Lathe tool holder bit hole angle?

[Turnaround]

This question has to show what little I know, sorry for its kindergarden tech level. Years age, to assemble my retirement play shop, I bought a new 14 x 40 Harbor Freight lathe, round column, belt drive drill mill, and a bunch of "car body" fabricator sheet metal tools. Now retired, its time to make stuff. I bought about twenty Armstrong (and others) lathe tool holder, and a gang of Ebay, already ground tool bits from 1/4" up to gnormous. Problem is nothing works. My tool holders mostly have the bit's holes leaving at an up hill angle, which, when added to the relief angle under the cutting edge of all my ground bits, just too great to work. I have to wedge the tool holder down hill at ridiculous angles just to get a sharp edge against the c/l of the stock. It looks like I need tool holders that have their cutting bit holes horizontal, not up hill. What in the world are all my uphill bit tool holders for? And where can I get horizonal tool holders?


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[RandyM]

Please post pictures of your set up it would be of great value to answer your questions.

 

[Charles Spencer]

Please post pictures of your set up it would be of great value to answer your questions.

Sure would. Could be the lantern tool post is too small, the rocker is incorrect, etc.

A quick solution would seem to be to grind the tool bits so that the relief angle is correct.

 

[wa5cab]

Turnaround,

It is my understanding that the reason for the design of the Armstrong style tool holders was to provide top rake with little or no grinding on the top of the cutter. Which is the hardest surface to grind without grinding your finger tips. From your description of the problem, I surmise that all of the pre-ground cutters that you've acquired were ground for use in either a 4-way turret or in a quick change tool post holder, both of which hold cutters horizontally. So your solution, rather than regrinding all of your cutters, is to acquire one or the other.

Between the two types of tool holder (turret and QCTP), given today's availability of cheap chinese QCTP's, that's what I would go with. 35+ years ago when I bought my lathe, the QCTP I bought after a week of fighting with the lantern type with the Armstrong style holders cost me the better part of a week's salary. Today, the numerical amount of dollars is about the same. So they're nearly dirt cheap by comparison.

With a 14X40 lathe, you will probably need the BXA size (from smallest up, they come in 0XA, AXA, BXA, CXA and maybe larger). The so-called complete kits (which are the cheapest way to acquire the start of a set) come with one only of each of the more common tool holder types. Be sure that you buy several extra of the Turning and Facing holders (may be called #201 or just #1). and a couple of extra Turning, Facing and Boring holders (#202 or #2). The reason is that any given turning job may require more than one cutter. If you only have one turning holder, every time you need to change cutters you have to get out the Allen wrench, remove the first cutter, install the second, and get it on center. Which takes several minutes instead of just lifting one holder off and dropping the next one on. At last count, I had 13 #1 and 4 #2 holders, most with a cutter in them, aligned and ready to go.

And if you ever decide to go with replaceable carbide inserts instead of HSS, get a #16 holder that holds inserts oriented such that they can turn to a shoulder (at least one that I've seen can't). They are pricey but It's my most commonly used holder.

 

[Charles Spencer]

Today, the numerical amount of dollars is about the same. So they're nearly dirt cheap

Ha! Reminds me that I told a younger guy that a cross peen hammer I had cost me $9.00 over forty years ago. I explained that was two hours gross pay for me as I was making $4.50 per hour. And I was making twice the minimum wage.

I agree that getting a QCTP would be much easier than regrinding your tool bits. Since you're likely to get one sooner or later it would also be easier than grinding them again to fit it.

 

[ELHEAD]

Ha! Reminds me that I told a younger guy that a cross peen hammer I had cost me $9.00 over forty years ago. I explained that was two hours gross pay for me as I was making $4.50 per hour. And I was making twice the minimum wage.

I agree that getting a QCTP would be much easier than regrinding your tool bits. Since you're likely to get one sooner or later it would also be easier than grinding them again to fit it.

And you still will need to learn to properly grind and set your bits to cut efficiently

 

[Kernbigo]

may not have a rock under it

 

[Bob Korves]

I agree with Robert's recommendation of a QCTP. I also recommend you keep your lantern stuff. Once in a while, they can get into a tight space that your other tools cannot.

 

[willthedancer]

The flat orientation tool shanks were for shapers and brazed carbide bits.

As said above, the angle buys you less grinding to get back rake on the tool. New bits are cut off at an angle to save grinding on the front clearance. That leaves you touching the front up, grinding side clearance and side rake.

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[RJSakowski]

The later edition of South Bend's "How to Run a Lathe" has a detailed description of the use of an Armstrong tool holder. I don't know what edition I have as the cover and front piece is long gone but I would guess that it is similar to the 1942 edition which is available as a reproduction for around$5 on Amazon.

IMO, the Armstrong tool holders have one advantage. They can get into tighter spaces than other types. To do so, though, they sacrifice rigidity. They are more difficult to set up as every time a tool holder is removed, it must be readjusted for proper cutting. Since going to to a QCTP, my Armstrong tool holder gathers dust in the tool box.