cutting steel - accuracy

[cirrusjock]

Hi

Another stupid question, I am cutting my steel using an angle grinder and cutting disk. Some of the angles have come out slightly uneven. This means when you put it against the next section there are small gaps. Particularly the 74 degree engine supports. I know these will be filled in when it is welded but will this be ok or should I redo it.

I am teaching myself to weld and getting there but am worried about the strength of the finished chassis. I have visions of it coming apart on the road:eek:

[MarkB]

If you are not sure then buy a ready made chassis, providing you don't modify that chassis you will be covered by their liability insurance should it fail.

[cirrusjock]

I was going to do that but I really do want to do everything myself. I would like to be able to look at the finished car and think, I built that.:)

I don't want to look at a load of metal scattered over the road though and think ' I built that':(

[flyerncle]

Mark the angles on the steel with a scriber and cut with a hacksaw,long winded but easier to file up,practise welding before you start the chassis for real.

[ayjay]

I used a 9" grinder to cut my steel at first but then found it better with a 4" using the thin slitting discs-a lot better control of the cut:)

[will_08]

If u really want to do it all then go for it, but as previously said dont practice welding on a chassis ;)

I couldnt weld have taught myself after my freind set my welder up, can lay some nice welds. but i plan to finish tacking it (hopefully soon :rolleyes: ) myself then let him fully weld it up.

I started exactly like you but logisticly its going to take me forever to fabricate everything from scratch and i dont think id want to take a chance on the suspension components when im not that confident.

As for the accuracy of cuts i got a Handy Andy flat pack so i cant comment on that.

Best of luck with your build mate

Will

[tkpm]

I used a Evolution Rage 3 from Screwfix,

http://www.screwfix.com/p/evolution-rage-3-255mm-compound-sliding-mitre-saw-230v/65730

Terry

[vmax1974]

I am using a 4 and half inch grinder with the thin 1mm cutting discs then doing any adjustments with a file find I am getting on ok with this although my grinder is about done in I also bought a trend digital angle rule which I find helps loads

[snapper]

As above....
Cut a little long with the grinder and surface grind or file to fit.

[robo]

If you are having problems with your freehand cutting get one of these gadgets http://www.ebay.co.uk/itm/4-1-2-ANGLE-GRINDER-CUT-OFF-STAND-tool-DIY-/110841163583?_trksid=p3284.m263&_trkparms=algo%3DSIC%26its%3DI%26itu%3DUCI%252BIA% 252BUA%252BFICS%252BUFI%26otn%3D6%26pmod%3D2709037 18333%26ps%3D54 The do them for 9" grinders as well. Used with a thin disc it would do all you need. Its not a good idea to gap craft the joints because the weld will pull and cause distortion making it harder to keep everything in check. Practice weld on all the off cuts of material before you start on the chassis, good luck.

Bon

[cirrusjock]

Thanks for all the advice.

That tool for the grinder looks good. I will order one of those.

I have redone the sections that I wasn't happy with. Cutting long and grinding to the marked line works well.

I am only tacking at the moment and practising fully welding on offcuts as I go. One of the reasons I wanted to do the whole thing myself was to learn new skills like this so its good to get advice on here and see my work improving.:)

Thanks guys.

[TheArf]

Good on you, its always good to learn new skills. The closer and neater you can make your cuts the easier it will be to weld, also make sure that where you are welding it is clear of rust and any protective coatings, i.e. oil are cleaned from the area, remeber clean is good


Arfon

p.s. im cutting mine with a rage3 evolution chopsaw

[brainbug007]

I was in a similar boat and wanted to learn some metal working skills while building mine. I ended up using a black perm marker to draw the lines for the cuts, then cut slightly wide on purpose with a cutting disc. I then slowly grinded away all the black ink from the pen using a grinding disc to get my final line and then took a metal file to it if it wasn't a flush fit.

[vmax1974]

Will take about 20 thin cutting discs to do a full chassis

[alga]

If you are not sure then buy a ready made chassis, providing you don't modify that chassis you will be covered by their liability insurance should it fail.

Has anyone actually ever heard of a self-made chassis that failed catastrophically?

[minicountryman1961]

http://www.youtube.com/watch?v=5ZTqM3uXlWM&feature=related

Watch what happens at the 5:30 point in the video.

[AshG]

he forgot to weld the bracket it was doomed to fail.

as for your gaps as long as they are less than 1mm then you will be fine.

[HandyAndy]

All great suggestions / ways of cutting the steel

As you are cutting by hand, here is an easy way to cut the compound mitre cuts......hope it helps ( its a little long winded to write down & to read but it works )

Lets use the bottom compound mitre cut on FF2/FF3 as the example.....

firstly cut the 26 degree cut....

Place the steel down so the 26 degree cut is facing down onto the workbench,
then
Scribe the 14degree angle onto the upper face of the steel ( eg..top right to bottom left as you look at it )
then
turn the steel over 2 flats(away from you ) ( so now onto the original bottom from the first position of the steel on the bench )
then
scribe the 14degree angle from bottom right to top left as you look at it
then
turn the steel BACK 1 flat(towards you) ( in effect on its side from original position ) & using a straight edge line up the points of the previous 2 scribe marks & scribe a line.

You should now have 3 scribed lines showing the compound angle of 14 degrees.

Place the steel in a vice in position to cut the 2nd scribed line you made, you will find it easier to cut if the steel is positioned in the vice at an angle downwards ,
then using a hacksaw or ( depending how confident you feel...and angle grinder with a 1mm cutting disk ) & cut that scribe line ( do NOT cut all the way thru the 3 faces of the steel, just cut that 1 scribe line )
then
Remove the steel from the vice & turn over 2 flats towards you ( you,ll be cutting the 1st scribed line you made ) , position the steel so it is pointing upwards, then cut that scribe line ( again do NOT cut thru any other faces of the steel ),
then
remove the steel from the vice & turn the steel 1 flat AWAY from you & position the steel in the vice angled slightly downwards & cut the scribed line.

You should now have a perfect 14degree compound mitre cut , use a file to smooth out the cut lines so they all run in 1 direction of the compound cut.

Don,t forget that all the compound mitre cuts on the chassis apart from SW1 & SW3( these are singular pieces within the chassis) that have duplicates ( eg SB5 & SB6, FF2 & FF3 etc) are "handed".

hope this helps, & I hope it makes sense :eek: :confused: :D .....it does work ;)


cheers
Andy

[shh120m]

Or...

Mark out the coumpound angle, place the tube in the vice so that one of the lines is vertical then cut the angle with the hacksaw so its like cutting a normal mitre.

[MarkB]

I don't have a problem with anyone having a go BUT if never welded before then making a car chassis is the wrong thing to learn on.

[baz-r]

omg i cant beleave someone would take a tack welded chassis for a spin on public roads what a tit!

as for cutting steel the only way to mark out is a scribe as if you need to work to the mm then anything thicker than .5mm is too fat
cut just off your line then file the last tiny bit back to the line
a tip is if your eyes are bad ir the steel is bright and hard to see the scribe line is to use marking out fluid or marker pen on the area where you need to scribe