[chola]

Hi :wave:

I know this is one of those questions that will probably generate the responses that go like, "why would you want to" and "just use the proper tool", but it also falls into the category of,"I'm curious and just want to know"!

While going through the local hardware store today I noticed some straight router bits (for wood routers) - not the usual router types with all sorts of bevels etc, a closer look also showed the cutting blades / edges are Tungsten Carbide (same as the replacement tips on my lathe cutters). I got to thinking :idea: these would be a great way to generate a perfectly round hole in alloy on my mini lathe (coz we all know drill bits aren't round right and reamers and ridiculously expensive). Eg: If I want a 7mm hole, drill out with 6.5 then finish off with suitable router bit mounted in the tailstock. Obviously this is subject to the router bit being the same as the required hole. Also of interest was the fact this same style of router bit went right up to 40mm.

Question is has anyone used these before to go through alloy, or is there some reason why it wouldn't work (after all is same material as the lathe cutting tools). I personally cannot see any reason why not if suitable speed and feed is used, along with cutting fluid.

Just a thought?

Thanks for any info.

COlin

[Geof]

Hi :wave: ...I got to thinking :idea: these would be a great way to generate a perfectly round hole in alloy on my mini lathe (coz we all know drill bits aren't round right and reamers and ridiculously expensive). Eg: If I want a 7mm hole, drill out with 6.5 then finish off with suitable router bit mounted in the tailstock. Obviously this is subject to the router bit being the same as the required hole. Also of interest was the fact this same style of router bit went right up to 40mm.

Question is has anyone used these before to go through alloy, or is there some reason why it wouldn't work (after all is same material as the lathe cutting tools). I personally cannot see any reason why not if suitable speed and feed is used, along with cutting fluid.

Just a thought?

Thanks for any info.

COlin

To answer your last questions first:

It may be carbide but it is not necessarily the same type and grade as used on lathe tools; probably is not, routing wood imposes less shock loading but is more abrasive so a more brittle but abrasion resistant grade may be used.

But they can cut metal; we use corner radius carbide router bits up to 1/2" radius for putting a radius on aluminum parts in the mill. But this is at speeds completely unattainable in a little lathe, 1300fpm, and flooded with coolant. Our experience is that they cut best going as fast as possible and last a very long time on aluminum.

Regarding using a straight cutter for making a hole from the tailstock; probably not feasible.

This is because the tailstock has almost no sideways rigidity. When it is holding a drill there is really no side load. The drill follows its own hole, if you start it on center it pretty well stays on center. Reamers follow the drilled hole, again no side loads. Also both these tools have minimal or no clearance immediately behind the cutting edge; that is why they follow their hole they are guided by rubbing here.

A straight flute router bit in the tail stock will almost certainly dig in unevenly and chatter around horrendously making a very rough and oversize hole. These cutters do have clearance behind the cutting edge so if they are not held very rigidly they will dig in.

Possibly if a holder for the toolpost was made to hold the router cutter perfectly on center and very rigidly they might work. But then you might just as well bore the hole to size.

[chola]

HI Geof,

Thanks for the detailed answer.

I can only imagine the noise of a router cutter going that fast through alloy!

I actually thought about the clearance and chattering problem problem you mention - admittadly after I wrote the post!!. I have drawn a quick pic of my solution. Again this is all in theory, but if the tip of the bit was ground in such a way it would 'self-centre' it may work - the pic on the right shows my thoughts. WOuld definately need some kind of self-centering feature as I wouldn't trust the tailstock on my mini lathe to be dead on.

Thanks again for the input.

COlin

[Mcgyver]

I've never found reamers to be that expensive, at least compared to router bits. Reamers are nice because the easily and quickly get you decent dimension accuracy. if not abused, a good reamer will last a very long time. reamers also will produce a non-round hole (depending on how fussy you want to be) and drill bits, if ground properly can be surprisingly accurate. However if a round, accurate bore is the desire, use a single point tool (boring bar).