pressbrake1
Member
- Messages
- 5,776
- Location
- Essex
A better average dim over more threads would be good incase it’s bordering 15tpi
- Thread starter Welderpaul
- Start date
brightspark
Member
- Messages
- 41,585
- Location
- yarm stockton on tees
the perkins manual will give all the details
Pete.
Member
- Messages
- 15,066
- Location
- Kent, UK
I agree with 7/8" -14 UNF the measurements work out.
1/14=0.071 (almost exactly your two-pitches measurement of qpprox. .140"
1/14 is also the double-depth figure so 0.816 +0.071 = 0.887" (or 7/8" plus 12 thou wear/clearance)
Run a tap in the hole and buy a new bolt.
1/14=0.071 (almost exactly your two-pitches measurement of qpprox. .140"
1/14 is also the double-depth figure so 0.816 +0.071 = 0.887" (or 7/8" plus 12 thou wear/clearance)
Run a tap in the hole and buy a new bolt.
- Messages
- 14,815
- Location
- UK
Thanks everyone!
- Messages
- 14,815
- Location
- UK
Slightly off topic, but the same bit of kit.
I want to check the clearance between the bearing shells and the crankshaft using plastigauge. So thats the clearance on the big ends of the con rods onto the crank, and the crank main bearings
Which are the clearance fgures i should be looking for?
I want to check the clearance between the bearing shells and the crankshaft using plastigauge. So thats the clearance on the big ends of the con rods onto the crank, and the crank main bearings
Which are the clearance fgures i should be looking for?
brewdexta
The biggest tool in the box
- Messages
- 5,756
- Location
- UK
Hi Paul, If it's the Dexta crank bolt, I can see what mine looks like, if I can find it in the various boxes of bits. From memory it was tight, but not chewed.
Agroshield
Member
- Messages
- 6,394
If they are, that would be a very strong argument in favour of the crank bolt being in the same thread system.
If all the other fasteners on the engine are UN form (standard A/F sizes, measure the tpi of a 1/2" coarse one and tpi of any of the fine threaded ones), then the crank bolt is likely to have that form.
If the engine fasteners happen to be Whit. form (A/F sizes, measure 1/2" coarse tpi, and tpi of any fine thread), then the crank bolt may have that form.
- Messages
- 14,815
- Location
- UK
Thanks everyone. I've bought a 7/8" x 14 TPI die to repair the bolt.
I have various sets of thread gauges but nothing fits the threads on UNC/UNF bolts. I need to find something.
Its it a whitworth form then? 55 degrees?
What do I need to turn the OD of the bolt to - 0.8750" / 22.22mm or a bit smaller?
I have various sets of thread gauges but nothing fits the threads on UNC/UNF bolts. I need to find something.
Its it a whitworth form then? 55 degrees?
What do I need to turn the OD of the bolt to - 0.8750" / 22.22mm or a bit smaller?
Agroshield
Member
- Messages
- 6,394
UN form is 60 degree angle. Whit. form is 55 degree angle.
The die you have bought will be UN form, 7/8"-14 UNF as discussed above.
Draper thread pitch gauges have served me well. See:
www.lawson-his.co.uk
Note that 51071 is UN only and 51072 is Whit. and metric.
If you are really keen, the only thing you need to add to those is a BA one (https://www.chronos.ltd.uk/product/ba-screw-pitch-gauge/).
The die you have bought will be UN form, 7/8"-14 UNF as discussed above.
Draper thread pitch gauges have served me well. See:
Screwpitch Gauges – Brand Catalogues – Draper – Engineering and Precision Tools – Thread Cutting Repair from Lawson HIS
Screwpitch Gauges – Brand Catalogues – Draper – Engineering and Precision Tools – Thread Cutting Repair
www.lawson-his.co.uk
Note that 51071 is UN only and 51072 is Whit. and metric.
If you are really keen, the only thing you need to add to those is a BA one (https://www.chronos.ltd.uk/product/ba-screw-pitch-gauge/).
brewdexta
The biggest tool in the box
- Messages
- 5,756
- Location
- UK
here's the bolt, its the crank bolt with the holder for the starting handle Not much use on a diesel but there is a petrol Dexta.
There's thick washer that goes with it, just in case yours is missing and why some numpty stripped the threads if it bottomed out.
its 4.5mm thick, OD 55mm ID 23mm
it has the printing on it, presumable the Fomoco part number
33125112TI
the thread is definitely 14tpi, difficult to hold the calipers/gauge and phone at the same time
I measured it with the calipers first, in metric, then the coffee kicked in and I got the thread gauge out
max thread diameter is 0.87 in, 22.21mm which is 7/8" UNF.
Cheers
Andy
There's thick washer that goes with it, just in case yours is missing and why some numpty stripped the threads if it bottomed out.
its 4.5mm thick, OD 55mm ID 23mm
it has the printing on it, presumable the Fomoco part number
33125112TI
the thread is definitely 14tpi, difficult to hold the calipers/gauge and phone at the same time
I measured it with the calipers first, in metric, then the coffee kicked in and I got the thread gauge out
max thread diameter is 0.87 in, 22.21mm which is 7/8" UNF.
Cheers
Andy
- Messages
- 14,815
- Location
- UK
Thanks Andy. Mine doesnt have the washer which might be the problem. Can soon get one of those laser cut 
Always wondered why there was the facility to put a starting handle in. I'm not sure that the hole in the nose is big enough to get a starting handle through.
Always wondered why there was the facility to put a starting handle in. I'm not sure that the hole in the nose is big enough to get a starting handle through.
