Miniature lathe boring tools

[David Morrow]

I've been working with carbon fiber (CF) for a recent project and needed to bore out a hole of about 1/4" diameter. CF can be really hard on tools so I bought some diamond cut burrs for my CNC router. When I needed to more accurately bore the final hole dimension, I found that not only did I not have a good tool for CF but nothing small enough for the smallish hole. So, I made a small holder for a 1/16" diameter burr with a piece of 3/8" diameter aluminum rod and a small set screw to hold the cutter. I mounted that in my boring bar holder on the lathe and went to work. It worked beautifully.

That got me to thinking about similar boring issues that come up from time to time in aluminum and brass. So, I took a single flute end mill and mounted that in the holder that I made for the burr and mounted that on the lathe and put a bit of scrap aluminum in the chuck. For those not familiar with single flute end mills, the working end bears a surprising resemblance to a boring tool. The single flute end mill did a great job on both the aluminum and the brass. Not a perfect finish but very good. While I was at it, I faced the bit of aluminum and it came out beautifully. I have a lot of 1/16" diameter single flute cutters and they will allow me to get into some truly small center holes on the lathe. Not for really deep cuts but I did test them past 1/4" and they worked just about perfectly. Just take very light cuts with the smaller cutter. If you want really small accurate holes, try this. You can buy them online for just a few dollars. I get mine from Drillbits Unlimited but there are other places out there as well.

 

[GailInNM]

I have done the same thing using 2 flute end mills down to 3/64 diameter to bore 1.5 mm diameter holes to a a depth of 2.5 mm. I am sure that the single flute end mill would give more chip clearance but it was not a problem for me. I did relieve the side cutting edge of the end mill before the spiral of the second side of end mill came around to the cutting point so therre would be no rubbing of the cut.

 

[David Morrow]

Gail, did you use the cutter like a drill or reamer or as a boring bar ? I ask because I also have some really large end mills that I use to hog out large holes in aluminum. But, with these single flute cutters, I used it like a boring bar with just that single point of contact and the tool on a slight angle taking multiple passes.

 

[GailInNM]

I used it as a boring bar. I did not set it at an angle as the spiral of the side cutting edge generates the clearance needed behind the point. I did relieve the second side cutting edge so it would not rub the cut when the cut was deeper than half the pitch of the spiral.
For the 1.5mm diameter I used a 3/64 2 fllute carbide end mill with an 1/8 inch shank. It had a chipped point on one flute. I have a home brew gang tool mount on my CNC lathe with 3/`6 tool mounting holes. I made a sleeve for the 1/8 shank to fit the 3/16 hole. After reliving the damaged cutting edge I Loctited the cutter into the sleeve. As I am visually impaired I used a microscope to set the cutter cutting point to the to be horizontal while holding the sleeve in a small insert vice then milled a flat on the sleeve so it would be orientated correctly when mounted in the gang tool holder. After mounting in the lathe I checked the center height of the cutter with a dial test indicator and everything was ready to go.

 

[SmithDoor]

Any time I have very small hole to bore I just a low cost drill bit.

I have also used taps for single point threading just grind off the most threads on tap.

Dave

I used it as a boring bar. I did not set it at an angle as the spiral of the side cutting edge generates the clearance needed behind the point. I did relieve the second side cutting edge so it would not rub the cut when the cut was deeper than half the pitch of the spiral.
For the 1.5mm diameter I used a 3/64 2 fllute carbide end mill with an 1/8 inch shank. It had a chipped point on one flute. I have a home brew gang tool mount on my CNC lathe with 3/`6 tool mounting holes. I made a sleeve for the 1/8 shank to fit the 3/16 hole. After reliving the damaged cutting edge I Loctited the cutter into the sleeve. As I am visually impaired I used a microscope to set the cutter cutting point to the to be horizontal while holding the sleeve in a small insert vice then milled a flat on the sleeve so it would be orientated correctly when mounted in the gang tool holder. After mounting in the lathe I checked the center height of the cutter with a dial test indicator and everything was ready to go.

 

[Badhippie]

Hello
If you are looking for miniature tooling this is a place I have used. Harvey Tool
Harveytool.com They have miniature cutting tools and tooling
Thanks
Tom

 

[ChazzC]

Hello
If you are looking for miniature tooling this is a place I have used. Harvey Tool
Harveytool.com They have miniature cutting tools and tooling
Thanks
Tom

Curiously, their larger diameter boring bars are significantly more costly than the tiny ones:

https://www.harveytool.com/products/boring-bars

While the longer bars would require more machining time and use larger blanks, you'd think that they would have a higher rejection rate from a 0.031" Ø bar than a 0.360" Ø bar.

McMaster also carries miniature tooling:

McMaster-Carr

While McMaster's bars also cost more as they get larger, not to the same extent as Harvey's; also, the really small ones do cost more than larger ones of the same style and with the same shank diameter. McMaster can also sell you a boring bar that will work in a 0.015" Ø hole.

 

[SmithDoor]

Looks great
But did see price.
This why I just use drill bit. It on hand and low cost.

I do like boring tool now if price was better it would fantastic too..

Dave

Curiously, their larger diameter boring bars are significantly more costly than the tiny ones:

https://www.harveytool.com/products/boring-bars

While the longer bars would require more machining time and use larger blanks, you'd think that they would have a higher rejection rate from a 0.031" Ø bar than a 0.360" Ø bar.

McMaster also carries miniature tooling:

McMaster-Carr

While McMaster's bars also cost more as they get larger, not to the same extent as Harvey's; also, the really small ones do cost more than larger ones of the same style and with the same shank diameter. McMaster can also sell you a boring bar that will work in a 0.015" Ø hole.

 

[Badhippie]

There is also micro100.com but I believe they are a branch off of Harvey Tool. But it’s something for you to look into
Thanks
Tom

 

[kwoodhands]

I have ground an allen wrench , the short leg for a boring bar.
Works well. I ground it like a carbide tipped one . I used it on both steel and brass .

 

[L98fiero]

Curiously, their larger diameter boring bars are significantly more costly than the tiny ones:

https://www.harveytool.com/products/boring-bars

While the longer bars would require more machining time and use larger blanks, you'd think that they would have a higher rejection rate from a 0.031" Ø bar than a 0.360" Ø bar.

McMaster also carries miniature tooling:

McMaster-Carr

While McMaster's bars also cost more as they get larger, not to the same extent as Harvey's; also, the really small ones do cost more than larger ones of the same style and with the same shank diameter. McMaster can also sell you a boring bar that will work in a 0.015" Ø hole.

If you don't need the tool right away, AliExpress has solid carbide miniature boring bars at a fraction of the price, probably not the same quality but then there are few with the equipment that could run at the speeds required for the tools anyway. I don't expect them to have the life of a Harvey Tool boring bar but I've bought these for one off jobs that worked as expected.

 

[SmithDoor]

The only downside to AliExpress is need to have bar on hand as shipping takes 1 to 3 month's.

There a good chance the Harvey Tool boring bar from AliExpress but they have it in the USA.

Dave

If you don't need the tool right away, AliExpress has solid carbide miniature boring bars at a fraction of the price, probably not the same quality but then there are few with the equipment that could run at the speeds required for the tools anyway. I don't expect them to have the life of a Harvey Tool boring bar but I've bought these for one off jobs that worked as expected.