Halls Rotary Engine

[Kim]

I'm pretty sure she use tool steel, which isn't HSS.  It is a high carbon steel that comes anealed so you can work it, but will harden easily(ish).  There is wattrr harden (W1), oil harden (O1), and air harden (A1).  And probably lots others.  I usually use W1.  You can get it from Online Metals or Speedy Metals, or McMastrr Carr, all the usual suspects.

Kim

[crueby]

I'm pretty sure she use tool steel, which isn't HSS.  It is a high carbon steel that comes anealed so you can work it, but will harden easily(ish).  There is wattrr harden (W1), oil harden (O1), and air harden (A1).  And probably lots others.  I usually use W1.  You can get it from Online Metals or Speedy Metals, or McMastrr Carr, all the usual suspects.

Kim

What Kim said!   On advice from here on the forum a few years ago (from CNR as I recall) I used some O1 to make a cutter, was able to shape it then hardened it, worked great.

[Jasonb]

She is using what we would call silver steel, a carbon steel that can be hardened.

Myself I just use mild steel untreated and replace them if they get worn as it is kinder to your files.

[redhouseluv]

Thanks all that's good to know; also while I was buying some new centre drills (due to the blunting process in my last post), I stumbled across another video regarding spot drill vs centre drills.

The long and short of it was as follows:

Centre drills - use when you need to locate a live/dead centre
Spot drills - use as for when you need to position a drill brill for drilling

Apparently using the centre drills for prior to drilling creates the wobble as the angle is not as shallow as drill bits? I had never come across this before and have used Centre drills for both - is this correct?

[Jasonb]

I've been using spot drills for 5-6 years now and would not go back to starting holes with a ctr drill. I just use a ctr drill where I need to use ctr support or if I want a 60deg hole for a steam union.

I do tend to use the 90deg spot drills which are still not as steep as a ctr drill but find they work well and can be used to pre chamfer a hole or even pre countersink if large enough. Although you can buy 120deg spot drills which suit the 118Deg of most drill bits I've not found the need.

[ettingtonliam]

Theres no 'right' or 'wrong' regarding the use of centre drills for starting a hole, IMHO. Both will do the job. Some folks say that the angle of a centredrill at 60 degrees is too shallow for a normal 118 degree twist drill to start. If thats the case, a 90 degree spot drill will also be too shallow.
Although I've got a few spot drills, mostly I use an appropriately sized centre drill.

[john mills]

Hi
50 years ago as apprentices and before that at school we were told you use centre drills for positioning and starting drills  but no CNC machining centers  as nc machines and then CNC machines became more available you soon find that centre drills failed too often and
at nite classes people how had worked in industry told us to use spot drills.in those day were not available  so you had to grind them
your self  usually from a drill a short one i used about a 7/16" which had been broken off short thin the point and grind to the 90 deg angle.the ones i ground were in the machines for years.And used smiler in other machines i programmed   
later you could by them.Using centre drills it was easy to break them specially in the harder tool steels i did a lot of machining in hot work die steels  we broke a few centre drills before i was told about spot drills. So i would recommend spot drills ,don't need to be big but keep them short.
John

[redhouseluv]

Thanks for all your replies and I got hold of some 120 degree spot drills.

On first use it seemed strange as its such a shallow hole compared to the centre drill, however, I could instantly see the difference once the drill bit enagaged in the hole!

[redhouseluv]

Finished off the governor cam which required a little 'artistic license' with a round file after machining, but pleased with the result.

The swivel is then meant to be heated until red hot and the cam shaft pushed through and then they lock together on cooling. However, I must have made the cam shaft slightly on/under size as it slipped on (and off) beautifully - not what is needed for this exercise.

I corrected this by tapping 4BA through the swivel and cam shaft and will put in a 4BA grub screw (as opposed to the stud in the pic) - not perfect, but solves the problem simply

On the other hand the end swivel bonded with its shaft perfectly using the 'heat shrink' method

[redhouseluv]

I made a ball drilling holder today; another new gadget I have never come across.

Hopefully, it will allow me to hold the governor balls and drill all way through for the pivot pin and tap a hole at 90 degress to that for the swivel arm.

For those of you who have followed my build, the bonus is .................... I managed to use a slitting saw without destroying my mill 

[Kim]

Congratulations on the successful use of the slitting saw! 

Nice ball bearing holder!  That's what I love about this hobby.  I learn something new every day!

Kim

[redhouseluv]

I agree Kim - everyday is a new learning day!

Used the ball holder and it worked a treat; I took heed of the cautions regarding the drilling and tapping of phosphor bronze and it was still quite hairy.

'600rpm, new drill bit, clear swarf continuously, using some cutting oil, nice new 2nd tap' - at each stage it felt like it was going to grab and break something!

[crueby]

Nice holding jig!  Is there a shoulder or groove to set the ball the right distance into the jig when tightening it down?

[redhouseluv]

The depth of the cavity where the ball is inserted is the same as the ball diameter allowing for the correct positioning of the vertical holes (see pic)

[redhouseluv]

A small problem......

The drawing shows the ball pivot pins with a diameter of 3/32" and the holes in balls at the same; I keep forgetting that'll never work! I got the pin truly stuck halfway through the ball and only just managed to withdraw it with a great deal of effort. I found a reamer which was 0.095" as opposed to 0.0938" and this was sufficient to get the pin passing through cleanly.

This phosphor bronze stuff is like a clamp or vice when it gets hold of things!

Other than that, I made the ball cages which still need holes drilled for the governor arms