Speeds & Feeds for Knurling
For convenience, Knurling is often performed at the same speeds used for turning operations when using high speed steel tool bits. But to prevent seizing of the rolls on the pin, we recommend a maximum surface speed of about 150 SFPM (Feet/Min) or 50 m/min. You may find you get longer knurl life and improved appearance by slowing down the spindle to about 50 SFPM (15 m/min) for harder steels and stainless. CARBIDE knurl pins are strongly recommended for all high speed knurl applications. DOWEL pins with a plus tolerance SHOULD NOT be used because of the possibility of the knurls seizing up and breaking.
For BUMP knurling with a SINGLE TOOL HOLDER from the cross-slide, the infeed would normally be .001-.004"/rev (.025 - .1mm) to roll the part complete 5/20 revolutions. When knurling stainless steels, it is important not to roll any longer than necessary as this material work hardens as it is formed. The total amount the tool penetrates into the workpiece is approximately 50% of the tooth depth of the wheel. You may have to travel more than this amount to allow for the flexing of the part or holder due to rolling pressure. Some trial and error will be required.
If you are using a two die STRADDLE HOLDER, the infeed rate should be 5 or 10 times faster because the wheels are coming in tangentially instead of head on. Before knurling, the holder should be set so that the distance between the two wheels is smaller than the workpiece diameter by approximately the depth of the knurl tooth. Then to knurl, move the holder so that the two wheels are as close to the centerline as possible to minimize the knurling pressure on work spindle and cross slide. To initially find the centerline using a two die straddle holder, you may use this method:
- Bring the the preset holder and knurls towards the workpiece up to just touch a flat plate of any thickness inserted between the knurls and workpiece.
- Remove the plate and advance the holder the thickness of the plate + 50% of the diameter of the knurl wheels + 50% of the diameter of the workpiece. The two knurls should then be over and under the centerline of the workpiece.
If you will also be axial feeding to produce a knurling pattern that is wider than the knurling wheels, chamfers should be on the edges of the wheels. If the knurling doesn't go up close to a shoulder, the use of our CONVEX axial feed wheels is strongly recommended to further reduce the knurling forces, extend tool life and improve the cosmetic appearance of the workpiece. The normal axial feed rates would be from about .004-.020"/rev. (.1 - .5 mm/rev). The slower feed for stainless steels and tough or semi-hardened steels and faster for mild steels, brass or aluminum. When using CONVEX axial feed wheels, even faster feeds may be used.
END KNURLING from the turret (axial feeding only) is usually done at .005/.030"/rev (.1-.7 mm/rev), using the slower range for coarser Knurling on high-alloy steels, faster for finer pitches and on brass, aluminum or mild alloy steels. Normally the dies are fed off the work about twice as fast.
CUT TYPE KNURLING is done at similar speeds and feeds as pressure knurling, but the method of initial contact is critical if clean knurling is to be produced. Please click below for recommended speeds and feeds.
IMPORTANT: If you are having problems with double or mis-tracking, it usually can be solved by increasing the infeed on bump or cut knurling. For end-knurling from the turret, increase the axial feed rate. The deeper and wider the penetration of the knurling wheel into the workpiece on the first revolution, the more likely it will fall into step the next time around.
An estimated best workpiece or knurling wheel diameter can be calculated, but it may not always work the first try. Variations in the material hardness, sharpness of the crest of the knurling wheel teeth, width of knurling, initial in-feed rate, or spindle speed all affect the initial tracking.
Another common way to correct a mis-tracking problem is to grind or stone a small flat of up to .004" (.1mm) or slightly more on the crest of the knurl wheel teeth. This also may actually improve tool life because the wheel is less likely to chip out. Usually, the flat in the root of the rolled workpiece is not noticeable.
When someone requests DIAMOND" knurl or wants to roll a "DIAMOND PATTERN" on a part, there are several questions that need to be answered. It is very easy to confuse what is required on the part and on the knurling die itself. First we need to know whether a MALE (raised pyramid) or FEMALE (depressed pyramid) pattern is required on the part to be rolled. If the print just says "Diamond Knurl", we assume it to mean "MALE DIAMOND" Knurl on the part. Then we need to know what type holder will be used.
Rolling a "MALE" Pattern from the Cross-slide
- Use a set of RH and LH Diagonal knurls if a double roll holder is available. The rolls can be fed axially at .005/.030" per revolution if necessary. Most of the knurling pressure will be absorbed in the holder if it can completely straddle the part, thereby greatly reducing part deflection and wear on the main spindle and cross-slide.
- If only a single roll ("BUMP") holder is available, a "FEMALE DIAMOND" knurling tool must be used. This method is fine as long as the knurled section is relatively narrow, close to the collet and large enough in diameter so as not to deflect/bend too much.
Rolling a "MALE" Pattern from the Turret
- If a Brown & Sharpe (or other brand) two die holder with swivel knurl blocks is available, us a set of (2) straight knurls set a 30° angle to the axis of the part. Feed axially onto the work blank at approximately .010/.030" per revolution. Bevels are not required on the knurls.
- If the knurl blocks do not swivel, or you need to knurl close to a shoulder, use a set of RH and LH Diagonal knurls (convex axial feed knurls are recommended, chamfered wheels as a second choice).
Rolling a "FEMALE" Pattern
- A female pattern on the work can only be produced using a "MALE" diamond tool. This is normally accomplished by using a single "BUMP" knurl tool from the crossslide. Although it is possible to use two knurls in a straddle type holder, it is not normally done because of tracking problems and the necessity of custom matching the tooth form of a set of knurls axially.
Under normal circumstances a single "MALE" or "FEMALE" knurling die cannot be fed along the axis of a part. If this is a necessity, the holder must be tipped slightly and the knurl fed axially so that it advances very close to one axial pitch of the tooth spacing for each revolution.
Surface Speed to RPM Conversions
|Work Diameter||Surface Speed (feet per minute)|