# Maximum Milling Cutter Diameter



## Green Frog (May 15, 2016)

I know I've seen it somewhere, but I can't seem to find it now.  Can anyone tell me what the maximum diameter would normally be for cutting tools to turn on an arbor on my MFC?  I see cutters with a 1" ID bore that go 5" or more for their OD, but I'm thinking I read somewhere that I should limit the OD of cutters I put on my MFCs arbor to 4" or maybe even 3".  Can anyone refer me to a paragraph in the shop manual or some other source that definitively says, or is the limit just what you can get the arbor to turn?  I know the over arm support sets a sort of limit by its very placement, but I'm guessing I should leave at least some amount of clearance there??  TIA for any help, as usual!


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## CluelessNewB (May 15, 2016)

Rudy Kouhoupt uses 4" slitting saws on a shop made extra short arbor in his videos.   I'm thinking 4" would be a bit much for wider cutters.   I believe Atlas didn't sell any cutters larger than about 2.5".


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## 34_40 (May 15, 2016)

4" as far as I know.


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## Green Frog (May 15, 2016)

Thanks.  Just thinking in terms of cut clearance now... the OD of the spacers is about 1.25-1.50" so if you limit yourself to a nominal 2.50" cutter you can only cut a groove of about 0.50" deep (or maybe a little less, really.)  Just trying to see what my capabilities might be...


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## Profkanz (May 15, 2016)

Cutter diameter is really dependent on the depth of cut (or clearance) required and the horsepower and rigidity of the machine. It was not uncommon in olden times to mount two cutters on an arbor for straddle milling. At the school shop where I teach we have 6 and 8 inch diameter cutters on the rack. But we also have a Milwaukee Horizontal Milling machine.


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## CluelessNewB (May 16, 2016)

Profkanz said:


> Milwaukee Horizontal Milling machine



Which weighs about 25x what the Atlas weighs!   
The Atlas weighs 278 lbs according to the catalog,  the K&T about 7000 lbs!


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## VSAncona (May 16, 2016)

A 4"-dia. cutter is the largest that will fit under the overarm bar.


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## Tony Wells (May 16, 2016)

It's not all about fit. It's also about surface speed. The larger the cutter, the slower the spindle speed must be to hit a target cutting speed. Using your lowest possible RPM (or lowest *practical* speed for you VFD guys), see how large a cutter you can hit, say.....100 sfpm with. Of course, then enters the material type. You cutting paper, or Stellite?


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## 34_40 (May 16, 2016)

Green Frog said:


> I know I've seen it somewhere, but I can't seem to find it now.  Can anyone tell me what the maximum diameter would normally be for cutting tools to turn on an arbor on my MFC?


 
The O.P. asked for the maximum that'll turn on an arbor. The answer is 4".

No one mentioned width or tooth count.  A whole chapter can be written about speeds vs feeds and various cutters.  Perhaps complete books! LOL


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## Green Frog (May 17, 2016)

The key words in my questions were "maximum" and "normally" so I took it as a possibility that there would be at least some "thread drift" with the latter... one man's normal is another man's extreme.  Actually, the concept of capacity vs capability is an important one, and even though the Atlas is a solid little machine for it's size and footprint, it's still a little machine, running on a little 110 volt AC motor, so it does have its limitations when it comes to "hogging" operations.  I'm wondering whether some of these 4" OD X 1/2" or 5/16" wide (or wider) milling cutters could be utilized, keeping in mind that speed and depth of cut would necessarily be fairly conservative (i.e. slowest speed on back gear and feed and very light cuts.)


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## VSAncona (May 17, 2016)

The Atlas instructions advise using the smallest cutter permissable to perform the operation at hand.


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## cjtoombs (May 17, 2016)

The number and range of speeds on the Atlas mill varied over it's production, but as far as I know it had speeds and feeds appropriate for medium to soft steels with a 4" diameter cutter (which, as mentioned earlier, is the largest that will fit and still use the overarm support).  My mill is one of the earlier versions that had 16 speeds, later versions came with 12, I believe.


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## wa5cab (May 17, 2016)

The M1, MF, and MH were 16 Speed.  The "A" models were 12 Speed.  And the "B" and "C" models were 8-Speed.

Note that AFAIK, none of the "A" models ever had an "A" on the nameplate.  Atlas renamed them retroactive when they came out with the "B" models around 1944 or 1945..  According to MMB-5 (parts manual), all M1, MF and MH with Serial Numbers between 1345 and 5465 inclusive are actually M1A, MFA and MHA.  However, there was one report of an MF with a serial number in the 900 range that had 12 Speeds.  I've been waiting for one with a serial number between about 1000 and 1344 to turn up but so far, nada.

From the specs in various year catalogs, the speed ranges of the three groups are.

Base... 54-3225
A..........61-2860
B & C.. 62-2870

So not much change at the low end.


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## Green Frog (May 17, 2016)

wa5cab, I'm sure the question has come up before, but I'll ask it again to get the information into this thread.  Is it possible (and practical) to retrofit my MFC and get 12 or even 16 speeds out of it?  Would the parts be hard to find and/or exceedingly expensive and would there be any over riding reason not to do it?


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## cjtoombs (May 17, 2016)

Green Frog said:


> wa5cab, I'm sure the question has come up before, but I'll ask it again to get the information into this thread.  Is it possible (and practical) to retrofit my MFC and get 12 or even 16 speeds out of it?  Would the parts be hard to find and/or exceedingly expensive and would there be any over riding reason not to do it?


You would have to make/acquire the pulleys, but once that hurdle is completed it wouldn't be difficult to install.  The 12 speed setup would probably be easier to find.  The 12 speed may be easier to find, the 16 speeds were only made from 1941 to 44.


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## wa5cab (May 18, 2016)

Is it possible, yes.  Is it practical - that  probably depends upon how much money you are willing to throw at it.  Just off the top of my head, I would guess that the least expensive solution would be to convert from the 1725 RPM single-speed single-phase motor to a variable speed three-phase motor.  The 8-speed system probably has enough range to get around the fact that there is no way that a variable speed motor is going to by itself be able to match the 60:1 speed range of the MF. 

There are quite a few differences between the MFC and the MF.  However, outside of the spindle and countershaft assemblies the other differences don't matter in terms of which cone pulleys are used on the spindle and countershaft.  You should download MMB-5 and compare the part numbers of the parts on those two assemblies to see what has to change.  Pretty much the entire countershaft assembly including belt guards is different.  On the spindle assembly, the spindle, bearings, bushings and gears are as I recall the same.  Just about everything else is different.  

The easiest way to find all of the necessary parts would be to buy an M1, MF or MH.  But you will probably get stuck with the leftover parts.  Otherwise, the parts availability on the 16 Speed and the 12-Speed machines is very poor.  The 16-Speed machines were made in 1941 and 1942.  The 12-speed machines were made in 1943 and 1944.  The two 8-speed models were made from 1945 until 1960.  And Sears was a second seller of the MFC (only).  Parts availability on the used market of 8-speed parts is relatively poor but much better than that of the earlier machines.  Clausing has almost no parts left for any of the mills except for maybe some of the ones that were also used on the 618 lathe and carried over to the mill.  Far fewer mills were made than lathes.  And their production ceased about 20 years before lathe production ceased.


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