Boring for a Beginner

[TerrydParticipant @terryd72465]

If I could only buy one book it would be GH Thomas’ ‘Model Engineering Workshop Manual’.   Before I could afford it I used to borrow it regularly from my local library.

 

On the subject of Boring, George  Thomas also includes instructions for making excellent D bits for accurate boring and I now use them for any bore up to about 12mm.  However you have to ‘engineer’ them rather than just grinding up a piece of  silver steel to a rough shape. It’s worth learning how to make them.

 

Terry 

[chris stephensParticipant @chrisstephens63393]

Sorry chaps, I was half a mile down the road when I realized I posted in the wrong topic, lesson to be learnt; don’t copy-paste in a hurry when following more than one topic. Post should now be in the right place.

chriStephens 

Edited By chris stephens on 24/03/2010 15:16:59

[CirclipParticipant @circlip]

Dear Mr editor, can you move the “Philosophers” posting into the correct thread, think he’s “Stoned”

 

  Regards  Ian.

[David Clark 13Participant @davidclark13]

Hi There

We do not have a philosophy thread.

Don’t think there is a facility to move threads either.

regards David

 

[chris stephensParticipant @chrisstephens63393]

Hi Circlip,

I wish I was, instead of having an active life away from the computer screen.

The post has now been moved to where it should have been placed to start with.

Shame there isn’t an emoticon for raspberry blowing, it might prove popular!

ATB

chriStephens 

[oilcanParticipant @oilcan]

The chapter on boring tools in ‘Model Engineers Workshop Manual’ by GHT , are these essentialy the same as the articles on boring which appeared in ME 3562-3564, which are in digital form on the home page of this web site?

[chris stephensParticipant @chrisstephens63393]

Hi Oilcan,

Yup, pretty much, still worth getting his book though.

It’s amazing what you can find in the dark and dingy recesses of lower half of the home page, I must scroll down more often.

christephens 

[mgjParticipant @mgj]

Well, to philosophise. I m sticking with carbide and my lovely Stellram bars which have coolant holes all the way down them. No they don’t use ISO SCLCR tips, but Stellrams specialist ones, and cheap at the exorbitant price if results are anything to go by.

 

Talking of results – can someone explain why its so easy to get a good internal finish, compared with external turning. Even with a really cruddy ground HSS tip it still comes out well –  usually. (9/10)

 

 

[chris stephensParticipant @chrisstephens63393]

Stop taking the pies chaps, it’s getting boring.. and I did fix it at the first opportunity.

 

And funny that, isn’t it. Could it actually be because of some spring in the tool compared to external work?

chriStephens 

Edited By David Clark 1 on 24/03/2010 18:08:32

[KWILParticipant @kwil]

Try setting the tool height better when turning externally.

[mgjParticipant @mgj]

Is that what it is?  I’ll bear it in mind. Probably my setting gauge is out- on external tools only?

[Ian S CParticipant @iansc]

The boring tool should if any thing be a whisker above center, the load brings it to center, and over load pushes it away rather than dig in(thats my story anyway). Ian S C

[KWILParticipant @kwil]

I do not use a setting guage, [I do not possess one even]. I always take a cut across the end of a bar when tool setting a QC holder. Look at the quality of the cut surface once all is running true, that and the “chip” quality will tell you whether or not the tool  height is correct.

Edited By KWIL on 26/03/2010 16:49:47

[chris stephensParticipant @chrisstephens63393]

Hi Kwil,

“Try setting the tool height better when turning externally.”

I am somewhat surprised that a man of your  obvious experience should think the answer should be so simple, but if you say so, I bow to your greater knowledge of such things.

chriStephens 

[Ian S CParticipant @iansc]

One of the first things I did on getting my lathe set up was to sit a 6″ square on the saddle, and with a hard center in the head stock mandrel scribed a line across the blade. I was going to make something better, but over the last 24yrs have’nt got round to it. Ian S C

Edited By Ian S C on 27/03/2010 02:09:36

[CirclipParticipant @circlip]

 For height setting, trapped rule always seems to work too.

 

  Regards  Ian.

[chris stephensParticipant @chrisstephens63393]

Hi Guys,

Since we seem to have changed the topic to centre height setting, here is my take on the subject.

I use an old Boxford comparator which, when sitting on the cross slide, is set to read Zero when exactly on centre height. You may ask “how do you know it is centre height” well the answer is that to set the comparator I mount an 18mm bar to run dead true in the Four-jaw . This bar has been very carefully machined at one end down to  exactly half diameter, in the manor of a “D” bit. When the flat of the “D” bit is horizontal it is perforce on centre height.

Clearly the above is over-kill for most purposes, but I was bored one day! Having said that if you have QC tool holders, it does make setting tool height a doddle.

 

For the benefit of any “Newbies”, shall we discus  the  necessity of tool height, and its increasing importance as work diameter reduces and why?

chriStephens 

[KWILParticipant @kwil]

Thats a good idea if they want us to.  Incidently I was taught in the real world on a Smart & Brown with an american pattern tool holder, you soon learn how to shim tools and height set that way,

Edited By KWIL on 27/03/2010 16:28:14

[Gordon WParticipant @gordonw]

Center hight, didn’t realise it was so difficult/ important. I do what I always thought was normal, I’ve a groove/ scratch on the tailstock mandrel, and for accurate setting there’s a bit of bar that is the right length when sat on the cross slide. But I don’t do very small dias.

[CirclipParticipant @circlip]

Nooooooooo, you’ve GOT to have a QCTP (prefferably fitted with a DRO) 

 

  Will another manufacturers comparitor work Chris??

 

   Regards  Ian

[chris stephensParticipant @chrisstephens63393]

My dear Circlip,

You mean you haven’t got QC holders nor DRO, how can you possibly work under such primitive conditions?

I will let you work out if another Comparator ( from the old French comparare, since you like picking me up on my spelling) will work, I will just say that on the Myford I use a Verdict one. It’s a lovely simple little lever operated thing that reads 15-0-15 thou, regrettably long since out of production. Anyone who went to the last Myford show would have had the opportunity to see it, had they bothered to look at things on show. And yes that makes two days that I was bored, when making these gauges seemed a reasonable time filler.

chriStephens 

[mgjParticipant @mgj]

I like the trapped rule as a quick guide – saves moving holders. I have a setsquare inscribed off a morse taper, and final adjustment is by facing.

 

I do have both a QCTP (on both machines) and a DRO, on one. I find them very convenient – I have no conscience or feeling of pain about owning either.

 

I also find them conducive to good work because adjusting height is not a pain and I am more inclined to do the adjustment rather than live with a small error. 

 

When it comes to finish, I personally find that speed and coolant and nose radius a lot more important than precise centre height adjustment.

 

Edited By mgj on 28/03/2010 17:20:36

[JohnFParticipant @johnf59703]

Hi, I agree with Nigel 21/03/10 regarding solid HSS–these are the best you can use,  I have quite a few boreing tools made from HSS round or square, all made by hand on a bench grinder. These have been in frequent use for some 30 years–made when i was in toolmakeing. also have several holders for grinding tool inserts for larger bars. If you would like a photo please message me and I will oblige.

Regards John.

[mgjParticipant @mgj]

Might I disagree please – and I too have a collection of solid HSS boring tools all ground up on a Quorn (just so the angles are right)

 

An indexable carbide tip in a tool is always set at the optimum angle, and in many cases the tool is drilled for coolant.

 

Having set all at centre height, you can rough with one part of the tip, and then spin the tip round and bring a nice new sharp edge into play for the final cuts, with no loss of centre height, and in all practical senses with no loss of position. AND with the right nose radius (which is a PITA to apply on a tool and cutter grinder and almost impossible to do by hand), you know you’ll get a good or even outstanding finish, in some cases nearly comparable with grinding.

 

For my money, the indexable boring bar fitted with a decent grade of tip, is a great deal more convenient than HSS bar, and produces just as good a result.

 

There is probably not a lot in it in terms of cost either, because these days decent HSS from people like Eclipse, Cleveland Sandvik etc is very expensive.

 

(My definition of a good result – diameter +/- .0002, and a nice shiny finish) 

 

Having said all that, I will accept that there are times when only a special tool will do, and then it has to be HSS, but for the general run of things indexable carbide takes a lot of beating

 

[Author]

Posts