Mag drills

[fizzy]

Just treated myself to a Rotobroach Puma. Nice bit of kit and nice to buy something British.
Some questions on use.
Is there any need to drill a small pilot hole?
Also regarding coolant.
All the videos I have seen you can see loads of smoke and hot chips flying around. I used soluble cutting fluid 10:1 with water sprayed with a plant sprayer. I got no smoke or any signs of heat. Are they supposed to run hot? Am I over cooling?
Finally is it safe to use the cutting fluid in the supplied fluid bottle?

 

[madwelder]

Personally I always drill a pilot hole, helps guide the drill all the way through the material. Using coolant will prolong life of your drill bits and I would also recommend always using it, especially on stainless steel which will work harden if you get it too hot.

Hot swarf and steaming coolant are pretty much a given whatever you do. Coolant should also be fine straight from the bottle it comes in.

Hope this helps

 

[dan.taylor.1]

Just watch, if you drill too big of a pilot the pilot/ejector pin doesn't push up and can block the coolant coming through the middle so you'll cook your cutter, also makes it a pain to get the slug out of the middle!

I've never bothered tbh, never had mine wander yet!

I always use soluble cutting fluid in the supplied bottle as it clips to the drill on mine, don't run it without something, even a spray of tapping fluid/foam as they blunt easily.

Mine nearly always throws 300mm long spiral swarf about when cutting right, just don't let the cutting edge sit on the steel with no downwards pressure as again this will blunt it. Very useful tools imho, mines payed for itself in two jobs!!

Dan

 

[wyn]

I just line the pilot up on a chalk mark...or if it's a bit technical a centre punch mark. I think drilling a pilot hole is sort of missing the point of what broaching cutters are for.

 

[Hitch]

A decent sized centre dot, surely there is no gain by drilling a pilot hole, except doubling the time it takes to drill the holes.

Cutting oil, we don't use the bottles, just use aerosol cutting oil. Mainly because we tend to use them on their side quite a bit.

 

[fizzy]

Thanks for the replies. I haven't seen steam or smoke so maybe I am running too slow or just because I am using a big flood of lubricant.

I will try without a pilot drill. When I did use one I drilled the hole and when I saw the slug the pilot was off centre anyway!

Anyone know of a cheap 40mm cutter?

 

[zzr1200]

What's the point of drilling a centre hole being as the centre pin is only pointed and not a drill, anyway if the hole is too big the pin will not push the slug out of the rotabroach cutter.

Centre punch the holes middle, the more cooling the better, cold cutter/drills will last longer.

The only time I use a pilot drill in my mag drill is when I am actually using a large drill bit (16 to 32 mm dia) to drill with, even then the drill bits will be of morse taper type.

Regarding rotabroach cutters, I always try to buy 50 mm length or longer, just keep an eye on fleabay (it does have its uses).

 

[dan.taylor.1]

There's a job lot of 40mm on eBay atm mate. They pop up brand new from time to time, that's where my 5quid batch of 3 Rotabroach cutters came from!

Dan

 

[Hitch]

Pumas run a bit on the fast side for 40mm bits really.
Push harder to slow it down a bit

 

[fizzy]

2 other questions

What is the biggest holesaw I can use in it? Can I use something like an 80mm ish size? Will it run too fast?

And is it normal for the drill to be very stiff in use? I was expecting a nice sprung action like a pillar drill but there is almost no feel to it.

 

[Jim Davey]

The dovetail slides have to be pretty tight or else the broach will chatter as it cuts risking damage to the teeth or breakage to the cutter itself. The dovetail usually has Allen screws or bolts to allow periodic adjustment to account for wear in the slides.

 

[wyn]

Rotabroach quote the max size cutter for a puma is 30mm.
You could go a bit bigger maybe but it gets close to the magnet and all the swarf jams up.

The gib strips are adjustable but it'll probably free off a bit with use and get too slack. The cutters then chatter and it can grab a bit when you first start cutting....enough to overcome the magnet and the whole drill goes shooting off to one side.

 

[fizzy]

just realised it is the Panther I bought DOH - takes up to 40mm!

 

[Dave Richards]

Same as other guys on here, centre pop, and ct90 aerosol spray just to protect the broach.