Volvo Penta MD series bolts/threads

mogmog2

mogmog2

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Hello,
I need 4 bolts/set screws for my gearbox. Does anyone know what system VP used in the 70's? I assumed metric, but a 3/8"AF fitted. So it would be UNF thread?
Many thanks
 
mogmog2 said:
Hello,
I need 4 bolts/set screws for my gearbox. Does anyone know what system VP used in the 70's? I assumed metric, but a 3/8"AF fitted. So it would be UNF thread?
Many thanks
Click to expand...

A 3/8" AF socket wont fit on an M6 so 1/4" UNF or UNC seems likely. 28 and 20 tpi respectively.
1/4 BSW is also 20tpi so if you have any Whitworth screws lying about try one to see if it might be 1/4" UNC
 
Last edited:
VicS said:
A 3/8" AF socket wont fit on an M6 so 1/4" UNF or UNC seems likely. 28 and 20 tpi respectively.
1/4 BSW is also 20tpi so if you have any Whitworth screws lying about try one to see if it might be 1/4" UNC
Click to expand...


Thanks. My concern was that it should have been metric, but had corroded to coincide with something else. I'll rummage through my collection. I've got a load from my mini days, I think theyre may be UNF. In there. I'll look at the threads tomorrow.

ghostlymoron said:
Most of the bolts/set screws on my 1965 MD 1 were metric but not all.
Sweden adopted the metric system in 1889.
Click to expand...
I think that's what I'm finding. Marvellous.
Thanks for the confirmation though.

It's not the coupling-that was yesterday's task! These are for the actuator cover. I have found that M6 fit without slop or binding. Not sure what thread metric bolts use, but as these are lightly loaded fastenings, I'll run with them and can fairly easily change them.
 
mogmog2 said:
Thanks. My concern was that it should have been metric, but had corroded to coincide with something else. I'll rummage through my collection. I've got a load from my mini days, I think theyre may be UNF. In there. I'll look at the threads tomorrow.


I think that's what I'm finding. Marvellous.
Thanks for the confirmation though.

It's not the coupling-that was yesterday's task! These are for the actuator cover. I have found that M6 fit without slop or binding. Not sure what thread metric bolts use, but as these are lightly loaded fastenings, I'll run with them and can fairly easily change them.
Click to expand...

If M6 fit then I'd think the originals must have been M6. (IIRC a 10mm spanner should fit.)

M6 has a pitch of 1mm

UNC is 20tpi ie about 1.27mm
UNF is 28tpi ie about 0.91mm
 
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VicS thanks, yes 10mm fits the M6 bolts I found.
As you say, it must be metric: I can't see the metric thread fitting more than a very few threads in a UNC/UNF socket and these are 20mm long and thread in sweetly by hand all the way.
Thanks for your help. Most reassuring.

Toolstation had bright plated high tensile set screws so all done now

All reassembled and appears to be working. Degreased, treated with Fertan and waiting for tbat to do its work then paint.
 
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