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Getting a good finish

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Stuart:
First don't shot the messenger

I hade a job in the lathe today which involved boring a hole 0.75 inches dia in a piece of 1 inch square stock 3 inches deep through not blind


I was using  one of the tipped boring bars that are common in the merchants store  ( Glanze omega at el )  my HSS bars are either to short or to big

as I stated with a 0.5 inch drill the boring bar was small and well extended the finish was terrible look like I had used a rusty nail ,

so  on when  a new tip the one they sell for steel no improvement tried it fast, tried it slow, tried it dry, tried it with cutting oil  still a very bad surface , but as the finish size was getting near desperate measures was call for.


the hole dis. still required the middle size bar  so a quick sort in the tip draw and I found some of those tips they sell for non ferrous metals nice and sharp with a good rake ( supplied from the  dunstable outfit )
so one it went the cutter it just hissed and the finish was superb, by this time I could get in with the larger bar with the NON ferrous tip on the results were the same a good ridge free smooth finish in the bore

now I realise that these tips would not hold up for any heavy cuts but for finish work they work fine on Steel

I do not Know the grade but it aint EN1A  it must be a form of GGQ   ( Good ? General Quality ) unmachinium

again its one of the thing that goes against the book but it got me out of a mess today

may be worth a try next time I have some nasty lumpy steel to turn


Stuart

Bogstandard:
Stuart,

If you have a mill boring head and can hold the part OK, I find that boring in the mill gives a far superior finish and size just using the crappy brazed tipped boring sets you can buy.

If I want ultimate finishes and sizes, then I use the HSS 'German' types of boring bars.

Top few on this page

http://rdgtools.co.uk/acatalog/TOOL_S_FOR_BORING_HEADS.html

John

Stuart:
thanks John for the info

Stuart

Arbalest:
Yes, thanks John. Not seen those type before.

Bogstandard:
The 'German' types of boring bar are the type that you can very easily make yourself using silver steel, but I am a great believer in not making tooling if it is available commercially much cheaper than it would cost me in time and materials to make them myself.

If I needed more robust ones, I would have to make them myself, as the ones I have seen available at reasonable prices are only in the smaller sizes.


John

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