1949 Dennis F1 Fire Truck Restoration

Whitworth and UNC are the same tpi except for 1/2" for some reason.

Bugly,
From your picture that bolt looks like 3/16 BSW as it is coarse pitch. There seems to be a bit of confusion caused by the marking on the spanners. During WW2, to save metal, the hex size of bolts and nuts was reduced. Eg. a post war 1/4"W nut had the same size hex as a pre war 3/16"W nut. So, unless working on pre war eqpt. ignore the larger W size on the spanner and just look at the smaller BS size. Post war BSF and BSW bolts and nuts of the same thread diam have the same spanner size.
Hope this helps.
Rod

Whitworth and UNC are the same tpi except for 1/2" for some reason
Whitworth and UNC are the same TPI but that

Bugly, I'd have to say you've got a 1/4" BSF bolt there, with 26 TPI.

The prize of a vitual bottle of Bundy rum goes to onetrack. I dropped into Darwin Bolt Supplies today to measure up the thread pitch with their gauge (26 TPI) and confirm the bolt size and type. It's a 1/4" BSF bolt, and as onetrack said they are hard to source. But at least I know what it is supposed to be!

So now I need to remove the broken bits from the block using the MIG tricks given by bigcam and loadstar. Then, as onetrack suggests, I'll drill to upsize the bolts to 5/16", either in S/S or in high tensile UNF. I'm picking that the cast block will be able to be tapped easy enough ... am I right?

The next task will be to sort out the pitted and holed side cover plate. I will be talking to a guy on Friday who is doing some metal spraying for me, so I'll see if he can build up the pits in the back of the cover plate ok. That way, I can retain the original plate, and can also re-drill to suit the larger fixing bolts. Also, before the metal spraying, I can weld a smaller plate to the inside to allow the drilling and tapping of a thread to suit the fitting of a water temperature gauge sender unit through the cover plate.

Thanks to Rusty Engines for the email and thread info, and Beaver, thanks for the info on the Gardener fuel pump. I had cleaned up the pump, but was reluctant to strip it down in case I damaged the diaphragm. So I'll see if I can hunt one down.

Bugly, I'd really give getting the origonal bolt out a go first. When you try drilling them out and going oversize, centre punch the centre of the origonal bolt, even if you do this you run the risk of the drill running off centre which will put you alignment out.
Another trick for getting broken bolts out if you arn't very confident with the mig is to put the welding tip in the oxy, heat up the bolt, then cool it with a houshold spray bottle with water in it, or even CRC, diesel etc. do this once or twice the get a little cold chisel or centre punch and see if you can tap the thread around.
If you manage to get all the bolts out and can't get any bolts, you might be able to get studs made up with BSF on one end and UNC on the other. I've got a couple of BSF die's, but I couldn't tell you what size, I know this because une of my apprentices cut a 3/4 bsf thread on a heap of spindles we had made up, he was Mr Popular.

Hi
These people say that they have BSF www.classicfasteners.com.au/cat2010.pdf
also www.statewidefastener.com.au/fasteners/l...=fasteners&cat=FA288
Ian

G'day Bugly,
I had phone contact with Classic Fasteners a while ago when I was looking for new studs to fit a bonnet pull on a White 9000 after trying all of the normal suppliers. They were unable to help as it is an American thread and they specialise in British stuff.
However,they were keen to try to help and appear to be the real deal as a business. Geoff

I've dealt with Classic Fasteners over the years. Mostly British as you say - specialise in stuff for bikes.

Professional seller with an interest in what they do.

Used to have a fairly comprehensive online catalogue, don't know if they still do.

Woo-hoo! Measuring with my virtual digital micrometer, on a virtual digital connection, I scored a virtual bottle of Bundy!
I'll have to pull my virtual digit out, and invite some virtual friends around, to share it with them!
With proven Internet skills such as I have now, I think I'll go into online brain surgery, next! ..

Bugly, cast iron will tap just fine. Make sure there's enough metal in the block to allow a bigger thread diameter.
Use a small drill initially for the pilot hole (1/8" or 3mm), then the correct drill size for the 5/16" tap.
I'd clamp or bolt the plate in position, and drill the larger holes through the plate into the block.
This ensures that all holes are correctly located, and the holes in the plate will assist in acting as a drill guide.

Make sure you use a depth stop on the drill, to prevent the drill bit going right through the casting.
Start with a taper tap, turn about a third of a turn, then back off to cut the thread chips.
Use a good thread tap lubricant .. Trefolex is my favorite.
Finish with a bottom tap, and ensure you choose a bolt length that allows a reasonable space between the end of the bolt and the bottom of the hole, for clearance.

Remember that all HT steel corrodes much faster than mild steel, so HT is not necessarily the best choice in this scenario.

Cheers - Ron.

trefolex is the most fantastic stuff known to the machineing race, There's rarley a hole I drill these days without it, Plus the residule splatter on you're clothes gives you a great "Man Scent", much more masculine than Brute