Ball turning using 50mm Vertex Boring Head for Lathe

[Chris MateParticipant @chrismate31303]

1-Decided to make a Ball Turning tool by using the MT-4 Boring head for lathe.

2-None of my boring bars are able to cut MT4 at 112mm stickout satisfactory, so decided to make a large boring bar from drill rod near 25mm thick as possible.
Using Tungaloy TNMG 160408-6 inserts I got for free a pack.
Decided to 1st Turn bar, make poket for insert, then experiment to find best cutting angle, then mill flats on bar to support that angle, guess its between 3-7 degrees negative from 9-Degree outside turning on lathe. I got a mirror vfininsh with these on lathe cutting the MT-4 outside sleeve/bearing from cold roll steel.

3-Today I made 4x bearing clamps(Yeollow) to hold round base of Trainrail V-Block in place as I can now easily turn it around to an angle.

See gallery for images till I figured out to post it here.

[Chris MateParticipant @chrismate31303]

 

file:///D:/Chris%20Mill%20Photos/Chris_train-Rail%20Milling%20V-Block2/CALL5269-BearingClamps_Paint.jpg

[Chris MateParticipant @chrismate31303]

https://www.model-engineer.co.uk/members/chrismate31303/mediapress/ball-cutter-50mm-vertex-boring-head-for-lathe/call5269-bearingclamps_paint/

 

https://www.model-engineer.co.uk/members/chrismate31303/mediapress/ball-cutter-50mm-vertex-boring-head-for-lathe/call5270-boringbar_paint/

 

Note:I cannot get the images to show here as before-?

[HuubParticipant @huub]

Nice job,

I would have chosen a small size insert so the locking screw has more support. Smaller size inserts are made for less aggressive cuts and the chip breaker will do a better job at modest feeds and speeds.

The larger the boring bar diameter, the smaller the clearance angle (side relief) can be.

For inner turning, I prefer a larger gap (side rake) between the stock and the insert for better chip evacuation so the chips don’t pileup so easily on the tip.

[Chris MateParticipant @chrismate31303]

Ok, I made 1st test cuts cutting a pype, not good material. See two photos added.

Note:Wild move=I clamped the boring bar thick round part in toolpost(Partially in) with two woodwork clamps till I milled the flats for permanent fit….It actually worked.

1-This boring bar has only max stickout, thats how it fits, no shifting around in toolpost. It can only cut through holes, no shoulder cutting, I do that with other boring bars.
2-To my surprise, I had to settle at Neg 12 degrees for bar angled to make the insert works. It cuts silent at max stickout this pipe. The cut feels very smooth, I am happy with this.
3-The bar may have a smaller diameter limit to probably larger than one would expect, I will see.
4-So I think I am going to mill the flats so it fits to toolpost and deliver the neg 12 Degrees tomorrow….and hope for the best at cutting the MT4 further to fit of MT4 Boring head.
5-If I am not happy enough, ….after some thought, I have a cheap other option(Way cheaper than a MT4 Reamer), that is to Cut a MT5, order a MT5-4 sleeve, and that way has a perfect fit for boring head, glue the MT5 sleave in bearing material(Bushing to be(Space thing compared to using beaerings)).

See two photos added:”Copy image location, instead of link location i figured out”

 

[DiogenesParticipant @diogenes]

Can’t your boring head shank be unscrewed and fitted with a straight-shank one?

[Diogenes]

On Diogenes Said:

Can’t your boring head shank be unscrewed and fitted with a straight-shank one?

Yes it can, but I decided I don’t want to take tools belonging together(Naturally for the fit like MT4 spindle) apart as far as I don’t have to, just a personal choice. THis is example where I don’t want to do that, nothing wrong with your suggestion, it did cross my mind initially, I also could not find to buy a straight shank to MT-4 sleeve, was told straight up “not available”..

[Chris MateParticipant @chrismate31303]

Boring bar completed, fitted to toolpost, test cut ok and smooth, no noises at full length extended. Now to setup lathe and cut the actual MT-4 to fit Boring head to barrel wich will become the inner part of of the bush for the Ball Turning Tool.

 

[Chris MateParticipant @chrismate31303]

Finished inner sleeve bush to be with MT4 bored and Boring Head -MT4 fitted.
-Needs to add a small washer/spacer with lockbolt like a drawbar.
-Add a handle.

–Make the outer bushing probably welded to a flat 20mm metal to fit in toolpost.
If this does not work out well, I just make a seperate toolpost for this.

[Author]

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