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Thread: Is bronze bushing necessary?

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    MBG
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    Default Is bronze bushing necessary?

    I am wanting to have a 1/2" or 3/4" steel shaft that will only rotate 90 degrees no further. Initially I was planning on a oil impregnated bronze bushing but now that I need to make several of these I am starting to question if the bushing is necessary?

    This is a shaft to be set screwed on one side (no movement) and on the other side a block reamed out for a press fit bronze bushing.




    For low speed (hand movement) is steel on steel contact okay?
    This will be rotated maybe 10 times a day for 10 years.

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    johnoder's Avatar
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    is steel on steel contact okay?
    If your goal is to have the most wear in the least time, yes.

    The are much better combinations - like your first idea.

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    CalG is offline Titanium
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    With adequate grease lubrication, ten cycles per day will likely be fine.
    Many machine tool operation controls are just that. Steel on steel.
    (there are many grades of steel!)

    is the load severe? Operation conditions "dirty"?, Original fit "good"?

    And most importantly, what are the consequences of wear?

    I would not be afraid unless there is some product functionality concern

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    I will add that it is much easier to replace just the bronze bushing than the entire steel part or both parts WHEN they wear out. A good rule of thumb is to design the part that is the easiest to make and/or install to be the first to wear out. This may or not be a big deal in your application.

    Thank you for correctly calling it bronze instead of brass. A pet peeve of mine is when machinist's who should know better call all yellow metals brass. There is a big difference in their properties & applications.
    oldbrock and lazlo like this.

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    Clive603 is online now Titanium
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    Glacier DU or similar dry bearing faced steel sleeve insert is a good fit for this sort of thing. Treat the shaft with some sort of "permanent" but slippy anti corrosive treatment and keep the weather out. Far as I can see it will last "forever". Did something similar a decade or more back with a simple dunk in hot oil job for shaft protection for Mr Pernickity Moaner and not heard a peep so its prolly still OK.

    Clive

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    thermite is offline Diamond
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    Quote Originally Posted by MBG View Post
    I am wanting to have a 1/2" or 3/4" steel shaft that will only rotate 90 degrees no further. Initially I was planning on a oil impregnated bronze bushing but now that I need to make several of these I am starting to question if the bushing is necessary?

    This is a shaft to be set screwed on one side (no movement) and on the other side a block reamed out for a press fit bronze bushing.




    For low speed (hand movement) is steel on steel contact okay?
    This will be rotated maybe 10 times a day for 10 years.
    Wear ain't likely to be the issue. Dirt and corrosion over a ten-year span is.
    I'd at least use a nylon or similar 'poly-whatever' sleeve if not bronze.

    Cheap, easily replaced, and 'sacrificial' .... as has been pointed out.

    Bill

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    surplusjohn is offline Diamond
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    I would go with a bushing of some sort, cost would be 1 or 2 dollars then you can forget about it. I have seen lots of assemblies like that with far more ware than you might guess at.

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    chuckster is offline Aluminum
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    Steel on steel yea that's the way it would be done in China. I would use a bushing

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    Hurrah for this!

    Thank you for correctly calling it bronze instead of brass. A pet peeve of mine is when machinist's who should know better call all yellow metals brass. There is a big difference in their properties & applications.
    Limy Sami and oldbrock like this.

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    thermite is offline Diamond
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    Quote Originally Posted by chuckster View Post
    Steel on steel yea that's the way it would be done in China. I would use a bushing
    Nah .. Not steel-on-steel in China.... Bamboo bushing soaked in soy oil reclaimed from stir-fry use... or 'almost-ball' bearings if shorter life was not a factor.

    Bill
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    willbird is offline Banned
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    Quote Originally Posted by chuckster View Post
    Steel on steel yea that's the way it would be done in China. I would use a bushing
    The old guy I worked for used to say that the key thing was for the two materials to be of different hardness's. A heat treated steel shaft and a soft steel gear for example would be fine with some lubricant. This is exactly what you end up with when you use shoulder bolts for example, and they are often used in steel parts with no brass bushings. Also consider that ball bearings use steel on steel (with a lubricant film between the two moving parts).

    Bill

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    Just to get back to the rolling element bearing, hardened material on hardened material, with excellent surface finish would be in my book the longest lasting. Just from a seat-of-the pants viewpoint, neither material has an "advantage" to wear out the other and both will be resistant to "embedding" by abrasive particles that would speed up wear.

    However, a bronze plain bearing would be generally simpler and lower cost to implement for many designs that aren't highly challenged on packaging or performance.

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    MBG
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    Quote Originally Posted by johnoder View Post
    Hurrah for this!
    Thanks, I always know that it is Powder Metal and that is how the oil impreg is done.

    While machining does pay my bills it is something I learned in an engineering class I took.

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    MBG
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    Quote Originally Posted by thermite View Post
    Wear ain't likely to be the issue. Dirt and corrosion over a ten-year span is.
    I'd at least use a nylon or similar 'poly-whatever' sleeve if not bronze.

    Cheap, easily replaced, and 'sacrificial' .... as has been pointed out.

    Bill
    I definitely agree on this. Dirt will be an issue as this will be used outside.

    Wear shouldn't be an issue because it is the "tightness" feel of quality. If or when it should wear it would just have a "loose" effect.

    Do the nylon sleeves work like the bronze bushings as in you press them in?

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    Limy Sami is online now Diamond
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    Quote Originally Posted by MBG View Post
    I definitely agree on this. Dirt will be an issue as this will be used outside.

    Wear shouldn't be an issue because it is the "tightness" feel of quality. IF or when it should wear it would just have a "loose" effect.

    Do the nylon sleeves work like the bronze bushings as in you press them in?
    IF as in IF it has a very high mechanical load, plastic will not be suitable - it squeezes out

    Dirt? go for nylon or a similar self lubing plastic and don't grease it - it attracts dirt.

    Yes ppress the plastic bushes in, up to 1" dia I go for 5 - 8 thou OS, but don't forget the bore will close up by as near as dammit the same amount.

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    Muffler Bearing is offline Aluminum
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    Millions of cars have assemblies which only rotate 90 deg a few times a day - their doors. They use bronze or plastic bushings and steel pins.

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    willbird is offline Banned
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    Quote Originally Posted by Muffler Bearing View Post
    Millions of cars have assemblies which only rotate 90 deg a few times a day - their doors. They use bronze or plastic bushings and steel pins.
    And millions of earth moving machines have steel pins that rotate inside a steel bushing that looks a lot like a roll pin. The tracks even have steel pins that run in other steel parts, in dirt and mud.


    Bill

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    Mike C. is offline Diamond
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    "And millions of earth moving machines have steel pins that rotate inside a steel bushing that looks a lot like a roll pin. The tracks even have steel pins that run in other steel parts, in dirt and mud."

    BUT, those pins are hardened and the steels they are running in are usually high manganese wear materials that work harden as the pin rubs against them, creating a virtually unmachineable contact surface. Those parts do indeed wear, but it is allowed as part of the design.

    For the OP's application, I'd say steel in cast iron is fine (SB9 spindle and headstock), but soft steel on soft steel is asking for wear and galling, even with very limited slow speed movement, especially is load is involved. Main thing is that the next guy that has to work on this will be delighted to find he only has to replace the bronze bushings 30 yrs from now.

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    Muffler Bearing is offline Aluminum
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    Quote Originally Posted by willbird View Post
    And millions of earth moving machines have steel pins that rotate inside a steel bushing that looks a lot like a roll pin. The tracks even have steel pins that run in other steel parts, in dirt and mud.


    Bill
    I'll be honest, that's something I haven't looked at at all. If it really is steel and steel, my guess is the area of contact (bushing length) is so large that the actual load pressure(and therefore, friction on bearing) is pretty low, and one steel is slightly harder than the other (Case hardened, 41xx steel, etc.) Or maybe something is made of a self lubricating material?

    ((Edited my post - Mike C. explained it before I finished typing - Thanks Mike!))

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    Clive603 is online now Titanium
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    Obviously peoples views are conditioned by their experience but pretty much every "un-engineered" plastic bush application carrying proper bearing loads I've seen has suffered excessive wear after inadequate life. Similarly oilite and plain bronze bushes also don't seem to do that well in part rotation systems. Proper spinning bearings are naturally a very different matter but even then I'd be careful of plastic bushes without full manufacturers data and proper load calculations. Its easy to be a bit too casual "shove in a bush, it'll be fine". Even fairly expensive kit from Mighty Great Big Manufacturing Inc can suffer.

    In contrast my, now perilously low, stock of Glacier DU dry bearing rod, coated wrapped steel bushes, and thrust washers seem to be up for everything I throw them into and last well. Least-ways I've not had 'owt back. Yet!

    Given that there are untold millions of perfectly satisfactory plastic bearings out there its clearly possible to get it right but I sure as heck don't know the secret. (Ever noticed that when you do a 15 Sunday fix on a 10,000 bit of kit which only lasts twice as long as OEM "150 to you sir, 3 week back order" the customer is seriously peeved at you when he comes back, not at Mr Machine Maker for messing up in the first place.)

    Clive

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