rrTV-PHOTO   New HD TV
HOME   rrTV-PHOTO   GALLERIES   MY GALLERY   HELP-FAQ
myHOME PM pmRR MEMBERS 266 ONLINE 29 EVENTS SEARCH REGISTER  START HERE
 
1 page636 viewsPOST REPLY
CarbonXtreme . Midland Helicopters . HeliProz

.
.
CAD - Engineering - Technical > How much distortion from hardening process
 
 
nigel99
Senior Heliman
Location: London

Hi,

I am going to start making my own main shafts and was going to use what we call "silver steel" here in the UK. This comes in stock sizes which are guaranteed to fairly fine tolerances as they are finished on centerless grinders. So I have ordered myself some lengths of 10mm bar; now as it comes even prior to any hardening its better than mild steel however after drilling the required cross holes and machining the odd shallow groove (where the retaining collars usually go) it would be nice to heat harden them however I understand that there is likely to be some distortion. For precision jig/tool making the items would normaly be made slightly oversize, hardened then ground to perfection.

So the question is how much distortion is likely to occur and can it be controlled/minimised to the point that for our purposes as a main shaft it would be acceptable.

Cheers Nigel
06-08-2004 Over year old.
 
 
TMoore
rrProfessor
Location: Cookeville, TN

Nigel,

Quote 
So the question is how much distortion is likely to occur and can it be controlled/minimised to the point that for our purposes as a main shaft it would be acceptable.


To answer the latter part, in a word, no. To answer the former, most likely several thousandths.

If you harden drill rod/silver steel, even the A series, which is air hardening, your only choice will be to polish and then hand straighten in a press. A-2 will normally come in at about 30-35-Rc on the hardness scale before heat treat. Once you harden and draw/normalize the main shaft you will need a press to get it straight, or at least a healthy lathe with a damn good 3 jaw chuck to work on the shaft. Unless your heat treater is using vacuum ovens there may be some scale issues as well even with a foil wrapped part.


What machine were you considering using this on?

Terry
06-08-2004 Over year old.
HOMEPAGE  
 
 
nigel99
Senior Heliman
Location: London

Terry

well I have several machines:- 2 of Xcell Pro2k's, Voyager 50 IMZ and 2 of Joker's. I do have an Industrial quality lathe (Colchester Student) with various accessories (travelling steadies etc) however I thought turning hardened steel was pretty much a No No.

I am not overly concerned to do the hardening (i am no 3d maniac) but if it had been easily possible -- then why not. actualy I prefer to go the Titanium route which although not as hard as hardened steel its resilience in minor crashes is very usefull plus of course its very light although rather expensive.

cheers Nigel
06-09-2004 Over year old.
 
 
jb_turner
Elite Veteran
Location: USA

2/1000 of an inch is the tollerance for a main shaft. Why risk that steel on a Heli?... why not just purchase the proper main shaft?. You are risking cracking that steel or splitting it. If I am not mistaken MA main shafts are hollowed and woven which makes it much stronger than silver steel such as you are working with.
06-09-2004 Over year old.
 
 
TMoore
rrProfessor
Location: Cookeville, TN

Quote 
hollowed and woven


JB,

That's a good one, where did you hear that one? I've been a toolmaker for 30 years now and that is a new term on me. How do the steel producers do that? The Min Air main shafts that I have seen thus far have been centerless ground round stock. If their main shafts were hardened you wouldn't see any impressions at the point that the collars located on the shaft, would you?

Nigel,

Plain drill rod/silver steel is hard enough. You can machine the grooves and cross holes and they will work fine. If you want to buy titanium that is up to you but there is little advantage to using it. There are very few machines that are using hardened steel main shafts as almost none need it. Most of the auto hubs have their own hardened sleeves that atttach to the main shafts. BTW, 10mm drill rod will have to polished slightly just to get it in the bearings.

In the CNC business we hard turn steel all the time, even carbide but your machine is useless for this. No, the intention was to use a lathe to straighten the shaft after heat treat. The problem with using hardened main shafting in a crash is all the stuff it will take out because the shaft won't bend.

Terry
06-09-2004 Over year old.
HOMEPAGE  
 
 
KCT
Veteran
Location: Ontario, Canada

I thought that once the shaft has been hardened it does need to be precision centerless ground.

Cheers

Kay


That's not flying, that's crashing with style...

TeamBob00, WildCat, Helitron
06-09-2004 Over year old.
HOMEPAGE  
 
 
nigel99
Senior Heliman
Location: London

Terry

I was intruiged by the "woven" bit personaly i would like a hand knitted shaft.

Anyhow as i said i wasnt overly concerned about the hardening more a matter of possibilities/interest. By the way what kind of lathe do you need in order to turn hardened steel. I am amazed that carbide can be turned.

Cheers Nigel
06-09-2004 Over year old.
 
 
TMoore
rrProfessor
Location: Cookeville, TN

Nigel,

In hard turning carbide I have had success using a slant bed, box way cnc lathe with special geometry PCD (poly crystalline diamond) inserts. The spindle bearings are usually a combination of angular contacts and heavy duty roller bearings. The clamping force on the turret is in excess of 12,000 lbs. Turning carbide is usually to get the blanks to a net shape suitable to finish grind. This is similar to hard turning steel except the insert composition is different. Steel uses CBN or Borazon (cubic boron nitride) inserts for the hard turning process.

Hard turning has been around for a few years now and the machinery and insert technology is now able to make this an everyday reality.

Terry
06-09-2004 Over year old.
HOMEPAGE  
 
 
nigel99
Senior Heliman
Location: London

Terry


Mmmm i want one of those lathes -- no doubt they are really really cheap. seriously though i would like to have a look out of interest do you know a web site where i can see them.

cheers Nigel
06-10-2004 Over year old.
 
 
TMoore
rrProfessor
Location: Cookeville, TN

Nigel,

Here you go: http://www.daewoomt.com/

Terry
06-10-2004 Over year old.
HOMEPAGE  
 
 
nigel99
Senior Heliman
Location: London

So I made a shaft from the silver steel

Terry you were quite right about needing to "polish" it for the bearings to fit but having done that I am very pleased with the result in fact the JR shaft is a very loose fit to the bearings and coupled with the softness of the metal and not having loctited the inner race to the shaft when i took the JR shaft out after about 10 flights there was already considerable wear on the shaft. WHen i flew my shaft it was much quieter and smoother no doubt due to a good fit on the bearings.

Cheers Nigel
06-14-2004 Over year old.
 
 
TMoore
rrProfessor
Location: Cookeville, TN

A good fit does make a difference. You will run into the same bearing issues when you make feathering spindles but the stiffer silver steel is much better from a woof and poof standpoint.

Terry
06-14-2004 Over year old.
HOMEPAGE  
 
 
1 page636 viewsPOST REPLY
ZoomsHobbies . HeliHobby . Ron’s HeliProz South

.
.
CAD - Engineering - Technical > How much distortion from hardening process
  UPDATE SCREEN   PRINT TOPIC Advertisers 

Subscribe to This Topic

Saturday, October 11 - 10:01 am - Copyright © 2000 - 2008 runryder.com | email | link to rr | runryder needs cookie