Cheaper boring tooling suitability

Although I have a couple of indexable-tip tools, and often use them, unless I've got quite a few similar components to make, I still find handgrinding HSS the most flexible method for tooling, whether turning, boring or flycutting.

I've just bought a new 3/8" boring bar that uses 1/8" square HSS bits. Very often I find I want to make an internal recess - for example to clear the thread runout from a plug tap in a flat-bottomed internal thread - so I'm quite likely to want some special shape. The only reason I bought a new bar is because the bit-clamp grubscrew thread on the old one gave up after I can't remember how many years.

I'm very glad of the time I spent in the past learning how to hand-grind HSS tools, and I think it would pay anyone to do so.

Thanks Neil, Jason and Ketan for your interesting input. Since my post yesterday, I've spent some further time trying out my 10mm boring bar. On the piece of mild steel that I was using I didn't make much progress.

I have a 0.8mm tip as well as the 0.4mm supplied with the bar which I tried. There was possibly some improvement, but not a great deal.

I then tried some aluminium bar and 316 stainless with the 0.4mm tip. Finish was much better, so some satisfaction!

I used moderate speeds for all cuts, and around 0.003" - 0.015" depth and 0.003" - 0.006" feed.

I therefore subscribe to the view that mild steel isn't always easy with carbide, a pity, since it's a staple material and I can usually wangle a decent finish on it with HSS or even silver steel tool-bits.

Maybe free-cutting MS would help, I'll try to get hold of some.

I oscillate between using HSS and Carbide. In my opinion they're both worth having but - as always - it depends on what you're doing and how you do it. HSS is easier to use, but it cuts slowly, isn't so good on hard stuff, doesn't last unless it's flood cooled, and you have to learn to grind. Carbide is easier to set up (no grinding or resetting tools) and - potentially - it lasts longer whilst removing metal much faster.

I dislike generalising about complex subjects but in my experience it's important to work carbide 2, 3 or 4 times faster than HSS, and to take deeper cuts, and - recent learning - to up the feed rate as well. Brutality is the order of the day and older kit may not be up to it. Myford lathes, for example, were designed to use HSS tooling decades before carbide inserts became widely available. Spindle speeds and motor power were decided with HSS in mind. On top of those restrictions an older lathe might be worn as well; if so, bad news - carbide needs rigidity.

My main problem with inserts is working out what to buy. I haven't found an easy explanation of what the different types are for. There are square, triangular, rhombic and circular inserts in a variety of rakes and geometries, with and without chip breakers. With luck CCMT060204 inserts are a good compromise for hobby work, but I don't really know.

Dave

That's only the half of it, what is written after that code can make a lot of difference too, each tip manufacturer may well have 10 or so different options for a CCMT 060204 insert. This is when they start to get specific for material, type of cut amount removed per cut etc. All good fun.

Hello Ketan and Tony,

I tried your advice and find that the finish is now much better. I will try the 0.8mm tips for my next trial. So it shows that you need to ask people who know about the product!

I can still get a better finish with HSS but the difference isn't so great after following good advice. I have a pal who uses carbide tipped tooling for everything including plastic and Perspex! He can't use HSS because he simply cannot grind a decent tool! I suspect I may finish up using carbide tips for roughing out ad swop to HSS for the final finish. let me see how the 0.8mm tips work out.

Andrew.

In recent years I have been using the high positive rake inserts designed for cutting aluminium. I use these on a Myford Speed 10 and despite the fact that it is a small machine this combination works very well. I find these inserts work equally well on aluminium and steel (including stainless ) .

Doug

Douglas, I assume you are using "GT" as opposed to "MT" tips for your results. I find the tips made for aluminium (the "GT" ones) give excellent results on mild steel for finish.

Hi Chris, yes the tips I use are the GT type. A while back a seller on ebay (engineering-r-us ) were selling Taegutec tips in lots of 50 and I dismissed them for ages thinking I did not need 50 of each type and they would be very expensive. I then started to see what price they were selling for and discovered that a lot of 50 were going for anything between £30 and over £100.

​ Being a cheapskate I kept bidding low and ended up with a few lots of 50 with an average price of less than a pound for each tip. These tips have transformed my cutting but you have to be careful since they do chip easily if you do not take care, but I am in the happy position of having enough tips to see me out.

​ Unfortunately the above supplier has not listed on ebay for a while as far as I can see and maybe they were just selling off bankrupt stock at any price they could get.

Doug