Furnace brazing... Anyone done it?

[gerg 10,871]

Gotta fill in some holes in my toploader bell and drill & tap some new ones for my T5. Was wondering if there are any folks here who've had some experience with furnace brazing cast iron and more specifically if this sort of heat will warp the housing so as to need machining again. No I'm not buying a Dellow or CRS housing. Cheers.

[PRO250 1,506]

i can offer any info on the brasing but when i did my bell for the t5 i just tilted my box so the bottom hole lined up and the all the holes would be clear of the holes that where allready there


I dont have any picture but only one of it bolted together but you cant see how i did it 

[gerg 10,871]

I think I know where you're coming from but mine doesn't line up with anything, no matter which way you rotate it. I have a feeling your bellhousing might have been for a narrow-pattern toploader, whereas mine is drilled for a wide-pattern. It has the bosses cast for either but only the outer ones are drilled. I've seen a toploader box with both patterns drilled (8 holes).

[wagoon 2,429]

Is it cast iron or cast steel? will make a big difference.

Have you thought about using a stick welder with cast electrodes?

Well you learn something everyday, just had a read on furnace brazing and it would seem like a good idea for the job. You would need to get your heat right, but because its only brazing you would only need cherry red so 750ish degrees. This should not warp the job BUT if there are stresses in the metal they may come out at even at such a low heat causing distortion. The only other problem I could see is if the bell housing has a few areas of different thickness of material which may cause some distortion due uneven heating. I think the most important factor is finding out if it is actually cast iron or cast steel.

[Jiminy Kriket 133]

Hi, first post but I hope I can help.

I'm a fitter/machinist by trade and in the past 5 or so years have converted 6 bell housings to suit the T5 gearbox bell housing.

Fist things first, is there enough material at the bottom of the bell housing to catch the bottom 2 holes on the gearbox?

If not, there needs to be a couple of bosses welded onto the bottom of the housing to get the holes in the right place.

Second, do you have any holes interfering with the holes for the T5 bolt pattern?

If there are overlapping holes, my fix for this is metal spraying up the original holes. Metal spray is an oxy acetylene welding process

that doesn't cause the same hardness or warping issues that stick welding can cause. 

Thirdly, Does the locating diameter on the T5 snout fit neatly into the bell housing already?

If it's too loose, the snout will need to be sleeved to fit. If it is too small for the snout to fit, the easiest fix is to skim the location diameter

on the snout down to suit the bell housing. You can bore out the bell housing to suit, but it takes longer set up.

Once you have all the necessary lugs and available material for the bolt pattern, it's simply a case of drilling and tapping to suit.

 

The cars I've converted include my 302 windsor powered xy, and 4 crossflows in xes and xfs. Biggest problem I found

was that the bell housings started to taper too high up and you couldn't physically get the bottom 2 bolt onto a flat surface, but as I said,

I have worked around that issue.

Hope this helps, if you have any questions on the welding process, just ask.

[gerg 10,871]

Thanks heaps for that guys. The machined mounting face on mine is large enough top and bottom to allow all of the T5 holes to see flat metal, with the bottom two actually lining up with the cast-in bosses. Top ones are the problem, where each of the new holes will have less than 1/4" of metal to the old holes, which doesn't make me feel comfortable about putting any torque load on them. They're the ones I want to fill: I'm thinking of plugging them with cut-off bolts and brazing them in place, or just filling them entirely with brass. I've used electric brazing rods on wrought iron with success, but cast might be a different story. I guess I'll tell what metal it is by grinding the bell a little bit and seeing the sparks it makes and also the shininess of the fresh metal. Pics tomorrow

[bear351c 10,273]

Could run a file over the housing, and catch the filings, rub them in your hands, cast iron will leave your hands grey/black. Steel shouldn't.

 

Reckon you could take some photos, gerg? Would be good for future reference.

[gerg 10,871]

Could run a file over the housing, and catch the filings, rub them in your hands, cast iron will leave your hands grey/black. Steel shouldn't.

 

Reckon you could take some photos, gerg? Would be good for future reference.

 

Thanks for that Bear, yeah thinking of doing a thread on it. Plenty out there already but none are done in the same way.

[Jiminy Kriket 133]

The holes are threaded, yes? You could get away with silver soldering threaded rod in there and then redrilling the pattern to suit.

The biggest problem you are going to have soldering or brazing the plug in Gerg is getting the bell housing clean enough down the threads before you

apply the solder or braze. Silver soldering would be preferred because there is a lot less heat involved in melting the solder. Silver solder is also

strong as hell when used this way. Just make sure you get the high silver percentage solder, not the plumbers solder. The higher percentage solder has

a higher bond strength.

The only steel bell housings i have seen are the pressed metal jobbies sold for drag racing applications like a lakewood and the like.

Other than that, you only have cast iron and aluminium as options for stock bell housings. 

And on a general note on welding/brazing/soldering cast iron, preheat is your friend. Get it hot enough so it's "smoking" before you try to do any repairs.

At work i use a 4 ring camp burner to preheat larger castings But at home, if it fits and the wife isn't home, into the oven at 150 for about half an hour before

I weld then back into the oven for another 20 minutes after I finish at 150, then leave it in the oven to cool off. This just stops any possible heat spikes that

may harden the cast iron or worst case scenario crack the housing.

[XPT 673]

I agree with silver soldering, a lot of the old lathe turning and milling (fly cutters etc) tools had the tungsten tips silver soldered on. They are under a fair bit of load at times especially taking an intermittent cut and you never see the solder break. Provided there is a good coating of flux and you use high silver (blue tip) solder. It would be much easier to get it to run right down into the thread with less heat. It would be very strong as Jiminy says

[wagoon 2,429]

When grinding to find out what cast it is cast iron has dull red sparks and there arent as many sparks. Cast steel with have the yellow colour sparks as normal steel. You can also look at the shape of the sparks but this is a bit harder to explain here.

I agree with pre and post heat. Anything cast needs heat before and heat after working and as Jiminy said say temp for both heats.

[bear351c 10,273]

And on a general note on welding/brazing/soldering cast iron, preheat is your friend. Get it hot enough so it's "smoking" before you try to do any repairs.

 

 

Yep, too right. As a fellow Maintenance Fitter, I agree with everything Mr J.K. has said. Pre heat, weld, reheat and let cool overnight in the oven.

Do not quench it in any oil, lime or water. It will crack.

 

If you're a bit hesitant, is there a local welding company who could do it for you? (Use their oven, wifey might like the idea) I know my Ex used to hate me putting my alloy heads in the dishwasher. Maybe, thats why she's my 'Ex" wife.

[wagoon 2,429]

Just to let you know lime is the best thing to maintain heat when cooling a job, it is not quenching when placing in lime. We have a lime box at work, after working steel which starts at around 1100 degrees C when we finish working the steel its around 750-800ish. If we place it in the lime box the next morning the job will still be over 300 degrees, where as if its just placed on the dirt ( I work in a blacksmith shop with dirt floors) it will be dead cold/room temp the next morning. If you are after a controlled temp drop use lime, a furnace is better though. Our furnaces are turned off at 1200 degrees at home time. The next morning they are still above 500 degrees no matter the outside air temp.

[gerg 10,871]

Thanks for all your advice fellas I found it very useful. Hope others can too. I'm convinced that silver is the way to go and I'll solder in some studs for the new box while I'm at it. I might start a T5 conversion thread as there seems to be a lot of interest in it.

[gerg 10,871]

I've read that cast iron is stable up to 600 deg, then it's structure starts to change and you can do some funny things to it. So I plan on using an old washing machine tub and putting timber/coals in to achieve a nice dense heat source, then place the bellhousing in it till it approaches said temp. I've got access to a laser thermometer. Then I'll silver-solder the parts in place with an oxy setup, cover with sand and leave overnight.

[Jiminy Kriket 133]

Sounds the goods. Just be careful with the coals temp... They can get hotter than you would think.

Don't forget photos... I always like learning new ways of doing things.

[wagoon 2,429]

If you can place a controllable air flow source down the bottom that blows air into the burning material this will allow you to control the heat better, you should also be able to reach the temp faster. Dont try and handle metal at that temp you are going to need something to lift the bellhousing. Also plan where you are going to be doing the welding and preheat the surface as the surface will suck temp out pretty quick.

Another thing to be aware of is using oxy on metal that hot may actually change the structure of the metal. Because you are introducing oxygen and fuel under pressure out of the torch you need to make sure you have a neutral flame.