Milling slots in 1045

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RSG
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Milling slots in 1045

Post by RSG »

Quick question.

I need to mill some slots in a piece of 1045 steel so I can mount it to my new rotab. It's 6.5" dia., 1/2" thick. Since I will be using HHS end mills would it make sense to start with a 1/4" E/M and work up to the 1/2" dia or just take several passes with the 1/2" E/M right out of the gate.

Thanks in advance.
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SteveM
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Re: Milling slots in 1045

Post by SteveM »

How wide of a slot do you need?

You may know this already, but if you need a 1/2" slot, you shouldn't use a 1/2" end mill.

A 1/4" end mill is a LOT more fragile than a 1/2" end mill.

A good way to do it is to plunge mill undersize along the slot with a center cutting end mill, then mill along it to clean it up.

Steve
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tornitore45
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Re: Milling slots in 1045

Post by tornitore45 »

The way I would do it is to drill 7/16 holes at 1/2" center to near depth or through. Then clean up with a 1/2" end mill.
2 reasons: my mill is not very rigid, I can resharpen drill bits but not end mills.
Mauro Gaetano
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SteveM
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Re: Milling slots in 1045

Post by SteveM »

tornitore45 wrote: Mon Apr 30, 2018 12:33 pm I can resharpen drill bits but not end mills.
Good point!
John Hasler
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Re: Milling slots in 1045

Post by John Hasler »

If the slots are to be 1/2" wide don't use a 1/2" endmill. That will give you an oversize slot with a poor finish. Open up the center of the slot to slightly less than full depth with a 3/8" or a 7/16". Finish to full width and depth by conventional-milling alternate sides.
SteveM
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Re: Milling slots in 1045

Post by SteveM »

If you HAVE to mill a 1/2 slot with a 1/2" endmill, use a 2-flute endmill - the forward flutes on the 4-flute will pull the cutter sideways, resulting in the oversize condition John refers to above.

Best is to do as John says and mill down the center undersize and then using the undersize cutter, do passes on each side to finish the width.

Steve
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Harold_V
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Re: Milling slots in 1045

Post by Harold_V »

John Hasler wrote: Mon Apr 30, 2018 12:48 pm Finish to full width and depth by conventional-milling alternate sides.
Even with a relatively light machine, finish passes (a few thou) are generally best taken by climb milling. The resulting finish is superior to conventional milling, especially if lubrication is provided to the cutter. If the cutter is inclined to pull the part, snugging the lock(s) will generally overcome the tendency.

I fully agree that rough cuts are best done conventionally, however. Even tight machines tend to have trouble with climb milling, especially in steel.

H
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Russ Hanscom
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Re: Milling slots in 1045

Post by Russ Hanscom »

1045 is a hardenable steel, we use it for mild duty springs and lock nuts at the RR. It may work harden. FYI
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warmstrong1955
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Re: Milling slots in 1045

Post by warmstrong1955 »

1045 machines quite nicely.
I make a lot of hydraulic cylinder rods out of chromed & hardened 1045.
For turning, I use carbide....to get thru the chrome.
Threading, HSS.

I also cut a lot a key-ways in 1045 bearing shafting.
Again, I usually use carbide (end-mills), as I'm trying to get 'er done.

Bill
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ChipMaker4130
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Re: Milling slots in 1045

Post by ChipMaker4130 »

Well, just how close to 1/2" do you need to be? And, what kind of slot finish is acceptable? Sounds to me like this might be some kind of fixture plate for your rotab. If so, fit and finish don't need to be perfect and you can save a lot of time and aggravation by using a 1/2" roughing cutter for the whole operation. That alone will cut your machine time to less than 1/4 of what you'll spend using a smaller smooth cutter and multiple passes.
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Harold_V
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Re: Milling slots in 1045

Post by Harold_V »

ChipMaker4130 wrote: Tue May 01, 2018 8:05 pm Well, just how close to 1/2" do you need to be? And, what kind of slot finish is acceptable? Sounds to me like this might be some kind of fixture plate for your rotab. If so, fit and finish don't need to be perfect and you can save a lot of time and aggravation by using a 1/2" roughing cutter for the whole operation. That alone will cut your machine time to less than 1/4 of what you'll spend using a smaller smooth cutter and multiple passes.
I'd suggest that it all relies on if the slot is a part of locating, or not. If it's simply a tie down slot, yeah, it just doesn't matter.
The problem with using cutters of the same size as the target dimension, aside from a less than good finish, is deflection, which is almost impossible to eliminate, and difficult to predict, as multiple things alter the amount, including depth of cut and feed rate. If location is critical, it's hard to beat using an undersized cutter. End result? On size, and on location, with a superior finish. That's assuming good shop practice is employed.

There's times when you're far better served to take a little more time to ensure the proper outcome.

H
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RSG
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Re: Milling slots in 1045

Post by RSG »

Thanks for the replies. I had forgotten about posting this question till now but have yet to do the work, it's Turkey season here you know... :lol:

I spoke to a machinist the other day who echoed pretty much what you all have said. One thing he mentioned (as did Torentore 45) was to drill holes along the slot first then come back and mill the final slot. To answer some of the questions raised here as well this is simply a hold down slot for the "T" nuts so it neither needs to be accurate nor have a pleasant finish. I machined the faces on the lathe using carbide and it came out beautiful but I don't care to buy a carbide 1/2" E/M so it looks like the drill method is going to be the best application. I'll take care to not allow work hardening.

Thanks for the help guys......
Vision is not seeing things as they are, but as they will be.
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