Hi All, I have seen, on handles and such, beads that have, what I assume are knurl marks, that are ninety degrees to the bead and evenly spaced. I have also seen them cut on an angle that gives the appearance of rope. If in fact these lines are made with a knurl I assume the diameter of the bead is important because the marks come out evenly and curved to fit the bead. I wish to learn more about this process and would like to be able to make them. Who can teach me?!! Any help is greatly appreciated. Rick
No snappy closing remarks, I am just interested in metalwork.
Well, I was hoping for some answers, too. I don't make these so can't give you a practiced description, but the old way was to cut the impressions on the knurl (or master knurl) by single pointing on a horizontal milling machine, between the centers of a dividing head and tail. The mill arbor would not be set in motion, but the table long feed moved to and fro for each line to be cut, then re-index, etc.
There's a Lindsay repro "Making the Small Shop Profitable," that has a circa
1918 Am Machinist article on it. It's in a collection of articles for the magazine done by John H. Van Deventer, one of the editors then.
The straight cuts on a convex bead are shown made from a single-point tool set up as a fly cutter would be, and the "rope" cuts (called spiral in the article) are shown done off of a right-angled fly cutter. (Instead of the tool addressing the top of the work, it touches in front of it. I suppose this is so you can use the swivel motion of a universal miller to give the curved cut.) There's also a bench fixture shown that holds a cutter on a pivot so as to give either an outside sweep for a convex (bead) knurl, or inside sweep for a concave-faced knurl--not unlike a lathe's radius cutter, but this one looks like it was intended for unpowered operation.
It would be interesting to know what the classic combinations of flat, convex, and concave knurling were, and on which devices they were most common.
Hi Frank, If knurl is being machined for a convexed bead, the knurl would be concaved I assume. Would the radius of the single point tool in the mill be the same as the radius of the bead?! I am trying to invision how straight cuts across the knurl with a single point tool would make a curved depression that would match the bead. It is tough to describe in words but I would like to be able to invision the knurl itself. Thanks, Rick
The bench-tool method uses the same pivoting tool holder concept of a lathe radius or ball cutter. The single-point tool cuts either concave or convex, depending on where you set the tool holder pivot pin.
For the bench type tool for making concave or convex knurls, you would have a right-angle plate (say 1/2 in. steel or iron) with a mandrel to hold the knurl blank (already radiused either convex or concave), like a nut mandrel. The mandrel sticks up vertically from the horizontal surface of the angle plate (clamped in a bench vise, perhaps). On the vertical inside side of the angle plate is a tool holder with a hole (or a series of holes) that fits a pin set into that side, the pin being centered to pivot the holder at the exact center of the knurl blank width.
You set the tool in the holder so that it is centered on the blank width and also centered on the vertical axis of the mandrel, swing the tool holder to take one cut, then index the mandrel for the second cut, etc. That is one way for doing convex straight or concave straight, but it won't do the rope pattern. Frank Morrison
Machinery's Handbook has a page or two on designing knurls including the rope style.
Good luck, John. _______________________________________________________
The bench-tool method uses the same pivoting tool holder concept of a lathe radius or ball cutter. The single-point tool cuts either concave or convex, depending on where you set the tool holder pivot pin.
For the bench type tool for making concave or convex knurls, you would have a right-angle plate (say 1/2 in. steel or iron) with a mandrel to hold the knurl blank (already radiused either convex or concave), like a nut mandrel. The mandrel sticks up vertically from the horizontal surface of the angle plate (clamped in a bench vise, perhaps). On the vertical inside side of the angle plate is a tool holder with a hole (or a series of holes) that fits a pin set into that side, the pin being centered to pivot the holder at the exact center of the knurl blank width.
You set the tool in the holder so that it is centered on the blank width and also centered on the vertical axis of the mandrel, swing the tool holder to take one cut, then index the mandrel for the second cut, etc. That is one way for doing convex straight or concave straight, but it won't do the rope pattern. Frank Morrison
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