Cutting Welded Donuts

[Craved]

Working on my intercooler piping atm

Just after some tricks on working out the angles and easy ways to cut up a welded alloy donut - 3 inch

Cheers

[Risking]

Cut them with a bandsaw, I have a smallish saw that I dedicate to cutting alloy tube.

As far as angles go you can use a sliding bevel to get close then I'd normally make small adjustments to the angle on a belt linisher

[Craved]

got any tricks for clamping a donut in the small vice on those types of saws?

think i worked out a way with the angles

clamped the 180 down to a bench and marked the exact centre, then used a protractor from that point squared up to the bench.

i THINK that should mean that the tube will remain 3inch on the cut

[scotty nm35]

I use a small vertical bandsaw, I can usually get the cut very close by hand/eye, then linisher to clean it up.

Its the main reason I prefer lobster bends as I find it much easier to cut the angle required in the brobo, I can also change the radius of the bend along with creating smooth spirals etc. Its a bit more welding but I need all the practice I can get with alloy.

[Craved]

yep, lobster is looking easier for this pipe

just cant decide, dont want to mix the 2 piping styles too much so was looking for ways to do it better.

would be alot easier with a vertical bandsaw, but the small ones i have used were crap as a vertical saw

[Risking]

I have machined up a set of mandrels and guides.

I'll use a 4in donut as an example.

A tight radius 4in might have an ID of 2.5inches.

So I've machined up an alloy mandrel from round bar which is 2.5 in diameter.

It also has been in the mill and a slot about 1/2pm wide cut along it's length.

It's about 3in long and has a 1in pair of flats milled on one end.

I removed the table from my vertical bandsaw and used the mill to cut a 1in groove in the dead center of the table inline with the blade.

The machined mandrel sits in the groove located by it's flats dead center to the blade.

The welded dounut slides over the mandrel and hence is located dead center to the blade as well.

The mandrel can slide in towered the blade and the donut is cut perfectly straight and always remains perfectly square. When you come to the end of the cut the bandsaw blade enters the slot I milled into the mandrel an doesn't damage the mandrel at all.

Rotate the dounut around to cut the section out your want and feed it back into the blade. Perfectly square and straight again.

I have several mandrels which all have the same set of 1in flats and all fit into the same groove on my bandsaw.

If I need to do an odd size I just machine a new one to suit the ID of whatever dounut I'm using.

Does that make sence?

[Risking]

Typically the only time I'd use dounuts is when I need a tighter radius than my mandrel bender will do or it's an odd size that I don't have mandrels for and couldn't be arsed to machine mandrels to do one or two pipes.

[Craved]

makes perfect sence, the 2nd time i read it lol

simple design but would be true each time like you say. i'll remember that, but alas i dont have the gear to make good use of it

[Craved]

decided to do it the easier but longer way

will keep your way in mind Brad, for later when i have the tools for that

[Risking]

Whe youbuy small bandsaw bring the table down and I an mill the groove in it.

If you buy some alloy bar and tack weld some of the common dounut sizes you want to use we can machine up some mandrels at the same time.

Doesn't take long on the machines I've got and saves you alot of time in the long rub

[battery]

when your doing lobster back piping do you change the cut angle or just the length of the sections?

Edited April 25, 2011 by battery

[zebra]

I think most people use 7 deg cuts for all but the end pieces.

not 100% on that as my best effort at fabrication is a flat piece of alloy with holes in it lol

[Craved]

Whe youbuy small bandsaw bring the table down and I an mill the groove in it.

If you buy some alloy bar and tack weld some of the common dounut sizes you want to use we can machine up some mandrels at the same time.

Doesn't take long on the machines I've got and saves you alot of time in the long rub

sweet offer, thanks brad!

got any pointers for the vertical bandsaws? for alloy i would think that with regular cleaning a woodworking bandsaw would suffice, but im open to good suggestions or examples of the type of vertical saw i should be looking for.

was thinking somethign like this

https://www.machineryhouse.com.au/Products?stockCode=W4224#

I think most people use 7 deg cuts for all but the end pieces.

not 100% on that as my best effort at fabrication is a flat piece of alloy with holes in it lol

hahahahahaha

yeah i use 7 degree cuts, varying the lengths to change the radius

[Risking]

Hafco gear is pretty good. I have a few things from there.

I'd also have a look on Greys online.

I started with a small ryobi saw from bunnings. Still use it too.

All you need is something with a decent bed so it can have a slot milled into it

[scotty nm35]

looks great Chris.

I use 6 degree usually but change to 7.5 or sometimes more for tighter work.

[bLaQ.bOi]

VERTICAL BAND SAW!! f**king need me one of them... but they are all for wood? im unsure about these things never used one! is it just a simple blade change for steel?

[scotty nm35]

Yep, I have a small band saw at the moment but I would love an old cast iron butchers one.

If you drop down to Hare and forbes one day bLaQ.bOi call in mate.

[gobble_doc88]

You can use a wood band saw for aluminium you just need to change the blade. Steel needs a slower speed(like all machinery) so you need a metal specific band saw.

[Craved]

im just using the wood blade for alloy, same as on drop saws - take it slow and there really isnt too much issues.

i picked up the H&F one i linked above already and it is handy as for small alloy jobs, heaps better than an alloy grinding blade

[bLaQ.bOi]

cheers scotty, once things get back to normal i will definatley look at buying one of these!

so easy to make y pieces with a bandsaw!