diy bearing idea

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Oilite bushings

Just my $.02 as an ex research machinist from the high tech sector.

Oilite busings, valve guides included... there is nothing even close to precise about them. It is presumed that you finish machine these after being pressed into place.

Reaming isn't exactly precise either...even stagger tooth helix reamers leave some small chatter marks, honing followed by roller burnishing and sometimes lapping is the usual when precise bores are required.

As a diy'er roller burnishing isn't likely an option, however careful single point boring followed by an adjustable barrel lap and Timesaver tm lapping compound (McMaster Carr Supply) could be made to work.

Personally if I had a mini lathe or mill I would set up a makeshift jig grinding fixture and grind the otherwise finished bearing with a metal plated diamond wheel of fine mesh.

For a real eye-opener find a sympathetic "old school" tool maker who will lend you a copy of Wayne Moore's (Moore Special Machinery) book on precision hole generation and location.

Cyclotronguy
 
Re: Oilite bushings

cyclotronguy said:

For a real eye-opener find a sympathetic "old school" tool maker who will lend you a copy of Wayne Moore's (Moore Special Machinery) book on precision hole generation and location.

Cyclotronguy


Or just find an "old school" tool maker, and bribe your way through :D

Any self respecting tool maker can make whatever bearing you want.

Magura :)
 
Lapping

Typically when we Lap a bore, we cast a solid lap of non shrinking low fusing alloy about 7X bore dia using the bore as the mold.

The cast plug is withdrawn 60% from the bore and charged with bort (diamond dust and oil).

By feel the lap is then moved axially along the bore (not rotated) searching for tight spots. Once a tight spot is located the lap is short stroked in the bore until the spot is not so tight.

Lap is then removed, bore cleaned and air gaged.

An air gage is a probe attached to a manometer, fed by a constant pressure source of air.

Once removed a lap is never placed back in the bore, a new one must be cast and recharged.

Cyclotronguy
 
Re: Tool makers

cyclotronguy said:
Old school tool-makers are difficult to bribe, they're mostly anti-social and usually have projects of their own.

At most they would likely only point you to this book with an evil grin!

http://www.mooretool.com/publication.html:D


You're probably not too far off the mark :D


Anyhow, if wanting a nice bearing, Hasco would be the first place I'd look for the parts.


Magura :)
 
My 85 yr old neighbour was a medical toolmaker in the 40's in England and has the skills to make anything.

However, If you ask him to do a job for you he will instantly re engineer the concept and make it totally different to what you wanted. It'll also take him weeks and weeks and then without notice he'll ask to be paid.

So you then have to wait weeks to get a different part than what you wanted and you have to pay for it.


funny thing is he comes over and asks all about my project and wants to help out and give ideas.

fun
 
Sorry, i should have clarified what I was talking about a little more.

What i was talking about in this case is drilling a hole in the plinth, not through the valve guide. This is to mount the valve guide into the plinth that allows a smaller diameter hole at the bottom of the drilled cylinder that will center the ball used to support the valve. Does this make more sense? Sometimes i open my mouth and nothing but alnwer;tamn comes out!!

Joe
 
Re: Lapping

cyclotronguy said:
Typically when we Lap a bore, we cast a solid lap of non shrinking low fusing alloy about 7X bore dia using the bore as the mold.

The cast plug is withdrawn 60% from the bore and charged with bort (diamond dust and oil).

By feel the lap is then moved axially along the bore (not rotated) searching for tight spots. Once a tight spot is located the lap is short stroked in the bore until the spot is not so tight.

Lap is then removed, bore cleaned and air gaged.

An air gage is a probe attached to a manometer, fed by a constant pressure source of air.

Once removed a lap is never placed back in the bore, a new one must be cast and recharged.

Cyclotronguy

:up: That's exactly what I meant by "lapping" when I posted earlier. With the exception of the more high-tech bits it is a technique that's open to the amateur without very high-precision tooling.

For an in-the-shed version I'd make a traditional copper lap and charge it dry with fine diamond dust by rolling between two steel plates and I'd have to substitute old-fashioned go/no-go bore plugs and engineer's blue for the modern test equipment. And I'd probably have to make the bearing 25-30mm longer than the finished size because the outer ends would finish up a tad oversize. Any of that, given a lot of time and a bit of care, could be done on a hobby-type lathe.


Aurora: For "honing", rightly or wrongly, I think of the kind of machine used to finish engine cylinder bores. In many cases it actually leaves a deliberate fine pattern on the bore of, say, a 45 degree cross-hatch to help oil retention.
 
Legacy technology

Perfectly fine results can be had just as you indicate, and well within the capability of one of the little innexpensive bench lathes in the hands of a careful workman.... though I'd rather have a nice Dean Smith and Grace.

Should you wish to air gage the bearing bore, they're cheap and easy to build too. Calibration for a couple bearings would be non critical

Certainly cheaper to build a water manometer for air gaging than buy a 0.001" x 0.0001" spread of Deltronics gage pins.

Cyclotronguy
 
Re: Legacy technology

cyclotronguy said:
Should you wish to air gage the bearing bore, they're cheap and easy to build too. Calibration for a couple bearings would be non critical

Certainly cheaper to build a water manometer for air gaging than buy a 0.001" x 0.0001" spread of Deltronics gage pins.

Cyclotronguy

Is there a link somewhere?

-and BTW - isn't a bore micrometer good'nuff ???
 
bore micrometer

The link is to a text book on making and locating holes by Wayne Moore at Moore Special Tool.... the bible on such things.

Bore micrometer in my world has some serious short falls. Rule of the first: Resolution is not the same as accuracy!

First fault: A bore micrometer will not gage "Round", not in an absolute sense any more than a conventional micrometer will judge round. Both presume round.

Second fault; A bore micrometer tells you nothing about how curvelinear (straight) a bore is.

Third fault; A Bore micrometer is very poor at identifying the nature of "local deviations" The physical size of the contacts bridge local deviations, typically making bores measure smaller than true average.

Cyclotronguy
 
Resolution

Resolution in a machine tool or measuring device IS NOT the same thing as accuracy, they are only slightly related to one another!!!!

That being said a CNC lathe may make a great bearing..... or not. Typically not the machine but the material, tooling, process and guy punching up the G-codes that makes all the difference.

Machining isn't always what it looks to be, when you start considering extreme accuracy.

Little things start showing up, tool deflection and wear. Thermal expansion of parts. Hard and soft spots in material. etc and etc.

I've seen many a day where the really astute guy turns out more and better parts on the 1942 Monarch Lathe than they guy with the brand new HAAS machining center.

Cyclotronguy
 
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