Slitting saw advice

I'm getting on with my Stuart 10V, and finding Andrew Smiths book invaluable. However the detail on the Conrod is a bit thin. His instructions are to "cut through the middle, either with a miniature hacksaw or a circular slitting saw". A google hunt for a miniature hacksaw throws up nothing helpful, so time to have a go with a slitting saw which is something new to me. I'm planing to use my SX2 mill, and plan to buy an R8 arbour that will hold a range of centres from 1/2" to 1" . My thinking is that this will be nice and rigid. Some advice on the following would be welcome:

I'm planning to buy a 3" 1/32" thick saw , or is it better to use the smallest diameter I can get away with?

should I saw the Conrod from the face or the edge?

fine or coarse teeth?

is there such a thing as a miniature hacksaw?

Thanks in advance.

Bob..

Thats the valve rod casting!!

By minature hacksaw he probably means a junior hacksaw which would give a narrower kerf than a standard hacksaw.

The thinner slitting saw blades can wander a bit if you are not careful, run them at your mills slowest speed and use some cutting fluid even with bronze.

I would cut it from te end but have the teeth in contact come across the work at about 45degrees, much the same as this

Edited By JasonB on 27/12/2013 20:29:08

Bob do a google search for junior hacksaw. That will find your miniature saw.

Brian

Have a look Bob at picture 53 here **LINK**

Harold

I'v got a power hacksaw that is powered by a small Stirling Engine, It uses junior hacksaw blades, and has been used to split big ends. It does a lovely job, your big end would take about 15 min, but that's not bad on a bit over 5 Watts. Ian S C

I tried one of those multisize slitting saw arbors in a R8 taper: basically useless as it didn't hold the saw anything like concentric or perpendicular to the axis. It went in the bin.

Even thick saws (>1/16" ) are prone to go walkies with any depth of cut on a single ended arbor. So I'd use the smallest diameter saw possible. I'd also go for coarse teeth. Fine tooth saws are ok for slotting screw heads but not much use for anything else, as the gullets get clogged.

If at all possible I use slitting saws on the horizontal mill. That's what I call rigid and I'll happily take cuts up to 15mm deep in one pass.

For the job in hand I'd use a junior hacksaw.

Regards,

Andrew

Edited By Andrew Johnston on 28/12/2013 11:22:46

The design should leave lots of spare metal for a junior hacksaw cut. Just make sure you are using the correct casting

I have no experience with these type of parts, but making an accurate long cut with a (junior)hacksaw is not something I am succesful in, if it needs to be reasonable accurate a slitting saw is the way to go. Niko.

Put the casting in a good vice or use packing with the line to be cut just proud of the jaws and then saw using the vice jaws or packing to keep your saw straight ie saw with the blade in touch with the jaws

Roy

I've never had much success with those wavy blades that are usually fitted to Junior Hacksaws. Does anyone sell a high-quality straight blade for jobs like this ??

MichaelG.

I'm with Andrew on these arbors, there isn't enough support to do a proper job.

I know is using tools to make tools but a decent home made arbor is not that much rocket science. Also make a series of support washers of different diameters.

You only need enough saw showing to do the job, if the rest is sandwiched between two decent washers it supports the saw and helps get a straight cut.

In Art Fenarty's Gearotic program it was originally coded to cut a spur gear using a normal end mill by making repeated passes whilst moving the blank over and dropping the tool so it cut a series of flanks. basically a poor man's Sunderland planer.

Biggest problem was on small gears it needed small cutters which as every ham fisted bloke knows are fragile.

I got Art to give the facility to cut on the side as opposed to the top using slitting saws. Problem there though is a very fine saw say 10 thou wide will cut a slot but won't want to do a side trimming cut, just deflect off the path.

In tests I was using a 10 thou saw with cheek plate washers that allowed just 40 thou of tooth to show and this was then able to side cut a 64 DP gear

Thanks for the comments. At present I'm working on the bed and frame castings, and am looking forward in the guide book making a tool shopping list. I haven't spent much time looking at the other components yet, just picking out tap and reamer sizes etc. I think I may cancel the R8 arbour plan and make a mandrill specifically for the slitting saw I buy to fit one of my larger taper collets. I'll figure out the smallest diameter saw I can get away with and as course as possible. Take it steady seems to be the order of the day.

Bob..

Bob, if you use a junior hacksaw, don't put much weight on it, the more strokes it takes to cut the metal the finer the finish of the cut surface, that's what happens with my little power hacksaw. If the cut goes through at a slight angle to the vertical, don't worry, as long as the cap is assembled the same way each time it will fit perfectly.

Ian S C

Hi Bob. Don't forget to drill taping size holes in the casting BEFORE you cut. Hope I am not teaching my granny to suck eggs here.

Cheers Derek.

You might find a suitable saw among the Dremel tooling, worth a look. Ian S C

FWIW I cut the eccentric strap for my 10V with a junior hacksaw as the only slitting saw I had at the time was 1/16" thick. There is plenty of metal for cleaning up the cut surfaces, even if a thin slitting saw wanders a bit.

Neil

Thanks for the advice all.

You could use a jewlers saw also available from a popular modellers' knife supplier. Will work on brass though it may seem cruel but even if you blunt the blade it is a minor 'consumable' cost. Don't try it on steel or especially piano wire - that is what the junior hacksaw excells at. Sometimes available at the ME and Ally Pally show on the shesto or other small tools stands. Also available from model railway shops and exhibitions.

Presumably it doesn't much matter how you cut the thing as long as you don't make a complete arse of it. You will need to bore the central bearing afterwards anyway, so you could easily skim both sawn faces in the milling machine which would be a very simple task and give a clean mating pair. As suggested, it may make sense to drill (and tap) the bolt holes beforehand. Once bolted back together, you can bore out the centre and Bob's your auntie.

When I make a con rod for one of my Stirling Engines, I drill the big end to take a bit of bronze for the bearing, and drill that under size, and drill the bolt holes tapping size, then I cut the bearing, drill the cap holes to size, and tap the big end, and fit the studs, now bore, or ream the bearing, the outside will be oval, and will stop the bearing from moving in the big end. If you like, a bit of Loctite will stop the bronze falling out. This works on any metal used ie., steel, aluminium, what ever. For a 10 mm/3/8" bearing, and above, an ordinary hacksaw/ band saw is OK.

Ian S C