Advice on making shaft

[Madbrace]

This will be a shaft for a needle bearing clutch that needs to be heat treated to 58C. OD .986" by .800" long with M14 thread. Tolerances are .001+- on the OD. This will be a high volume piece.
The plan right now is start with 1” E52100 and machine on the CNC to correct dimensions then heat treat.
Could forging this piece be a better idea? We are trying to keep cost down.
What do you guys think?

 

[unclesyd]

I would definately look at using AISI D2 tool steel for this part. You can get Rc 58 with by air hardening. There is almost no dimension change on heat treating of a part this size.

 

[CoryPad]

Is the hardness requirement just on the surface or does it need through hardening? I imagine it only needs to be surface hardened, which means you could consider different steels and either induction hardening or carburizing. I imagine your cost structure won't allow D2 tool steel. For reduced manufacturing costs, you could consider cold forming the part instead lathe turning. Regardless of the process, likely you will need to do final machining (hard turning or grinding) after heat treatment for critical locations like bearing seats, etc.

 

[mfgenggear]

upto 5000 pc's
bar feed chucker or screw machine
heat treat
then centerless grind

for over 5000 pc's
multi spindle screw machine

 

[Madbrace]

I would really like to avoid grinding if possible after heat treating. D2 sounds good but like someone said price will be a issue, could A2 be an alternative?

Thank you very much for the input guys.

 

[BobM3]

There's also "hard" turning. I believe they (manufacturers of the machines) claim they can turn Rc60 with these machines. Google "hard turning".

 

[unclesyd]

Yes you could use A2 though it isn't as stable as D2 but in your size it dosn't matter. I think you will be able start with size, thread and heat treat with no problem.

 

[juergenwt]

Madbrace - How about posting a print?
There are a few things that ring an alarm bell. Looks to me like you have a metric print. Most likely 25mm shaft. I would check the tolerance given. It should read something like this:
25h7 or some other designation. Since this is a high volume part it pays to be sure you are doing it right. I have seen many mistakes made in situations just like yours.
Material: Not D2! almost no resistance to shock. It is very stable in heat treating but tough to machine. Good for high volume punch and dies with a solid punch and die block.
If tool steel - I would go to S7. Otherwise use low or medium carbon steel and case harden.

 

[Madbrace]

I am replying from my phone so can't post prints. It is for a 25mm needle bearing the dimensions used for the OD are the ones in the bearing manufacturers shaft specs.

 

[unclesyd]

juerqenwt,
I really like S-7 but it will not get the hardness required in the OP without case hardening. I believe that D2 gives excellent wear resistance along with adequate toughness for this part. We use it for all our small gear pumps along with most components in the drive system. This is a pretty rough environment requiring a tough material. Some of these parts have been running on a continuos basis for over fifty years.
By using A2 you give up a little in hardness and wear but again I think this part made from A2 will also be good.

We don't find D2 or A2 hard to machine on modern machinery.

 

[EdDanzer]

Depending on the duty cycle and actual load you may be able to case harden C1018 and either grind or hard turn.

If this has a high load case hardening 8620 and finish grinding or hard turning would be the next lowest cost.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[TVP]

If "high volume" means more like 500,000 pieces than 50,000 pieces, then cold forming/forging followed by a secondary machining operation will likely be the lowest cost, especially if the shaft has several different diameters. While I understand the logic behind unclesyd's recommendation, using D2 or A2 as a starting material for a truly high volume bearing shaft will likely be too expensive.

 

[mfgenggear]

TVP

you sparked my interest how would these parts be forged?
from a bar loader as not to cause handling issues.
in other words how would this be automated.
or do you mean forged bar.

the secondary operation would require load & unload,
with an automated robot.

High Volume > 10000 pcs
or > than 100000 pcs
or > than 1000000 pcs


A-2 & D-2 are expensive materials,
I guess with out knowing the exact application & budget
it could be cheap material like AISI 1095 or is corrosion an issue.

Madbrace

what qty's
centerless grind could be avoided by not recomended to so for bearing application.

 

[Madbrace]

First of all I want to thank everyone for their advice.

Qty will be around 2000-5000 pcs a month.

 

[juergenwt]

Unclsyd - One can not argue with success and in your case and for your product D2 seems to be the material for a reliable good quality part. Unfortunately we do not know the use for the part Madbrace is making.

 

[unclesyd]

juerqenwt,
I whole hardly agree with you about the part in the OP. I guess I'm too old to change my way of thinking, have to watch the loading on the brain cells, that in making a part or component start with the best possible and work down form there. Fortunately I'm not a straight line thinker as I have been certified a "zig-zag" thinker by testing. In other words I can change my approach on fly no as a sycophant but by thought and reason.

Like I'm still thinking about making this particular part by rolling the thread on the appropriate stock , heat treating and the centerless grinding.

And as you say we don't have a handle on this part to where one is able to look for the best approach to making it.

 

[TVP]

mfgenggear,

Shafts for the automotive industry are cold formed/forged on horizontal presses (also called headers, cold formers, etc.) or on vertical presses (both mechanical and hydraulic). Typically these are not one-piece flow items, meaning that the parts are accumulated into bins rather than proceeding directly to the secondary machining operation via a robot or conveyor system. The bin of formed parts is then transferred to a machining cell where it is either manually loaded into the machine or some type of automation is used with a robot, conveyors, etc. Parts are handled extremely carefully after machining, on the way to the final processes (heat treating, grinding, etc.).

 

[Tmoose]

Is this a rotating or oscillating application? Is some axial motion required too? What are radial loads? I think for anything but the lightest duty, shortest life anti-friction bearings, the roundness, surface quality, and case depth requirements will mean finish grinding is required.

 

[unclesyd]

I would definitely look at the thread grinding approach to your part. The part could be at size on the diameter made from either a through hardened (like A2) or carburized material ( like case hardened 1060) and then have the threads ground.
There are any number of ways to approach manufacture if your part if you go with thread grinding for finishing.

http://www.drakemfg.com/threading.htm

http://www.bostoncenterless.com/index.htm