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iMisspell
12-25-2013, 04:01 AM
Some where along the lines i want to make an arbor press/vice.

What would be the best material to make the main pinion out of ?
I plan on turning a piece of bar stock down and cutting the teeth so its a single piece/unit, not a gear fastened to a rod.

Use of the press; pressing bearing, broaching nothing too heavy duty.

Below are some images/drawings of what i plan on making... aside from it being an arbor press, i want to be able to use it as a vertical vice also for some wood working i do (segmented turnings) so thats what the hand wheel in the middle/top is for. When using as a press you would turn/pull down the arm on the right like a standard arbor press.

Anyway... what would be a good material to make the main "axle/pinion" out of ?

I planned on screwing and then tack welding a store bought "rack" to the quill, so that will be probably be "plain steel"... humm.... did i just answer my question ??? a piece of cold rolled 1018 would probably work, no ?

http://i1284.photobucket.com/albums/a570/iMisspell/Projects/Metal/Arbor_Press/Arbor_Press4_zpsd7f63b1c.jpg (http://s1284.photobucket.com/user/iMisspell/media/Projects/Metal/Arbor_Press/Arbor_Press4_zpsd7f63b1c.jpg.html)


http://i1284.photobucket.com/albums/a570/iMisspell/Projects/Metal/Arbor_Press/Arbor_Press3_zps8ff0a5dd.jpg (http://s1284.photobucket.com/user/iMisspell/media/Projects/Metal/Arbor_Press/Arbor_Press3_zps8ff0a5dd.jpg.html)


http://i1284.photobucket.com/albums/a570/iMisspell/Projects/Metal/Arbor_Press/Arbor_Press2_zps12eb191d.jpg (http://s1284.photobucket.com/user/iMisspell/media/Projects/Metal/Arbor_Press/Arbor_Press2_zps12eb191d.jpg.html)

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Jaakko Fagerlund
12-25-2013, 04:51 AM
Buy a steel rack big enough and thus there is no need for machining anything other than the end so that you can attach whatever you want to it. Racks come usually in squares and with diferet module teeth cut in them, so there is plenty to choose from. And usually they are steel.

becksmachine
12-25-2013, 06:26 AM
You would want to use the toughest material that you have the capability to machine.

The pinion needs to be made with as few teeth as possible (smallest pitch diameter) to maximize the mechanical advantage. Because of this small pitch diameter, this also causes the strength of the tooth on the pinion to be by far the weakest as compared to the tooth on the rack.

Using a mild steel rack of 1018, a pinion made of pre-hardened 4140 might give approximately equal tooth strength.

Dave

metalmagpie
12-25-2013, 04:20 PM
You need to sharpen your pencil and actually design the thing. Start with the maximum load you want the press to handle. For example, you might choose 2 tons, or 4000 pounds. Now look at the cross sectional of a gear tooth at its root and figure the maximum shear load you are putting on it. For example, if your gear tooth were 1/4x1" it would be 1/4 square inches. Thus the max shear on that tooth for a 2 ton loading would be 16000 pounds per square inch, or 16 ksi. This would be well within the parameters of most steels. If your gear tooth were significantly smaller and your max load were more, you might have a problem.

Then think about wear. How hard do you think the surface of the gear teeth should be?

The easiest thing to do is just to copy someone else's design, or to overdesign it. But you might want to take the time to really think it though, and thus learn something.

metalmagpie

darryl
12-25-2013, 05:43 PM
I tend to agree with becksmachine- go for a higher strength of material, yet one which is still machinable. I haven't researched the alloys, but he might be on to something suggesting 4140.

Just recently someone posted a chart, or a link to a chart, which showed the properties of materials, specifically steels and other metals useful in the shop. Memory isn't serving particularly well at the moment, but I do believe the chart showed some steels in common use (and available) which were stronger and more wear resistant than the typical cold rolled, etc.

ezduzit
12-25-2013, 08:00 PM
Why build one when used ones are so cheap and plentiful?

lakeside53
12-25-2013, 08:24 PM
huh? because we can! ;)

iMisspell
12-26-2013, 12:20 AM
Thanks for the insight, everyone.

As for wear, im not gonna be using the press all that much, a few times a year and i will be the only one using it.

Gears (and physics) are kind of new to me, so please be gentle.

Using this calculator i came up with the following (using .245 for the "Lewis Factor").
http://www.engineersedge.com/calculators/gear-tooth-strength-calculator.htm


Using an 8 pitch 20 pressure angle rack with a 1-1/2 wide face
A pinion made from HT-4140, 1-3/4 OD, 12 teeth with a tooth thickness of 0.196 (t = 1.5708 / Pd (http://www.cage-gear.com/spur_gear_calculations.htm))
Should with stand 2,143 LBS of 'Maximum transmitted load ' (??? what does that mean ???)

Does that mean the tooth can hold 2,000 pounds of weight before it fails ?
or
It can with stand 2,000 pounds of presser before it fails ?

speedymetals says that 4142 Pre-Hard Cold Roll Steel has the 'tensile strength' of 140,000 PSI (used 46,666 tensile strength for the 'Maximum bending tooth stress' field in the engineersedge calculator).
https://www.speedymetals.com/information/material44.html

Came across the following (seams to make sense), since i will be making the cutter, ill do more research and make the fillet radius as big as possible.

Its actually bending stress that is the failure driver in gear fillets. As Fred said, MUCH of the stresses depend not only on the fillet radius, but even how the fillet was formed (hobbed, ground, etc).

Being the amount of times im gonna be using the press as a press and not a vice will probable be about 5 times a year, it seams that heat-treated 4140 should work, but knowing a little about this would be nice.




Why build one when used ones are so cheap and plentiful?
I really dont need a high tonnagle press, i need a large work envelope for the woodworking aside and i do not have alot of space at home for mutipule tools/machines, so if i build this right, it should fit my needs nicely. As of now im getting by using a mortise machine to press and broach when needed... last night i needed to press a bearing and the thought of this press/vice popped back into my head.


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darryl
12-26-2013, 12:42 AM
Even though you may not be using it often, I would still use one of the higher strength steels. Just be sure that the machine you use to cut the teeth and the cutter itself is up to the task. Don't overdo the cutting speed.

doctor demo
12-26-2013, 01:27 AM
Ya know there isn't a law that says there is a one pinion limit, or a one rack limit either.

Steve

darryl
12-26-2013, 01:35 AM
I built a press using steel cable- 8 separate wires wrap around a solid rod which is turned. Got a little complex to string, and get the tension equalized, but it's been working fine.

iMisspell
12-26-2013, 01:53 AM
Ya know there isn't a law that says there is a one pinion limit, or a one rack limit either.
Hummm... this is true.
The numbers i ran where with a 1-1/2 wide rack, doubling it to 3" would also double the strength. I had plans on using a piece of three inch box tubing for the ram, upping that to 3-1/2 so two racks can fit side by side would not be a big deal.

Thanks for the idea.

darryl, any chance you have a pic or two of that press ?

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vpt
12-26-2013, 09:57 AM
An old camshaft?

Rosco-P
12-26-2013, 12:38 PM
Why build one when used ones are so cheap and plentiful?

Have to agree with ezduzit. Found a used 3 ton Greenerd for $75 including a heavy home made stand. Only downside was that it isn't the ratcheting version, but that can be fixed with time and a little money.

If I were building a press, I'd look at an existing arbor press to size the components like the arm, pinion and rack. Re-inventing the wheel is fine, just don't make another square one.

darryl
12-26-2013, 02:41 PM
I don't know if you'll get anything out of this, but here's a few pics. This was built to press dovetail drawers together, so without modifying or moving and repinning a pressbar or whatever, it has a range of 8 to 36 inches. Probably not suitable for pressing bearings, etc, but good for other applications.

http://img.photobucket.com/albums/v136/heinrich/drawerpress1.jpg

http://img.photobucket.com/albums/v136/heinrich/drawerpress4.jpg

http://img.photobucket.com/albums/v136/heinrich/drawerpress3.jpg

This works by having the cables pulling downwards on the 'actuating arms'. This means that to keep the cables tight, there has to be an upward force on the arms. This is provided by the single cable in the center of the assembly- the force on this cable being provided by gravity. There's a brick tied to the end of it-. Such a mechanism could be built using a double-acting cable arrangement, thus dispensing with the need for the brick. There does need to be something to keep the cable wraps tight.

This machine has a ratcheting mechanism which allows me to raise or lower the press bar to working height, then I have about an inch or so of movement as I pull down on the handle. I thought I might run into problems with the cable wrapping becoming loose, or changing tensions between the 8 cables, but so far it has performed well. I've been using it for a couple years now, and it has not needed any attention or adjusting- just blow the dust off and use it.