Yet another knurling question.

[JasonBModerator @jasonb]

Some form of slotting would do your internal straight "knurls" for one or two just doing it with the mill's quill would be OK rotating the work on a rotary table if it's a lot then something less time consuming would be best. Either CNC that can rotate the part and time the slotting stroke or make a splined tool that can be pressed into the hole to cut the internal splines.

[Martin ConnellyParticipant @martinconnelly55370]

I had some collets made for a CNC pipe bending machine with an internal parallel knurl, like a very fine spine in some respects. It was done on a vertical shaper by the "light machine gallery" as it was called at work. They did all the jobbing work that nobody wanted to put on the expensive CNC machines because of very low numbers or because they were one offs. Sadly it was shut down and such work became sub-contract operations or bought out items as a result. The best option now would probably be wire EDM. Another option for split collets would be to make a very hard knurl that the collets can be squeezed down onto before they are also hardened.

Just as an after thought, the moulds for plastic bottle caps have to have a form like a straight knurl. Find the people who make these moulds and you can get them to do some tooling for you.

Martin C

[John HinkleyParticipant @johnhinkley26699]

Boiler Bri,

As Jason has said, the solution is very much dependent on the quantity and size. I imagine that if you are lining with rubber the internal diameter is greater t han 10 – 12 mm. I think my first approach would be with a rotary broach mounted on the lathe cross slide. Some while ago, I made such an animal from a redundant rotating centre and made my own broaches from hardened silver steel rod.

It was quite effective, producing reasonable hexagonal holes in brass. Straight flute broaches are available commercially if you are into quantity production and would thereby justify their cost. Alternatively, a carbide burr such as the two in the middle of the picture below might do the trick.

Certainly easier than hardening yourself and available for less than a tenner the set from the Far East and probably closer to home, too.

John

[bernard towersParticipant @bernardtowers37738]

Recently had to do some long straight knurls but could not keep the lines straight so ended up cutting them on the shaper with a 5c indexer. Now they are straight. this is on 16mm 316

[HopperParticipant @hopper]

Internal knurling could be done with a single straight knurling wheel mounted "sideways" on the end of a piece of square bar held in the toolpost. As long as the diameter of the hole is bigger than the knurling wheel.

I suppose could do internal diagonal knurling similarly by using one wheel first, then the other, to get the right and left hand spirals.

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