Tool bits, cranked or straight.

Reading 'Our Point of View' in The Model Engineer 1920, Vol. XLIII, No. 1018, Page 342, mention is made of how straight tool bits had replaced the cranked variety.

Comparison was made, saying that cranked tool bits cut the metal away sweetly, whereas straight tool bits tear or crush the metal away.

One example given was where a new foreman replaced all cranked bits with straight ones, with the result that everybody on the shop floor became miserable!

Where they referring to carbon steel or HSS tooling I wonder?

Geoff - Pruned rose bushes this afternoon & got 'thorned' in the process

that must be why all my work comes out rubbish...I knew it wasn't my fault

Given that the cutting conditions are set by the angles ground on the tool the whole proposition seems incredibly unlikely unless the straight tools were incorrectly shaped. I suppose a cranked tool is marginally less stiff than its straight counterpart due to the sideways overhang of the business end relative to the shank so a spring tool effect is possible. But if that variation is enough to make a consistent difference something is very wrong with the set-up. Whether by engineering, application or implementation.

My experience with this sort of logical till you think about it "works for me" processes is that the whole thing falls apart when you go back to first principles and do the job properly Doing it properly also gives rather better results than the evolved trick.

Clive

Early inserted toolbit holders often supported the bit rather poorly (due to the issues of creating accurate square holes), which could have been a source of problems.

Neil

Geoff, watch it when pruning roses. While I was training as a nurse we had a couple of people in with Tetnus that was got from rose scratches. And I,v got a viral infection that I picked up a couple of weeks ago in the garden. Bl**dy gardens.

Ian S C

Geoff,

I agree 100% with Ian

I don't want to start a "worst story" competition, so will leave it at that.

MichaelG.

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Just a thought: Were they actually referring to the "Swan Neck" style of tool or toolholder, rather than what we now describe as "cranked" ? ... Those "Spring Tools" were renowned for sweet cutting.

MichaelG.

Rose thorns not nice...

**LINK**

Neil

Wore gloves after the first couple of pricks. I'm not being rude, promise

"Bl**dy gardens". I second that comment!

There was no mention of the type of cranked tool/s being referred to, but have read that the swan necked ones do a good job. Never had the opportunity of trying one, but may make one in my 'spare' time.

I didn't realise that inserted holders where in use in the 1920s.

Go on, be a devil MichaelG, you know you do

Geoff - The other two rose bushes can wait.

Edited By OuBallie on 28/11/2014 10:29:53

Saw a surprising ad in Home Shop Machinist. Inserted tools with HSS inserts!

Neil

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O.K. Geoff, if you insist ...

Back in the mid 1970s, I worked with a chap whose father had stood on a particularly vicious Rose Thorn, whilst working in the garden.

It went through his shoe and pierced his foot.

Tetnus and Gangrene set in, and his foot was amputated: They obviously didn't catch all of the infection because later his leg was amputated at the knee; and later still, at the hip. [no Rose pun intended]

MichaelG.

MichaelG,

Bl**dy h*ll !

I see why you where reluctant.

They must have been monstrous thorns.

Geoff - Thick gloves from now on.

Tetanus is very nasty indeed! If you have not already done so, see you doctor about a anti tetanus injection. One injection every 10 years or so. If you are a gardener or work on the land it's particularly important to get this done because the bug lives in soil.

I believe the old inserted tools referred to are the holders for rocker toolposts that held a bit of HSS or carbon steel.

Spring tools were used for finishing, these were formed with a loop, with a heavy cut, the cutting edge moved down, away from the work. They are often shown fitted upside down in old illustrations. Not so necessary with modern machines unless the feedscrew is worn, allowing the tool to be dragged into the cut.

Dave

The only cranked tool I have are ones pointing left and right. I would like to try a swan neck tool. Tool holders for a inserted tool were available in 1898 as there was an article that year in Model Engineer, Carbon steel tip, mounted as a tangential tool as in the "Eccentric" tool advertised at the top of the RH column.

Ian S C

Last time that I saw a swan necked tool being used was in the late 1960's. The tool shank was about 4 inches wide and 10 inches deep and around 5 feet long. It was used to rough out the grooves in a 6 feet dia forging for a rotor shaft in a steam turbine. Don't think I will ever need to remove that much metal in my garage

"Saw a surprising ad in Home Shop Machinist. Inserted tools with HSS inserts!"

" I believe the old inserted tools referred to are the holders for rocker toolposts that held a bit of HSS or carbon steel."

HSS inserts are freely available in TLOTF for the "Modern" (Carbide?) insert toolholders. Seems that we don't NEED carbides with everything.

Regards Ian.

PS., might cranked tools give extra clearance between the toolpost and the chuck jaws??

Edited By Circlip on 29/11/2014 15:29:20

We may have them over here, but I've never come across them.

Neil

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Reviving this topic, because of the recent interest in parting tools ...

Here is a fine example of a 'spring' holder

MichaellG.

Hmm . . .

Just finished pruning the roses and spreading horse s**t on them. Must check my vaccination record.

Russell.

Cranked tools used to be quite popular for shapers. This includes both the ones with just a bit of an offset and the ones with a full spring. I have some that came with one of my shapers. With a standard type of tool, any flex in the shank of the tool tends to make it dig in. If the cutting edge is shifted back behind the neutral axis, this reduces the tendency to dig in.

They used to be more popular with lathes when lathes tended to lack rigidity, probably for the same sort of reason, eg if correctly designed they will spring in a way to slightly reduce the cut, rather than digging in. The modern approach is to make everything more rigid, which also allows heavier cuts.

As far as the roses go, bear in mind that horses are quite prone to tetanus, which is one reason that it used to be more common. Both horses and humans are often vaccinated now, which is another reason that you don't hear of it so much. However, if the owner of the horse that provided the manure is a cheapskate the horse may not have been vaccinated. So it pays to renew your vaccination.

John