Inspired by Andew’s and mgj’s postings I did my own trials. Where possible I used identical conditions to those used by Andrew for a comparison. So, excuse my plagiarism and herewith the result. Photos (not very good) are in my Badger’s Bum album.
Lathe: Colchester Student 1800, running from an inverter supply.
Workholding: Burnerd Multi-size collet chuck
Material: 1.375" diameter steel – horrible old gas or water pipe, probably galvanised.
Depth of Cut: 40 thou, ie, 80 thou off the diameter.
Feed: 4 thou per rev.
Coolant: Rocol Multisol, 20:1 Dilution
Tool Tips: I used two different inserts and M42 HSS tangential tool.
The inserts were:
Korloy
CCMT09
Grade NC3120
0.2 mm tip radius
Sumitomo
CCGT09
Grade T1200A
0.2 mm tip radius
The tangential tool is the Oz version from Eccentric Engineering. I gave it a quick sharpen and a slight radius.
The Sumitomo inserts are the Titanium Carbide grade that is claimed to be effective at much lower surface speeds than nor
Oh, b****r, and I've just spent an evening doing more trials on different materials, only to be beaten to publication!
Mind you the evening hasn't been entirely wasted, as the CNC mill has been whirring away in the background making another prototype bevel gear pinion for my traction engine.
1: Badgers bum, rough appearance, rough feel. Small swarf, no oxide colour
2: Similar to 1. Slightly rougher. Very small chips, dark blue
3: Much better than 1 & 2. Smooth to touch but fine scoring felt with nail.
Small chips, gold colour.
4: Better than 3, feels smoother. Scoring as 3. Small chips, very dark gold.
5-8 Sumitomo
5: Best overall finish. Very smooth and no scoring although slightly more matt finish.
Small chips, no oxide colour.
6: Brighter than 5 but feels rougher and more scoring. Small chips, dark straw colour.
7: Very similar to 5, smooth to touch, very fine scoring. Long spirals, dark straw colour.
8: Better than 7, smooth and brighter. Same amount of scoring. Long spirals, very dark blue/straw colour.
9-11 M42 HSS
9: Matt finish, rough to touch, worst so far. Long spirals, no colour.
10. Rough, slightly shinier than 9. Gets slightly smoother with INCREASING depth of cut. Long spirals, no colour.
11: Best of the HSS finishes, smooth to touch but scratchy to fingernail. Long spirals, no colour.
Overall it was clear that the Sumitomo inserts gave the best results. I don’t have enough experience to know if the finishes I got were good, bad or indifferent but at least I could see – and feel – the difference. I was a bit surprised that the HSS results were not particularly good as I found when cutting 303 grade stainless that the tangential tool gave an excellent finish. Not having a surface roughness meter, the only criteria I could use was feel and appearance. Interesting that even where the surfaces of Trials 3 and 4 felt smooth to the fingertip, they still felt rough running my fingernail along them Not so with the Sumitomo finishes even though the surface had a more matt appearance.
If I get the energy, I will carry on and try a selection of tests on some ‘proper’ EN1A to see if this gives such a noticeable range of results. I would also like to compare how easy it is to make very fine cuts – say about 1 thou.
Thanks for that- I have long colums of print and an invitation to ignore or restore members? Apart form that!! its an excelelnt post.
Clealry Sumitomo are better in htis instance, and better wet at all speeds - and that speed isn everything. Buto f course that doesn't mean to say that would be true for all materials.
What isclear is there is a difference between tips, I love SECO, but when I next buy some I will try these Sumitomo jobs - though I was looking faround Ebay for APKT milling tips, and see that ISCAR are sellincg CCMT0602 04 tips very cheaply. SECO wil chip too , but one is dealing with a brittle sintered material and that can happen.
There is probalby a great deal of difference between HSS - some being good, some being bad. Some being well ground, and some not. I will post a pic of what I reckon an HSS knife tool should look like a bit later.
Incidentally, one of the advantages of tipped (indexable) tooling which no one mentions is the shape of the holder. The cutting tip is alway clear of the shank so you never have to adjust the toolpost angle - you can set it square and swap between a knife or parting tool without any changes in set up. And it will face across any size of disc without fouling.
Hi Hugh, all I can say is that you'v done well with galvanized water pipe, its a pig of a stuff to get a good finish on, although I have used it for a power cylinder on a large (2" boer) hot air engine. The only problem I had was that just as I got the bore nearly true the weld let go and the pipe opened upabout 6 mm. I closed it up and welded it, then finished the cylinder, its still works OK, it took a while honing then lappingto get a good finish, it runs with a cast iron piston, with next to no lubrication. Ian S C
A small point; I've found that the finger nail is an excellent comparative tool for surface roughness. It is possible to tell the difference between surfaces that vary by rather less than 1µm
I have put a link to the Sumitomo catalogue, as you will no doubt know there are a myriad
of different tips to choose from. Personally I prefer "positive" tips ( it's much easier to make holders that have horizontal seats for the tips) and a "finishing" or "fine finishing" chip breaker. Speaking of which, close scrutiny of the little graphs showing the chip breaker characteristics will be worth the effort, most enlightening.
When selecting one tip for a very large selection one has to be careful to pick the one that serves your purpose best. It should also be remembered that just because a manufacture produces some particularly good tips, it does not mean that every tip they produce is good, for your use. A rough milling tip will NOT produce a mirror finish when used for finish turning, and this I feel is the problem with buying surplus industrial tips, you have no idea what they are designed to do.
Its like GTN tips. They are a negative rake parting tip. Dimensionally and in the catalogues they are interchangeable with GFNs - they look so similar. In fact the difference being that the GFNs are positve rake, whihc is a huge difference in characteristic.
If you look at SECOs on line cataloge they list in CCMT -06 30-40 different tips. Iscar about the same
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