nut from McMaster Carr later today. I looked at the lead screw again and as best as I can tell without an acme thread gage is that the lead screw is 1/2 x 10 tpi LH. If I am wrong on this would someone please let me know. My lathe is a craftsman 12x36. I have some 1/2" StarBoard on hand which I will use for the end plate StarBoard is polyurethane plastic that I have used on my boats. If this taper attachment works to my satisfaction I will replace the StarBoard with steel. I am going to use a 3/4" shaft and will turn down one end to 1/2" to fit into the coupler nut. I will drill and tap the coupler nut and the shaft for a screw. Either 1/4x20 or 10x24. The other end I will turn down to 3/8 and thread for a 3/8x16 nylock nut. This will leave a shoulder on the shaft for the wheel to fit against when tightened with a nut. I have a piece of 3" diameter aluminum on hand and will make a wheel out of this.

So that's my plan of action at this point. I could use some help on the math to calculate the diameter of the wheel.
 

Tozguy

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#26
Back in the 60s I used to carry a spare half axle in the boot of my Bugeye Sprite because they were not very strong and sometimes had to change it at the side of the road to get home again. Then I shoehorned a 1500 engine into the Sprite. The rear axle splines were cut off and a stronger spline from a scrapped transmission was welded on. I had it done and don't know which transmission the stronger splines came from but they never broke after that.
Growlerizing makes sense to avoid concentrating stress at the end of the spline but does it make the axle stronger?
 

mickri

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#27
When MG went to the 1275 cc engine in 1967 they also changed the steel in the half shafts from EN7 to EN17. I have put a 1969 rear axle in my midget so I have the stronger half shaft. From what I have read on the various midget forums is that it was not that the axles weren't strong enough but were too stiff. Growlerizing allows the haft shaft to flex a little and eliminates the hard stress point. A late model haft shaft is supposedly good for 100 hp or a little more. Growlerizing increases this to around 150 hp. I am going to swap a toyota engine with 75 to 90 hp which I might modify up to around 100 hp.
 

Tozguy

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#28
Sounds like you are having fun. Makes me wonder why the factory did not pick up on concept and 'Growlerize' OEM axles at some point.
 

mickri

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#29
I don't know if growlerizing was known during the production run of these cars. Also these cars were low end price point cars and growlerizing would have required extensive machining adding to the cost of these cars. The original bugeye sprites had round rear wheel arches which allowed owners to fit much larger wheels and tires. This contributed to haft shaft breakage. Rumor is one of the reasons MG changed to the square rear wheel arch was to prevent owners from doing this. It was cheaper to change the stamped steel rear fenders than to make stronger half shafts.
 

Tozguy

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#30
The principal behind Growlerizing is not new. It has been used extensively for bolts and screws in high stress situations like connecting rod bearing caps and cylinder head screws for a long time now.
In post no.27 there is mention of upgrades by the factory and by then the R&D types must have known about that option.
 
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