5mm slot in 5mm bar

[Wightsparks]

Need to make a 4-5mm wide slot/cut, about 10mm long across 5mm x 25mm mild steel bar.
Which is easy for a one off but I need to do it 160 times (both ends of 80x 500mm bars)
My TCT is 1.7mm and two cuts is 320 cuts! Widest cutting disk I can find is 3mm, a grinding disk is very hard work.
I could cut a V shape 10mm deep - but again 320 cuts and not exactly fast also depth needs to be consistent. Basically don't want to spend hours on it if I can avoid it.
Any ideas please? Thanks!

 

[Wendelspanswick]

Flypress and a slot punch.

 

[Paul.]

Get them in as a laser cut profile, not worth wearing cutters or blades out on a job like that.

 

[HMB]

Plenty of firms out there that will do it. I use Parker Steel

 

[Wightsparks]

Probably should of mentioned this is for me, not for production or to sell. Just looking for any ideas of the best way to do it myself.

 

[Wendelspanswick]

With limited tools I would drill a 5 mm hole then use a 1 mm slitting disc to do 2 cuts ending up at the hole.
If you have a bench shear available you could drill as above but shear upto the hole.
If the slot wasn't critical I would make a template/ jig and plasma the slots.
If I was gearing up for production and didn't want to outsource it I would fork out for a slot punch and die or utilise an existing one and use a press of some sort (Fly/Ironworker/Mechanical type not a garage press).

 

[Northumbrian]

What tools do you have to hand?
Knowing that might help others come up with more suitable suggestions on how to proceed.

 

[Wightsparks]

Good idea.
TCT chop saw
4.5 and 9" grinders
Drills
Bench drill

The hole and cut idea is a good one thanks

 

[Northumbrian]

I'd use the bench drill, and setup some stops, that way I could carry out one hole at a time, but in the same place on every single piece.
Then move the stops, for the next hole etc.
Not the fastest way, but with what you have...

 

[Wightsparks]

What about a 5mm milling bit in a low speed mains drill. Mounted upside down through a table hole - like a router table. With a guide on the top. ?

 

[Kent]

Re design it or find someone who is kind enough to lead you the use of thier milling machine. Failing that drill two holes and get a cutting torch or plasma on them. If it was just a couple I might chain drill them and file up.

 

[Wightsparks]

I have re-designed it - from a V shape to a 3mm slot easily cut with a 3mm cutting disk - then I discovered that the galvanising means that slot needs to be 5mm wide and hence the problem!

 

[Wendelspanswick]

What about a 5mm milling bit in a low speed mains drill. Mounted upside down through a table hole - like a router table. With a guide on the top. ?

No chance, you need rigidity and pressure to mill and your not going to get that with a drill and hand feeding.

 

[Revs1972]

I have re-designed it - from a V shape to a 3mm slot easily cut with a 3mm cutting disk - then I discovered that the galvanising means that slot needs to be 5mm wide and hence the problem!

Most galv will be around 50-80 microns on steel of that size
Why do you need to go 2mm bigger ?

 

[Wightsparks]

That was exactly my question too! http://www.mig-welding.co.uk/forum/threads/rust-proofing-dip-plating.69793/#post-963802

 

[Revs1972]

I have had a read of that, and yes you can get that surface tension happen, but then if you don't , then you will end up with near enough 5mm gap
If you do go along those lines, then make 5-10 more because they will inevitably lose some in the bath (they can lose whole beams sometimes)
Apparently it can be quite interesting to see what they pull out when cleaning the baths.
Have you thought about zinc spraying / powdercoating ?

 

[Wightsparks]

Yes I looked at it - 10-20 times the cost, which on 40 of them (x 4 slots on each) makes it prohibitive. The exact gap is not crucial it just locates the corners of the frame on square tubes. As a solution appropriate to the cost of the finished item is proving elusive I may stick with the V or a 3mm slot and file/touch up if required.

Thanks for the tip @Revs1972 - I shall be sure to count them in and out!

Thanks @Wendelspanswick won't bother with that then. - You did however prompt me to grab a bench shear for a tenner that just appeared on our local classifieds - just too late for this project but sure it will come in useful.

 

[Wightsparks]

I solved this with the TCT (and yet another blade!) by jigging and cutting all 80 bars both ends with an 11mm slot, then changing the angle of the blade to 20degs and re-jigging cutting another 160 cuts to make 11mm V's with a 4mm gap at the top. Total cutting about 40 mins plus 10 mins each jig.