Aluminium bronze shrink fit bush, post installation sizing

[GeorgeMe]

Hi all,
I have been exploring methods of sizing shrink fitted bushes post installation i.e. during the freeze fit installation the bush compresses by c.20 microns and this then has to be opened back up to size.

the current methods used are jig boring, honing and hand reaming.
- jig boring takes an age to set up and then has to be cmm'd to ensure the bore position hasn't moved/been set up incorrectly.
- honing is carried out manually and also is very inefficient and relies on the skill of the operator not not oversize the bushes.
- hand reaming, this is the best practice we have although it can only be used on the product groups with a small I/D requirement.

all the products have 2/3 co-axial bores with bushes spaced approx. 80mm apart with the I/D range between 20 - 50mm.

so I ask does any one have any experience with sizing shrink fitted bushes with a high variety product types and what are the methods of sizing used elsewhere.

note; we have been trying a powered reamer solution in a zero g floating head but this float has been working against us during withdrawal of the cutter the transition of the ream can chatter against the primary bush.

 

[berkshire]

Have you checked for " Reamerless" bushings ? Some manufacturers offer bushings that are slightly oversized to compensate for the shrinkage during pressing or freeze fit installation.
B.E.

You are judged not by what you know, but by what you can do.

 

[rb1957]

Can you increase the ID of the bushing so that the installed ID is what you want ? This is calculate-able (from Timoshenko) and you have lots of experience. Can you control the process (manufacture and installation) sufficiently to achieve the desired tolerance (without reaming) ? How critical is the installation ? "critical" to safe and continued flight ? "critical" for very controlled interface ??

another day in paradise, or is paradise one day closer ?

 

[WKTaylor]

GeorgeMe...

1. You have NOT been very specific regarding...

(1) alloy/temper/hole-size(s) for the structure where the bushings will be installed;

(2) bushing Al-bronze-material [alloy/spec/OD-finish];

(3) desired interference within the structure holes;

(4) Your expected tolerances for 'reamed/bored structure-HOLE(s)', and the 'Bushing machined-OD' and the 'bushing reamed/bored-ID tolerances and machined-finish requirements'... Example: X.XXXX-Y.YYYY or X.XXXX+/-0.000Z, 16/32/64/125/etc-microinch machined-finish;

(5) Also... are You intending to install the Bushing 'dry' or with 'wet-primer or sealant'?

NOTE. Are we to assume that the bushing-bore(s) does(do) NOT require plating [are left 'bare']?

NOTE. Will Your Bushes have any special OD edge treatment [low-angle chamfer, etc] for ease of installation?

2. Have You considered bushings 'similar-to' NAS537 or NAS538 [flanged] 'BUSHING, [SLEEVE] or [FLANGED], PRESS FIT, UNDERSIZE INSIDE DIAMETER'.

Ream-bore the structure hole to accept the press-fit US-ID Bushing [with Your desired level of interference].

Line-ream/bore the installed US-ID Bushing hole(s) to final size.

NOTE. Relatively simple tooling is available for line-reaming/boring thru multiple bushings [small/large], with high precision.

CAUTION. Sharp cutters and appropriate interference levels are require to prevent bushing from 'spinning' when machined thru the ID.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[Tmoose]

1 - I think of most aluminum bronze alloys needing excellent lubrication to wear well.

2 - As others have said, the lack of tolerance etc. info really hamstrings attempts at useful responses. "Be extremely subtle even to the point of formlessness. Be extremely mysterious even to the point of soundlessness. "

2 - "all the products have 2/3 co-axial bores with bushes spaced approx. 80mm apart with the I/D range between 20 - 50mm. " Are the holes in the "products" machined precisely as you like? Then I'd experiment with very nicely made finished bushings with barely slip fit ODs installed with one of the many 600 series Loctite retaining compounds.

 

[WKTaylor]

FYI ONLY...off subject...

Tmoose... thanks for the great quote... which really works here [I collect quotes]!

For the record here is the entire quote by Sun Tzu [went on-line to flesh-it-out]...

"Be extremely subtle even to the point of formlessness. Be extremely mysterious even to the point of soundlessness. Thereby you can be the director of the opponent's fate.” ― Sun Tzu, The Art of War

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[GeorgeMe]

Hi all, thanks for the responses, and apologies for the delay thought id provide a follow up...
for this we'll take an example;
(1) alloy/temper/hole-size(s) for the structure where the bushings will be installed;
Aluminium detail supplied I/D 25,521/25,500 (H7) to accept a aluminum bronze bush supplied O/D 25,548/25,535 (S6)/ I/D 22,246/22,225 (H7).
(2) bushing Al-bronze-material [alloy/spec/OD-finish];
IP
(3) desired interference within the structure holes;
H7/S6
(4) Your expected tolerances for 'reamed/bored structure-HOLE(s)', and the 'Bushing machined-OD' and the 'bushing reamed/bored-ID tolerances and machined-finish requirements'... Example: X.XXXX-Y.YYYY or X.XXXX+/-0.000Z, 16/32/64/125/etc-microinch machined-finish;
Aluminium detail supplied I/D 25,521/25,500
Bronze bush supplied O/D 25,548/25,535
Bronze bush supplied I/D 22,246/22,225

Final bore size required post installation 22,246/22,225 (H7) 0.8Ra Micro-meters
(5) Also... are You intending to install the Bushing 'dry' or with 'wet-primer or sealant'?
bushes are installed using sealant, this is applied to the detail bore prior to installation.

NOTE. Are we to assume that the bushing-bore(s) does(do) NOT require plating [are left 'bare']?
correct, no further treatments required to bore post installation & sizing
NOTE. Will Your Bushes have any special OD edge treatment [low-angle chamfer, etc] for ease of installation?
yes, bushes have a 30 degree chamfer to aid installation.
2. Have You considered bushings 'similar-to' NAS537 or NAS538 [flanged] 'BUSHING, [SLEEVE] or [FLANGED], PRESS FIT, UNDERSIZE INSIDE DIAMETER'.
all bushes are 'drawn parts'
Ream-bore the structure hole to accept the press-fit US-ID Bushing [with Your desired level of interference].
Line-ream/bore the installed US-ID Bushing hole(s) to final size.
due to part variety maintaining perpendicularity to a spindle would require bespoke jigging for all parts.

NOTE. Relatively simple tooling is available for line-reaming/boring thru multiple bushings [small/large], with high precision.
Do you have any links or images would be useful to see if there any different to our current set-ups.
CAUTION. Sharp cutters and appropriate interference levels are require to prevent bushing from 'spinning' when machined thru the ID.
Found this out the hard way!

Many thanks

 

[Tmoose]

".... to see if there any different to our current set-ups."

What are the honing tools you are using?

So you are already hand honing or hand reaming to finish the bushings? To me that means the perpendicularity of the finished hole is at best the concentricity accuracy of the bushing ID/OD , and possibly a fair bit worse.


I figure your interference 14 - 48 um / .0006 - .0019".
With the 1.6mm/.065" bushing wall thickness I'd expect bushing ID to close up nearly the full amount of interference.
I'd have a look at something like this.

https://www.precisionballs.com/Ball_Sizing.php

http://www.itiball.com/products/tungsten-carbide/ballizing-ball-burnishing/

It might be as simple as ordering a bag of these.

https://www.mcmaster.com/9528k32

 

[WKTaylor]

GeorgeMe... I can deal with SI units, but...

I am still confused/head-scratching regarding the aluminum alloy/temper/finish that bushings will-be pressed-into.

Likewise for the bushing bronze alloy... alloy/temper/finishes.

Your material [part?] 'codes' are inscrutable to me, a US aero-engineer.

WHAT ARE YOUR WORKING SPECIFICATIONS?

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[OldME]

I pre-size bushings prior to installation to eliminate the problems regarding surface finish and degree of difficulty handling fully processed aircraft parts i.e. putting the finished part back on a machine and boring the bushings after installation. This involves measuring the bore, measure the OD of the bushing, calculate the interference, estimate the amount of collapse (usually 70 - 90%) of the interference. Oversize the bore holding the bushing in soft jaws on a toolroom lathe, basically simulating the installation parameters.