Squaring up steel in the mill

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ttabbal

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So, I wanted to work on a project and decided to practice squaring stock on the Bridgeport. Grabbed the fly cutter and promptly killed the HSS bit running too fast. :) Yeah, I know, my own fault. I didn't account for the material difference and was set up for aluminum. The HSS did not like 1018 @1000 RPM and 2" on the fly cutter. Go figure. :)

So I can regrind it and run at a much more sane 100 RPM or so. But that seems like it will take a while as I would need a matching slow feed rate. I could live with that, but it's nice to know what options are out there.

I tried a 3/8" carbide endmill. Worked great, though once I ran the numbers I was babying it and it probably would have worked better with higher RPM and feed. A larger carbide endmill might be an option here.

The insert based fly cutters and face mills seem like they would work faster, but I know I've read that interrupted cuts are not a great idea with inserts. This is working with about 1" material, so it would be interrupted. Eating inserts doesn't seem like a great plan. Even larger parts would have some interrupted cutting with a fly cutter at the ends. Are the inserts used for these tools somehow better for interrupted cuts?
 
The face mill is the way to go, in my commercial shop I had two insert facemills for the Bridgeport type mill; the used TPU inserts and held up well they work best if at least two cutting teeth are engaged in the cut at all times; also shell end mills work well for such work; I think nothing looks worse that a multitude of small end mill traces on a large surface, a cutter should, ideally cut the surface in one swath, except for quite large surfaces where it would be impractical.
 
I've been using a Sherline carbide insert flycutter for almost 20 years now and a Tormach Superfly (uses a single insert) for several years and have had no issues with the insert being damaged by the interrupted cut as you run onto or off the edge of the work. The inserts last a long time, too. The Superfly can extend about 3" from center so it can theoretically face a 6" piece in one go. Works good, too, although you won't get mirror finishes with it. Outlasts HSS by a long shot and works on low HP mills.
 
Thanks guys. It's good to know that the inserts don't get messed up too fast. I didn't want to spend a ton replacing them. HSS is easy to sharpen, but I can't do much about chipped carbide inserts.
 
Brazed carbide lathe tools are also good for interrupted cuts with a fly cutter or face mill. They are tough, less brittle, and can be pretty easily reground on a carbide grinder. Look for good brazed carbide, vintage USA over Asian imports. It is pretty easy to make a head to hold a brazed tool or four. There are also old heads that will do the same job a lot cheaper than the latest and greatest. Sometimes a face mill that accepts square shank lathe type brazed carbide tooling can be had really cheap without a full set of cutters. Make your own or regrind brazed carbide lathe tools!
 
Hmm, don't think the tool budget will let me buy a carbide grinder at the moment, but perhaps a deal will present itself. Always nice to have options.

And just because I already have it, I sharpened up the HSS and adjusted the speeds and feeds. MUCH better, and the HSS is still nice and sharp. Slow, yes, but once I got a feel for it I could set up, turn on the power feed and clean up another area of the shop, check the bandsaw cutting the next part, etc.. The chips look like the ideal lathe chips.

IMG_20190103_000150.jpg
 
I'm with Bob, brazed carbides are quite effective and a very cheap way to get experience. I got the cheapest ones I could find on Aliexpress. They hold up just fine except when I drop the fly-cutter. I just bought a green wheel for my bench grinder to sharpen them. A dedicated carbide grinder would be nice......someday.
 
ttabbal said:
Hmm, don't think the tool budget will let me buy a carbide grinder at the moment, but perhaps a deal will present itself.

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Looks like you have it all worked out.
If you later decide to go to cemented carbide, you can get a diamond cut-off wheel at HF for $10.99. I made an arbor and use it in a drill press. Works great, and it cuts fast. I get a mirror finish on aluminum and almost as good on mystery steel with cemented carbide in my shop made fly cutter. By the way, when I use the fly cutter I take light cuts so the interrupted cut is not a real issue.
 
There are lots of ways of working around buying a carbide grinder. You can use green silicon carbide wheels, followed by a diamond tool, which could be a hand file, a $15 import diamond plated plate, diamond lapping compound charged into a wheel, or lots of other choices. Spending big money is not necessary. I got my HF carbide grinder from my brother, in new condition but missing some small parts, for $80. Keep looking for deals and ideas...
 
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