alan2525

I'm currently having a play with milling some small parts and am looking for cheaper alternatives to 1mm slot drills...

...last night I decided I'd just check I had the right cutter for the job in hand and was just putting a 1mm carbide slot drill back in it's tube and putting the piece of foam in the end to stop the tip rattling around and breaking...

...little did I know that the other end of the tube wasn't pushed on...it slid out, quite slowly and slow enough for me to notice but too fast to do anything about it...anyhow it landed on the floor with a thump and thinking to myself...did it land on the 1mm tipped end, I then heard a little..."kerplink" sound of the broken slot drill ricochet across the room and bounce off the wall...

After about half an hour of muttering general expletives and assorted four letter words to myself...it dawned on me is there a cheaper alternative?

Can small diameter carbide burrs be used to machine and engrave various plastics such as High Impact Styrene and Acrylic?

The main problem seems to be chip removal and having enough extraction to prevent chips from building up on the tooling and generating heat...I'm imagining a rasp would be pretty hopeless as even the purpose designed slot drills have a tough time. But as I'm cutting out very thin sheet like 0.5mm and 1mm maybe it would work reasonably.

Failing that does anyone know a good supplier of Carbide Slot drills approx 0.5mm - 3mm diameter with a 3.17mm 1/8" shank.

__________________

Bunkerbarge

I think burring tool tips will clog with most plastics as you rightly say due to the fact that the chip does not break. However with some high impact plastics which are quite brittle it may just work. The trouble is that the heat generated with machining softens the plastic and the chip stops breaking again. Maybe a good supply of coolant will help?

At the end of the day you can but try.

These are a couple of good tool suppliers that may be worth a call for the tips you are after:

http://www.chesteruk.net/

http://www.chronos.ltd.uk/

http://www.maccmodels.co.uk/

http://www.theengineersemporium.co.uk/index.html

__________________

“Dirty British coaster with a salt-caked smoke stack, Butting through the Channel in the mad March days"

alan2525

After emailing around a few places I found this site:

http://www.chilterntooling.com/shop/17/index.htm

They have a massive range of HSS and Carbide tooling in sizes from 1mm upwards and I found some economy cutters for about £3 rather than £25 a shot.

I haven't got the faith to use a £25 1mm slot drill so I'll see how I go with the £3 jobs first! Obviously you get what you pay for in this world but in styrene I imagine / hope they should work just as well.

__________________

kevingambrell

why on earth are you using carbide? go to tools steel/hss or make your own from silver steel, save your self a fortune.

I cut everything from gunmetal to cast iron to nylon and never use carbide. I only go to caride if its specified in the job or im on a lump of stainles steel .

My CNC machines run tipped tools but thats another task all together.

Plastics just dont need tipped tools and especialy in that size. what feed and speed are you using?
by the sounds of it too much of both, set the feed and speed to the material your working on. Also consider running coolant to help prevent the plastic plasticising around the cutter.

all the best kevin

alan2525

I'm using carbide as that seems to be all that's available in the sizes I was looking for and the size of shank for the machines collet.

It's also the tooling that Roland Supply, and using the recommended spindle speed and feedrates.

Can you recommend any Suppliers for 1mm - 3mm slot drills?

Also regarding making my own slot drills...I think it'd be easier to just buy them.

-----


... we're using some new tungsten carbide drills for the preliminary coal-face scouring operations.

Oh that sounds nice, dear

... Tungsten carbide drills! What the bloody hell's tungsten carbide drills...

__________________

kevingambrell

Alan
Im seriouse try dropping the speed and feed.

I buy all my cutters from Horley Drill services, Yahoo them and youl find them. prices are good and what they dont know dont count.

making small cutters is no problem, if you go for single flute it can be done with a file in silver steel and then just harden and temper the bit.

kevin

alan2525

I think I'll see how I get on with the Micro Carbide Slot drills. I think producing my own and heat treating them myself would probably work out more expensive than the £2.58 each I paid for the bought items. I'd also be a bit concerned about cutting the flutes precisely enough to get any degree of chip clearance.

One of the benefits of HSS is the relative ease in which tooling can be sharpened, but in sizes as small as 1mm - 3mm it's probably more economical to just buy disposable cutters and carbide still keeps it's edge longer than HSS.

I know Carbide bits are much easier to break than the HSS equivalent, but in smaller sizes breakage is always going to be a possibility, although I have used some supoposedly carbide tipped tools in a router where the brazed on tips themself have bent.

__________________

Bunkerbarge

Lets see if John thinks that an "Engineering" forum is a worthwhile addition and we can put some of this usefull stuff together for the benefit of others.

This could include all aspects of machine tool operations, techniques for making parts for all models, steam, safety etc, etc.

__________________

“Dirty British coaster with a salt-caked smoke stack, Butting through the Channel in the mad March days"

alan2525

The Roland EGX-300 Engraving machine I'm using has a hollow spindle, the cutters it uses are approx 100mm + long and when installed the shank protrudes through the top of the spindle.

Cutters are held by a lower collet fitted with a grub screw which clamps the shank of the cutter, there is also a small brass collar which attaches to the other end of the tool and is used as a depth stop to allow tools to be changed keeping their depth setting.

The problem is, the purpose made tools have a very long shank and are expensive at approx £25 + delivery for a 0.5mm carbide slot drill. I've now used a 1mm slot drill and it works great but I'm a little aprehensive about shelling out £25 for a tool which will break.

Could a longer shank be brazed onto a carbide cutter?

I'd have to source the rod the required diameter, 4.36mm or alternatively I guess I could use an old tool with a 4.36mm shaft.

Any advice on brazing carbide tools?

The load on the tool would be carried by the lower collet with the brazed on part purely as a means of attaching the depth stop collar.

__________________

Bunkerbarge

Alan, as with anything like this you don't know until you have a go. Carbide tips are often braised onto a steel shank but I couldn't tell you what the rod consists of. I would ahve a look at the big welding rod manufacturers sites such as Unitor in the Marine world and see what type of rod constituent would be suitable for such a joint.

__________________

“Dirty British coaster with a salt-caked smoke stack, Butting through the Channel in the mad March days"