6 BA hexagon headed screws

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John,

I know them as Rose Bits [or Rose Cutters] ... but that may not be standard nomenclature.

MichaelG.

Once again thank you for all your replies and suggestions. I seem to have opened up quite a discussion on BA stuff. Good job we still have engineers left in this country of ours - so I'll ask for help on a couple of other topics all for the same project.

First - like an idiot - a machined a pinion blank out of EN 24 !!!!! and was disappointed when my cutter went blunt The cutter was 9DP for 15 teeth. So I machined up another blank out of ordinary MS which I should have done in the first place. Used a cutter meant for a lot more teeth and it worked fine - pleased with the result but of course it didn't roll into engagement smoothly with the 114 Tooth gear it was mated with. So ah says me I'll trim the top of the teeth with the proper 15 tooth cutter which would probably have been OK for the job except that I took it to the same depth. PILLOCK! Now it engages OK but with a little bit of play and it does look too rounded at the crest. Anybody got a 9DP Gear cutter to suit a 15 teeth pinion that they can flog me?

Second request which should be easier. I am looking for a couple of tension springs to hold the latch down on a quadrant lever - something like on a valve reverse gear except that it is for a dog clutch shift collar. Ideally they need to be 3/4 inch long and 3/32 inch diameter. Model shops that used to have this kind of thing are rapidly disappearing. Any help much appreciated.

You may have been running the cutter too fast or without any cutting fluid? You should be able to 'resurrect' it if you can find a way of grinding it on the face (only) of each tooth - you will need a means of indexing it around each tooth in turn.

Neil

They are described in this thread under that name on here

**LINK**

Seems that they are also used to cut pivots - Cousins sell them at £26 plus vat each but a limited range of sizes.

I'd guess this sort of thing could be turned in the normal way with a cutter without any sort of rad on the end. I suspect that's the problem even with a cut of only a few thou. The rad makes the swarf bend as it comes off putting more stress on the work.

. I just size them in one go but there is some bend in the work due to cutting pressure so there will be a bit of taper narrowing towards the chuck. I suppose one answer would be to use something like a jacot tool or part hole of the right size as a steady. Turn a short length to suit that and then use it as a travelling or fixed steady. The thumb screws I made were about 2 1/2 in long, most being at a low diameter. with an M2 thread at the end about 1/2in long.

John

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The cutter does actually look pretty blunt Neil and I did investigated the cost of having it reground. Unfortunately there are fewer tooling services around these days and since I have been quoted £40 to regrind I thought it would be cheaper to get hold of a good second hand one. Thanks for all you other replies and suggestions guys. Good to know you are out there.

When I spent some time on a Ward 2a capstan lathe back in the 1950s, the cutters to reduce screw shanks to size were known as hollow mills,and mounted in one of the turret stations,ok for fully threaded screws but not brilliant at producing a good finish on a plain shank,despite stoning the cutting edges,threading was usually button dies for for smaller BA sizes and self opening die heads for 1 and0 BA . If you need to turn a long thin screw shank make the screw a bit longer and centre drill the end and support the screw shank with a small centre,then reduce the length to remove the centre or use a travelling steady,for small dias use a home made steady device to fit the tool post.If only a part of the shank is threaded,hold the material in a collet with just enough protruding for the thread,turn down the length to be threaded ,thread it then feed the rest of the screw shank forward and turn that down,