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Spindle Taper R-8 Cat 40

pbiebach

Plastic
Joined
Dec 11, 2009
Location
Victoria, BC Canada
I have been looking at various used mills on craigslist etc and see most are either R-8 or CAT-40 and I'm wondering what the practical differences are. Is tooling more readily available/cheaper for one?
I am new to machining and am approaching this from a hobbyist viewpoint, but quality is still important to me.

any tips/comments are appreciated

Thanks
 
I doubt it is CAT40 unless CNC machines.... Probably NMTB40..

MNTB40 is miles ahead of R8 provided the mill has the rigidity to handle the bigger tooling NMTB40 is caqable of handling...

In the typical the typical bridgeport with 3 3/8" quill diameter I doubt there is much advantage...
 
40-taper tools are larger in diameter and have longer tapers, both of which increase rigidity. Despite the shorter taper, R8 tools have longer shanks, requiring additional headroom to change tools. For quality drill chucks and collet chucks, pricing is similar for either taper.

As RC stated, Bridgeports have 3-3/8" diameter quills (85mm for the clones) for R8 tooling, whereas larger mills have 100mm quills for 40 taper tooling. Some machines have 85mm quills for 40-taper tools... kind of pointless, if not detrimental due to the unnecessary extension.

More info on tooling in this video: Crash Course in Milling - Tool Holding

-Sol
Glacern Machine Tools
 
Let's not forget that although the NMTB-equipped machines can usually take bigger tooling (and heavier cuts), they usually have the downside of slower spindle speeds. This can be a limiting factor when trying to employ modern carbide tooling or using small-diameter drill and end mills.
 
Sol said it, but to reword it for a newbie. If the choices are R8 or 40 taper, the 40 taper is probably just moving the tool holder further away from the spindle bearings. When you add in the effect of the longer 40 taper tool holders moving the cutting area even further away from the spindle bearings, I think the R8 would be better.

In a Bridgeport sized machine, there is sometimes a 30 taper option. R8 and 30 taper have the same gage diameter. The 30 taper has the advantages of positive drive tangs, rather than the easily sheared set screw, and the 30 taper is shorter, requiring less headroom for tool changes. The 30 taper is an improvement over the R8, and an Erickson Quick Change 30 is better yet.

Now if the 40 taper machine has larger diameter spindle bearings to allow the cutting area of the tool to be a relatively similar distance from the spindle bearings, the 40 taper would be an improvement. However, unless the rest of the machine is also beefed up, you will not get any advantage from the larger tool gage line. The series 1 Bridgeport is very appropiately sized for a tool with a 1 1/4" gage diameter, such as R8 or NMTB 30.

If you need a Bridgeport with a 40 taper tool, look at a Bridgeport Series II.
 
Some of the remarks above are generalizations that don't *always* hold.

I have a CAT-40 machine with a 6,000rpm spindle. (About a 4,000# bed mill - so bigger than a bridgeport, but not huge.)

I have another CAT-40 machine with a 12,000rpm spindle. (It's a 17,000# machine.)

40-taper tools are repeatable - meaning you can put the tool in, measure it's length (offset), take it out, put it back, and have it be in the same place.

I do not know if this is true of R8.

Seems to be me there are more choices of types of adapters for CAT-40, wider range of collet chucks, bigger face mills, extension shafts, etc.

That said, both cat-40 and r-8 are widely available, and to be honest it is likely everything you will ever really want to use on a bridgeport size machine will be available in both.
 
Manual, or CNC?

One thing that hasen't been addressed yet from the hobbiest point of view...

A full set of R8 collets are alot cheaper than a set of Cat40 tool holders, which is a big help for the hobbiest budget, on a manual mill.

However if you are looking at cnc mills, you'll never get it done with an R8 spindle, unless you can get the adapters to hold the tool holders. The R8 could work however, if you could run the program without needing to change tools.

Hope this helps,

Kevin
 
One thing that hasen't been addressed yet from the hobbiest point of view...

A full set of R8 collets are alot cheaper than a set of Cat40 tool holders, which is a big help for the hobbiest budget, on a manual mill.

Kevin

+1 ! ! ! ! ! !

I fully agree on all the points about tapered toolholders, whether they be 30 or 40 or CAT or NMTB. For a hobbyist, the startup cost on an R-8 spindle machine are going to be much lower. There are going to be more options toolwise/toolholderwise with the Cat40 machine. But if you're like most hobbyist and you're going to be dealing with drills, endmills, and maybe a small ( 3" ?) facemill, then I think I'd just get an R-8 machine and a set of collets.
 
An R8 is essentially equivalent to an BT30 in gage dia and therefore stiffness. The 30 taper will allow you to gage tool length off the machine, i.e. preset tools. Reduces the fuss if you use multiple tools for a job.
There are ways to set tool length dynamically on tool change. I know of a guy doing manual tool change on a 50 or 55 taper machine. He calls it the "Armstrong tool changer". Machine has a 10' x 6' x 6' workspace. Stiffness in machine tools is really good but can be expensive. Well worth it.
 
NT40 or NST 40 spindles as some Taiwanese manufactures call them have about 4.125 diameter quill. It seems some change the spindle to 40 taper. Others have a much larger heavier machine. Front back nod might not be available because of the size of the head. That might not be a bad thing. Conversion to CAT40 tooling is very straight forward. Change drawbar length and you are likely done. Spindle block did not need to be changed out. Very easy. Many more options with CAT40 tooling compared to Nt40 and r8.
 
An European perspective (OK, UK perspective) - used, 40 taper tooling is cheaper than R8 as all the hobbyists are using MT2 and MT3 spindle mills and move up to R8 BlidgePolts and similar when they can afford to / build a bigger shed. New tooling, the exact reverse, R8 is by far cheaper!

Dave H. (the other one)
 
Since we are for some reason relighting a 10 year old thread, I'll update my 10 year post. In the years in between:

1. Tormach has popularized their TTS system, which allows use of automatic-tool-changers with R8 spindles. In my shop we use it to get somewhat repeatable, easily obtained, tool holders that we grab with a morse-taper#4 collet in a Deckel FP1. To the "no ATC for R8" argument isn't fully true anymore.

2. In the same period, I helped select a Taiwanese Turret Mill (think big beefy version of a bridgeport) which, if I recall correctly, is actually a CAT-40 machine. As I recall, it had full head movements as well. (This was a remote spec thing, I never saw the machine in person, so take this with a grain of salt.)

3. In the 10 year gap, both iso 30 and the smaller HSK sizes seem to have become more visible on the web - so perhaps more common. ("more" doesn't mean "actually common" - it just means less obscure than they seemed to be in 2010.)
 
3. In the 10 year gap, both iso 30 and the smaller HSK sizes seem to have become more visible on the web - so perhaps more common. ("more" doesn't mean "actually common" - it just means less obscure than they seemed to be in 2010.)

Capto would be nice, but whom but maybe Jay Leno can justify it for a "hobby"?

In the 70-odd year 'gap' R8 is still the grip equivalent of B&S #7, not even B&S #9.

So the comparison with ANY of the "40 taper" tribes is one of cost and convenience ONLY.

They are a country mile or three apart in stiffness, grip, repeatability, RPM, and power transmission levels.

No room for 40-taper?

I HAVE # 9 B&S and it works just as well this century for milling as it has the previous .. what? 150 years, already? Or is it only 140 years?

"Are ate" is what happens to the shanks of the endmills poorly gripped, is it not?

No shortage of folks doing that already. Why would one want to emulate a deal so thoroughly done when there is work to do, cats to kill, snakes to BBQ, fish to be electrocuted, tree-rats to be machine-gunned, cockroaches to be cluster-bombed, hornets to be lasered, and chickens to be choked?

:D
 








 
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