13 replies to this topic

[crn1969]

Need to check clearances on diff side cover plate bushes to see if I need to renew.Haynes says 1.5 tho but is that all round ? Or is that at one point with drive shaft pressed against one side and then slip feeler gauge in opposite side? I will have all parts on a bench so can measure either way?

[dklawson]

Measure the axle journal and measure the inside diameter of the bushing.  Subtract one from the other and that is the diametrical clearance.  That's what they want you to hold to 1.5 thousandths.  Don't forget to take measurements at several points as the wear may not be even.

[crn1969]

Okay thanks.will have a go tonight.

[MRA]

Another method it to wrap it in a single sheet of paper, do NOT overlap it, if it slides in, then it is outside of the tolerance and should have a new bush fitted and honed.

[ACDodd]

The side plates are quite poor. The bush needs to be concentric with the shoulder on the plate. For this reason, the bush needs to be bored on a lathe with reference to this and not reamed or honed as these processes follow the centre of the bush. I have had side plates that were so off centre it bored right through the bronze surface to the steel beneath on one of the bearing. Irrespective of factory clearance I bore them to +0.001" bigger that the journal that rides in it.

Ac

Edited by ACDodd, 21 March 2016 - 05:03 PM.

[MRA]

The side plates are quite poor. The bush needs to be concentric with the shoulder on the plate. For this reason, the bush needs to be bored on a lathe with reference to this and not reamed or honed as these processes follow the centre of the bush. I have had side plates that were so off centre it bored right through the bronze surface to the steel beneath on one of the bearing. Irrespective of factory clearance I bore them to +0.001" bigger that the journal that rides in it.

Ac

 

What tolerance do you apply on your 0.001" ?

 

Nobody would hone to size without boring first, it would take an hour or more to remove that much, but in reality. how it is held and in what machine would also determine the outcome, holing in a 3 jaw chuck will be about as good as using a file so far as accuracy is concerned, the accuracy of some jigs and fixtures I have seen leave a lot to the imagination, boring on it's own will not give a very round hole or a very good oil retentive surface, it should be honed afterwards.  

Edited by MRA, 21 March 2016 - 05:51 PM.

[ACDodd]

Factory bored, and i bore mine by mounting them in a recessed tool then secured using the flange. They are machined as used.

 

Tolerance is half a thou.

 

 

AC

Edited by ACDodd, 21 March 2016 - 06:27 PM.

[MRA]

Factory bored, and i bore mine by mounting them in a recessed tool then secured using the flange. They are machined as used.

 

Tolerance is half a thou.

 

 

AC

 

That's some lathe you have there AC to be able to hold 0,0005" very impressed, what model is it ?

[Spider]

The side plates are quite poor. The bush needs to be concentric with the shoulder on the plate. For this reason, the bush needs to be bored on a lathe with reference to this and not reamed or honed as these processes follow the centre of the bush. I have had side plates that were so off centre it bored right through the bronze surface to the steel beneath on one of the bearing. Irrespective of factory clearance I bore them to +0.001" bigger that the journal that rides in it.

Ac

 

I've also found on every gearbox case I've had my hands on that the side plate faces on the case itself are never parallel, I've found they all taper towards the bottom.

[ACDodd]

Bored then finished by hand. Its an old Colchester 6 x 24 round head.

Ac

[MRA]

 

The side plates are quite poor. The bush needs to be concentric with the shoulder on the plate. For this reason, the bush needs to be bored on a lathe with reference to this and not reamed or honed as these processes follow the centre of the bush. I have had side plates that were so off centre it bored right through the bronze surface to the steel beneath on one of the bearing. Irrespective of factory clearance I bore them to +0.001" bigger that the journal that rides in it.

Ac

 

I've also found on every gearbox case I've had my hands on that the side plate faces on the case itself are never parallel, I've found they all taper towards the bottom.

 

 

Yes by quite an amount too. but also they are very slightly concave.... but then that is what gaskets are for.

 

The drawing has quite a high tolerance for the parallelism and width deviation

[MRA]

Bored then finished by hand. Its an old Colchester 6 x 24 round head.

Ac

 

I would be very surprised if you where holding the tolerance you believe ...  to hold that tight a tolerance you would need a stable temperature environment, what is probably happening is you are "matching" parts together ie a pot joint and a side cover, so your clearances are maintained but, as metal gets cold we all know about thermal linear transformation or size change due to heat so as your mic gets cold and your pot joint also gets cold your measurements appear to be the same as when they where warmer. 

 

If on the other hand you were making it to drawing then you will see exactly what I mean when you come to fit it all together, I sometimes have to make parts that are fitted together in a cold warehouse type workshop, so I will sometimes compensate to achieve the desired results.... ie they fit together.

 

What do you mean by finished by hand ?  with wet & dry or something ?

Edited by MRA, 21 March 2016 - 08:51 PM.

[ACDodd]

Yup 320 finish.

Ac

[MRA]

Yup 320 finish.

Ac

 Lol nice one, I hone them using 320 grade on a semi auto Delapena speedhone.