Yet Another Tangential Tool Holder

[Jim GreetheadParticipant @jimgreethead]

Thanks for the tip Chris, obviously solid carbide is not too brittle in this mode. Can you recommend a source?

 

Happy 2012 to all

 

Jim

 

[Billy MillsParticipant @billymills]

Hi Jim, one of the points about the Brunel Cutter is that it took round toolbits so for home metalworkers (who have the odd broken carbide drill or mill  )  there is now another re-cycling route. The Brunel Cutter is also a lot easier to make as you only need to make round holes for the toolbit.

 

Carbide will last longer but for a tangential tool the re-sharpening is so easy and quick that the extra hardness of carbide can be reserved for tougher materials.

 

One other little point about the round bit is that if you turn the toolbit you have a shear tool with a very easy to change angle!

 

Billy.

Hope everyone has a great New Year.

Edited By Billy Mills on 01/01/2012 11:49:36

[BazyleParticipant @bazyle]

Having read around the links provided I have missed one aspect – what is the suggested grinding angle for general use? I think I saw 30 degrees mentioned but not explicitly as the grinding angle. One could presumably do the other end at a lower angle for brass.

Also what is the angle to grind the sides for a screwcutting tool at 55 & 60 degrees?

The Brunel tool would seem to provide a method for getting corner radii by making a silver steel tool with an appropriate head. However can a maths gemius suggest a formula for head dia /tilt angle/desired radius.

 

[chris stephensParticipant @chrisstephens63393]

Hi Jim,

I bought mine from a second hand tool shop just south of Beaconsfield, now sadly a coffee shop. BOO HOO!!

 

I have noticed that MSC/J&L sell solid carbide 6x6x100mm for about £12 +VAT. If one buys IMP sizes the price rockets, 12″ of 1/4Sq is over £80 by the time VAT is added.

Having said that it works, which of course it does, there is still the brittle nature to over come. When the cut is taken a Tangential tool holder puts the carbide in compression , where carbide is strong, but the actual cutting corner is weak so a pronounced radius is required, I use something in the order of 0.5mm. Luckily, as with all Tangential tooling, once you have put the radius on it is there for the whole life of the tool.

I also grind the top at slightly less that the normal 30 degrees, to reduce the top rake angle and thus increase the strength of bit that matters.

chriStephens

PS I don’t think I can recommend Carbide Tangential tooling as a mass market technique, but worth trying if you like to experiment. It does have the advantages of normal tangential tooling, ie economy of materials, but carbide is relatively hard (pun?) to grind and some would find this too much to cope with.

 

[chris stephensParticipant @chrisstephens63393]

Hi Bazyle,

The end is ground in a jig set at an angle of 30 degrees, resulting in the end of the HSS being ground at 60. You can indeed grind the other end but, despite what the old books say, I have not found it not necessary to change the angle for different materials.

 

Differing angles are/were recommended to improve the life of the tool. Ideally for ease of cutting there should be a high degree of top rake but this reduces the edges resistance to wear, but this is OK for soft metals like Aluminium. Metals like Steel or Cast iron would soon wear away the a very sharp edge, so a lesser degree of rake is used to make the edge stronger. Well, that was the case, in industrial applications, before the last war and it rather stuck for home users because they knew no better and blindly followed what the big boys did. The “big boys” had of course moved onto carbide and now ceramics or Diamond. For our home use, where time and money are not our prime concerns, you will find that using the one tool with a fair degree of top rake can be used for almost anything. There is a proviso in that abrasive work pieces need something that will stand up it, hence the use of carbide, or you could reduce the rake but HSS will still wear away.

There is nothing to stop you grinding whatever angle you like, if you find it beneficial, it is the matter of a few seconds to change the angle and I would strongly recommend that you do indeed try differing angles and find out for yourself what works for you. As I say a Tangential tool is very, very easy to sharpen well and quickly, so if it does wear you can quickly sharpen it and continue to cut metal.

I hope the above makes sense, but bear in mind it is New Years Day and I went to bed very late last night, no, make that this morning. Cheers.

chriStephens

[BazyleParticipant @bazyle]

Thanks, Chris. Have another glass on me

[Jim GreetheadParticipant @jimgreethead]

Thanks Billy, might be time to have a look at that Brunel cutter although I don’t have any broken carbide drills or milling cutters at present. On the other hand …

 

Chris: Thanks for the source of carbide. And what you say about angles makes really good sense. When I researched (flash word for googled) the various angles recommended for HSS tooling for different materials, every source seemed to track back to the work done in the 1930s by Taylor who, as you say, was trying to optimise the production of components.

 

As I recall, he established a lifetime between sharpening for the tool and then changed the angles to maximise the volume of metal removed during that lifetime.

 

As hobbyists, we are not so concerned about tool lifetime in that sense but there might be tool geometries that give better surface finish on different materials – like backing off drills for brass etc.

 

Jim

And ‘ave a good 2012

 

[chris stephensParticipant @chrisstephens63393]

 

Hi Mick H,

“Has anyone ever invented a tangential parting off tool….“

The answer is now “yes”. Well not exactly “invented” but at leas “made”.

Early days yet but we will see if there are any benefits.

Before anybody asks, no photos and there will be non till it has been proven to be worth the effort.

chriStephens

Edit, Tangential using a standard parting blade, not a especially ground one, that will come later.

Edited By chris stephens on 01/01/2012 23:18:45

[michael howarth 1Participant @michaelhowarth1]

Hallo Chris……when I posted that question I wondered whether someone would pick it up and run with it…….you were an obvious candidate. Can’t wait to see what you have come up with !!!

[chris stephensParticipant @chrisstephens63393]

Hi Mick H,

Had another play with it today, after doing a few household chores, like fixing the hole in the workshop roof, and it shows promise. There is one big benefit for the inexperienced parter-offer, a dig in should not cause problems as the blade should slip before breaking. I could not ascertain if this true, as I could not make it dig in. How do you get dig ins?

 

Anyway to sum up, initials tests have shown enough promise even using some unknown origin piece of tat blade, so mark two, using a decent quality blade is the next step.

Watch this space!

chriStephens

PS Are you going to Ally-Pally, if so you might be able to see your invention.

[michael howarth 1Participant @michaelhowarth1]

Hallo Chris….. what took you so long??? Seriously…..what you are doing sounds really good ……..your invention,by the way, not mine….I only asked a question. About dig ins….I have no problem creating them if I get a bit too enthusiastic over the feed rate. My lathe is a Warco 918…very light….. and the tool post is prone to a bit of flexing…so all the ingredients are there. Rear tool post does it a bit better but the cross slide T slots are not ideal in size or positioning for fixing it……..so any help on the tangential front is welcome.

 

Shan’t be at Ally Pally unfortunately. We used to live about 5 miles away in New Barnet but we now live 125 miles away in Lincolnshire so it is a bit too much of a trek. Do you remember the horse racing track at Ally Pally? I have only been model engineering for a couple of years and it was stimulated by what I saw at our local show…….so it’s a bit ironic really that the Ally Pally show was on my doorstep when I had not even heard of model engineering………and now I have to travel miles to get to a show…….Warwickshire and Harrogate are my nearest.

 

Looking forward to progress reports.

 

Regards

 

Mick

 

 

 

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