My first attempt at a sawnut

I am about to commence the build of a number of backsaws. This is likely to be a long project interspersed with other projects in my usual manner because I suffer from Aprosexia and cannot stay on any one task for a prolonged period. Anyway, I thought I would start out by experimenting with making my own sawnuts.

I had some brass barstock so I chucked a piece up in the metal lathe and just went through the procedures to make the desired item. I made no real attempt to make this to any particular size to fit known forstner bits or anything, just making a sawnut that will never be used to get the procedures worked out.

I was pretty amazed that I fitted all the necessary features into 11/16" on the first go. I aim to make the "users" able to be used in a 7/8" to 1" thick handle so now I am pretty confident of being able to achieve that easily.

I still need to shape the round bit above the thread into a square and also cut the screwdriver slot on the end of the nut. I aim to make a couple of holding fixtures to be able to achieve that accurately and repeatably on the mill.

I am looking forward to my brass supplier reopening next week so I can get the sizes I need to get going.

I have had the metal lathe and milling machine for a while now but this is the most complex task I have undertaken on them and it is going better than I thought it would.

Attachment 447730Attachment 447731

Very nice Doug
Well there nicely done nearly, did you use the lathe to cut your threads.
Or do like me, because I’m not that advanced on my metal lathe and just use a tap and die.
I think from your pics M6/M8 1.5 but that’s just a guess.

Will you give them a full spit and polish as well.
Can’t wait to see the saws,pics of course.

Cheers Matt,

As an alternative to making a milling jig to cut the screw slots you can put a parting off tool sideways in the tool post and cut the slot by winding the cross slide back and forth. Just put the geared head into the lowest speed to effectively lock it up and prevent any accidental rotation.

Quote:

---

Originally Posted by Chief Tiff

As an alternative to making a milling jig to cut the screw slots you can put a parting off tool sideways in the tool post and cut the slot by winding the cross slide back and forth. Just put the geared head into the lowest speed to effectively lock it up and prevent any accidental rotation.

---

Not sure that would apply to my lathe, Chief. speed control is through a VFD. Having said that I am a rank amateur on the lathe so I could be wrong.

Quote:

---

Originally Posted by doug3030

Not sure that would apply to my lathe, Chief. speed control is through a VFD. Having said that I am a rank amateur on the lathe so I could be wrong.

---

Can you lock the spindle?

Quote:

---

Originally Posted by Simplicity

did you use the lathe to cut your threads.
Or do like me, because I’m not that advanced on my metal lathe and just use a tap and die.

---

Tap and die at this stage of my professional development as a machinist, Matt. Maybe try cutting them on the lathe another day though

Quote:

---

Originally Posted by Simplicity

I think from your pics M6/M8 1.5 but that’s just a guess.

---

M5 0.8

Quote:

---

Originally Posted by Simplicity

Will you give them a full spit and polish as well.

---

At the moment the prototype is a WIP and has had a few modifications since the picture was taken. I am refining the shape and finish as I go.

I will stop refining if and when I am happy with it, so, like you I will have to wait and see.

It would be easier to mill the square shoulders before parting the head of the screw from the rest of the stock. Then no jig would be needed.
Cutting accurate square shoulders normally requires the use of an indexing head or a square collet block.
That aside, given it's a small shoulder and brass, I would just file the square shoulders using a fine file. :oo:

I've found the cleanest most accurate screw driver slots are obtained with a slitting saw on the mill.
If you don't have a slitting saw holder then they are not that expensive and worth investing in.

Quote:

---

Originally Posted by BobL

It would be easier to mill the square shoulders before parting the head of the screw from the rest of the stock. Then no jig would be needed.
Cutting accurate square shoulders normally requires the use of an indexing head or a square collet block.
That aside, given it's a small shoulder and brass, I would just file the square shoulders using a fine file. :oo:

---

Me being me, I like stuff to be repeatable and identical so that if I pull a saw apart and lose a nut (there's an opening for a smartasre comment if anyone is interested) I can repeat what I did, and any nut will fit any hole in any saw I make. There is bound to be a better way of achieving this but where I am at the moment I see a square plate with a hole in the dead centre threaded the same as the bolt, with the bolt held secure by a nut tightened down on the other side. Four opening and closings of the vise to reposition and I have repeatability

Quote:

---

Originally Posted by BobL

I've found the cleanest most accurate screw driver slots are obtained with a slitting saw on the mill.
If you don't have a slitting saw holder then they are not that expensive and worth investing in.

---

Slitting saw is on the shopping list. I have identified the need for a few tasks coming up. As much as I was tempted to buy all the tools I could possibly need when I got the lathe and mill, I just got a selection of "basics" and buy whatever else I need as I identify the need. Is there a problem in using a small endmill in the mean-time?

Quote:

---

Originally Posted by doug3030

There is bound to be a better way of achieving this but where I am at the moment I see a square plate with a hole in the dead centre threaded the same as the bolt, with the bolt held secure by a nut tightened down on the other side. Four opening and closings of the vise to reposition and I have repeatability

---

Not sure I understand this. Are you suggesting using the square hole in the plate as some sort of a "die".

Quote:

---

Slitting saw is on the shopping list. I have identified the need for a few tasks coming up. As much as I was tempted to buy all the tools I could possibly need when I got the lathe and mill, I just got a selection of "basics" and buy whatever else I need as I identify the need. Is there a problem in using a small endmill in the mean-time?

---

I agree about buying the basics and taking it from there.

Nice looking screw driver slots are a lot narrower than many people think, ie around the 1mm mark, and around 0.7mm for smaller screws.
End mills of this size are very fragile and in brass also have to be driven a very high speeds, eg a 1mm diameter end mill should be driven at between 12000 and 16000 rpm!, and the max depth of cut possible is about 0.1mm per pass otherwise they will easily snap. Even a 3mm end mill in brass should be driven at 6000 rpm. Lower speeds will still work but it will be very slow cutting.

A slitting saw will do the slot cut in one pass.

Quote:

---

Originally Posted by BobL

Not sure I understand this. Are you suggesting using the square hole in the plate as some sort of a "die".

---

Not sure I can explain it any clearer, but in time I can post a photo. :2tsup:

Quote:

---

Originally Posted by BobL

I agree about buying the basics and taking it from there.

---

I came to the conclusion that I really did not have the background knowledge to make a decision on what to get right at the start and the learning curve does go in directions I was not anticipating at the time.

Quote:

---

Originally Posted by BobL

Nice looking screw driver slots are a lot narrower than many people think, ie around the 1mm mark, and around 0.7mm for smaller screws.
End mills of this size are very fragile and in brass also have to be driven a very high speeds, eg a 1mm diameter end mill should be driven at between 12000 and 16000 rpm!, and the max depth of cut possible is about 0.1mm per pass otherwise they will easily snap. Even a 3mm end mill in brass should be driven at 6000 rpm. Lower speeds will still work but it will be very slow cutting.

A slitting saw will do the slot cut in one pass.

---

I don't think my little mill will spin that fast. :rolleyes: I had been thinking about a design for the nut that involved the slit not running all the way across the end of the nut. Maybe my ambitions and my capabilities are in conflict again.

Quote:

---

Originally Posted by doug3030

I don't think my little mill will spin that fast. :rolleyes:

---

Not many mills can do this.

Quote:

---

I had been thinking about a design for the nut that involved the slit not running all the way across the end of the nut. Maybe my ambitions and my capabilities are in conflict again.

---

They look nice but then you need a custom made driver.
I used that approach on my plane makers floats handles but the slots were initially cut all the way across.
Attachment 447776

If you need to make a dedicated driver a simpler approach uses two holes spaced across the usual line of the screw slot.

Doug, I'm a non-machinist too, but I've been mucking about making saw bolts & nuts for a few years now and figured out a few dos & dont's. I started with simple split nuts , but eventually got the courage to make the more 'modern' sleeved nuts. They are actually almost as easy to make, as I eventually discovered. I usually use 7/16 or 1/2" diameter heads & nuts with 5mm shafts & M5 threads. For the smallest saws, I think 3/8" heads & 4mm shafts look better.

An example of each type: Attachment 447819

Cutting lots of little threads with the lathe would be tedious in the extreme - you'd have to set-up for each bolt, then change everything back to prepare the next one for threading. It's far quicker & easier to cut little threads like these with a die-nut. I made up a holder as my first exercise in boring: Attachment 447818
It slides on the 5/8" shaft, which is held in the tailstock chuck, & keeps the die running co-axially (nothing worse than a wonky thread!). Simple, quick, & easy. As you can see, my early attempt at knurling would get a 1 out of 10, but it's enough that I can thread up to 4mm brass without resorting to the tommy bar (which becomes essential for threads of M8 & up).

Although I have a slitting saw, I have no way of using it for this job, so screwdriver slots are cut with a hacksaw. If you cut carefully & keep the saw straight, you can get a very clean slot. I use the centre-mark from facing-off as my guide, cut the slot, then put the nut back in the lathe & dome it using a file. If you make sure your heads are all the same width, and count the file strokes, you can get the domes remarkably consistent. Being a 40 year veteran on the wood lathe, I have few qualms about a bit of hand-shaping. :;

Likewise, I file the square shoulders on the bolts. If you don't have a safe-edged file just take one to the grinder & make it so. Again, if you turn your shoulders to the same diameter & count file-strokes, you can get a very consistent product. In any case, small differences won't matter in this context, wood doesn't need the precise fit that metal demands.

Slotting the old style split nuts is a bit of a challenge for my ageing eyes. There is no neat centre point to guide you once it's drilled & tapped, so a bit of guess-work is called for. However, take a look at a bunch of old split-nut saws & you'll see that the slots are all over the shop, very few are centred precisely. I prefer the look of centred slots, but if you want to go for an 'authentic' look, just whack the slot in anywhere but the centre. :U

One last point: we are spoilt with drill presses and (reasonably) precise bits like Forstners, so you can make 1/2" heads or nuts to fit exactly in a 1/2" recess, but if you want to go for the really tight, squashed-in fit you see on the old Beech handles, you need to drill slightly undersized recesses and put lots of taper on the nuts & bolt heads so they can be pulled in very tightly. I found this out when I made a set of bolts for Bushmiller & put too little taper on them - he had to rig up a jig & add more taper to get them to seat properly....

I still can't decide which is preferable, domed or flush heads. Some days I think the domed bolts look better, sometimes I prefer flush: Attachment 447816 Attachment 447817

Cheers,

Here's how I cut small brass and Al threads on my MW lathe.
Put the workpiece in the lathe chuck and slightly taper the edge of the end of the brass piece to be threaded.
Turn the lathe off.
Place a die in a standard die holder hand hold it up against the taper using the front of a regular chuck (with laws retracted) in the tailstock.
This holds the die square to the workpiece.
Then rotate the lathe chuck forward a turn or two (and then momentarily back to break the developing chip) whilst applying accompanying light pressure with the tail stock.

My lathe has an exposed spoked secondary drive pulley between the motor and the spindle so I find it easier to turn this pulley than the lathe chuck itself.
I also have the possibility of locking the chuck so can use the lathe reverse to remove the die from long threads. I manually back the die away from the end of the thread a couple of turns and then set the VFD to very low speed to doubly check the direction is right before increasing the speed.

Quote:

---

Originally Posted by IanW

Doug, I'm a non-machinist too, but I've been mucking about making saw bolts & nuts for a few years now and figured out a few dos & dont's. I started with simple split nuts , but eventually got the courage to make the more 'modern' sleeved nuts. They are actually almost as easy to make, as I eventually discovered. I usually use 7/16 or 1/2" diameter heads & nuts with 5mm shafts & M5 threads. For the smallest saws, I think 3/8" heads & 4mm shafts look better.

An example of each type: Attachment 447819

---

Thanks Ian,

I actually have four sawnuts which I believe were made by you (sawmaking course at Holmsglen TAFE a few years back now) as per the ones on the right in the picture. Thanks for the background information on your methods of manufacture.

Reading machinists sites they seem to want to cut threads on the lathe as they can be done more accurately that way than using a tap and die, but for now I think the tap and die method will be fine for sawnuts.

Currently I am just experimenting and probably will not use the first half dozen nuts produced while I perfect the process. I aim to play around with tapering on the bolt heads. My handles are Walnut so I will have to work out how much taper and oversizing will work with that I guess.

I made up a little holding jig with a male and female end so that I can reverse it to hold either a nut or bolt in the chuck to work on it after it is parted off so I can experiment with tapers without having to make a new nut each time.
Attachment 447821

Anyway I am having a lot of fun and learning heaps as I go and I really appreciate the help I have received.

I will continue to post the progress with the sawnuts here and will start a new thread when I get started into the backsaws.