Slitting saw blades for brass

Boris Ludwig

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Hope everyone here has been well. In Sydney, everyone I know is fine.

I'd like to make some screws and parts for a few fishing reels that have whitworth screws in rare sizes. I was fortunate enough to get some dies and taps of those thread sizes. I'm thinking about how to slit the screw head. Been searching this place but haven't quite found my question answered.

1. How many teeth per inch on a slitting saw for small brass screws should I use?
2. If the screw head is all of 5/32" dia what diameter saw should I use?
3. How fast should I go for such a thin saw blade? 1/32" is the thickness of the slit I need.
 
Pretty much any jewelers slitting saw will work. I would try a 0.032" blade. The arbor hole will depend on the slitting saw holder you have. These blades will walk right through brass with no problem. Speeds are not finicky at these shallow depths of cut. I've cut slots in brass at 400 rpm or so with a 2-1/2" diameter blade and it cut clean.
 
I'm really starting from the beginning. I have no saw, arbor, or screw holding collets etc.

I have 5C collets for holding the arbor. I plan to get a saw, make an arbor and buy ER32 collet holder in a hex block to hold the screws in my milling vice.
 
I'm really starting from the beginning. I have no saw, arbor, or screw holding collets etc.

I have 5C collets for holding the arbor. I plan to get a saw, make an arbor and buy ER32 collet holder in a hex block to hold the screws in my milling vice.

For fine work like this, a 1/2" arbor will be more than enough. Slitting saws with 1/2" arbor holes abound on ebay and are often listed as jeweler's saws. You don't need a lot of cutting depth so just about any saw 0.032" thick in the 2" OD range will work and it will have more than enough teeth for a smooth cut. Almost all of these blades will be flat ground, meaning the teeth should not be offset. You don't need lubricant with brass but speed helps.

If you plan to make an arbor, your fits need to be very tight; on the order of 0.001" or less.
 
Use the largest diameter saw that you have and plunge it to depth instead of cutting straight across. If you look at most screws that have come off a screw machine, the slot is concave, though it may be hard to see'
 
Great advice, Mikey & 4ssss. thanks.
Just another question before I shell out my hard earned - is it worthwhile continuing with 5C, which will mean a collet block also, but bear in mind it adds to my overall collet sizing for holding small screws. Or should I get an ER 32 collet block and small collets (works out marginally cheaper)

Perhaps it's not that important in terms of how effective the tool is?
 
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If holding screws which are a bit undersized, ER-32 may be better because of the wider clamping range vs. 5C. The clamping range of 5C is very narrow requiring more collets. Part of the equation is if you need the 5C for another machine, or not. Down side of ER-32 is that is does not clamp short stock well because both sides of the collet collapse, there is also an issue that the collet does not protrude so using a slitting saw may interfere with the nut.

In the lathe I use 5C for threaded stock and very short stock. I guess if you only have a few thread sizes then maybe 5C.
 
Thanks, mksj. just the sort of comments I was looking for. I can see holding very short & small screws for slitting would be better in the 5C. I hadn't thought about the nut interfering with the blade. Below is an example of the screw size.

20200507_145000_001.jpg
 
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