Turning Tool And Facing Tool Questions

[Joe Pitz]

Jim, Currently I am having trouble getting the angles going the right way, Once I start to get the hang of grinding I will switch to tool blanks
and then, as you say, be able to test out my grinding.

Good tip.

Thanks

Joe

 

[JR49]

Joe, I would like to suggest two posts for you to read. I watched the Tubalcain and Halligan videos as well as others, and learned a lot from them. However, after reading these 2 posts, and lots of practice, I consider myself an excellent tool grinder (although I still don't even qualify as a very novice machinist). They are, "Advanced tool sharpening for the lathe by Conrad Hoffman" (find this post right here at the beginning of the Questions and Answers forum). This one shows the little tricks to help you grind freehand. The other is on another forum, http://www.chaski.org/homemachinist/viewtopic.php?f=44&t=76065 (hope its Ok to put that link ) Harold_V Shows that the single biggest thing you can do for successful grinding is being able to see what you're doing, so, get rid of the tool rest (NOT THE SAFETY GUARDS), and hold the tool below the centerline of the wheel. Hope this helps, JR49

EDIT, I should add that Harold_V talks a lot about using only the correct wheels for grinding HSS. He is probably right, but I have had success using the wheels that came with my grinder

 

[mikey]

I start out facing the end of the stock with the facing tool, then I switch to the right hand turning tool to rough out the O.D. (this forces me to change the angle of the tool holder) Then I have to switch to the facing tool again, which causes me to have to change the angle of the tool holder again. When I attempt to then match the correct O.D. I have problems holding the same dimensions at the shoulder, or if I have to increase the depth of the shoulder I end up messing up the O.D.

Also question on the new tool holders, Is is true that the new indexable tool holders have the geometry to both face and turn without having to change the tools?

It sounds like you're using inserted carbide tools, at least until you learn to grind HSS. If you wish to turn and face without turning the tool post then the SCLCR (RH tool) and SCLCL (LH tool) turning tools would serve you well. These tools have a built in 5 degree clearance angle on the side and end so that the tool will both turn and face with the shank of the tool held perpendicular to the work; no angle changes are required. They use both CCMT or CCGT inserts that come in a variety of grades and nose radii that allows you to cut almost any machinable material. The tool holders are standardized and made by many makers; I prefer SECO or Iscar but there are many others. Inserts are also made by many makers and are popular on ebay.

If you go this route I would choose a tool holder maker and download their literature on turning tools and inserts and then learn how to choose the insert you need.

If you go with HSS then things get more complicated because the various angles change depending on the material you are cutting. With no offense meant, I am going to suggest to you that relief and rake angles make a huge difference in cutting forces, cutting temperatures, finish and tool life. Getting it close is not as good as getting it right.

It is rather simple to grind a general use tool shape what will both face and turn with equal ease; all you need is to be sure that the angles at the tip are less than 90 degrees. That is, the angles between the side and end cutting edges need to be about 80-85 degrees to each other. This allows you the clearance you need to turn the OD or turn into a shoulder and face out without any of the edges rubbing against the work. Note that we are simply addressing tool shape here and are NOT talking about relief or rake angles. A worthy tool shape might be one that is halfway between a roughing tool and a facing tool.

As I implied, the relief and rake angles will differ with regard to the material you are cutting if you want optimal performance. However, you can choose angles that will work with most materials, though they will be a compromise. This would be well beyond the scope of this discussion so I will desist. Just keep in mind that with HSS tools you will, and should, change the angle of the tool (this is called changing the lead angle) to suit your purposes - more lead angle when possible to enhance finishes and less lead angle to reduce chatter and enable deeper cuts or to approach and cut/face a shoulder.

Anyway, look into the SCLCR/L tools - they will suit your needs very well.

Oh, and when you get to grinding HSS I suggest you choose 6061 Aluminum or 12L14 mild steel to practice on. These materials are hard enough to let you see how the tool is cutting (sizing accuracy, finish, chip shape, etc) and soft enough not to present a challenge when learning how tools and materials like to cut.

 

[Joe Pitz]

thanks JR49, great info, I will check out the material you recommended, as I am having trouble with the tool grinding.

Joe

 

[Joe Pitz]

Thanks mikey, great info on indexable tools and tool grinding angles, everyone tells me the relief angles are not critical, I will do some more research on grinding and in the mean time look for some good SCLCR and SCLCL tool holders.

Joe

 

[mikey]

Thanks mikey, great info on indexable tools and tool grinding angles, everyone tells me the relief angles are not critical, I will do some more research on grinding and in the mean time look for some good SCLCR and SCLCL tool holders.

Joe

Joe, you will find that the smaller the lathe and the smaller and harder the work piece, the more important those relief and rake angles (and nose radii) become. Cutting forces are a big deal when rigidity is limited and accuracy matters. You never mentioned which lathe you're using - would you share that? Not all lathes benefit from carbide, as I'm sure you know.

 

[Joe Pitz]

mikey, I started out with a 7x10 mini lathe from HF, but I was so disgusted with the quality, I found an old Clausing 6316, just picked it up last week, so I am getting up to speed using it. I guess I am using carbide currently as I don't know how to how to grind HSS, I was going to stay with carbide, but after watching a bunch of videos and everyone telling me to use HSS, I started last night, attempting to grind, I picked up some 3/8" cold rolled square bar stock, cut it up into tool blank sizes. I am now practicing.

Thanks

Joe

 

[JimDawson]

You'll get it figured out Joe. Pretty soon, you'll have one of those Ah-haaaaa moments and it will all come together.

 

[Joe Pitz]

Thanks Jim

Joe

 

[mikey]

mikey, I started out with a 7x10 mini lathe from HF, but I was so disgusted with the quality, I found an old Clausing 6316, just picked it up last week, so I am getting up to speed using it. I guess I am using carbide currently as I don't know how to how to grind HSS, I was going to stay with carbide, but after watching a bunch of videos and everyone telling me to use HSS, I started last night, attempting to grind, I picked up some 3/8" cold rolled square bar stock, cut it up into tool blank sizes. I am now practicing.

Thanks

Joe

That's a 12" lathe so you should have the power and rigidity to use carbide, especially if you can get the SFM into the range you need to use those tools effectively. Those SCLCR/L tools will work well for you, I think, and will get you up and running while you learn to grind your own tools ... and well beyond.

I'm a HSS user and have been for a long time. For smaller lathes, like your 7X10, I wouldn't recommend carbide at all. Your Clausing is another story and you have the option of using HSS or carbide or both. With modern carbide insert and tool geometry the line between what works better is blurred. There are inserts with very sharp edges and positive tip geometry that approach HSS in effectiveness, especially for Aluminum.

In any case, as Jim says, you'll sort it out. I agree with using mild steel keystock to learn to grind tools - it is a skill well worth learning.