Aluminum: Good Finish w/End Mills & Fly Cutters

[DMS]

Keep in mind that the fly cutter speed should be around 400 RPM, not 4000 RPM

Slowing the feed rate down definitely helps surface finish (to a point) as does a small radius on the cutting tip. Looks like things are improving for you, and the fly cut surfaces are not bad. One question on the 3rd pucture, did you stop halfway through a cut with the end mill? If not... it looks like you are getting some pullout, which can be a real pain. I would recommend getting some anti size compound, and adding it to your drawbar threads and thrust washer, as well as the outside taper of your collets (not the inside, where they grip the end-mill). Also make sure that your tool shanks are clean and dry before you install them in the collet. What kind of machine are you working with here?

 

[Phil3]

Keep in mind that the fly cutter speed should be around 400 RPM, not 4000 RPM

Slowing the feed rate down definitely helps surface finish (to a point) as does a small radius on the cutting tip. Looks like things are improving for you, and the fly cut surfaces are not bad. One question on the 3rd pucture, did you stop halfway through a cut with the end mill? If not... it looks like you are getting some pullout, which can be a real pain. I would recommend getting some anti size compound, and adding it to your drawbar threads and thrust washer, as well as the outside taper of your collets (not the inside, where they grip the end-mill). Also make sure that your tool shanks are clean and dry before you install them in the collet. What kind of machine are you working with here?

Thanks for all the replies. I checked the tram and found it quite off...I think. I really don't have a good setup for measuring this. I do have a test indicator. I attached it to a 1/4 aluminum bar that was inserted into a collet and swept the table that way. But honestly, the entire setup just seemed rather flimsy. The table is trammed within .001"...and I get repeat measurements. Anyway, I adjusted things and tried a cut in aluminum with a 3/8" 4 flute end mil. 2500 rpm. A little slow, but the next speed is 5200. Using the end of the mill, the cut in one direction was a series of closely spaced opposing semi-circles. Coming the other direction, just closely spaced semi-circles, but non opposing. If the mill is left running, and I stop moving the table, an impression of the end mill is left in the aluminum. Moving a finger across the aluminum, it feels smooth, even across the end mill impression. I tried taking a photo, but hard to see what I am talking about.

I'll try the anti-seize. As you will see below on my mill, I have no drawbar threads.

What kind of machine am I working with? Well, its different, that's for sure. It is a Rotex, from around the early fifties. It is a knee mill with a 5" x 20" table. It is both a horizontal and vertical mill, using two separate motors. Photos are below. It uses a XX or YY collet, or something like that. The person I bought it from built and added a vertical extension (large diameter steel bar) to raise the head. The head normally mounts directly on the large horizontal spindle that the extension bolts onto. The head can still mount at both angles (horizontal and vertical) because it can tilt more than 90 degrees. I may change it back, but it seems like everything would be quite low.

The cutter I believe is quite sharp. It has not been used much and has been used exclusively on aluminum and some brass. WD-40 does seem to help. I am really unsure how deep of a cut I can take with the end mill at what speeds. I think I am being far too conservative. A bit fearful of something breaking. But, have also heard too thin a cut can allow chips to get under the tool and cause a poor finish. This is when I need a mentor!

On the pics... The red strap is attached to a roof rafter so the head does not come crashing down as it pivots when adjusting X axis tram. There is nothing to stop it if it gets loose. Ask me how my body knows this when trying to intercept it. The shaft in my hand drives the table left and right, but am missing some parts...and parts diagram.

Phil

 

[NoShopSkills]

The video above is very good. He's a bit chatty, but definitely worth the watch, there's a lot of great info in there.

A bit chatty? I thought maybe I'd found my next night time viewing venue seeing how I've seen almost all of Messrs. Fenner and Pete, but I couldn't sit through even one of his full length videos.

He did however inspire me to drill the stripped out, metric set screws out of the cheapo Asian fly cutters that have been sitting in the tool box since they couldn't hold a bit tight. Put in new threads and bigger standard sets, but the bottom line is the holders are still non hardened garbage Chinese steel.

What a curse cheap tools are.

 

[Bill C.]

Thanks for all the replies. I checked the tram and found it quite off...I think. I really don't have a good setup for measuring this. I do have a test indicator. I attached it to a 1/4 aluminum bar that was inserted into a collet and swept the table that way. But honestly, the entire setup just seemed rather flimsy. The table is trammed within .001"...and I get repeat measurements. Anyway, I adjusted things and tried a cut in aluminum with a 3/8" 4 flute end mil. 2500 rpm. A little slow, but the next speed is 5200. Using the end of the mill, the cut in one direction was a series of closely spaced opposing semi-circles. Coming the other direction, just closely spaced semi-circles, but non opposing. If the mill is left running, and I stop moving the table, an impression of the end mill is left in the aluminum. Moving a finger across the aluminum, it feels smooth, even across the end mill impression. I tried taking a photo, but hard to see what I am talking about.

I'll try the anti-seize. As you will see below on my mill, I have no drawbar threads.

What kind of machine am I working with? Well, its different, that's for sure. It is a Rotex, from around the early fifties. It is a knee mill with a 5" x 20" table. It is both a horizontal and vertical mill, using two separate motors. Photos are below. It uses a XX or YY collet, or something like that. The person I bought it from built and added a vertical extension (large diameter steel bar) to raise the head. The head normally mounts directly on the large horizontal spindle that the extension bolts onto. The head can still mount at both angles (horizontal and vertical) because it can tilt more than 90 degrees. I may change it back, but it seems like everything would be quite low.

The cutter I believe is quite sharp. It has not been used much and has been used exclusively on aluminum and some brass. WD-40 does seem to help. I am really unsure how deep of a cut I can take with the end mill at what speeds. I think I am being far too conservative. A bit fearful of something breaking. But, have also heard too thin a cut can allow chips to get under the tool and cause a poor finish. This is when I need a mentor!

On the pics... The red strap is attached to a roof rafter so the head does not come crashing down as it pivots when adjusting X axis tram. There is nothing to stop it if it gets loose. Ask me how my body knows this when trying to intercept it. The shaft in my hand drives the table left and right, but am missing some parts...and parts diagram.

Phil

Nice machine. I always called your type a mill a "Universal". I would use a thicker rod of aluminum or steel to mount the indicator. The round column machines seem to need more alignment checks. Just make sure all the clamping bolts are tight that hold the head in position. Still you have a good looking setup.

 

[Phil3]

I tried my best using the video mentioned earlier to make a good flycutting tool. Still lots of swirl marks, both from the leading edge and back cut. The finish is smooth. Perhaps more of a radius on the tool? I am using 2500 rpm and a tool diameter of about 1.75". Very slow feed. A few thousandths on depth of cut. Things are getting better, and for this newbie, I did noticed things worked better when I kept everything quite tight, and no tool bit, stock or anything else hanging out too far, minimizing flex. If it makes any sense, the cutting seemed smoother. But, the side cut is still rough. As in my pic further up in this thread. Lots of vertical marks. I can't seemed to fix this no matter what speed, feed, depth of cut, direction of cut, or anything. It is remarkably consistent in bad finish. I don't have a good way to use the end of the end mill to finish this surface. Ideas?

Phil

 

[DMS]

Since you don't have a drawbar, add a little bit of anti seize to the collet nut threads. Neat little machine by the way. As far as surface finish on the side cut, I never get as good a finish as I do cutting on the end, or with a fly cutter, though it's not bad. One thing that can help is if you lock all of your unused axes. For example, if you are feeding in X, lock the Y and Z. It can make quite a difference. You may also check the play in your gibs. The surface finish looks like something is moving on you (could be spindle runout, could be play in the axes).

How does it sound when cutting? Is it smooth, or do you get a lot of "chunk chunk chunk"? Also, how wide is that piece you were profiling? Looks close to 1", which may be a bit much to ask in one pass. You might try an experiment, and take a cut at about 0.010" at about 0.5" and see if that improves things or not.

 

[David Kirtley]

No expert here but I am looking at your machine (Which I like a lot) but that looks more like a drilling head attachment to a horizontal mill rather than a vertical milling head. Why not go horizontal and use it at it's strength? You are going to need to take light cuts with that vertical head regardless. (added: The lack of a draw bar makes me even more suspicious that it is a drilling and not a milling head)

Looking at picture 5, I would guess that rigidity is the problem.

You could also adjust the rake on the cutter to give a more shearing cut. It could reduce the cutting pressure.

 

[pineyfolks]

I have a Rotex also. No vertical head though. You will get very good finishes with a flycutter in the horizontal spindle and it will be a lot more solid too. Those machines have plenty of power and spindle speed to work well flycutting.

 

[Phil3]

Re: Aluminum: Good Finish w/End Mills & Fly Cutters

No expert here but I am looking at your machine (Which I like a lot) but that looks more like a drilling head attachment to a horizontal mill rather than a vertical milling head. Why not go horizontal and use it at it's strength? You are going to need to take light cuts with that vertical head regardless. (added: The lack of a draw bar makes me even more suspicious that it is a drilling and not a milling head)

Looking at picture 5, I would guess that rigidity is the problem.

You could also adjust the rake on the cutter to give a more shearing cut. It could reduce the cutting pressure.

I believe the head is a milling head. The reason is that Rotex made a vertical only mill, and as best as I can tell, it came with this same head. While the head in this photo may have been changed, you can see that mill here with the same head as mine.

http://vintagemachinery.org/photoindex/detail.aspx?id=14563

http://www.practicalmachinist.com/v...nchtop-vert-mill-bill-s-rotex-mill-large-.jpg

It is possible someone yanked the vertical head off the Rotex vertical and mounted it on this horizontal. I don't know if Rotex sold a horizontal/vertical combo mill.

Can you tell me what differentiates a drilling head attachments from a vertical milling head? I would like to know what makes you suspect it is a drilling head.

Thanks.

Phil

- - - Updated - - -

I have a Rotex also. No vertical head though. You will get very good finishes with a flycutter in the horizontal spindle and it will be a lot more solid too. Those machines have plenty of power and spindle speed to work well flycutting.

I am pretty unfamiliar with the horizontal setup, and have never even used it. Fact is, the motor for that is not yet connected, but can get that going. I agree, the thing is a little tank in the horizontal spindle area and should be very solid. I know next to nothing about tooling for horizontal setups. I have a few cutting tools for the horizontal, including this slab cutter which must be 2" or more wide. I have the spindle for horizontal use. What kind of holding fixture do I need for horizontal use? Does not seem like a regular vise would work for this.

Phil

 

[David Kirtley]

Re: Aluminum: Good Finish w/End Mills & Fly Cutters

The biggest difference between a drilling head and a milling head would be the bearings. The real reason behind my suspicion was the head doesn't look like the same scale. The rest of the mill is so massive.

You will be better off to turn your vise 90 degrees so the side of the vise is pointing to the spindle. Then you can mill on the side as well as from the top. Some good precision angle plates will really open up the clamping possibilities.