# M6-501 milling attachment for Atlas 6" ??...



## 56type (Jul 30, 2019)

OK, so I just picked this up off ebay and had a few questions about it's use & if it's missing anything...







It came with the draw bar & cutter holder which I was wondering if the draw bar might be missing the tapered collar that goes up by the handwheel ?? Looks like it may be missing the solid jaw for the vise too but as I understand it the solid jaw is just a piece of flat bar stock so I should be able to source that easy enough. So I was watching some mrpete222 (tubalcain) videos (shop tips #68,69,70) to get an idea on it's correct usage and wasn't clear on a few points.

I know it was said to avoid "climb milling" with this attachment but wasn't real clear as to why ?? I'll be making small parts like this that will need some notches cut in & flats milled...






A dedicated mill isn't in the budget nor space limitations currently so for $320 I think this set up would give me some light milling capability. Just needed to know if there are any extras I'll be needing to get it up and cutting ?? Collets or mill cutter holders ?? It will be mounted to my Atlas 10100 Mk.2. I did some searching here on the site but didn't come up with much info. on what was originally included or needed for setting up the milling attachment for the Atlas 6". Thanks.


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## T Bredehoft (Jul 30, 2019)

If you don't know the difference between climb and conventional milling, find out.  Avoid climb milling on your set up like the plague. Climb milling will pull the work into the cutter. I have a MK2 lathe, there is far more slop in the set up, (rail to saddle, saddle to cross head, cross head to compound, compound to milling( attachment. that will wreck anything tiny or not. 
Conventional milling will put pressure on the work and put load on every connection without causing a train wreck. 

With lathe running normally, push the work against the top of the cutter.  If you push it against the bottom, the cutter will climb onto the work. Do NOT all this.


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## wa5cab (Jul 31, 2019)

To add to Tom's description of Climb Milling, it is also any operation where the reaction to the cutter against the work would tend to lift the milling attachment away from the bed or dovetail.  So if you were milling or widening a vertical slot or surface with the side of an end mill, you would want to start the pass with the part low and in front the cutter.  And lift it up past the cutter.  Also, if the part isn't too large to fit under the cutter, start with the part behind the cutter and pull it toward you under the cutter.  The reaction forces will not only not be trying to pull the work into the cutter but will be trying to hold the cross slide and milling attachment down, in the same direction that gravity is trying to move it.

The milling attachment vise originally came with two hardened pieces of flat bar about the same size or slightly larger than the fixed jaw.  One bar is about 1/4" thick and flat on both sides.  The other one has two 90 degree V-grooves cut into one face, at 90 degrees to each other.  This one is used for holding round stock.

Yes, your draw bar does seems to be missing the beveled collar that came with it.  However, I found that having to hold the tapered end of the collar into the bevel in the left end of the spindle until the threads got tight was an annoying.  So I made a new one out of steel round bar.  Instead of beveling one end, I cut a step that on yours (mine was for a 12") would be 1/2" diameter and sticking out about 3/16" to 1/4".  I found that it tended to stay centered up without having to consciously hold it pushed to the right while tightening the draw bar.


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## 56type (Jul 31, 2019)

Thanks...Now I know how to cut the flats. How should I go about cutting the notches ?? I'll be using a 4mm center cutting endmill most likely. to get the notch the right size. It would seem that to replicate the notches, and sometimes the flats on some pieces the work will need to feed into the center line of the cutter to achieve the desired cut...Here is a pic of what I'm trying to reproduce. The one second from the top in the pic. I'm trying to figure out how to duplicate the cuts without being guilty of climb milling. Cutting on edges  of work I can understand. But when cutting wrench flats in the middle of a round work piece it has me scratching my head since I'm unsure of how the cutter will "view" the work when feeding directly into the center of the cutter, if that makes sense. I keep thinking it will be doing both climbing & conventional milling at the same time and don't know if that is correct or how to set up for it...


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## Downunder Bob (Jul 31, 2019)

Not climb milling again. Some people seem to love it, possibly, because, if done right it can give a better finish. However climb milling can not only wreck your little project, it can and often does wreck your precious machine.

Climb milling should only ever be used, on a proper milling machine, for a very light final cut, and yes if done like this it will give better finish. I cant support climb milling on a lathe milling attachment, it's just asking for trouble. I have seen too many machines, even heavy duty mills, damaged and one even wrecked by operators climb milling. Never use climb milling for roughing or hogging cuts.

Yes I know, 50,000 hands just went up and every one yelling "I've been doing it for years, and never had a problem".Well you've been lucky, so far. Hey if it's your machine go for it, just don't ever say you weren't warned.


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## 56type (Jul 31, 2019)

Downunder Bob said:


> Not climb milling again. Some people seem to love it, possibly, because, if done right it can give a better finish. However climb milling can not only wreck your little project, it can and often does wreck your precious machine.
> 
> Climb milling should only ever be used, on a proper milling machine, for a very light final cut, and yes if done like this it will give better finish. I cant support climb milling on a lathe milling attachment, it's just asking for trouble. I have seen too many machines, even heavy duty mills, damaged and one even wrecked by operators climb milling. Never use climb milling for roughing or hogging cuts.
> 
> Yes I know, 50,000 hands just went up and every one yelling "I've been doing it for years, and never had a problem".Well you've been lucky, so far. Hey if it's your machine go for it, just don't ever say you weren't warned.



I'm not trying to advocate for climb milling, since I've been advised it's a bad idea, especially on a lathe. I'm trying to sort out the details so I don't make the mistake of setting up the work to the cutter and creating a climb milling situation thru my own ignorance and damaging the part, the machine, or both.

I want to understand, particularly, how to go about cutting a notch that goes straight into the work. The piece I'm making calls for a locking notch at 12, 3, 6, 9 (as in the pic I posted above) and two wrench flats. Since I can cut the flats on the edge of the work it's easier to understand how to set up to do it correctly. The notches seem to pose a different problem (to my thinking), since those need to be cut directly into the edge of the work on the center of the cutter, not the edges. To my way of thinking, the cutter is going to first encounter the work on an outside edge of the cutter but since the work is feeding straight into it, the cutter could be considered to climb on the top while being conventional on the bottom.

I'm asking those more experienced than myself "how can I expect the cutter to react ??". Will it try to climb the work ?? will the forces balance out as it proceeds to cut on straight into the work as the cutting edge is trying to remove the same amount of material from either side of the cutting edge ??...


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## Downunder Bob (Jul 31, 2019)

56type said:


> I'm not trying to advocate for climb milling, since I've been advised it's a bad idea, especially on a lathe. I'm trying to sort out the details so I don't make the mistake of setting up the work to the cutter and creating a climb milling situation thru my own ignorance and damaging the part, the machine, or both.
> 
> I want to understand, particularly, how to go about cutting a notch that goes straight into the work. The piece I'm making calls for a locking notch at 12, 3, 6, 9 (as in the pic I posted above) and two wrench flats. Since I can cut the flats on the edge of the work it's easier to understand how to set up to do it correctly. The notches seem to pose a different problem (to my thinking), since those need to be cut directly into the edge of the work on the center of the cutter, not the edges. To my way of thinking, the cutter is going to first encounter the work on an outside edge of the cutter but since the work is feeding straight into it, the cutter could be considered to climb on the top while being conventional on the bottom.
> 
> I'm asking those more experienced than myself "how can I expect the cutter to react ??". Will it try to climb the work ?? will the forces balance out as it proceeds to cut on straight into the work as the cutting edge is trying to remove the same amount of material from either side of the cutting edge ??...



Sorry I jumped before I had properly read your post,and climb milling is my pet hate, I guess you've noticed. There is a lot of confusion about what is and what isn't climb milling. Essentially if the cutter as it rotates will have a tendency to pull the work into the cutter that IS climb milling, if on the other hand it has a tendency to push the work away from the cutter that is NOT climb milling. It's really as simple as that. 

Where it can get confusing is when you have a bit of both forces happening at the same time. Consider you already have a 1/4 inch slot and you wish to widen it to 3/8 or any other size. You have a 3/8 cutter and you set it up so that the original 1/4 slot is exactly in the middle of the cutters path, such that one side of the cutter is climb milling and the other is not. provided that you set it up exactly in the middle no harm done, but you only have to err on the side of climb milling by as little as a thou or two and you have the potential to create a climb milling situation. 

If this procedure is carried out on a robust milling machine with all the proper care, then it should be safe and every one is happy, however I would never recommend it for a lathe milling adaptor. Just asses every new job as you set up and it will soon become second nature to you.

Good luck and happy chip making.


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## wa5cab (Jul 31, 2019)

First confirm that your carriage lock is in good condition and works properly.  Same for the lock that should be installed in place of the center gib screw on the milling attachment's vertical slide.  And replace the center gib screw on the cross slide with another of the same T-handle lock screw found in the vertical slide (the vertical slide on the milling attachment is the same part number as the cross slide on the 6", 10" and early 12" and uses the same gib screws on the late 12").  Then Rule #1 is to always lock  during a cut whichever two out of the three movable members are NOT being moved in order to make the cut.  This includes when doing facing cuts (not a milling operation).

For cutting wrench flats, I would use what is normally a horizontal mill cutter.  You will need to obtain an arbor to hold the cutter.  Cutters for small horizontal mills are available with 7/8", 1" and 1-1/4" ID's and in various OD's and widths.  Depending upon the width of you wrench flats, you may need to stack two narrower cutters onto the arbor.  Position the work behind and below the cutter and pull it toward you to make a cut.  There are tables in every Manual of Lathe Operations for determining what spindle RPM to use, depending upon material and cutter diameter.  

For the narrow notch, either use an end mill of the proper diameter or if one is not readily available use a smaller one and make the first cut offset half the distance between the cutter diameter and the desired slot width such that the second cut will not be climb milling.  Unless there is some reason not to, use the cross slide as your movable member and make the cuts by moving it toward you.  Finally, by preference, always adjust the height of the work by lifting the vertical slide to its final position, not by lowering it.


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## 56type (Jul 31, 2019)

Downunder Bob said:


> Sorry I jumped before I had properly read your post,and climb milling is my pet hate, I guess you've noticed. There is a lot of confusion about what is and what isn't climb milling. Essentially if the cutter as it rotates will have a tendency to pull the work into the cutter that IS climb milling, if on the other hand it has a tendency to push the work away from the cutter that is NOT climb milling. It's really as simple as that.
> 
> Where it can get confusing is when you have a bit of both forces happening at the same time. Consider you already have a 1/4 inch slot and you wish to widen it to 3/8 or any other size. You have a 3/8 cutter and you set it up so that the original 1/4 slot is exactly in the middle of the cutters path, such that one side of the cutter is climb milling and the other is not. provided that you set it up exactly in the middle no harm done, but you only have to err on the side of climb milling by as little as a thou or two and you have the potential to create a climb milling situation.
> 
> ...



Thanks, your second paragraph clears it up nicely as to what I needed to know. I'll be cutting the notch into the rounded edge of the work as in pic with the different nuts charted in my earlier post. Knowing that centering the cutter (or perhaps offsetting by 0.00025-0.0005 to the conventional milling side of intended cut) is paramount for keeping the cutting operation running as it should.

The notches in question accept a spring loaded pin that acts as a locking mechanism to keep the nut from backing off once threaded into place. So I'll need to cut 4 total. I was thinking of using the rotational capabilities of the milling attachment vice to ensure the notches were indexed correctly since I don't have a dividing head. My thought was that once one notch was cut I could rotate the vise in 90 degree increments thru it's 180 degree range to avoid introducing any error by repeatedly removing the work from the vise & setting it up again. Does this sound like it's sound in principle ??...


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## 56type (Jul 31, 2019)

wa5cab said:


> First confirm that your carriage lock is in good condition and works properly.  Same for the lock that should be installed in place of the center gib screw on the milling attachment's vertical slide.  And replace the center gib screw on the cross slide with another of the same T-handle lock screw found in the vertical slide (the vertical slide on the milling attachment is the same part number as the cross slide on the 6", 10" and early 12" and uses the same gib screws on the late 12").  Then Rule #1 is to always lock  during a cut whichever two out of the three movable members are NOT being moved in order to make the cut.  This includes when doing facing cuts (not a milling operation).
> 
> For cutting wrench flats, I would use what is normally a horizontal mill cutter.  You will need to obtain an arbor to hold the cutter.  Cutters for small horizontal mills are available with 7/8", 1" and 1-1/4" ID's and in various OD's and widths.  Depending upon the width of you wrench flats, you may need to stack two narrower cutters onto the arbor.  Position the work behind and below the cutter and pull it toward you to make a cut.  There are tables in every Manual of Lathe Operations for determining what spindle RPM to use, depending upon material and cutter diameter.
> 
> For the narrow notch, either use an end mill of the proper diameter or if one is not readily available use a smaller one and make the first cut offset half the distance between the cutter diameter and the desired slot width such that the second cut will not be climb milling.  Unless there is some reason not to, use the cross slide as your movable member and make the cuts by moving it toward you.  Finally, by preference, always adjust the height of the work by lifting the vertical slide to its final position, not by lowering it.



Carriage lock seems to be in good working order. I'll check the lock on the milling attachment as soon as it arrives. Are the T-handle lock screws still available from Clausing ?? BTW, the steel gibs stiffened up the little 10100 substantially.

I had to do an image search for horizontal milling cutter as I'm not all that familiar with the various cutter shapes & intended cutting function at this point. Is there any reason I shouldn't use a regular end mill ?? The wrench flats are 0.185 in. wide, Just curious as I have a couple end mills already.

Do you think my plan of rotating the milling attachment vise to index the notches is sound ?? My thought was I'd be way more likely to introduce error by removing the work from the vise once set up and rotating it to index the next notch to be cut. Loosening the locks & rotating the vise, then locking it back down, using the degree scale to index the next notch *seemed* the best way to avoid introducing any error apt to pop up from me removing the work & resetting for each subsequent cut. Thanks.


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## pontiac428 (Jul 31, 2019)

You don't necessarily need to use a horizontal cutter for the flats.  You can make a facing cut with an end mill.  Then you could, without moving the part from the milling attachment vise, rotate the vise around to do the plunge cut as wa5cab describes.

You probably don't have to worry much about indexing for this part.  If you can hold it firm, you can machine it.  At the end of the day, the AK will fire whether you make your mark or miss it by a mile.  The photo of your part examples and the wide margin of tolerances proves my point.  If you get the features positioned within 0.010" of where they "should" be, you're probably way ahead of the factory in Izhevsk, which has been fueled on vodka for 60 years.


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## wa5cab (Jul 31, 2019)

The parts are smaller than I was thinking.  I went back and looked at your photo showing four different makes of the part and this time noticed that there was a dimension shown.  

Another type of cutter that would be less expensive than the arbor to hold a standard horizontal mill cutter and is probably available in sizes large enough for your purposes is called a key seat cutter.  Look that one up.  It has a round shank or shaft typically of a diameter between 3/16" and 3/8" with what may look like a  small but thick saw blade on the end.  Or like a miniature version of the arbor and milling cutter I mentioned earlier.  You would hold it with either a collet or a spindle drill chuck.  You could if necessary have the cutter on the end ground to the proper thickness to cut the notch.

But to answer your last question, you might be able to lock the part in the vise with its axis exactly parallel to the spindle axis such that you could cut one wrench flat with the vise bolts horizontal and pointed toward the operator and then rotate the vise so that the bolts pointed to the rear and cut the second wrench flat 180 degrees from the first.  But the only notches that you could cut like that would be round bottom. not flat bottom.  For which the detent pin would have to have a ball end, not flat.  

If you rotate the entire milling attachment 90 degrees so that the vise is on the operator's side of the attachment, you could cut flat-bottom notches with an end mll with the vise bolts pointed up, and toward the tailstock.  Whether you could cut the other two notches without the bolts striking the headstock or bed, I don't know.


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## 56type (Jul 31, 2019)

pontiac428 said:


> You don't necessarily need to use a horizontal cutter for the flats.  You can make a facing cut with an end mill.  Then you could, without moving the part from the milling attachment vise, rotate the vise around to do the plunge cut as wa5cab describes.
> 
> You probably don't have to worry much about indexing for this part.  If you can hold it firm, you can machine it.  At the end of the day, the AK will fire whether you make your mark or miss it by a mile.  The photo of your part examples and the wide margin of tolerances proves my point.  If you get the features positioned within 0.010" of where they "should" be, you're probably way ahead of the factory in Izhevsk, which has been fueled on vodka for 60 years.



Yeah, that pic of various countries version of the part is kind of my reason for making my own. The Polytech/Norinco chinese version of the thread protector/muzzle nut is a bit longer than standard & hasn't been imported for 30+ years so finding them is getting difficult.

Another country's version will fit but you have to pick which end you want to look wrong as the others won't completely cover the threads as intended and leave a gap between the front sight base & the nut, or exposed threads at the muzzle. I thought making a few would be a good first project for me as well as allowing for indexing the initial notch that the pin will lock into to the rifle for best fit. Good practice for getting some basics for making different ones.

Even though it's not a critical part I didn't want to start off making a part out of spec. if I could help it.


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## 56type (Jul 31, 2019)

wa5cab said:


> The parts are smaller than I was thinking.  I went back and looked at your photo showing four different makes of the part and this time noticed that there was a dimension shown.
> 
> Another type of cutter that would be less expensive than the arbor to hold a standard horizontal mill cutter and is probably available in sizes large enough for your purposes is called a key seat cutter.  Look that one up.  It has a round shank or shaft typically of a diameter between 3/16" and 3/8" with what may look like a  small but thick saw blade on the end.  Or like a miniature version of the arbor and milling cutter I mentioned earlier.  You would hold it with either a collet or a spindle drill chuck.  You could if necessary have the cutter on the end ground to the proper thickness to cut the notch.
> 
> ...



Here's a pic of a drawing of what I was thinking of doing...







The view is from behind the headstock looking thru it toward the tailstock. The operator's side of the lathe is the right side of the page. You had advised against lowering the part onto the cutter so I thought perhaps rotating the the vise in the illustrated manner would allow for indexing all four notches without the need to remove the work from the vise. The two arcing arrows represent the rotation of the vise to account for the how the cutter would approach the work to avoid climbing as much as possible. I numbered the cuts to show the order & feed direction in case those needed additional review to get it correct so as not to stress the machine or work.  I'm trying to keep the feed isolated to the cross slide as much as possible to maintain the most rigid set up. Thanks.


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