Drilling hardened steel shaft

[Zephrant]

The local shop that can order me 3/4" steel shaft wants an extra $200 per 12' to have it pre-drilled every 6" with 10-32 blind holes. Since the shaft is only $97 undrilled, I'm looking for cheaper options. The shaft is Rockewell 50-55C (AISI 1566 steel), similar to McMaster-Carr pp 898.

A local machine shop claims that it is too hard for them, and suggested an EDM tapping setup.

Any other suggestions for getting it drilled? This is so I can mount it with a continuous support block behind it, for the X axis of a gantry setup. I'll be using open pillow blocks, probably synthetic lined (instead of ball bearings).

Thanks-

Zeph

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[wms]

Zeph,
We use alot of Electreat 50 from The Steel Supply Company. We use it for guide rods and piston plungers. We just machine the ends, (threads or keyways), and go.

http://www.steelsupply.com/

They don't show this grade on the web site but you can call and request a buyers guide.

Electreat 50 is 50-60c rockwell and you can machine it fairly easily.
You probably would use a carbide drill, but you can get away with cobalt. If you slow things down.

It has a hard case, 115,000 KSI tensile, 100,000 PSI minimum yield, precision ground or chrome plated.

They also have #2 piston material, ground and chromed.

[HuFlungDung]

Yikes, drilling in hard steel is one thing, but tapping is another.

You could consider chrome plated shafting (usually for hydraulic cylinder applications), and hope that the chrome will stand up to a bit of use, as it is quite hard and low friction, too.

However, normal chrome plated shafting is not hard under the plate, but is just a C1045 grade steel bar. If anything strikes it, it will dent.

If you want, you can also buy induction-hardened, chrome plated, which would have the maximum life, and would be dent resistent, too. This gets you right back into the tapping problem. You would need to clearance drill at least 1/8" deep to get through the hard case, then you can drill and tap in the softer interior just like normal.

The straightness of 3/4" shafting is not something that you can rely much on, so you really need to have a straight rail to fasten it to. In that case, you might as well get something a little higher class to start with, like those fancy aluminum extrusions, or a larger diameter round bar.

[cbcnc]

Hi,

It is possible to buy it predrilled. I believe I saw it in the Reid Tool online catalog. But it is available elsewhere.

Chris

[hardmill]

I have thread milled 10-32 holes on steels as hard as
62rc. If you like we can talk.
E-mail me hardmill@rockhardmilling.com

PEACE

[wms]

Guys,
Just ran a TEST.
Grabbed a 5/8 in dia. piece of Electreat 50.

Drilled a #15 (.1800 dia) hole, normal for 10-32 form tap would be #16 (.1770 dia). Used Guhring screw length HSS.

Drill speed was 260 rpm. No problem. By looks of drill, easy 20 holes per drill.

Then tapped hole with a regular 10-32 3fl OSG tap, with Tapmagic PRO TAP lube.

Kind of tough but ok.

Then ran 10-32 FORM tap in same hole, (to open up) again Tapmagic PRO TAP lube.

The hole will not gauge with a 2b thread gauge, but a 10-32 screw will thread in no problem.

By the looks of the form tap, probable 8-10 hole per tap.

If a guy were careful and didn't have hundreds of holes it's an option.

[Rekd]

Keep in mind that on harder materials the percentage of thread is considerably less. In that material, the bolt would break before the threads would strip using 50% or less engagement.

I have thread milled 10-32 holes on steels...

What threadmill you use? I haven't done it that small or that hard, but I know it can be done easily. I love the control of threadmilling as well.

'Rekd teh simpleton

[hardmill]

The mills were Greenfield, all they had were tin coated,
they did the job but tialn coated works best.
And your absolutely right 'rekd you can't beat 'em.

PEACE

[HuFlungDung]

Would you thread mill a single turn at a time in something that hard?

The only thread milling I've done so far is 1" NPT and 2"NPT threads in aluminum plate. I sure appreciated not having to turn those taps in by hand

[hardmill]

I usually prog. about 1-1/4 threads w/ multiple passes.
Per pass depending on material.

PEACE

[Zephrant]

Wow guys, thanks for the help!

I'll talk to the local shop again, maybe I can convince them it is worth the effort. I have thought about trying it at home, but am concerned that I would not line up the holes accurately enough. Maybe I need to find some scrap and try it out.

Thanks again-

Zeph

[Zephrant]

I've got about zero experience with steel in a mill, I've been limited to aluminum and various plastics so far. You guys make it sound easy, but I'm not convinced that I can get it right the first time. If I snap a tap off, I don't have the tools needed to extract it.

Hu- I am planning on bolting it to an 80/20 extrusion.

Hardmill- I greatly appreciate the offer. If you were closer I'd be on your doorstep with a case of Henry's.

WMS- Thank you very much for your testing- I am convinced that it is possible, but am not sure I can convince a local shop to help me.



I did come up with a simpler alternative (for a price of course). I can purchase 6061-T6 shaft with a ceramic coating on it, for about 20% more than steel shaft. That is something that I certainly could drill and tap.

Anyone use it? It's manufactured by a company called Simplicity, and is called feather-shaft.

http://www.pacific-bearing.com/files/pdf/shafting.pdf

Zeph

[Zephrant]

I got a quote back of $57.60 for 6061-T6 ceramic coated shaft, 3/4" x 12' long (plus shipping), so that is looking like the cheapest option for me.

Thanks again for the help-

Zeph