Building a bed turret

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RSG
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Re: Building a bed turret

Post by RSG »

Thanks Pete!

I think I might have a large dia fly cutter for a HSS blank if that's what you are referring to! You think I should give it a try? As you mention I am learning to run the machine based on listening and watching how it's acting. The problem is that without the experience of others I might think something is not sounding right when it actually is. I have yet to buy is a Machinery handbook. I guess it's time to spend money where it counts.
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pete
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Re: Building a bed turret

Post by pete »

High speed steel will work just fine, at large diameters though you'd need to get the rpm way down. Try grinding and honing the tool tip with a fairly large radius with the slowest feed rate you can manage. That very slow feed isn't textbook correct, but it can leave a beautiful finish at the expense of a bit of tool life. NOT recommended with work hardening material though.Fwiw my 28th edition of MH shows 75 ft per min rpm maximum with HSS for ductile iron.With my VFD, step pulleys and the mills back gear I can get down to 30-50 rpm pretty easy if I don't try to run too long at that speed for motor cooling. So a 6" - 7" diameter fly cutter can work. Unlike what a few manufacture's and video creator's show on YT, fly cutters are ONLY a very light finishing tool. But they save a huge amount of hand work if the surface finish aesthetics are important. The only reason to buy a new Machinery's Handbook would be for there large print edition. I'm now old enough to appreciate that. :-) In a home shop with manual equipment everything your ever going to need plus a lot that's been dropped from the newer one's will be in one from the 1940's - 1970's. It's not hard to find those in very good condition on Ebay for about $20. One of those plus a Machinery's Handbook CD allows printing off the most used charts and formulas you happen to use in your shop and for what your doing the most. Sine tables as just one example. The book because of how thick it is will be almost impossible to scan and print from it. I keep a shop 3 ring binder with my most used MH prints, machine and tooling manuals etc. in it. That alone saves a huge amount of time.

One thing I haven't mentioned, those plates are still a cast material. It will have built up stresses in it just from the way it's processed. Probably less than in a sand cast part, but there will be some.Ideally you want the same amount removed from each side of the plate. So constantly flipping the part from side to side as each cut is taken will help keep them flat. And it's worth while to constantly check for any warp or twist as there being cut. Having a really nice finish on a banana shaped part really hurts the ego. :-(
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Harold_V
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Re: Building a bed turret

Post by Harold_V »

While I'm a strong fan of HSS, in this instance I'd be quick to promote the use of carbide for the finish cuts. It is less critical of surface speed, and is far more resistant to dulling, assuming the proper grade is selected. Because of the large size of your project, there's a lot of miles that must be traversed without wearing the tool. You'll find that a C2 grade will provide exceptional longevity, so the long cuts attempting to create nice surface finishes won't be an issue.

The advice to grind a large radius needs some attention. Too large of a radius in a large fly cutter is an opportunity for chatter to develop. If that happens in your finish pass, which is generally quite light, you may not be able to eliminate the problem without sacrificing a dimension. That may not be an option for you, so make the radius reasonable. With fine feeds, there's no need to go beyond a 1/32" radius, although the cut may tolerate something as large as a 1/16" radius.

H
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RSG
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Re: Building a bed turret

Post by RSG »

Thanks for the feedback gentlemen. I'll take the advice.
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GlennW
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Re: Building a bed turret

Post by GlennW »

Back to my post #4 in this thread, I was running 400 ft min speed with around 20 in min feed with a 2.5" carbide 6 insert face mill and was getting an excellent finish.
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BadDog
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Re: Building a bed turret

Post by BadDog »

I didn't see anyone comment on the inserts shown. I've got some that look just like that and are for aluminum. Converts aluminum blocks into aluminum snowflake blizzards as fast as you can run it, but I don't think they would last any time in steel or cast iron, though I have nothing but gut feeling to base that on.

Using a shop vac with nozzle conveniently located by whatever means are necessary will help a lot with chip interference, and eliminating that horrid black graphite that gets EVERYWHERE. However, depending on filter element, it can clog fairly fast.
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Harold_V
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Re: Building a bed turret

Post by Harold_V »

BadDog wrote: Tue Dec 01, 2020 10:35 pm I didn't see anyone comment on the inserts shown. I've got some that look just like that and are for aluminum. Converts aluminum blocks into aluminum snowflake blizzards as fast as you can run it, but I don't think they would last any time in steel or cast iron, though I have nothing but gut feeling to base that on.
While modern carbide designations may not find that insert compatible with cast iron, the old C2 designation, which is for non-ferrous, stainless and cast iron, would be very much in keeping with a good choice. Needless to say, surface speed would not rival that of aluminum. I strongly suspicion it would do just fine @ 175 sfpm, however.

H
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RSG
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Re: Building a bed turret

Post by RSG »

GlennW wrote: Tue Dec 01, 2020 9:25 am Back to my post #4 in this thread, I was running 400 ft min speed with around 20 in min feed with a 2.5" carbide 6 insert face mill and was getting an excellent finish.
Yes, I must have missed that....again :roll:
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RSG
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Re: Building a bed turret

Post by RSG »

BadDog wrote: Tue Dec 01, 2020 10:35 pm and eliminating that horrid black graphite that gets EVERYWHERE.
Ya, Harold mentioned that dust, I thought he was talking about the chips, not that fine dust that keeps pluming from the cutter. It's all over the place, even in my anodising room which had a sheet covering the door! :shock:
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BadDog
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Re: Building a bed turret

Post by BadDog »

Harold_V wrote: Wed Dec 02, 2020 2:56 amWhile modern carbide designations may not find that insert compatible with cast iron, the old C2 designation, which is for non-ferrous, stainless and cast iron, would be very much in keeping with a good choice. Needless to say, surface speed would not rival that of aluminum. I strongly suspicion it would do just fine @ 175 sfpm, however.
Yes, modern carbide structure/substrate and coatings are a study on their own, more so for mills than lathes. But I was mainly talking about the form. The big long polished "top" rake and polished "bowl"(?) speak of aluminum to me. I've got pricey hard to find Mitsubishi inserts that look just like that, and (to my eye), the geometry wouldn't hold up in any ferrous metal (maybe 12L14?). I've got a few other insert face mills with steel inserts, and they are FAR more robust (to the eye anyway) than those. Both more support for the edge, and much smaller/narrower/shallower rake/chip-breaker profiles. I assume mine like those pictured have big clearance is for ridiculous feed rates in aluminum. I run it very fast, and feed with a servo just about as fast as rapid traverse. It's silly what that thing can do to aluminum (mostly 6061-T6, but also 7075-T6), and I've successfully run it at rates that start to scare me if something went wrong, but I have no sense it was reaching it's limit.

But maybe that's just my limited knowledge, I really only know (vaguely) about the ones I use, but I'm well satisfied with them for my needs and have had no real pressure to expand.
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RSG
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Re: Building a bed turret

Post by RSG »

Actual Russ, you are correct on those inserts you thought were for aluminium. I talked to the guy that supplied them and he said that's exactly what they are. So I'm sticking to some other C2 inserts he gave stating they are a "multi purpose" insert. So far they are holding up well and doing the job.
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RSG
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Re: Building a bed turret

Post by RSG »

So I'm at the stage where I've machined the blocks to rough thickness using my vise and was ready to square up the blocks on all sides. I set the first one using Glenns suggested method (shown in the pic) but I'm having difficulty believing this method is providing a flat surface across the parallel. The reason I am questioning this format now is due to the clamping method. In my mind clamping one side (as shown in the pic) and milling, then swapping out the clamps to the other side to repeat the process puts uneven pressure on one side while machining the other. I did as Glenn said and didn't un-clamp the first side before setting up the clamps on the other side.

Wouldn't doing this warp the part as the bottom surface might not be flat across the parallel? Before I get too far, is my concern unfounded?

Image
Thanks in advance
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