Press fit bush

This topic has 22 replies, 12 voices, and was last updated 14 September 2016 at 19:02 by SillyOldDuffer.

Viewing 23 posts - 1 through 23 (of 23 total)

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13 September 2016 at 18:05 #255687
Daniel
Participant
@daniel
Hello All,

I need to make a bronze bush to fit into a cast iron tractor clutch pedal.

The clevis pin hole is well oval.

I have plunge milled the pedal out to 14mm and the clevis pin is 10mm.

With a 2mm wall on a bronze bush having an interference fit (pressed),

into cast iron, what outside diameter would be recommended for the bush?

I imagine a slight tad over 14, but how much would this slight tad be ?

Exactly ?

Thanks in advance for any help
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13 September 2016 at 18:05 #8288
Daniel
Participant
@daniel
13 September 2016 at 18:23 #255689
Michael Gilligan
Participant
@michaelgilligan61133
Posted by Daniel on 13/09/2016 18:05:36:

I have plunge milled the pedal out to 14mm and the clevis pin is 10mm.

With a 2mm wall on a bronze bush …

I imagine a slight tad over 14, but how much would this slight tad be ?

Exactly ?

.

I flatly refuse to discuss exact tads with a man who works in whole millimetres

… But you may find this useful:

http://www.tribology-abc.com/calculators/e3_8.htm

**LINK**

MichaelG.

Edited By Michael Gilligan on 13/09/2016 18:27:38
13 September 2016 at 18:28 #255690
Martin Connelly
Participant
@martinconnelly55370
Loctite it to avoid tensile forces in the cast iron.

Martin
13 September 2016 at 18:36 #255692
JasonB
Moderator
@jasonb
I would also check your hole as plunge milling may be spot on but more likely a tad under or a tad over 14mm.

For a practical idea I have just mic'd a sintered bronze bush and it is 0.003" oversize on 3/4" nominal size, not tapered. So thats a a tad over 0.075mm for the press if but if the iron is a bit thin you may want to try 0.04-0.05mm over bore dia
13 September 2016 at 18:49 #255694
Neil Wyatt
Moderator
@neilwyatt
If feasible, ream the bush after fitting, if the fit is critical, (which I guess it isn't).
13 September 2016 at 19:11 #255702
speelwerk
Participant
@speelwerk
I support Martin, a 2 mm wall in cast iron will fracture without warning. Niko.
13 September 2016 at 19:15 #255704
JasonB
Moderator
@jasonb
We don't know how thick the iron pedal is.

The hole in the pedal is now 14mm, the pin it pivots on is 10mm which gives the BUSh a 2mm wall thickness
13 September 2016 at 19:51 #255718
HOWARDT
Participant
@howardt
Have a look at Oilite, Manganese Bronze. Although these are not re-machined after fitting, they achieve the correct bore after being press fitted into the correct hole.
13 September 2016 at 20:06 #255723
Daniel
Participant
@daniel
Posted by Michael Gilligan on 13/09/2016 18:23:53:

I flatly refuse to discuss exact tads with a man who works in whole millimetres

… But you may find this useful:

http://www.tribology-abc.com/calculators/e3_8.htm

**LINK**

MichaelG.

Edited By Michael Gilligan on 13/09/2016 18:27:38

Thank you for the link. That is a cool calculator.

The complete absence of any decimal points, let alone anything after them, was an effort to maintain the agricultural spirit of the adventure. However, even as I pressed the "create thread" button, I saw that this was doomed. At some point I would need to resort to something a bit smaller. It's a pity that the DRO doesn't do Tads, really.
14 September 2016 at 06:54 #255780
Daniel
Participant
@daniel
Thank's everyone for the replies. Last night's forum time was cut short by a storm and power failure.

Martin – I had temporarily forgotten about Loctite; that is most likely the way to go.

Neil – I will ream the bush after fitting. Critical it isn't, by any stretch of the imagination, but seems good form.

Jason – The pedal is about 15mm thick. My tape measure is not equiped with smaller increments.

And, of course, for the loctite solution, the finished article only needs to be a Tad, or two, under 14mm.

No unnecessary stresses, etc, either on me, or the pedal, and not a decimal point in sight.
14 September 2016 at 08:30 #255790
JohnF
Participant
@johnf59703
Daniel, if it's the clutch foot pedal I doubt it is cast iron, more likely a steel forging. What tractor is it ?

John

Edited By JohnF on 14/09/2016 08:31:12
14 September 2016 at 08:59 #255795
Michael Gilligan
Participant
@michaelgilligan61133
PostScript: … For the benefit of those who may not be familiar with the term:

A 'tad' [or more properly, T.A.D] is a Tiny Atypical Dimension

Example: On a drawing generally dimensioned in inches; one micron would be a 'tad'

or, when referencing whole millimetres; tenths of a thou would be 'tads'

MichaelG.
14 September 2016 at 09:24 #255798
MW
Participant
@mw27036
Posted by JohnF on 14/09/2016 08:30:41:

Daniel, if it's the clutch foot pedal I doubt it is cast iron, more likely a steel forging. What tractor is it ?

John

Edited By JohnF on 14/09/2016 08:31:12

You're probably right, i can't imagine that being a casting either.

Michael W
14 September 2016 at 09:48 #255803
Neil Wyatt
Moderator
@neilwyatt
Posted by Michael Gilligan on 14/09/2016 08:59:44:

PostScript: … For the benefit of those who may not be familiar with the term:

A 'tad' [or more properly, T.A.D] is a Tiny Atypical Dimension

Example: On a drawing generally dimensioned in inches; one micron would be a 'tad'

or, when referencing whole millimetres; tenths of a thou would be 'tads'

MichaelG.

[ BLUFF ]
14 September 2016 at 10:04 #255806
Chris Evans 6
Participant
@chrisevans6
From a practical point of view it would not matter if the bush was loose on the peddle hole by a couple of thou. It will not wear the peddle out in your lifetime and will be retained by the peddle fixing.
14 September 2016 at 11:19 #255822
Neil Wyatt
Moderator
@neilwyatt
Posted by Michael Gilligan on 14/09/2016 08:59:44:

PostScript: … For the benefit of those who may not be familiar with the term:

A 'tad' [or more properly, T.A.D] is a Tiny Atypical Dimension

Example: On a drawing generally dimensioned in inches; one micron would be a 'tad'

or, when referencing whole millimetres; tenths of a thou would be 'tads'

MichaelG.

[ BLUFF ]
14 September 2016 at 12:59 #255839
Daniel
Participant
@daniel
Micheal – That saved me the trouble of some research. I was convinced that a Tad was a more or less precise measurement. It's true that whole millimetres can be a bit (tad), cumbersome.

I've sometimes been known to use "half a Tad", but that is only on extremely precise work., and somewhat rare.

The (non) deliberate mitsake of referring to the clutch pedal as cast iron is just that; a mistake.

As pointed out, it is most likely a steel forging or similar.

The tractor is a Someca 40 & French.

Chris – quite agree with you, that the bush could even float. I just wanted to do a reasonable job for the simple pleasure of doing so; as with most of what we get up to. Avoiding any unnecessary accuracy, of course.
14 September 2016 at 13:00 #255841
Daniel
Participant
@daniel
Sorry – can I change the thread title now ?

I'm thinking "Loosely Fitting Bush", may be more appropriate.
14 September 2016 at 15:43 #255859
duncan webster 1
Participant
@duncanwebster1
Posted by Michael Gilligan on 13/09/2016 18:23:53:

Posted by Daniel on 13/09/2016 18:05:36:

I have plunge milled the pedal out to 14mm and the clevis pin is 10mm.

With a 2mm wall on a bronze bush …

I imagine a slight tad over 14, but how much would this slight tad be ?

Exactly ?

.

I flatly refuse to discuss exact tads with a man who works in whole millimetres

… But you may find this useful:

http://www.tribology-abc.com/calculators/e3_8.htm

**LINK**

MichaelG.

Edited By Michael Gilligan on 13/09/2016 18:27:38

For the diehard Imperial brigade I'm considering making a Micrometer which reads in 1/1024" increments. That's 2 to the power 10, and is a logical extension of 1/8", 1/16" etc. Any takers?
14 September 2016 at 15:59 #255863
SillyOldDuffer
Moderator
@sillyoldduffer
Posted by duncan webster on 14/09/2016 15:43:35:

…

For the diehard Imperial brigade I'm considering making a Micrometer which reads in 1/1024" increments. That's 2 to the power 10, and is a logical extension of 1/8", 1/16" etc. Any takers?

Works even better if we redefine the inch to be 25.6mm as well.

Dave
14 September 2016 at 18:55 #255882
Michael Gilligan
Participant
@michaelgilligan61133
Posted by SillyOldDuffer on 14/09/2016 15:59:23:

Works even better if we redefine the inch to be 25.6mm as well.

.

Couldn't agree more, Dave

deja vu **LINK**

http://www.model-engineer.co.uk/forums/postings.asp?th=94488

MichaelG.
14 September 2016 at 19:02 #255884
SillyOldDuffer
Moderator
@sillyoldduffer
Posted by Michael Gilligan on 14/09/2016 18:55:20:

Posted by SillyOldDuffer on 14/09/2016 15:59:23:

Works even better if we redefine the inch to be 25.6mm as well.

.

Couldn't agree more, Dave

deja vu **LINK**

http://www.model-engineer.co.uk/forums/postings.asp?th=94488

MichaelG.

Well I never! One day if I keep trying I might have an original idea. I'm leaving it a bit late though.

Cheers,

Dave
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