Bunkerbarge

I have just received my new Quick Change Tool Post from Littlemachineshop.com and what a lovely little piece of kit it is. No more messing around with shimming up tools now, I can't wait to try it out. Everything looks very nicely made and finished and the fit of all the moving parts feels precise and not sloppy. After messing around with a pack of feeler gauges to set tool heights up it is going to be such a luxury to drop a holder in and start machining instantly.

If anyone is interested in such stuff this shop gives superb service and their site contains all sorts of usefull info, manuals and hints and tips.

I also got a boring bar set to fit the tool post and a new set of tools. They also do spares kits for all sorts of mini lathes and mini mills so they are a usefull point of contact for a lot of machining stuff.

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

alan2525

Regarding feedrates for engraving styrene. I'm still having problems with chip clearance. What is happening is that along one edge of the cut there is a slight ragged edge which is curling up, the cutter then picks up that piece of styrene which wraps it'self around the cutter. The chips then have nowhere to go and build up on the cutter and quickly melt into a small blob.

Using a 0.5mm cutter and taking passes at 0.2mm per pass with the spindle speed approx 20,000rpm, feedrates on x and y at 2mm per second. Those were all the manufacturers recomendation.

Any ideas? Faster feedrate and a shallower cut so there's less time for the cutter to heat up and plasticize the styrene?

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kevingambrell

whats the profile on the cutter? and what rake on the cutting face? Or is it a carbide bur.

alan2525

It's a 2 flute carbide slot drill 0.5mm diameter

Bunkerbarge

Does your set up allow the use of coolant?

kevingambrell

coolant was my thinking and if memory serves i did put the idea forward a few days ago (could be a week memory faids). Id think about using water with a few drops of washing up liquid to a pint. Styrene has a low melt point and plasticises very easily. A .5 cutter just wont transfer heat up the shank that fast so you will get heating. Also 20,000 rpm seems way too high for the material but about OK for the size of cutter. Drop your feed and your RPM by 25% and 50%.

The slot drill isnt perfect for the job your doing. try taking an old blunt cutter and grind it into a single flute or a D bar with no rake. can be done on a cutter that small with a diamond file.

kevingambrell

Alan just a thought

If you want il make you a cutter, all I need is the shank size and the holder type. if your interested my email is kevingambrell@hotmail com

alan2525

I'm not sure what you mean by "D Bar" - is this the kind of cutter you are refering to?

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kevingambrell

thats the one, you could put a slight lead on the cutting face but no more than 1/2 degree and absolultly no rake, the rake will induce heating.

GEEDUBBYA

Howdy Guys,

Ok, I have been abit lax in keeping up with this thread since I began working really odd hours at work. However, I have made "ICT's" (Improvised cutting tools) lol on more than one occassion for my Dremel Rotary tool.
Now being a machinist, I have access to some tools most ppl wouldnt have, but, these little bits can be made with nothing more than a coat hanger wire small diameter steel rod, a file or bench grinder and a little patience.
My drawing below shows how to make a simple "cutting bit for a rotary tool" , and not having realized your problem with "chip clearance until just a minute ago, with a few minor alterations, these home made bits can be made with a "chip breaker" which is merely a small groove in the upper part of the cutting surface (along the shank of the "bit").
Please remember if this bit is to be used in a rotary type tool, the stock material needs to be as straight as possible...especially at high speeds. Otherwise you may be visiting your local Dr. to have it removed from under your skin. And as always, wear eye protection when using any cutting bits.
The "bits" I have built in the past have usually been made of drill stem material from broken drill bits, however, wire from a coat hanger will work for use on plastic. Brazing rods or welding rods can also be used if availible.



As I said, a "chip breaker" can be easily made by cutting a "notch" along the cutting edge of the Shank of the bit (right side shown in dark grey in drawing above, about 1/2 way in face of cutting edge).
As stated above, this is the same principal as used in making a screw self tapping, using a file or grinder, you merely cut away an area with a 90 degree face (for cutting metal). However, in a self tapping screw application, no chip breaker is required due to the threads of the screw preforming that function.

I hope this makes sense and if it does, I hope it helps.

Have a good day,

Greg