Machineing Steel Rod ?'s

gonefishinNovember 20, 2004

I am sure that this is something that is simple to those of you that know, but I do not know the answers, so I seek your expert knowledge and help.

I may be trying to make, or have made for me, some pieces of cold rolled 7/8ths steel rod 3.35" long with one end rounded and a hole centered in the other end that is 3/8ths X 1.75 deep. (picture below). I made a little trial run with the inadequate equipment that I have, using some scrap that is not the right dimension, yesterday to kinda get the feel of what is going to be involved. To do it myself will probably involve buying some more equipment and / or rigging up something to hold them the right way under my drill press and an easier way to round the end. They need to end up smooth enough to have them powdercoated. I have downloaded the eMachineshop from the net but have not yet mastered the CAD drawing thing, and would like more info before I approach any local machine shops. Several questions that I have are as follows if anyone with that knowledge would be so kind as to answer them.

1. Suggestions on the easiest way to make them.

2. If I have them made, a ball park estimate of what would be a reasonable cost in lots of say 5, 10 or 20 ?

3. How much would the change to a little different dimensions, an inch longer, or smaller diameter affect the price ?

4. Would stainless steel be much more expensive ? (I know that it is harder to work, I can cut it with a chop saw and weld it, but never had much success trying to drill it.

5. Does freezing stainless steel for a week or 10 days increase the hardness of it ?

6. If I wanted some of the parts with a slight taper getting smaller toward the rounded end, I assume that would have to be done on a lathe or milling machine, how much could I expect that to drive the price up ?

Any suggestions and help would be apprciated, thanks in advance and see pictures below.

Bill P.

Pattern I am trying to follow:

First practice effort on scrap without regard to precise dimensions.

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spambdamn_rich

1. Suggestions on the easiest way to make them.

I would make these on a lathe.

2. If I have them made, a ball park estimate of what would be a reasonable cost in lots of say 5, 10 or 20 ?

This looks like a pretty simple part. If they are all the same size, that would be even easier. Pricing would depend on tolerances (how precisely/accurately you want them to be made) and finish. Offhand I'd guess that for +/- .010 these could be made for about $25 each for 10 or more. I don't think you're going to see a big price drop until you are talking about hundreds.

3. How much would the change to a little different dimensions, an inch longer, or smaller diameter affect the price ?

If you mean two different parts, each with different dimenions, that might increase planning and set-up time, so it could drive the price up a bit, depending on volume requested.

4. Would stainless steel be much more expensive ? (I know that it is harder to work, I can cut it with a chop saw and weld it, but never had much success trying to drill it.

This would depend somewhat on the type of stainless steel. Some are easier to machine than others. The more difficult types get harder as you machine them.

5. Does freezing stainless steel for a week or 10 days increase the hardness of it ?

No. Again, depending on the type of stainless, but most are hardenable by cold working. Some, like that used for knives, are hardened by heat treatment.

6. If I wanted some of the parts with a slight taper getting smaller toward the rounded end, I assume that would have to be done on a lathe or milling machine, how much could I expect that to drive the price up ?

These parts need to be made on a lathe, anyway. There is no economical way to make them on a drill press, IMHO. A taper would add to the cost proportional to the amount of time needed to set up the taper equipment and produce the taper. Again, tolerances would impact pricing.

You don't need a cad/cam drawing to get a price quote, but you will need a definite drawing, dimesions, tolerances, finishes, materials specified. I don't think it could hurt to go to a machine shop and discuss your general plan so you can get a better idea of what they want to see up front.

Remember, a drawing is a contract and if the shop makes what you show them on the drawing, and then you decide it wasn't what you wanted after all, you're still responsible to pay for what they made, if it was made to the spec of the drawing.

You can probably count on being charged about $1 to $2 per minute of machinist time it takes to make these parts. Multiple specs, fine finishes, small tolerances, complex shapes of course will take longer and will drive up the price.

If you need hundreds to thousands of these parts, then a shop could program it into a CNC lathe to make, which could drop the cost significantly per part. But you need the volume to cover the cost of CNC - the machine, the programming time, the operator time, maintenance, etc. I don't think anyone would want to run the CNC just to make 20 parts, but you could always ask. Again, settling on a single design would save time and money.

    Bookmark   November 20, 2004 at 8:31PM
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gonefishin

Thanks Rich, I do appreciate it, and gave a little more detail to your posting on the tempering metal thread.
Bill P.

    Bookmark   November 20, 2004 at 10:36PM
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spambdamn_rich

Re: freeze hardening of stainless.

I was wrong, some stainless steels can be hardened by freezing. However, we're not talking your average chest freezer. The temperatures required are cryogenic, as in liquid nitrogen. The process is intended for stainless steels designed for and put through a heat treament hardening process. Finally, the process must be carefully controlled and followed up with a second tempering heat treatment, or the result will be too brittle (as will heat hardened steels that are not tempered).

It may be that stainless steels not designed for heat treatment hardening might experience some hardening after cryogenic treatment. But I'd think that for a guitar slide, the best course, if a hardned product is needed, is to use a heat-hardenable alloy and rely upon standard heat treatments for wear resistance.

Here is a link that might be useful: Crygenic

    Bookmark   November 21, 2004 at 12:13AM
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gonefishin

Thanks for the info Rich, and the link. I checked it out and know that I will not be trying anything like that. I would also expect that to send them to those folks to have them done would probably be pretty expensive. However I guess if there is a market there to justify such for him, it might be worth it. There are still things that supprise me, that is for sure.
Bill P.

    Bookmark   November 21, 2004 at 9:20PM
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