The Dimple bars work great. I have a few and think they are great. I use these inserts in the ones I have. CCGT060202MP-CK PR1425 These inserts are by Kyocera but fit the Dimple bar really well. I have the 10mm shank dimple bar , and the 8mm shank bar, that both take 6mm series insert. These have a small 0.2mm nose radius and are very positive and sharp cutting geometry. Will cut all material, even ball bearing race ways. I also brought an external holder to use these same inserts for OD turning.

The only other option I think for boring bars are the vibration dampened bars from people like Sumitomo Corp, and others. They have a Carbide weight that floats around near the head of the boring bar, and cancels out a lot of the vibration, but they are quite pricey. The moving weight type are also made by Kennametal ,and Sandvik, or used to be anyway.

Neil

It depends what size you want to go down to, Iscar do some very nice small tooling in their Picco range and their small insert RH and LH boring/threading bars MGSIR/L are available in 6mm and 8mm, for bores of 8mm and up the Cham-Groove tooling has a wide range of tip profiles for boring, grooving, back-boring and threading with MGCH bars accepting both left-hand and right-hand tips.

– Nick

That's them Muzzer, I have them at work also, but in the larger sizes. The through coolant of commercial machines is nice, but at the same time, don't want to be showered in coolant at home. In the smaller sizes I like the CC style inserts, in the larger I like the DC style inserts and the TN style for roughing in the larger bars, ie the 32mm and 40mm shank bars.For Home I have the small ss inserts, the TNMG16 as a std oiuter turn tool, and the DCMT11T3 inserts for outer turning as well. For jobs where the work piece is like a bell and sings, then I like to use in those cases the tools with the active vibration dampening, ie the ones with a floating weight. Regular steel bodied tools can be dampened by drilling a hole and fitting a loose piece of carbide in the hole. So a 5mm hoe is about right for a piece of Ø3/16 carbide piece. The carbide slug wants to be big enough that when it vibrates it makes the bar sound dead instead of ringing. For boring bars, I make the hole no more than 50% of the area of the boring bar, and plug it with a brass plug. This can also be done to external tools as well, and is good when you have tools sticking out a long way, and a work piece that is likely to be vibrating itself. Work piece harmonics and cutting tool harmonics is an interesting subject all on it's own. Neil

Interesting, Danny. Do you have any idea of the price?

Roger

I buy what I can as making things takes time. Not retired, I would rather just buy and use it. I only make special tools that are not available, like a threading tool to cut M5X 0.5 pitch thread that goes into a 45 deg cone, it is only 0.4 mm wide at the business end.

Neil

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Thanks for the link, Danny … They do look rather good

I do, however, find this little warning note [whilst perfectly reasonable] rather scary:

… It's a very fine line between reaching "the center line of a workpiece" and crossing it.

As illustrated; one gives a perfect hemisphere, and the other a ruined tool and maybe a ruined job.

MichaelG.

Danny

You might also have a look at Micro 100 small carbide boring tools.

Catalogue: http://www.micro100.com/catalogs.htm

Quite a few on eBay USA, some of which may be suitable for you. Not sure how the price compares to Mitsubishi, though.

Dave
The Emerald Isle

Michael, I have found the same applies to any size finely ground carbide tooling, solid or insert are both likely to chip on the cutting edge with even light reversed cutting forces as would be the case by going beyond the centre of the bowl shown.

Emgee

Mike G, The same applies to any turning tool that is rubbed from the reverse. It is worse on a inner sphere as described, you have the work piece acting as a lap over the cutting edge. The above refers to only a solid turned sphere. If there is a small hole or if the bottom of the sphere is formed some other way it is ok. The problem with any small tools is the very centre of any part. As it has zero surface speed, it can only be removed by deformation or by the chisel effect. Very small tools are just not that strong in their geometry and by their nature are weak. That makes them very susceptible to centre line height setting. Often when boring having the tool slightly above centre height is an advantage as the loading of the tool, then deflects down and in doing so reduces very slightly the cutting load. When the tool is exactly on centre line, when it deflects down, it will take a very slightly bigger cut. When it is set below centre line, it will have the tendency to be digging in and taking cuts big enough to either damage the tool, or leave a very poor surface finish. So with small tools, the more rigid the material the tool is and the lighter cuts makes for the tool lasting a long time with good surface finish. Cutting fluids that promote the shearing of the material, ie reduce cutting forces, help a lot as well. On small stuff, I keep the corner radius to less than 0.2mm or 8thou. On micro bars, less than Ø3mm diameter, I have the tool radius at 0.1mm or 4 thou. This allows at a 1 thou per rev feedrate to get accptable surface finishes. If I need a very good finish, I hand feed at about the 0.01mm per rate approx. So when the spindle is doing 600 rpm, I feed the main hand wheel so that I do 1/4 turn every 7 seconds, or 1 rev in 30 seconds. This is for the 0.1mm nose radius tool. With .2mm radius tool it is turning the hand wheel 1 rev per 15 seconds, or 4 revs per minute. The myford box does not allow 0.001 inches per rev feed rate. It takes time to learn to turn a handle at a feedrate, but is really worth while to learn.

How do I edit a post and correct spelling?

Sorry Michael, oh well no more shortening of names from now on.