Go/no-go on purchased face mill

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Hi guys,

A face mill I purchased from Amazon a few days ago showed up today and first thing I dragged it into the shop to measure how well-placed the inserts are. It's a 2", 90-deg R8 unit that employs 5 APKT inserts. Measurements indicate there is about a 0.001 variation in the depth of seating across the insert set. I have no way to know if that's a good number or not. My instinct is that it's so-so but again, I don't have the credentials to do more than speculate. If that amount of variation is questionable to someone with face-mill experience, I'll send it back and wait until something with more definitive lineage appears.

This was more of a pushup than I thought it would be. My sole recommendation for this was the Amazon recommender system, which I presume skews toward the inexperienced end on cheap tooling. This tool did have more "endorsements" than I could find for anything else. It's not what I wanted other than it's a face mill... my research lead me to prefer a 2.5" (max) 45-deg SE indexable with a high positive rake but once that theoretical objective had been fixed, I was unable to find much of any data that pointed to a particular implementation. 1 or 2 semi-passing comments here/there but nothing that seemed worthy of making the commitment. What say you fellow Romans? Thumbs up or down?
 
The K in APKT is the tolerances of the inserts themselves.

tip radius - 0.0005"
thickness - 0.001"
inscribed circle - 0.005"

The fact that you are within 0.001" is pretty good when you consider the inserts themselves can have a decent deviation from one to another. Personally I don't think you can expect much more from a cutter that doesn't have adjustable seats.

here you can see a video about adjustable seats.
 
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The K in APKT is the tolerances of the inserts themselves.

tip radius - 0.0005"
thickness - 0.001"
inscribed circle - 0.005"

The fact that you are within 0.001" is pretty good when you consider the inserts themselves can have a decent deviation from one to another. Personally I don't think you can expect much more from a cutter that doesn't have adjustable seats.

here you can see a video about adjustable seats.

Thank you.. excellent point. If I were to rephrase the question to... how much variation across the insert set does it take to degrade the finish? I'm sure this is not a crisp point on the number line but perhaps some target that people who actually know what they're doing (i.e. not me) strive to meet in all cases. Thanks again...
 
Thank you.. excellent point. If I were to rephrase the question to... how much variation across the insert set does it take to degrade the finish? I'm sure this is not a crisp point on the number line but perhaps some target that people who actually know what they're doing (i.e. not me) strive to meet in all cases. Thanks again...

The variation in the insert projection, isn't the only factor that effects surface finish. Tip radius of the insert, feed, and rpm all play a part. Think of the insert with the most projection as a fly-cutter taking a light finishing pass, the quality of the finish is directly related to the feed and rpm. If your rpm is to low, or feed to fast, the finish will look wavy.

If all the inserts have the exact same projection, you can feed faster, at the same rpm as above and get the same surface finish.

Basically its a work envelope type of problem. hopefully that makes sense, it's hard to explain without graphical aids.
 
Again a great concise explanation Dan.. thank you. It goes a long ways toward shaping how I think about this. In the interim, I did a second more careful measurement this time and the variation is a little bit north of 0.003"... Drizzle, drazzle, drozzle, drome; time for this thing to go home. Heartbeats:) Turns out I read your first reply in "suboptimal conditions" and I completely missed both your comment about adjustable seats and the video. I'll ping YT after I send this but just in case it's not there, is there some other way you can specify it? Either way, wonderful reply. Much appreciated.

20171129_234716.jpg
 
Turns out I read your first reply in "suboptimal conditions" and I completely missed both your comment about adjustable seats and the video. I'll ping YT after I send this but just in case it's not there, is there some other way you can specify it? Either way, wonderful reply. Much appreciated.

The video shows adjustable seats.

lower end face mills won't have adjustable seats, your talking hundreds of dollars (600 or 700+) to get a new facemill with adjustable seats.

If you want a really good finish across a range of materials in a home shop environment, you best bet is a fly-cutter.
 
Personally, I see no problem with the face mill you bought. Run it and see how it performs in operation. Then decide if it's worth it or not. Also, the insert plays an important part in the quality it cuts. They make several different configurations on the nose radius, which includes slight flats that act as an wiper as it comes around to bigger or smaller radii's. Different grades for different materials and different face configurations also. They all play an important part in surface finish quality and machinability. I feel in the long run you will be completely satisfied with what you bought there.
 
Personally, I see no problem with the face mill you bought. Run it and see how it performs in operation. Then decide if it's worth it or not. Also, the insert plays an important part in the quality it cuts. They make several different configurations on the nose radius, which includes slight flats that act as an wiper as it comes around to bigger or smaller radii's. Different grades for different materials and different face configurations also. They all play an important part in surface finish quality and machinability. I feel in the long run you will be completely satisfied with what you bought there.

Great replies Dan... again I thank you for taking the time. In a former life, I designed and contributed to other's designs of hyper-precise networks of signal distribution. They were a bunch like my neophyte-grade idea of how this tool is supposed to work in the ideal case... all the inserts assault the surface at EXACTLY the same time in exactly the same way, though your answers lead me to think that I will ultimately be revising that. I'm stuck with today's belief system as I type here:) So... in those networks, back in the old days... sometimes you'd encounter a requirement for total system precision that more stringent than the elements that made up the system, so you didn't just take things off the shelf... you sorted them. Ray ([sic] intentional) had a little room where they hand sorted ("graded") the parts that made up the distribution networks in their hand-built systems. I've been wondering if buying a couple of dozen inserts would allow me to create either:

1. sets of 5 identical inserts, to be used as a group... which assumes the face mill itself is perfect or...

2. After characterizing the errors of the insert slots, associate each slots with graded inserts that negate that variation.

Overthinking I'm sure. Might play with it anyway. Really appreciate your thoughts. Thank you again.
 
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