Intro: Setting Up Carbide Tooling on a Lathe
Whether you just bought your own lathe, or just passed the SBU for the metal lathes at tech shop, you're now going to need some tooling for the lathe. This instructable aims to guide you in choosing and setting up indexable carbide tooling, primarily at the techshop. If you don't know what the techshop is, you check it out here www.techshop.ws, they have lots of great tools including lathes for you to use. The lathe in this instructable can be found at the San Jose branch.
Step 1: Different Types of Tooling
There are many different types of tooling you can use on the lathe. The simplest and most common is high speed steel (HSS) toolbits. These toolbits typically come as sqaure bars, and are then hand ground on the pedastal grinder. If you took the metal lathe SBU at Techshop, you probably used HSS tooling.
HSS Tooling can be very versatile and economical, especially if you don't plan on using the lathe very much, or you don't know what kind of parts you will be making. HSS square blanks are around 4$-7$ depending on size (From KBC. Tools), and pre-ground tools can be found for around 20$-30$ (From Mcmaster-Carr).
However, while HSS tooling can be very cheap initially, it can have drawbacks. Mainly, if you're not a professional, chances are grinding tools will take you significant time, and your tools will not always the same. HSS tooling also has a significantly shorter lifespan than other types of tooling, especially in hard materials.
Step 2: Different Types of Tooling (Cont.)
Brazed carbide tooling would be considered the next step from the basic HSS tooling. These tools feature a steel body, with a carbide tip brazed onto the end. While these tools are quite common (Most techshop lathe tools are brazed carbide), I have never had good success with them. From my experience, they are difficult to get good finishes with, and are require a green wheel to sharpen.
Brazed carbide toolbits can be similar in cost to regular HSS toolbits, or three to four times more expensive. While I don't recommend it, if you do want to go with brazed carbide toolbits, you can see extended tool life over HSS, especially in hard materials.
Step 3: Different Types of Tools (Cont.)
Indexable carbide tooling is the third type of tooling for lathes. Indexable tooling uses steel tools, with a screw or clamp securing a carbide insert to the end of the tool. Indexable carbide tools and inserts are widely available, as they are almost unanimously used in CNC Turning. Indexable tools and inserts come in many different varieties, one can be found for almost any job. Unlike HSS or brazed carbide, carbide inserts require no sharpening prior to use. Most inserts have at least 2 separate cutting edges, and can be rotated when one edge dulls. Indexable carbide tooling as does not typically re-adjustment of the tool height when swapping inserts.
The primary drawback of indexable carbide tools is the initial cost. Most common tools start around 30$ for import tools, and can run up to 200$ for high performance on brand tools. The inserts themselves are typically around 5$-10$ depending on geometry and grade. Additionally, if you need a special tool, you must buy an additional tool, rather than grind it yourself. However, if you don't like grinding your own tools, and just want to make a lot of parts, indexable carbide is my favorite way to go. The inserts cut very well in a wide range of materials, and require little to no time after setting the height once.
Step 4: Choosing Indexable Carbide Tools
There are many types of carbide tools available on the market today. Choices range from small threading tools, to massive 2" boring bars. Choosing the best ones for you can be difficult. If you do not have in a mind a certain type of part you'll be making, a general purpose group of tools, that can turn, face, and bore will probably be your best bet. The KBC Tools catalog has a great section on indexable carbide tools, with diagrams as to what type of cutting each tool and insert can do. If you don't have print catalog, you can download a pdf here, (http://kbctools.com/usa/download.html) or use their online version (http://kbctools.com/usa/Navigation/NavPDF.cfm?PDFPage=0248). I chose an 5/8"s SCLC-R turning and facing tool, and a 1/2" S-SCLC-R boring bar, from Shars Tool. Both of these tools use CCMT 32.5x inserts, and as such one insert is completely interchangeable between them, saving money. If you are unsure about what to get, those two tools will cover most all of your turning, facing, and boring needs, at a great price.
Once you have tools, you will need inserts. Most tool stores that sell indexable carbide tools, will also sell the inserts. KBC, Shars, MSC all sell carbide inserts and tools. Each tool you chose should recommend an insert type to use, and you should then be able to find the same inserts in a catalog/webstore. If you have trouble finding the inserts, you may want to look into a different tool, one with more common inserts, as this will save you time and money later. Again, the KBC Catalog has a great section describing almost all common inserts, and breakdown of the naming conventions. I bought my inserts from maritool.com, one of my favorite carbide sources. All of the inserts I chose are CCMT 32.52, which have a .031" nose radius. Large nose radiuses (.031") can increase surface, but will leave a radius on your parts. I chose a selection of inserts, positive rake, Kennametal K68 inserts for aluminum, and neutral rake CeraTip CA6515 inserts for steel and stainless. Positive rake inserts will reduce horsepower requirements in soft metals, but can break off in hard materials. Neutral or negative rakes are much stronger in hard materials, but require more horsepower to push through the cut.
Step 5: Choosing a Holder
Toolholders are what attach your tools to the lathe. Most modern lathes , and all the techshop lathes, are equipped with quick change tool posts (Shown above). These are special tool posts, that allow you to quickly swap tools, while maintaining the same height for each tool. The majority of the rest of this instrucable will cover set-up with quick change posts. If you have another type of toolpost, the same general rules apply, but the methods for setting tool height will be different.
Quickchange toolposts have standard sizes, 100 series (AXA), 200 series (BXA), 300 series (CXA), etc. If you just got your lathe, the toolpost should say which series it is. Techshop lathes use a 250-222 toolpost, which is a 200 series/BXA toolpost. All 200 series toolholders will fit the 200 series toolpost, and similarly, for 300 series holders and posts. However, a 200 series toolholder would not fit on a 300 series toolpost.
The toolholders themselves are also standardized. Different varieties typically come in all common toolpost sizes. Again, most tool supplies should have a wide selection, KBC, MSC, SHARS, etc. For most turning and facing tools, a #1 or #2 toolholder will be the best choice. For boring bars, a #2 or #4 holder will be best. Keep in mind, the toolholders have a maximum tool size, for 200 Series/BXA toolholders #1 and #2, a 5/8ths tool will be the largest you can hold. You have to choose smaller tools based on your toolpost.
Here, I chose a single BXA #2 toolholder. This holder accepts the SCLC tool, and has a v-groove for the S-SCLC boring bar, meaning only one holder is necessary.
Step 6: Setting Up the Tooling
Once you have your tooling and holders, you need to prepare everything to go in the lathe. If you tooling didn't come with inserts installed, that will be your first step. Changing the inserts is very simple, simply unscrew the clamping screw, and remove the insert. You will want to be careful of chips and debris when changing inserts, as they can cause inconsistencies between inserts. For setting the tool height, it also recommended that you use an insert you don't care too deeply about, as it is possible to break.
Next, install a tool into your toolholder. You can choose whatever tool you want to start with, but I usually start with the turning/facing tools as they are a little easier than the boring bars. Again, be sure to clean both the tool, and the toolholder, as even small chips will cause inconsistencies. Place the tool in the slot, and tighten the set screws as shown. You will want to get these set screws decently tight, if they are loose they can vibrate free.
Now that your tool has inserts installed, and is in a toolholder, you are ready to install it on the lathe. It is again recommended to clean all the surfaces on the toolholder, and toolpost. To install your toolholder, rotate the large handle on top of the toolpost counterclockwise, until the small gibs raises up. Then slide you toolholder onto the approiate dovetail slot. If you have a turning/facing tool, install it perpendicular to the spindle axis, if you have a boring bar, install it in the slot parallel to the spindle axis. Push the tool all the way down, and rotate the handle clockwise until tight.
Step 7: Setting the Tool Height (rough)
In this operation, you will be setting the tool height relative to the machine. The ideal height for each tool varies, because the cutting edges sit at different heights on each tool. However, all tools will cut best when the cutting edge is directly on the centerline of the spindle. For quick change toolholders, the height is set by adjusting the thumbscrew and locking nut. On traditional 4 way toolposts, shims must be added under the tool.
To set the height you will want something long, and relatively flat, with two parallel edges. A steel rule, works great for this. You will also want a piece of round of decent diameter. This method will in theory work with any diameter, but it will be more difficult as the diameter goes down. I used a piece of 2" 7075 aluminum round I had leftover.
With the machine off, chuck the round stock in the chuck, and tighten. You will be cutting with it, so don't skimp on the chucking.
Next, move the tool until the cutting edge is in a position to contact the outer diameter of the work piece. Back the tool along the X axis until there is about 1/4" between the tool and the stock. Take your rule, or other object, and hold it so it so the cutting edge of the tool is roughly centered on the length of the rule. Then, advance the X axis until the cutting edge just contacts the rule. Be careful, to much pressure will break the carbide.
You should now be able to let go of the rule, and it should stay in place. If not, keep putting light pressure on the axis until it stays. Now, postion yourself so you can get a good look directly at the front of the spindle. If the tool was perfectly level, you would see the rule perfectly vertical, however, unless you are extremely lucky, it is most likely angled. If the rule is angled such that top is closer to the spindle center, the tool is too high. Similarily, if the rule is angled such that the bottom is the closer to the spindle center, the tool is too low.
Take note of the angle of the rule, and decide which way to move the tool. Then, remove the tool from the toolpost. Loosen the locking nut on top the thumbscrew, and rotate the thumbscrew so it moves either up or down. There is no direct science on how much to move the thumbscrew at this point, so you should use your best judgement, if it is wrong, there will be no harm. Once you have moved the thumbscrew, tighten the locking nut, and re-install the tool.
Repeat the rule test, and thumbscrew adjustment until the rule is too your best judgement, vertical. It does not have to be dead nuts perfect at this point, as you will continue to dial it in.
Step 8: Setting the Tool Height (Fine)
Now that you have roughly set the tool height, you can begin taking cuts to dial in the height. Be sure to make sure everything is tight and secure, and follow all your good lathe practices before taking cuts.
You'll want to take facing cuts, at a D.O.C. as large or larger than the nose radius of the tool. My inserts have a .031" nose radius, so i started with 40 mil (.040") D.O.C. . Take one facing cut, all the way to the center of the stock, and then stop to look at it. *Be sure the lathe can't start while your looking at it*. If the tool is perfectly centered, you will see a smooth finish all the way to the center. If the tool is beneath the spindle axis, you will see a small stub of material that was above the tool and wasnt cut. If the tool is above the axis, the same stub would have been present, however, it is likely that you pushed it off with the non cutting surfaces of the tool. You should still be able to see some marring on the workpiece, but mainly, you will be able to tell because it should take more force to cut the last little bit.
Just as before, you will have to take the tool out and adjust the nuts. Be aware, that you are dealing with much smaller distances this time, so smaller adjustments should be made. Keep taking cuts and observing, until you feel a smooth cut all the way through, with no stub. The tool is now perfectly centered.
Step 9: Setting Heights for Multiple Tools
If you have other tools to set up, and you have a toolholder for each once, you can simply repeat the process for each tool, and leave them in their respective holders. You should never have to reset the heights until you move to different type of lathe.
If you have multiple tools, and only one holder, don't fret, you still can do this only once. Once you have set the height for a tool, get out a set of calipers, and measure the distance between the top of the toolholder body, and the thumbscrew. Write this number down somewhere obvious, on the tool itself is great place. Whenever you need to set the tool height again, you can simply adjust the thumbscrew until you see the same distance. You can repeat the process for as many tool as you like.
Hope this helps you set up your tooling,