Final (?) design for tangential holders for my Boxford (Southbend clone).
Pure Lathe work
The one shown takes 4 mm toolbitts (Because I had two 4 mm bitts ) .
Body is milled in the lathe.
Two round holes and wedges are lathe work.
The tool cuts 3.5 mm deep in mild steel,makes blue chips and everything OK.
Prototype was made in 3.5 hours .
Next takes less than two.
Have made and used three types of holders.The easiest to make is the uppermost.Toolbit slips when going gets tough.
The middle one was inspired by an Australian device and can be made with a milling maschine.Mine is showing weakness in the grip area and this indicates need for a better material and heat treatment.
The lower is by far the best but I need the good will of my wirespark-er friend to make it.
Not everybody has access to such things.
The lower one gets some 5 mm square tool bits from Fagersta WKE 45 and easily eats silversteel with a depth of 4.5 mm and a feed of 0.003 inch per rev on a Boxford lathe
Next test is to try to repeat that with a carbide stick but much faster.
I was given a stick of solid carbide by a friend at SMEE to use in my Tangential tool. It works fine but does need a noticeable radius at the working corner to prevent chipping it.
He, the friend, uses his to turn the case hardening off gearbox shafts so that new inner tracks can be fitted with new bearings. It seems that modern gearboxes have bearings running on bare shafts, which soon wear out! Progress, yer right!
My first carbide test went wrong exactly because the corner radius was to small.
Another reason was that when tool bit is canted 15 degree as shown the side clearances are 12 degree which is way to much.
I am making a new holder where tool tilt angle is 12 degree giving 9 degree clearance angles.
Carbide inserts normally are working at 5 to 7 degrees clearance but going steeper still than 12 degree for the tool is next to impossible if I want to keep a Small toolbit-section stable and that is the whole point of the exercise.
Another strategy can be to facet the cutting edges ever so sligthly as shown.
Your Emco is no match for my Boxford on the Rock,but if You care to measure the distance from top of compound slide to centerline You can borrow the second best of my holder family and try for Yourself.
I've been watching this thread because I bought a tang. tool here in Oz when I first started machining 10 years or so ago (found brazed carbide wasn't the best option) and used it almost always. Then I started to learn how to sharpen and shape HSS tools and now it spends time in the cutter tray. It still gets used but not as often and I still have some carbide tipped tools but usually to rough down a large lump close to size then out with the HSS tool. The main reason I bought the tang. tool was the ease of shapening and I could use round stock as well though I haven't as yet but may try some after reading this.
I see the main advantage in the stiffness.Compare the loadpath from tip of carbide stick to top of compound slide.
The homeground carbide did 4.5mm deep and 0.003 feed at 1000 rpm on some 100 mm scrap iron yesterday.It still looks and cut as a new insert.
I do like the lathe,but I am to old to divorce my Boxford.
Are the bedways hardened?
The crossslide with lot of T tracks would be handy on a Boxford also.
You can borrow a tangential holder from me but You will have to remove cirka 2 mm from underside.Putting the toolbit 2 mm lower is not enough for clearance reasons.
Latest design for a tangentialholder using 4 or 5 mm square toolbits of carbide or HSS.
It was tested yesterday and works very well .The idea is that the block can be any kind of banana iron and the pull in thing is made from a 12.9 quality Allen bolt.
This is as strong as any unhardened steel normal mortals can get.
The tool fore and aft angle is 12 degree giving clearance angles around 8,5 degree for the cutting edges.
My wife is ill so I go to the workshop and improve the design to ease my mind.
Going commercial is not an option for the time being and the uppermost model is very easy to make Yourself.
It is not a heavy duty thing compared to my favourite version but still very good.
It eats 3.5 mm wide swarf at lowest axial feed of my BoxRock.If I try to up feed it chatters and lower tool and my favourite pull inn thing do not.
Your Myford has not power enough to go into that country.
Let us make a design exercises for a suitable 12 degree holder for a Myford using 4 mm square bits.
Measure height of centerline over compound surface.It is 25.14 mm on my Boxford.
Put a piece in the lathe and turn it round and measure diameter and divide by 2.
Remove toolholders and and put top of compound slide under Your round thing and use feeler gauges to measure the missing distance.Calculate the wanted dimension.
Non Myford or Boxford owners are welcome to join the game.
I made a couple of tangential tools by brazing a stub of stellite onto a steel shank which was milled at an angle on the end to receive it. They work fantastically well. I've just about worn one out and the other I gave away but I'm making a few more shortly.
Have become Stellite/Tantung addicted and like to show my sharpening procedure.
It cuts very well and fast for a long time without the cooling water mess.
Carbide can do the same but is not quite so easy to regrind.
First picture is my present bid for the ideal amateur cutting tool.
Name is TanTool, very original.
The Tantung 4.76 mm bit is tilted 12 degree giving 8.5 degree clearance on cutting edges.
Top of block is exactly on lathe centerline making adjustment easy.
One of the bit edges is rounded as shown.
The rake is ground using the TanTool as holding tool.
I find that the fore and aft rake angle is not that important .20 degree looks fine to me and cuts well.
A little top honing is not harmfull and easy to do.
The 8.5 degree clearance angles is really to much.Something like 5 to 7 degree makes tool edge everlasting and as I do not cut/feed very aggressively it is OK
Facetting is done as shown and last picture is ready to cut.
Regrind ca 2 minutes and a new one ca 5 minutes.
Regarding the holder shown in the pic in the reply immediately preceding this one, I gather that it offers the most rigidity/stability of the different designs discussed in this thread. Obviously it requires an EDM to make the square hole in which the HSS sits.
Just wondering, on behalf of those of us who have mill and lathe but no EDM . . . what if one made a circular hole instead of a square one? Granted, it wouldn't be as nice as one which secured the cutter using all four sides. But one would have two sides (as milled into the main/biggest piece) plus the opposing edge of the cutter by which to grip it.
In other words, the HSS cutting piece would contact the main body of the holder on the usual two sides as always (darkened sides in crude drawing) and the pull-thru piece of the holder would contact the cutter at one point/line (darkened dot).
Very interesting and sent me thinking.
Start make parts as shown,put in a good quality bit,give it a real fore and aft pressure and make all the nice clearance milling-gs afterwards.And please tell us how You improved the procedure?