17-4 ph vrs 303

[RSG]

Hey gang!

I know that 303 has sulphur which makes it easy to machine and I have lots of confidence using it, but I'm told it's wear resistance is not favourable.

I've redesigned my spool clicker on my reels using a clicker plate out of 303 but now want to use 17-4PH instead. My question is, will I be able to make these parts without much difficulty using 17-4 like I can with 303 using the tooling below? I can't really say how much contact they will have as it's periodic with usually about 10 turns of the handle every now and again when engaged. Basically it's only in use when travelling from spot to spot so the spool doesn't turn....I know, not much to go on eh!

Lathe - Carbide inserts, Mill - HSS .053" ball nose end mill



Thanks in advance
Ron

[GlennW]

I'm surprised you haven't had rust issues with 303.

[Harold_V]

The makers of 17-4PH suggest that the material not be put in service without heat treat. It is generally provided in the solution annealed condition. I don't understand why they make the recommendation.

Heat-treat of 17-4 is quite easy. No quench required, and the material can be machined after heat treat, although condition H900 is a little harder than one might enjoy. The higher the condition, the softer the part.

17-4 machines just fine, although it is not free machining. Because it is precipitation hardening, there is little to no distortion upon heat treatment, and the low temperatures involved do not scale the material. It does come out of heat treat colored, however. Generally anywhere from bronze to deep blue color. The H condition to which it is hardened reflects the required temperature. The material is known to shrink upon heat treat, but that is a predictable number, which is on the insignificant side of things unless one is trying to hold a tight tolerance. If memory serves, it shrinks .0006"/inch.

You likely would encounter a little difficulty using a small ball end mill. Certainly, more difficulty than you'd experience with 303, but if you've achieved success with 303, you'd likely be able to overcome the problem. Lighter passes would be in order.

The rusting Glenn mentions can be eliminated by passivation of the machined part. Proper passivation does nothing to the size of the part, but removes any free iron that might result from machining. If there is rusting, it is usually just superficial.

H

[RSG]

Thanks Harold, I currently take one pass with the ball nosed endmill at .014" so perhaps two then, I run the mill at 4200RPM for the small endmill but any particular speed/feed for the lathe work or is it consistent with 303?

Glenn, I've never experienced rust in my parts ever! Now perhaps a different issue if the reels were used in salt water but they are designed for fresh water fishing.

[partime]

I prefer not to machine 17-4 in the annealed state. Would far sooner turn or mill as H900 or H1150. One of my favorites for stability, finish and strength. I find it machines excellent with an excellent result. Not free machining as has been noted but that should not deter you. Agreed that it is not always easy to find and is $$.
Perhaps it would be worth your time to source a scrap piece form a local machine shop and test it out. Just my .025.
T.

[Harold_V]

I currently take one pass with the ball nosed endmill at .014" so perhaps two then, I run the mill at 4200RPM for the small endmill but any particular speed/feed for the lathe work or is it consistent with 303?

Depends on the condition. In condition A (normally provided this way) it has a machining rating of 48%, while 303 has a rating of 78%.
Condition H1150 comes close to 303, though. It rates at 76%. In that condition the material yields 33Rc on average.
Condition H900 typically yields a hardness of 43-45Rc. While it machines in that condition, it isn't as friendly as higher conditions, including A. That said, for the 1/16" ball end mill, you most likely could stick with the 4.200 rpm, as it's about the right speed for the operation. I do think two passes would be in order, though, to offset the tougher cutting condition. I'd likely try something like a .010" pass to rough, followed with a .004" pass for finish. A little experimenting on your behalf would certainly be in order. I could be wrong.

Once heat treated, 17-4 cuts nicely, often yielding a superior surface finish (which is really good in all cases, assuming sharp tools), but tool life begins to suffer as the material gets harder.

The percentage ratings mentioned above are in relationship with 1212, it being 100%.

H

[RSG]

Partime - So I could machine it easier in its H900 state, then heat treat it! Would I have to send them out to be professionally heat treated or could I do in my shop?

Harold -Thanks, more very helpful information as always.

[Conrad_R_Hoffman]

These guys are our go-to for passivation solutions. Much safer than nitric acid and they make recommendations for just about anything if you call them.
http://citrisurf.com/

[partime]

Ron,
H900 will be a step up in difficulty from 303 however very manageable. You will find it similar to 4130/40 HT. It can be a little tough to drill and tap with hss but for your detent wheel it should work well.
Heat treating would not be required, it's a once an done deal. As Harold said, you have RC 40-45 with H900 and if RC 30 is fine then H1150 machines even better. If subjected to saltwater then passivation as Conrad mentioned, may be in order after machining but I have not dealt with that in my applications.

[partime]

Ron,
I would certainly advise that you try and locate short crop to do a little testing on, especially if you choose H900. I don't want you to think it is an easy material to work with just didn't want to deter you either. My preference is H1150. And if you find it is too difficult then making the parts in condition A and sending them for heat treating remains an very viable option.

[Harold_V]

To be clear, the conditions mentioned ARE heat treated, aside from condition A, which is the solution annealed condition in which the material is normally provided. It is that condition that is not recommended to be put in service.

My thoughts on this matter are as follows.

If you have acceptable performance from a piece machined from 303, either S or Se, the same part made from pre-heat treated to condition H1150 would be superior, as it would be harder than 303 and offer greater wear resistance. It would also machine very similar to 303, although slightly tougher. Surface finish will be superior, assuming sharp tools. 303 S cuts with a slightly frosty surface, while Se is somewhat more shiny. 17-4 machines with a bright surface finish. Light feed rates and positive rake are in your favor, but cuts should never idle, as that encourages work hardening.

It isn't beyond your capability to do the heat treat at home, assuming you have a small oven that is capable of achieving the required temperature (1,150°F), and can time the process. A small burnout oven used for investment casting would work just fine, assuming you'd like to give it a go. Until I put my large McEnglevan heat treat oven in operation, I used such an oven for heat treat.

H

[RSG]

Great advice, thanks!

But!, After speaking to my friend in Ohio who has the grinding shop he said he uses 420 stainless in his rels as it has the amount of hardness required yet has corrosion capabilities without having to have it passivized (thanks for the info btw Conrad_R_Hoffman).

So, with that said would 420 be much more difficult then 303? I think I can do it, just want to hear opinions here as I value them.

Regards
Ron