Machining HSS

What's the heat-treat condition of the shaft you're turning? If it's annealed, it is possible to cut it with a HSS tool, but it's truly miserable.

Carbide is a much better bet. It's also hard enough to cut fully hardened HSS, but you need an absolutely rigid setup and a good, tight, and rigid lathe for that kind of work.

BTW, the "tin" coating actually is TiN: titanium nitride. It helps with tool life but it doesn't do much to improve the hardness of materials you can cut -- after a few seconds of use, anyway.

-- Ed Huntress

Thanks Ed. After Googling some more, the general concensus seems to be that Dremel plus abrasive cutoff wheel will work (shaft is only

3/16"). I should be okay there but need to turn down a portion of the shaft from 3/16" to 1/8" after cutting. Is this a waste of time or worth a try?

Oh, anything is worth a try. Since you're only knocking off 1/16" from the diameter, you probably could grind that off with the Dremel, too, if you're only talking about a short section. Just rig up something to hold the Dremel in the toolpost and go *very* slowly. Cover your lathe bed and as much of the saddle/cross slide/compound as you can. I like using aluminum foil for that job but oiled newspaper works fine, too. Just leave a few spots oil-free so you can tape the paper down.

For example, I have a table clamp, or whatever they call it, for my Dremel, which holds it in position for hands-free grinding. If I take it apart I can get the stem of the holder in my rocker toolpost. This is adequate for very light and non-precision grinding, and probably would do the job for you.

I've even held the Dremel in place with duct tape when I had to. (I could lose my amateur machinist credentials for that one. )

-- Ed Huntress

"Ed Huntress" wrote: (clip) Cover your lathe bed and as much of

^^^^^^^^^^^^^^^^ See, this is an example of why it is good to check threads you think you're not interested in. Here's a good suggestion that would be easily missed.

While we're on this subject, old machining books tell you to used oiled rags. That was back when they told you to tuck your tie inside of your shop coat. Don't do it -- rags have gotten caught in turning chucks and they can raise hell.

Aluminum foil is neat and easy. Just don't slip up and dump the grinding grit in your chuck or on the bedway when you take it off. I try to make a sort of tray out of the foil, so the grit doesn't just fall off. Oil on the paper will hold some of the grit, but don't count on that, either. I spray the paper with WD-40 because it's easy, not because it's the best way.

And don't grind on a good lathe any more than you have to.

I'm sure most members here know these things but some newbie may find it worthwhile to consider.

-- Ed Huntress

Haven't heard the oiled newspaper one before. Overlapping way covers from aluminum foil, I've heard about.

Does the paper overlap or does it just bunch up?

Wes

It depends on how crafty you are.

I do not grind long shafts on my machine, so I haven't had much experience trying to make it all behave like a fancy way cover. I think it would be very difficult.

-- Ed Huntress

Disaster! The tip of the insert broke off.

Here's the story....The drill chuck I have is limited to a capacity of

1/8" and I want to use a 3/16" counters>

Disaster! The tip of the insert broke off.

That's a mighty small drill chuck. I would be worried about springing it, with a larger bit that has a reducing shank. Are you drilling steel?

Good luck!

-- Ed Huntress

Looks like it's my lucky day. The drill press manufacturer was able to hand pick a 0JT mount Jacobs 5/32" chuck with capacity just greater than 3/16". I'll just buy that al>

Great. That sounds like a much better solution.

FWIW, you may be interested to know that typical HSS drill bits -- good ones, that is -- are hardened at the tip and up through the flutes, but that the butt end of the shank is left somewhat softer, to allow the bit to take some bending stress without breaking. That's why it's so easy to raise big burrs on even a quality HSS bit when the bit slips in the chuck under power. So the part you were trying to turn is not very hard.

Even so, you saw how difficult it can be to turn or mill. Unless you have modern production machines and tools that are made for hard turning, you're going to find machining HSS to be nearly impossible, even when it's not fully hard. If it's fully annealed, you can just do it. But machining it hard, or somewhere in between (like drill bit shanks) is going to be very difficult or impossible on flexible machine tools.

-- Ed Huntress

IIRC, there is a Jacobs chuck which is 3/16" which has a J0 taper.

====================================================================== Capacity Dimensions Minimum Maximum Closed Length Open Length Sleeve Diameter Hard Pin Grip Torque Runout Model in mm in mm Mount Key in mm in mm in mm Ft-lb Out Nm Out in mm 0 0.0135 0.000 0.156 4.000 0JT K0 1.450 36.800 1.100 27.900

0.850 21.600 2.00 2.71 0.004"@0.75" 0.10mm@19mm ======================================================================

O.K. This one is not quite as large as you would like -- only 0.156" (4.000 mm), which is just below 5/32". This must be the one which I was remembering. I had one of those and a 1/8" Albrecht which spent time on a Cameron Micro Precision sensitive drill press.

Indeed so. DoN.

I don't know, Ed, when I've needed to turn down a drill shank I've just chucked the drill in my lathe and turned it down - I never noticed a problem - I don't remember picking up any special tool, but I probably used either brazed carbide or an Aloris BXA-16 that has the triangle inserts - I would think that in these days everyone with a lathe, even a little one, would have a few suitably sized carbides - they are often cheaper than HSS. My lathe is not a "modern" one, though it is not an antique (Logan/powermatic 12 inch).

Carbide is the right tool material, and if it's sharp, and if your drill shank is properly annealed (partly, I guess, or given their first tempering at a higher temperature, because they aren't dead soft), it's probably not a problem if you're practiced at getting everything right. But a 3/16" bit is going to limit the overhang, and the OP says his HSS cutoff blade wouldn't touch it and that he broke the tip off a carbide bit trying to turn it.

He may need some more practice, or maybe the shank of the bit is too hard. But cutting stuff like that on an old toolroom-sized lathe or a small Chinese lathe is not a job for someone just getting started, IMO. I was trying to emphasize the importance of rigidity. And if the HSS is fully hardened, that's a hard-turning job for a modern lathe, also IMO.

-- Ed Huntress

Similar scenario here, it's a Cameron MD-70 (deep throat) drill press with the Albrecht 1/8" chuck. It's converted to CNC with 12"x8" XY travel. In terms of drilling it's far more useful than the other drill presses and the mill I have here except for the capacity. Need to drill and countersink fairly precisely over 1000 holes for #2 flat head screws. The drilling is the easy part, however, a 3/16" countersink is needed for the countersinking. As stated earlier, Cameron was able to hand pick a 0JT Jacobs 5/32" chuck capable of opening beyond 3/16" so should be good there as well. Another alternative they offered (at nearly twice the price) was a 1/4" 1JT chuck/spindle combo. Thanks!

>

It was a shiny HSS countersink BTW.

>

An alternative is to let the Cameron drill the holes, then use a piloted countersink in a Micro-Stop ball bearing cage to control countersink depth on a manual drill press. These piloted countersinks and MicroStop cages are used for countersink rivets for aircraft use, so there should be something available with a small enough pilot.

At least the hole location would be pre-determined by the CNC modified Cameron so you just slide the workpiece until the pilot goes in and countersink.

Best of luck, DoN.

P.S. It is amazing how much the cost of those has gone up. I paid $150.00 for one which had just been used to demonstrate around the lab for one day, then the orders were placed (including by our particular section), and I bought the demo unit for home. (I knew that it had been used only for that one day, because I helped unpack it and pull the heavy-duty staples from the box. :-)

Right now I'm using the Cameron to drill the holes then use a drill- point countersink (aka center drill) in the mill and use the mill's depth stop for countersink depth. Was using a collar at first but that mars the surface too much. It's after seeing how quick and effortless the drill routine was, compared to the countersinking, that I decided to CNC the countersinking as well. Will be using a six flute countersink BTW.

Tell me about it, mine cost me an arm and a leg 5 years ago. They probably cost two arms and two legs today. No complaints though, they're accurate, fast enough and easy to convert to CNC. Use it mostly to drill PCBs and solder paste stencils.

>

A center drill? What angle of countersink do you need -- or does it not matter -- just chamfering of the holes?

The MicroStop countersink cages don't mar -- very good thrust ball bearings to serve as the stop, a wide smooth flange, and they are available with nylon or some other soft plastic face on the flange when you really need freedom from marring.

I've got a couple of them -- one with a full circle flange, and the other with a cutaway so the flange covers perhaps 190 degrees or so, cut away flat to allow you to work close to a step. Both of mine came from eBay auctions, with a mix of piloted and pilotless countersinks and a few cutters designed to cut a rivet head flush to the metal. The "stop" part of the "Micro-Stop" can be adjusted in steps of 0.001" to select the depth which really works best for you. You can even use them with a drill motor -- or an air drill motor and still not get marring or distorted holes.

O.K. The six-flute ones (Severance, I presume) I find I get more chatter-free operation if I bring the cutter into light contact with the workpiece, then start the motor, and plunge to preset depth. (Obviously not MicroStop there, since they don't have the six-flute countersink bits.)

O.K. That is what I got it for, but I've used it for a lot of other things, including making keys for a rack-mount disk drive housing with six plug-in disk carriers which came from a hamfest -- but which did not have the keys, which were needed to turn the disks on after plugging in. Luckily, they were unlocked, so I was able to take out one switch-lock, pick it to a half-way point, measure the depth of the pins (4-pin barrel key) and then use the Cameron with an index head for a Unimat to drill them with a tiny end mill to the proper depths.

Yes -- I know that is pretty close to milling with a drill press, except that I had no side motion, just plunge so it worked well enough.

Does yours have the 1" travel dial indicator to determine plunge depth?

Enjoy, DoN.