Member postings for Alan Jackson

I copied his triangular gib in my Stepperhead lathe and have to say it works very well in alignment. As a multifunction machine it may save money over separate individual machines but there are advantages in concentricity in being able to make a component say like a gearwheel at one setting, rather than transfering it to a second machine to cut the teeth for example. Adding a vertical slide to a lathe is after all an example of creating a multi function machine.

Alan

Edited By Alan Jackson on 07/08/2012 10:26:57

I thoroughly agree with Ian and John H about polyvee belts, they give all the power you need and can be made as wide as you choose for extra grip. As to suppliers I have found www.essexbearings.co.uk to be very helpful. They even dropped the belts in the post to me then invoiced me afterwards. Great service and I have no personal connection for this plug.

Alan

Edited By Alan Jackson on 05/07/2012 09:20:48

I worked in various drawing offices for many years and checking drawings often took more time than drawing them and mistakes still got through the system. To sign off a drawing as checked meant that you were responsible for the design even though you were checking something that you thought was a bad design or idea it became your responsibility. There is always opinion in checking due to not liking the particular way it is designed (I would not have done it that way) and personal preference so it is a minefield for politics and dissent. Because the checking process was so time consuming and always at a time when everybody required the drawings yesterday the checking process was subject to, shall we say shortcuts. I was once asked to do an 80% check to save time. You know just check the bits that are wrong not all of it. The only way to find the bits that are wrong is to do a 100% check. I also do not think the process improved when computers replaced drawing boards. You could see at a glance on a drawing board if the draughtsman was up to scratch and this is completely masked in the uniformity of computer drawings they all look good.

Regards

Alan

Edited By Alan Jackson on 12/05/2012 11:22:43

In order to clarify the operation of a vertical parting tool here is my rather macabre description of how I think it works.

Imagine that you are the parting tool holder whereby your two hands are held straight out from you body. You hands are gripped together and your fists are the cutting edge. You have a friend who represents the metal being cut and he (If you are a front parting tool) pushes down on your hands while you do you best to resist him pushing down. You can see that he can quite easily push your arms down. If you want to now become a rear parting tool you can turn round 180 degrees and your friend would now push your hands upwards, still he can easily overcome your resistance to him pushing up. So in order to stiffen you up, say you are frozen solid or have rigor mortise and are wearing a large pair of lead diving boots to anchor you down. When your friend (or should I now say de-parting undertaker) pushes down on you hands he will not be able to move your arms down because they are rigidly fixed to your body and he have to apply more force until you tip forward on you toes. Note that as you tip forward you rotate about your toes moving your cutting tool hands deeper into the metal being cut. If you are now rotated 180 degrees to become a rear parting tool your friend (some friend) now has to apply more upward force until you tip backwards on your heels. Also note that your cutting tool hands now move away from the metal being cut as you rotate backwards on your heels. Now you have to play the part of a vertical parting tool as I am proposing, so you now can be thawed out or de- rigor mortised. So lay flat on your back and push one arm vertically upwards and clench your fist to form the cutting tool. Your friend now has to apply considerably more force to overcome your vertical arm. Your arm will be in direct compression and until your elbow or wrist give way you will have much less a problem resisting his downward cutting force. It will also not matter if you are a front or rear vertical parting tool as long as the rotating force is pushing down on your hands. You can now get up and go back to your work or whatever you were doing. I apologise for being so flippant but I hope it does explain the reasoning.

Regards

Alan

Andy & David I do agree with what you say but a vertical parting tool seems to be an approach not tried. Because it avoids the rotating forces applied to the topslide and cross slide whether the cutting tool is mounted on the front or rear of the lathe. I suggesthese rotating forces create movements at the cutting tool which can create chatter and dig ins etc. Even with well fitted slides etc when a parting tool digs in it is suprising how much movement is instantly created. So that is my reasoning/justification/food for thought.

SteveW, I have added a couple of pics in my album I don't know how to do it here in this message hope they are more illustrative

Regards

Alan

Andy1 & David littlewood, Thanks for your interest and you certainly have not rained on my parade. My reasoning for a vertical cutting tool is that in both cases front or rear mounted parting tools, the cutting tool is subjected mainly to bending stresses. The greater the cutting depth the bigger the cantilever and the greater the bending moment. In essence the extended cutting tool is just like a ruler in classroom; where kids love to hold it extended over their desk edge and flick it so that it viabrates. By mounting the cutting tool vertically it is supported from below and the cutting forces are mostly directly downwards putting the cutting tool in compression rather than bending, because the cutting edge is directly supported below with no cantilever. I suggest that this avoids resonance due to a cantilevered support and avoids the stress concentration where the cutting tool meets it support block. It also allows the cut swarf to freely exit over the top of the tool. All these advantages allow the cutting edge to be thinner which also reduces the cutting forces. The downside is that you have to have a lathe that can safely rotate the mandrel clockwise without the chuck unscrewing, so threaded mandrel noses are no good for this. Parting off has always been a problem with model engineer size lathes which has been helped by the greenwood tool mentioned but the geometry still exists.

Alan

Edited By Alan Jackson on 23/04/2012 15:59:41

Yes John it is cutting mild steel

I have just made a vertical parting tool for my Stepperhead lathe. I first tried a normal parting tool mounted vertically but it suffered from scuffing on the parallel sides of the tool which is at the last part of contact with the metal being cut. So I made a one piece tool by silver soldering a small part of a high speed steel parting tool to a slightly thinner sheet of steel. Then I ground the high speed part to have clearance in both directions and it worked very well. It is nice and rigid in the cutting directions, with no bending for the parting tool. The mandrel rotates in a clockwise direction for a rear tool post which will be a problem for lathes with screwed on chucks so they would have to have the tool mounted at the front of the lathe. Here is a short video of it operating. It is only cutting off a 20mm dia. because I could not hold the camera and apply cutting oil with a brush at the same time but I will try it with larger diameters. But so far so good. Why has this not been tried before?
http://www.youtube.com/watch?v=S8HvS...lSWeYLoFlU2iA=
Alan

Edited By Alan Jackson on 22/01/2012 12:39:24

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Edited By Alan Jackson on 28/09/2011 11:56:49

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Edited By Alan Jackson on 19/01/2011 17:44:19