Straddle Type

General Instructions

These holders are designed to fit small CNC machines and Swiss type automatics. They are supplied as right-hand style, but may be reassembled as left-hand style. You can use one right-hand and one left-hand knurl to produce a diamond pattern. Straddle holders may also be traversed to produce long knurl patterns. Convex axial-feed knurls are recommended when traversing. Straddle knurling produces much less work deflection than bump knurling. This allows knurling on longer parts or smaller diameters.

Setting Up

For rolling a "full" straight or diagonal knurl pattern with standard 70°, 80°, or 90° knurls, first determine the proper pre-knurl blank diameter if it is not known. We would normally recommend subtracting the approximate increase in knurled diameter (see Table I) from the approximate maximum finish knurl diameter specified on the drawing. Then your minor diameter would be approximately your just determined blank diameter minus this same roll up amount. 

To make it easier to set up the job, you might want to make a set up pin to put in your machine spindle prior to running your first piece. This pin would be the approximate minor diameter just figured. With the holder open, run it up to the set up pin and then just snug the two arms of the holder against the pin while at the centerline (see determining centerline). Now if you take out the set up pin and put your part in, it should roll up close to full form. A minor adjustment may be necessary to achieve the desired results.

Speeds & Feeds

The recommended speed for knurling is the same speed that you would turn the material being rolled using a high speed steel turning tool. If the knurls get excessively hot, reduce the speed. The feedrate should be from .005" to .015" / revolution. Too low a feedrate causes flaking of the work. Too high may cause excessive feed lines in work and premature knurl failure.

Knurl Adjustment

Adjust the two screws on the top of the holder until the knurls just contact the work. Retract the holder from the work. Tighten the screw closest to the knurls a small amount and make a test roll. Examine the knurl pattern and adjust if necessary.

Changing Knurls

Loosen the set screws locking the knurl pins. Remove the knurl pins, then replace the knurls. Replace the pins and tighten the set screws.

Changing from right-hand to left-hand

Loosen the set screw on top of the mounting shank. Loosen the two screws on top of the holder. Remove the mounting pin that attaches the holder to the shank. Re-install the pin from the opposite side. Insert into the mounting shank from the opposite side and tighten the screws.

General Instructions

These holders are designed to fit most medium to large size CNC machines, and to roll more difficult jobs. They are supplied as right-hand style, but may be reassembled as left-hand style. You can use one right-hand and one left-hand knurl to produce a diamond pattern. Straddle holders may also be traversed to produce long knurl patterns. Convex axial-feed knurls are recommended when traversing. Straddle knurling produces much less deflection than bump knurling. This allows knurling on longer parts or smaller diameters.

Setting Up

For rolling a "full" straight or diagonal knurl pattern with standard 70°, 80°, or 90° knurls, first determine the proper pre-knurl blank diameter if it is not known. We would normally recommend subtracting the approximate increase in knurled diameter (see Table I) from the approximate maximum finish knurl diameter specified on the drawing. Then your minor diameter would be approximately your just determined blank diameter minus this same roll up amount. 

To make it easier to set up the job, you might want to make a set up pin to put in your machine spindle prior to running your first piece. This pin would be the approximate minor diameter just figured. With the holder open, run it up to the set up pin and then just snug the two arms of the holder against the pin while at the centerline (see determining centerline). Now if you take out the set up pin and put your part in, it should roll up close to full form. A minor adjustment may be necessary to achieve the desired results.

Speeds & Feeds

The recommended speed for knurling is the same speed that you would turn the material being rolled using a high speed steel turning tool. If the knurls get excessively hot, reduce the speed. The feedrate should be from .005" to .015" / revolution. Too low a feedrate causes flaking of the work. Too high may cause excessive feed lines in work and premature knurl failure.

Knurl Adjustment

Adjust the two nuts on the eyebolt until the knurls just contact the work. Retract the holder from the work. Tighten the nut closest to the knurl a small amount, lock the other nut against it and make a test roll. Examine the knurl pattern and adjust again if necessary.

Changing Knurls

Loosen the set screws locking the knurl pins. Remove the knurl pins, then replace the knurls. Replace the pins and tighten the set screws.

Changing from right-hand to left-hand

Loosen the set screw on top of the mounting shank. Remove the mounting pin that attaches the holder to the shank. Re-install the pin from the opposite side. Insert into the mounting shank from the opposite side and tighten the screw.

1. After setting the holder with the proper opening (at the minor diameter), back it off slightly.
2. Use any flat strip of metal or hard plastic and just touch the two knurling wheels to this strip and the strip to the workpiece blank diameter at the same time.
3. Now remove the strip and advance the holder by the radius of the knurling wheels (1/2 the diameter of the wheels) + the thickness of the strip used + the radius of the workpiece (1/2 the blank diameter). Now the wheels in the holder will be very close to the centerline.