Home Made "Inserts" -Feelin' Groovy.

Now I'm sure that this not a new or original idea but I'd thought I'd share it anyway.

I need to cut some 0.5mm wide grooves around 2mm deep in 1/2" brass bar. I don't have access to a grinder and the only insert system i can find for that size is the "Mini-Thin" from MSC at around £70 for a holder and £18 each for the inserts.

I had some small scrap pieces of 1/16" Ground Flat Stock and some mild steel 1/4" square bar so made these-

The pictures are self explanatory. The top "insert" has been filed to shape, hardened, tempered and sharpened with a diamond lap. The bottom insert is a soft blank.

Some more photos-

This hasn't been a success so far. After cutting two good grooves things got a bit noisy and warm. The blade has lost it's temper now and will need rehardening. I will also have to pay a bit more attention when it comes to sharpening.

I didn't put any rake on this as it was for brass but I've noticed that a lot of parting/grooving systems seem to have a negative rake. Is there a reason for this?

Any hints, tips or questions are more than welcome.

Cheers, Steve

Edited By Steve Crow on 27/08/2019 14:28:47

Edited By Steve Crow on 27/08/2019 14:29:27

Edited By Steve Crow on 27/08/2019 14:31:12

Edited By Steve Crow on 27/08/2019 14:32:42

Edited By Steve Crow on 27/08/2019 14:33:15

Edited By Steve Crow on 27/08/2019 14:33:31

Nice work, Steve

It would obviously involve much more effort, but I think your next try should be to replicate the idea using HSS: Machine Hacksaw blades being an excellent source of material.

MichaelG.

If the ground flat stock is gauge plate, it is the equivalent of silver steel. I would try hardening it, polishing it and then heating it very slowly from the other end until the tip area is light straw, before quenching. After tempering, finish hone with a fine diamond lap. If the dimensions allow, grind the end so that the plan view is biased to the right, yours is to the left, which is not so well supported by the groove in the holder. So far, I haven't needed anything narrower than 1.6mm, the width of my smallest carbide inserts for 26mm blades. I'm not sure of the best profile for brass, it is a matter of trial and error.

I tempered it in a domestic oven to around 190 - 200C then stuck the tip in a potato and re-tempered the shank. This was from Tubal Cains heat treatment book.

The cutting part is on the right so I can get as close as possible to the chuck - even a couple of mm helps.

Thank you Michael, that got me thinking. If I hand grind the teeth of a piece of junior hacksaw blade, it will fit nicely in the 5mm slot of the holder. I could sandwich it in place with a rectangular insert with about 3mm of blade protuding.

Do you think this might work?

The trouble would be finding all-HSS junior blades and then drilling a clearance hole for the M2.5 screw.

Sorry, I don't understand when you say the cutting part is to the right, (picture 5). As for chuck clearance, what about the SHCS sticking out? I also cannot understand why the steel should go blunt so quickly in brass. Have you tried a file on it after tempering, if the steel is low carbon mild steel, it will still be soft after any heat treatment.

Edited By old mart on 27/08/2019 17:36:18

Sorry, my mistake, I meant the left.

The screw on the left was unavoidable without a lot of messing about. Anyway, with my tiny Sherline 3 jaw it actually gives enough clearance. It's fine with collets too.

The steel is gauge plate. I've used the same piece to make cutting tools before. I always test with a file.

As for the bluntness, my fault. Not sharpened correctly which caused it to rub. I'd forgot to put back the tailstock centre, The work shifted slightly in the chuck, this cause a lot of heat and led to loss of temper.

.

I would probably avoid 'Junior Hacksaw' blades ... many of them have a wavy set to the teeth and the steel is of questionable quality.

Ordinary 10" or 12" 'Hand Hacksaw' blades might be a suitable source of material though; and they conveniently have a hole at each end.

The reason I suggested 'Machine Hacksaw' blades is that they are [or at least were] more readily available in solid HSS. [but I accept they are over-size for what you are making].

An abrasive cutting disc should make easy work of roughing-out pieces from a Hand Hacksaw blade and it also is possible [but rather demanding] to work HSS with Carbide tools.

Experiments are definitely in order, I think.

MichaelG.

I have found old hacksaw blades to be almost as useful as new ones, since they make perfect grooving tools.

I have used broken standard 12" blades and blades from power hacksaws, and have found them better than any insert, and a lot cheaper !, have even used them for parting, not my favourite operation.

I had the work shift slightly in the chuck when parting off, and it destroyed one end of my Kennametal 26mm blade which holds the 1.6mm inserts. I am very careful with it now, only one end left and 7 new inserts which only fit that exact blade. I try to avoid parting off in a three jaw chuck, four jaw independents are much more secure.

I always lock the saddle when parting or grooving.

Edited By old mart on 28/08/2019 20:44:52

Hi , I've made a super thin parting tool which I use for brass, bronze and small diameter steel. It's just a broken HSS hacksaw blade silver soldered into a bit of square steel [ I saw cut a slot in it]. The tool bit protrudes about 1/2 inch. I've been using it for a couple of years with no trouble. It saves a lot of material when parting off brass which is so expensive these days. I ground the teeth off the blade of course. I didn't bother putting any side clearance on it but it still works fine.

Jigsaw blades come on a variety of materials and could make a fairly cheap source of material for such a system, but it would probably mean some form of clamp to hold the blade, rather than a hole.

Regards

Gray,

A useful insert can be made from a piece cut from a carbide tipped circular saw blade (note that each alternate tip is handed left and right. These blades are regularly thrown out when a tip is damaged). I have used these tips in ordenary lathe tools and boring bars, I choose ones that are about 1.5 mm squ x 3 mm long, they come in smaller and larger sizes.

Ian S C

A piece of saw blade with a tip on it, and a hole in the side would make a parting tool of your holder. You should grind the end of the tip square(green grit wheel or diamond). With a little tool like this take things quietly, don't just rip into a great big lump of steel bar at a million rpm..

Ian S C

A quick update.

I didn't have a huge amount of success with my home made inserts and for an ongoing project I need to cut some consistent size grooves in a variety of materials including EN16T and silver steel. Also I wouldn't mind being able to part pivot steel.

I don't like to spend more time sharpening than turning so I cheated and bought a "Mini-Thin" 0.5mm insert and the torx screw in case it was an odd size (it was).

Once I'd recovered from the cost, I knocked up a toolholder from 3/8" square bar.

I've not tried it out yet but if I'm happy with it I might get the threading insert. Should be good for making screws from pivot wire.

It's got me thinking about making other toolholders now for other types of inserts.

Steve

Edited By Steve Crow on 10/09/2019 18:53:12

Looks a neatly made holder.

They should be fine in silver steel as that is what I originally bought mine for - cutting grooves for E-clips in silver steel. I't is now my goto tool for any parting below 10mm dia and general small grooving jobs like piston ring grooves.

MSC often have the inserts on offer but still about £10. Warner do HSS inserts should you ever need them

This is Len Mason's take on a small parting and grooving tool in "Using The Small Lathe":

I've just used mine to cut grooves for 3mm E clips

You do need to make sure that the hacksaw blades are solid HSS not Flex Bi-metal.

Rod

Ah yes ... I remember it well, Rod

Unfortunately a little wide [as is] for Steve's 0.5mm grooves, is it not ?

... Which is more-or-less where we came in.

MichaelG.

One point about using hacksaw blades for parting-tools - as I found when I tried it some time ago - there is no relief on the section, so unless you grind the flanks appropriately, they soon start to bind as the cut deepens. They'd be fine for circlip or O-ring grooves or parting thin-walled tube though. One solution might be to leave the teeth on to shave the sides of the kerf by the tooth-set width - though I have not tried this, and it may well also produce a rough finish.

'

Reading Len Mason's article quoted above, he talks of grinding a parting-tool end at an angle to obviate that usual pip. I'd always done that until only quite recently learning (on this forum??) that doing so is very likely to cause the tool and swarf to jam in the cut, because the chip is now wider than the blade thickness.

If you examine an insert-type parting-tool you see it has a square-across end, and a shallow V-groove that both gives side rake and tends to turn the chips inwards, so presumably slightly narrower than the kerf, and often breaks them up.

I can obtain - for free - used bandsaw metal cutting blades - fairly big about 25 to 30 mm wide, quite thick, and about 6 TPI. Sometimes they are not worn out, but have broken (snapped). Has anyone tried these as a parting off tool? Power hacksaw blades are a bit scarce and expensive where I am. Any advice would be welcome.

Thanks,

Alan.