Atlas Mfc Mill Arbor Drawing ?

[Mondo]

Clausing responded this morning. Neither the 7/8" or the 1" arbor are available. Neither are the drawings. So if anyone needs an arbor they are on their own to find one for sale from a scrapper, or make one based on your drawings!

Spiral_Chips

 

[Wheels17]

I recently purchased Craftsman horizontal, which is missing the drawbar, arbor support bracket, and arbors. I missed the tools4cheap arbors by about a month. When I contacted him, he said his inventory had been sold to an ebay vendor, and the vendor no longer lists the arbors for sale. So, I took Rob's pictures above and created a drawing for the 7/8 arbor. I would like to have others on the forum check the drawing against their real arbors so that I can correct the drawings. I made three changes from Rob's sketches:

1. I narrowed the drive slots from .289 to 5/16, for better fit to the .25" driver pins.

2. I specified the depth of the slots a bit shallower, again to better fit the driver. I measured my driver and checked an on-line drawing of the driver to make my decision.

3. I show the keyway on the shaft rotated 1/4 turn from the location on his picture. This was because I forgot to put the slot in the drawing originally, and if I showed it in line with the drive lugs the drawing would have been less clear. I would welcome feedback on the importance of the location of the keyway.

I've attached a .pdf of the drawing. Please comment and suggest corrections, and when it looks to be right, I'll modify it for 1" and 1 1/4" arbors as well and put them in the files section. I can provide it in cad drawing format if anyone needs it that way.

(P.S. I previously uploaded an arbor draw-in bar drawing, but nobody has commented... I've attached that as well)

 

[wa5cab]

The only thing that I see is that in your comment #1, you meant 9/32" instead of 5/16". You should probably add the word "TYP." after R0.0938. And I noticed that you increased the diameter of the 7/8" portion to exactly on 7/8". Did you you measure the ID of some 7/8" bore cutters and confirm that they are all over 7/8"? Also, you probably need to show pretty tight tolerance on that diameter as well as the pilot diameter (for the arbor support bushing). I am not absolutely sure that this is still the common practice, but assumed unspecified tolerance used to be (back when I still had a day job) +/- 0.005", which wouldn't work on those two diameters. Based on what I know that Atlas specified the 10" and 12" (and I assume same for the 6" and mill) spindle register to, I would suggest 0.8750"/0.8745".

If you will make those minor changes, I'll put the drawing on an Atlas template with your name on it (you'll have to send me that) and put it into Downloads.

I can't see what difference the angular relation between the arbor driver pin slots and the key slot would make. But I'll look at both of my arbors and see which way the factory made it. It might not be a bad idea to make that one detail different from the factory arbors for future identification.

 

[wa5cab]

And the reason that I haven't commented on your drawbar drawing is that mine is still in the crate.

 

[Wheels17]

At least you know where your drawbar is.....

Thanks for the comment on the dimension in the comment. I was a chemical engineer before I retired, so my mechanical and drawing skills are still developing.

I looked at Colvin, 1945 and on page 396 he comments "Hole tolerances are all from basic to .001 inch oversize."

I looked in my drawer of cutters, and found I have very few 7/8" cutters. Most are gear cutters. And their keyways measures about .133 wide, not anywhere near .250.

I did find an interesting table on page 1360 in my grandfather's 1943 Machinery's Handbook "American Standard Keys and Keyways for Milling Cutters and Arbors".

For 7/8" arbors, they specify 1/8" nominal keys, with a range of .125 to .126 for the keyway. The bottom of the keyway is .8075 to .8125 from the opposite side of the shaft..

For 1" arbors, they specify 1/4" nominal keys, with a range of .250 to .251 for the keyway. The bottom of the keyway is .8438 to .8388 from the opposite side of the shaft.

For 1 1/4" arbors, they specify 5/16" nominal keys, with a range of .3125 to .3135 for the keyway. The bottom of the keyway is 1.063 to 1.058 from the opposite side of the shaft.

On page 1361, they have a table specifying the "American Standard" hole diameters for single angle cutters, exact diameter to .001 over. Page 1375 shows the same for Stagger tooth milling cutters and slitting saws.

So, the picture must be a 1" arbor with the .250 keyway. Measuring the flange and the arbor, it also works out to 1". I also noticed that the keyway just runs off the end of the shaft, as opposed to my drawing.

One other area that I really need confirmed is the length of the MT2 up to the flange, and the depth of the drawbar thread hole. New drawings in a few days.

 

[wa5cab]

Wheels,

I have a factory 1" arbor but it will take daylight to figure out where I put it. I also have a factory 7/8" arbor but it is probably also in the crate. However, there is a small chance, now that I think on it, that I may have kept it out of the crate when I opened it up late last year. I will know tomorrow.

I did measure the key ways in a number of 1" nominal slitting saws and thicker cutters plus several keyed spacers up to 1/4" thick. The range of keyway widths ran from 0.254" to 0.260". Need to measure some key stock, too. But this tells me that the key slot in the arbor needs to be opened up to around 0.255".

Also, I measured the nominal 1" holes in all of them and found at least all of the cutter ID's to be bang on 1.0000 +/- 0.0005". Which means that the arbor diameter needs to be slightly under 1".

When I get to my 7/8" arbor, I'll report the key width and diameter.

I think it is going to be a while before anyone should start making an arbor.

I'll also check whether the key way runs off the end of the 1" and 7/8". I can't think of any reason for it not to.

Of course, anyone else with any of these parts on hand and accessible, feel free to chime in.

 

[Rob]

In my previous post I have a picture of what I believe is a atlas 1" arbor. The key way does run off the end.

 

[wa5cab]

Right. Forgot to go back and look.

 

[Wheels17]

Rob, I based my drawing on your pictures, but wasn't sure if running the keyway off the end of the arbor was standard.

I see by your picture that the nut is about 3/4" thick, with a relieved area. McMaster sells an extra wide 3/8-16 that's 47/64 wide, or .734". I was planning to use that nut and bore it out to match your picture.

If you could provide the length of your morse taper section, it would really help me out. The taper is shown with a gauge length of 2 9/16, but there's usually a bit that's beyond the gauge line, about .20" in most references. I've shown it in the drawing at the gauge length, but I'm not sure that will seat properly with the drive nut and lugs.

 

[CluelessNewB]

Here are pictures of the 1" Arbor that came with my MFC. I assume it is original. The keyway measures between 0.249" and 0.251" wide as best I can measure with my digital calipers. Note the keyway runs right into the drive pin notch. The overall length of the morse taper is about 2.35" as best as I can measure it.