Cast Iron Boring Head

[Jeremy_BP]

Hi all,
One of the projects I'm going to tackle is building a boring head for my mill. I'm planning to use Steven Campbell's design.
I can get cast iron in ~1.5" size cheaper and easier than mild steel. Would it be suitable for such a thing? My thought is that since machines are made from it, why shouldn't the accessories be? However, I really son't know if it would work or not, hence my asking here. What do you guys think?

 

[steamer]

Got a picture of this design?....the answer is probably...but would like to see it.

Dave

 

[Jeremy_BP]

Here it is on dean's site: http://www.deansphotographica.com/machining/projects/mill/boring/boring.html

 

[Mike N]

Hi all,
One of the projects I'm going to tackle is building a boring head for my mill. I'm planning to use Steven Campbell's design.
I can get cast iron in ~1.5" size cheaper and easier than mild steel. Would it be suitable for such a thing? My thought is that since machines are made from it, why shouldn't the accessories be? However, I really don't know if it would work or not, hence my asking here. What do you guys think?

I would definitely make it out of a piece of tool steel (A2), or 4140.

 

[Mosey]

Definitely Tool Steel.
In smaller sizes, you can do as I did, when I picked up an old square-head Criterion for very little off EBay some years ago. It is better than the one I had made.

 

[Jeremy_BP]

What kind of tool steel would you recommend? A2?

My thinking on cast iron was based strictly on price. For example 1.5" diameter rods 12" long cost me:
4140: $30
12L14: $30
1018: $25
A2: $57
P20: $62
Cast Iron: $17

Mosey:
Looking at those prices, maybe I should just buy a cheap import. :-\

 

[kuhncw]

For occasional home shop use I would think cast iron or 12L14 would be adequate for making a boring head.

Regards,
Chuck

 

[Jeremy_BP]

Out of curiosity, what would make cast iron not suitable for such a thing, and what would make various steels more suitable?

 

[steamer]

the only thing cast iron lacks over steel in this situation is
A; stiffness...steel is twice as stiff as cast iron...regardless of hardness
However, for a hobby machine and or shop...I doubt it will matter much.

B; Cast iron doesn't have the ductility of steel, which for dovetail gib of the flexure type (like a criterion head) , could be a problem for if it's flexed too much it could break.
hence the reason for me to see the design that you have. if it's a traditional gib strip affair like a lathe carriage....made of cast iron.....it will work fine.

Dave

 

[Swede]

If you want to make the boring head as a challenge and/or for fun, by all means, go for it. If it is to save $$, that is going to be very hard to do. Some tools are often better bought than made. But again, I want to emphasize, making tools is an awesome activity and if that is what you enjoy, please do it!

I do believe steel is a better choice. I have a fear that hard, interrupted cuts with a CI boring head could fracture it across the dovetail or some other weaker area.

 

[pete]

Ductile cast iron at a minimum. Much better to use tool steel IMO. You'd need good quality set screws to retain the boring bars and slide lock. You need the same idea for the female threads too.

Pete

 

[Jeremy_BP]

Hi all,
Thanks for your responses.
Dave, the design I was looking at has a gib. Gives me a bit of wiggle room to mess up the dovetail.
Swede, there really is no reason for me to make one over buying one. It's probably going to be fun, and I'm sure I'll learn something in the process.

So over all it seems CI is a bad idea. Too brittle. I guess I'll either start looking for other scraps of an appropriate steel or a cheap used boring head.

 

[arnoldb]

Jeremy, it's a fun build if you decide to go for it.
I'd also recommend rather using steel than the cast iron though.

I built one from Steve's design, though I scaled it up a bit:

Dean's build log is excellent, and I shared my build here on HMEM as well.

Kind regards, Arnold

 

[tel]

I wouldn't have any concerns with using cast iron, or even mild steel - tool steel for an item like that for home workshop use would be way overkill IMHO.

 

[steamer]

Gotta agree whole heartedly with TEL Absolutely I would build that with cast iron in a second....think about it....its got a brass gib and made on a machine with cast iron dovetails.... :

Dave

 

[Mainer]

I don't see why not. You have no thin sections that would be susceptible to cracking. IMO something like 1144 would be a better choice, but CI ought to be perfectly adequate. The one thing I question is the quality of threads that you get in cast iron is not always all that great. It depends on the characteristics of the cast iron.

If it turns out to be a flop, you will have had a Learning Experience ??? and can always make another one. But I think you'll be fine, except possibly the threads. Since I assume you'll be using Dura-Bar or something similar, you should be okay.

 

[steamer]

Mainer has a good point about the threads...but Durabar is great stuff.

Dave

 

[Lew Hartswick]

Personally I'd use 12L14. That give the best compromise of strength and machinability.
It will also give more " Bling" (is that the right term?)
...lew...

 

[Tin Falcon]

the build thread that is mentioned recomends 12L14. it is the easiest steel to machine and it should be plenty strong.
Tin

 

[Jeremy_BP]

Well, maybe I'll give it s shot anyway. And afterwards I'll have a lump of cast iron and some brass sitting around, which is never a bad thing.
And I guess at the worst I end up with a boring head shaped scrap. I would start today but I seem to have missed the deadline for will call orders by 30 minutes. D'oh. Now I have to wait until next weekend.