Face Mill on Bridgeport Series 1 Mill

[eKretz]

thank you both for the polite, informative, and prompt replies. That does make some sense. One thought I had was that in the following example the larger cutter is running more unsupported which might effect it? I'm literally just spitballing things that make some sense to me. Maybe i'm way oversimplifying the sfm theory which as I read more seems to apply to CNC but how would it also not apply to big old slow shit.

Without knowing any formal training. I was trying to do the math about chip load lets say a 3" cutter digging straight through a 4" part (180 degree engagement) vs a 5" cutter spanning it in one shot. Is the 4" segment of the 5" cutter a smaller cut than the 3" engaged a full 180 of it's diameter. Cut length of the 3" cutter is simple, piD/2 since it's engaging half the cutter. The 5" i had to consult a triangle calculator to find an included angle of 106*. Legs of 2.5, 2.5 and 4.

3" cutter is engaging 2.356" of material per rotation (based on L= theta/360 * piD)
5" cutter is engaging 2.318" of material per rotation

help me understand how the load can be different. The way I'm thinking (remember... ignorant) the 5" cutter would run at a lower overall load given the rpm adjusted for the cutter diameter. And if I'm missing something huge please help me fix this now. Thanks! I'm trying to wrap my mind around the forces at the spindle given the different radii. Oof. oh wait I think I get it. It's like using a longer wrench but in reverse because its the torque at the fulcrum. So i did some calculation but not nearly enough.

You're welcome, and yes, you got it at the end. The lever arm works in every direction also, not just torque in a radial direction. Tool pressure pushes on a cutter in many different directions at once. The longer the lever arm, the less rigid the outer unattached end of it will be. Eventually with higher DOC or feedrate you reach a point where it can't be held rigidly enough to combat the cutting forces and you get chatter. Or movement of the head, like plastikdreams noted.

 

[jutny]

Here's my thoughts. Torque felt at the spindle = (cutting force at the insert) * cutter radius... so even if the cutting forces were the same at each insert, the 5" cutter would apply more torque at the spindle due to the larger radius.

Secondly, as an insert sweeps through the material the chip that it cuts is not of uniform thickness (see the picture below). The chip is thickest when the insert spins through the point directly ahead of the cutter (in the feed direction) but thins out before and after this point. At 90 degrees to the feed direction the chip drops to its thinnest. Since the 3" cutter is fully engaged in the material it gets to take full advantage of that chip thinning, but the 5" cutter does not. Thus, all other things (spindle rpm, feed rate, insert geometry, and number of inserts) being equal, the 5" cutter would see higher cutting force at each insert since it will cut a slightly thicker chip on average.

Thirdly, each insert on the 5" cutter will start into the material thicker chip than the 3" cutter. This might not be too important on a large rigid machine, but on my Bridgeport it is really obvious when a cutter "hits hard" as each insert enters the material. If you watch my video in the original post with the sound on you can hear that the cutter is much quieter when fully deep in the material, and noisy at the start and end of this cut (due to the same effect).

That is a fantastic explanation. Thank you for taking the time to make that work for me. I did notice the sound difference. It probably runs with less chatter when its fully submerged like that. So for my 1hp machine I should stick with the 2". My machine didn't come with much tooling, just nifty workholding bits.

 

[plastikdreams]

Here's my thoughts. Torque felt at the spindle = (cutting force at the insert) * cutter radius... so even if the cutting forces were the same at each insert, the 5" cutter would apply more torque at the spindle due to the larger radius.

Secondly, as an insert sweeps through the material the chip that it cuts is not of uniform thickness (see the picture below). The chip is thickest when the insert spins through the point directly ahead of the cutter (in the feed direction) but thins out before and after this point. At 90 degrees to the feed direction the chip drops to its thinnest. Since the 3" cutter is fully engaged in the material it gets to take full advantage of that chip thinning, but the 5" cutter does not. Thus, all other things (spindle rpm, feed rate, insert geometry, and number of inserts) being equal, the 5" cutter would see higher cutting force at each insert since it will cut a slightly thicker chip on average.

Thirdly, each insert on the 5" cutter will start into the material thicker chip than the 3" cutter. This might not be too important on a large rigid machine, but on my Bridgeport it is really obvious when a cutter "hits hard" as each insert enters the material. If you watch my video in the original post with the sound on you can hear that the cutter is much quieter when fully deep in the material, and noisy at the start and end of this cut (due to the same effect).

You are incorrect on most of your comments.

1) the noise at the beginning and end is from the inserts slapping the material as its an interrupted cut, this vibration is transferred to the spindle and the bearings which amplifies the noise.

2) when you are making a full width cut you are making a conventional cut, the largest amount of material is taken at the beginning but it carried that chip size until it breaks or exits out the back.

3) if you split your cut you could climb mill and put less stress on everything.

You are right about it quieting down at full engagement.

I rarely do a pass down the center first unless I'm using an endmill, even then it's pretty rare.

And if you want to get rid of the waves, run the table the opposite way and don't change anything.

 

[CompositesGuy]

I too, rarely plunge down the middle of a part like I did in the video. I figured this would use more horsepower than cutting with a partial width of the cutter... and I wanted to see how much this cutter would bog/stress the machine.

All milling is an interrupted cut, right? In each revolution of the cutter, each insert enters and exits the cut. That's the definition of an interrupted cut. Contrast this with a cut on the lathe where the tool may continuously produce a chip for many part revolutions. So, I have to ask why in my video (contained in the original post of this thread) the cutter is louder at the beginning and end of the cut than when it is fully engaged in the part. My take was that each insert was "slapping" into a thicker chip at the beginning and end of the cut... and "easing-in" to a much thinner chip when the cutter was fully engaged. Or... perhaps its more complicated. At the beginning and end of the cut the force on the insert as it enters the material has a large component perpendicular to the feed direction. This component reverses directions as that insert exits the material. Thus, for each entry and exit the force on the spindle reverses (in the direction perpendicular to feed). When the cutter is fully engaged in the material the entry force on each insert is probably more aligned with the direction of feed.

 

[plastikdreams]

It's taking the same amount of material but once it's fully engaged it balances out as there are more inserts in the cut. Push it too hard and you'll hear it come back.

 

[eKretz]

It is loud on entry and exit because it's only loaded for a very small amount of the revolution of the cutter and also because only one insert is engaged at a time. Tooth hits the material and wham! The cutter is loaded, whacking the spline tight on the driving side. Then the tooth is unloaded and the spline gets hit on the unloaded side when the torsional load is released and the spindle unwinds like a spring. Until the load is constant due to multiple teeth engaging, that's what you'll hear. If you really want to hear some wham bamming, use a 3 or less toothed cutter with straight teeth... Oh my.

 

[car2]

I'd like to do a similar test with my Glacern FM45 face mill to the video in the original post, except this time cutting in steel. I purchased the Kennametal inserts shown below that Glacern recommends, but they don't have any rake angle (other than being mounted at an angle in the cutter). I like the idea of having some rake angle molded into the insert, since that should make the cut smoother. Do you all have any recommendations for inserts of this style that would work well in steel?

I've noted that Iscar sells SEMT-style inserts that have a molded-in rake angle, but the insert is only 1/8" thick instead of the 3/16" thick for the ones that Glacern recommends. Does a thinner insert mean that it is more fragile?

I've always used the Iscar SEHT 43 AFN-P (seht 1204 AFN-P) IC20 K10 in the F45ST face mill; they are positive-rake (the center is actually "depressed" to create a positive rake on the cutting edge), uncoated, polished--and are sharp. These work great for aluminum, steel, cast-iron, plastic. I've never had an issue with durability of these in any material--and it took a very long time before I even rotated them to a new edge. In any case, even with these inserts, in steel and cast-iron, on a BP about 0.03" cuts in crap steel, and 0.04" in free-machining steel and cast-iron is about the limit of the BP, not the face-mill and inserts.. I think they're actually "recommended" for cast-iron and general-puropse. I don't think any insert that isn't polished, uncoated, positive-rake works very well in a BP (tried a couple, bad vibration, chatter, surface finish), you really need that sharp positive edge to reduce cutting forces in the limited stiffness and HP of a BP. Don't scrimp on the inserts with "mystery" inserts. The above Iscar inserts are frequently available on Ebay for a reasonable price. Cheers

 

[eKretz]

I've always used the Iscar SEHT 43 AFN-P (seht 1204 AFN-P) IC20 K10 in the F45ST face mill; they are positive-rake (the center is actually "depressed" to create a positive rake on the cutting edge), uncoated, polished--and are sharp. These work great for aluminum, steel, cast-iron, plastic. I've never had an issue with durability of these in any material--and it took a very long time before I even rotated them to a new edge. In any case, even with these inserts, in steel and cast-iron, on a BP about 0.03" cuts in crap steel, and 0.04" in free-machining steel and cast-iron is about the limit of the BP, not the face-mill and inserts.. I think they're actually "recommended" for cast-iron and general-puropse. I don't think any insert that isn't polished, uncoated, positive-rake works very well in a BP (tried a couple, bad vibration, chatter, surface finish), you really need that sharp positive edge to reduce cutting forces in the limited stiffness and HP of a BP. Don't scrimp on the inserts with "mystery" inserts. The above Iscar inserts are frequently available on Ebay for a reasonable price. Cheers

That's not so in my experience... I have used many a TiN coated edge prepped SEKN insert in 2" cutters with .100" DOC in mild steel and nary a problem. And yep, in B/Ps. Smooth as buttah. Perhaps you need to check your spindle bearings.

 

[CompositesGuy]

The Iscar SEHT 43 AFN-P IC20 look nice but are $16 on carbide depot, and $24 from the only Ebay dealer that I see. That's a bit rich for me. I'll keep an eye out though.

eKretz. Do you have a model number or brand that you recommend?

That reminds me. I often scope out Ebay for deals on inserts, but recently I got bit. I found some ISCAR HM90 APKT 1003PDR IC908 that looked good at a price that was hard to ignore ($2 per insert). I tried cutting some 304 ss and instantly shattered the cutting edges. I turned the inserts around, slowed feeds and speeds and shattered the edges about 2 inches into the cut. Then I put in some old trusty IC328 inserts that I had on hand and cut the rest of the job with no issues. I told this to the Ebay seller and they immediately refunded my money. I suspect they were some Chinese knockoffs because the seller had an unlimited supply, but I've also never used IC908 before.

 

[eKretz]

The Iscar SEHT 43 AFN-P IC20 look nice but are $16 on carbide depot, and $24 from the only Ebay dealer that I see. That's a bit rich for me. I'll keep an eye out though.

eKretz. Do you have a model number or brand that you recommend?

That reminds me. I often scope out Ebay for deals on inserts, but recently I got bit. I found some ISCAR HM90 APKT 1003PDR IC908 that looked good at a price that was hard to ignore ($2 per insert). I tried cutting some 304 ss and instantly shattered the cutting edges. I turned the inserts around, slowed feeds and speeds and shattered the edges about 2 inches into the cut. Then I put in some old trusty IC328 inserts that I had on hand and cut the rest of the job with no issues. I told this to the Ebay seller and they immediately refunded my money. I suspect they were some Chinese knockoffs because the seller had an unlimited supply, but I've also never used IC908 before.

Those Iscar were definitely knockoffs. I've used the originals and they are excellent. I've also used some sourced from eBay like yours and they were absolute shite. Exact same symptoms as you described.

The SEKN we always used were Seco, don't remember the part number offhand - maybe SEKN42 and grade T25M? But they will be no good in your cutter anyway, they were clamp-in style with no screw holes. Other than clamping method they are pretty much exactly the same though.

 

[rons]

2 cents:

Somebody mentioned to me about tilting the head on the mill ever so slightly, either right side or left side higher. Then sweep either right or left.
Even without doing that I always notice a better finish on either going right or left. My explanation for that is after I do the best tram job there is
always going to be a slight tilt. Don't recall which way works better but it's easy to test. I use a Walter with 5 cutters with 8 sides to a cutter.

 

[Peter S]

FWIW - I have been using a 50mm Iscar Dove IQ Mill IQ 845 face mill and it works well on a 1.5hp Bridgeport. It's a 50* cutter.

I was looking for a Seco face mill (R220-13 or modern version) but the Iscar came up, "as new" and cheap. (A while back Iscar in NZ was selling these face mills for $1 per mm diameter plus you had to buy 10 inserts at normal price. I guess you can see their strategy).

The inserts have 8 faces (4 on each side), though probably unique to Iscar.

The Seco R220.13 series (obsolete I think) was made for low horsepower machines and they were good. We used SEKR 1203 AFTN-ME10 T25M inserts for mild steel work. The one we had was 63mm diameter but with 40 taper in a BP-type head (Holke, Spain).

I also have a Seco R220.53 Quattromill face mill, but haven't used it yet. It uses SE_X 1204 inserts e.g. SEEX 1204 AFN-E08 H25 recommended for aluminium.

Also have a R220.13.0050 (50mm diameter) but not set up yet.

I was using the Iscar last night machining square ends on 304:

 

[CompositesGuy]

If you really love that Dove IQ mill there's one on Ebay right now (the 63mm version which is about a half inch larger than yours) for cheap! The seller offered it to me for $59 when I put it on my watchlist. See item 115246766853. I considered buying it instead of my Glacern, but there doesn't seem to be a large selection of inserts for the Dove IQ line.

 

[Deerhurst]

One of the guys at work got one of those fancy aggressive cutters for his mill. I've borrowed it a few times for various non steel materials and I'm blown away. I need one for me. I was taking 0.150" cuts at 1600RPM in aluminum with no cutting oil running the power feed as fast as possible throwing chips 10+ feet and it was leaving behind a fantastic finish. I'm completely sold on it compared to any of the other face mills we have.

 

[p-moon]

When I had the shop, we were using 2 in dia high positive, 8 sided cutters on a 1.5 hp series 1 as our rougher mill. Used to take .250 depth of cut full width on tool steel at about 1300 with a relatively slow feedrate. Never stalled it out. That put bucketloads of chips on the floor, and you could hold the workpiece in your hand when you were done. Changed the inserts maybe once a day? Guy who taught me how to use these cutters (or thought he did) insisted on .050 max depth, 2000+ rpm, and max feedrate. At the time he was my foreman, so I did, and changed the inserts about hourly. Workpieces were smokin

 

[CompositesGuy]

I'm a bit confused. In the video from my original post in this thread I showed that I'm was using Korloy SEHT SEHT43 AFFN - X83 inserts, recommended for aluminum cutting. I got these off Ebay, but Glacern and Maritool also offer the same model number for sale on their websites, and a number of forum posts speak favorably of these inserts. So.... I thought I'd wonder over to Korloy's website and learn if they offer this insert in a grade that is recommended for steel. To my surprise their website and catalog don't even mention SEHT style inserts, and X83 seems not to relate to their 6-character grade numbering scheme. I must be missing something, or perhaps all of these Korloy inserts are just Chinese knockoffs with that brand slapped on.

I'm keen on buying some Iscar SEHT 43 AFN-P or perhaps just AFN inserts, but I can't find anything under $16 per insert.

 

[eKretz]

I'm a bit confused. In the video from my original post in this thread I showed that I'm was using Korloy SEHT SEHT43 AFFN - X83 inserts, recommended for aluminum cutting. I got these off Ebay, but Glacern and Maritool also offer the same model number for sale on their websites, and a number of forum posts speak favorably of these inserts. So.... I thought I'd wonder over to Korloy's website and learn if they offer this insert in a grade that is recommended for steel. To my surprise their website and catalog don't even mention SEHT style inserts, and X83 seems not to relate to their 6-character grade numbering scheme. I must be missing something, or perhaps all of these Korloy inserts are just Chinese knockoffs with that brand slapped on.

It looks like they just switched to a new grade designation system. The X83 is probably from the old system. Not sure on the lack of SEHT unless they're deciding to discontinue production in favor of more profitable complex molded stuff.

 

[Conrad Hoffman]

Late to the party because it took me a while to look this up. We used https://www.secotools.com/article/p_00086839?language=en on our Bridgeport and it works incredibly well. We keep two types of inserts, sharp high rake for aluminum and something with less rake for steel. It will run about as fast as a Bridgeport will turn and easily take a .15" or more cut in aluminum. I think having an odd number of inserts contributes to smoothness. Need to get another as the guy who owned it took it with him when he left.

 

[eKretz]

Late to the party because it took me a while to look this up. We used https://www.secotools.com/article/p_00086839?language=en on our Bridgeport and it works incredibly well. We keep two types of inserts, sharp high rake for aluminum and something with less rake for steel. It will run about as fast as a Bridgeport will turn and easily take a .15" or more cut in aluminum. I think having an odd number of inserts contributes to smoothness. Need to get another as the guy who owned it took it with him when he left.

That looks just like my Iscar. Good cutter.

 

[CompositesGuy]

Follow up video in steel:

Not quite as happy with the results in the video as I was cutting in aluminum in the original post. The surface finish wasn't great, and the clean up passes after this video were pretty loud. Any suggestions? I'm really curious about the posts claiming much deeper cuts with similar face mills, in steel on a Bridgeport. I didn't push any harder than what's in the video, but it didn't sound like the mill had much more to give (and I'd hate to break something on my personal mill).