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SmoggyTurnip
03-06-2008, 08:13 AM
I recently bought some turning tools from Little Machine Shop:

http://www.littlemachineshop.com/products/product_view.php?ProductID=1669&category=

I can't seem to use them for more than a couple of minutes without having the insert becoming loose. I have to retighten the screw. Am I doing something wrong or is this just a bad set of tooling or a poor design. Is there a better design for an insert holder (for similart cost)? or mabey something I can make?

torker
03-06-2008, 08:26 AM
Do the inserts tighten up hard against the back of the holder?
Are the seats flat? (the inserts don't wobble around with no screw holding them?)
I've even made a few holers (in a hurry) that where kinda rugged looking but have never had that problem.
Russ

wierdscience
03-06-2008, 08:28 AM
The picture shows extra screws,have you tried changing them yet?It's possible the screws are soft when they shouldn't be.Maybe measure one of the screws that keep coming loose against a new one and see if the loose one has grown any.

I don't like that type holder,a lot depends on that tiny little screw and that dinky little torx wrench.A fix would be to drill and tap an extra hole right near the back edge of the insert and use a small button head allen screw as an additonal clamp to hold the back side of the insert opposite the cutting edge down.

SmoggyTurnip
03-06-2008, 08:37 AM
Do the inserts tighten up hard against the back of the holder?
Are the seats flat? (the inserts don't wobble around with no screw holding them?)
Russ

If the screw is loose at all then the insert does wobble a bit. The seats are flat.



Do the inserts tighten up hard against the back of the holder?
Are the seats flat? (the inserts don't wobble around with no screw holding them?)
I've even made a few holers (in a hurry) that where kinda rugged looking but have never had that problem.
Russ


I thought about doing the same thing but I can't think of a way to get the screw hole in exactly the right place - any tips?

Davek0974
03-06-2008, 08:40 AM
I started off with the exact same set! And had the same trouble.

The insert is not located positively and depends totally on the screw. There is little to counteract side pressures on the tip which is what loosens the screw.

After a while, i learnt that i got what i paid for and have started a collection of holders for CCMT06 tips. My holders are by Glanze Tools Ltd but there are plenty more makes, this is a very popular tip for small machines.

Dave

SmoggyTurnip
03-06-2008, 08:41 AM
The picture shows extra screws,have you tried changing them yet?It's possible the screws are soft when they shouldn't be.Maybe measure one of the screws that keep coming loose against a new one and see if the loose one has grown any.

I don't like that type holder,a lot depends on that tiny little screw and that dinky little torx wrench.A fix would be to drill and tap an extra hole right near the back edge of the insert and use a small button head allen screw as an additonal clamp to hold the back side of the insert opposite the cutting edge down.

Yes I have tried the extra screws - I was forced to because ruined the heads of some of the screws by trying to tighten them up real hard. - I will try your suggestion about the allen screw.

torker
03-06-2008, 08:54 AM
Just a thought...are the screws bottoming out?
Weirds idea is good. You might could even copy some of the other clamping devices that other mfg's use.
OK..here we go...probably not right...but when I made mine, I set the insert on the seat, then got a drill that just fit the hole in the insert. Put the drill in (with a hand drill) and spun it enough to make a spot. then I removed the insert, put a punch mark just a bit above the marked hole. This made the screw put pressure against the back. Hillbilly but it worked well. This was maybe for a bigger insert than yours though and the screw was probably stronger on mine.

John Stevenson
03-06-2008, 12:09 PM
Biggest problem with these tools is the design is cheap.

Often the pocket is just milled out with parallel sides so the insert is on point or rather line contact along one edge if it's machined correctly.

The pockets are often deeper than the insert meaning that the unused sides get a hammering and fine chips before they come into play.

If you want to make your own then treat yourself and measure the angle of the insert and buy a tapered milling cutter to suit.
They are available, J&L sell them in 1 degree increments. Next mill the pocket about 1O to 15 thou shallower than the insert so the cutting edges can't get damaged by fretting.

Lastly and most importantly, measure the hole in the insert using a drill shank then using the next size down spot the hole whist keepint the drill to the back edge of the insert, i.e. away from the cutting edge.
The drill this hole for the tapping size you want.

The idea is to get the hole off centre so when the screw is tightened it pushed the insert hard into the pocket.

If you look at a professional one these are done this way.

Smoggy, sometimes we have to make these mistakes to learn. The trick is not doing it too often :D

.

Alguy
03-06-2008, 01:35 PM
I once made a fly cutter to use inserts i got from flea bay , they would become loose i used a method similar to Sit John's it has proven to be effective. i did use super glue to hold the insert prior drilling (to make locating where to drill easier), just get it to hold against the edge of the pocket tightly and you will be fine.

BadDog
03-06-2008, 02:39 PM
Or just buy good Kennametal (or other) holders in common (cheap) sizes, then cut them down. I've bought several 1" TPG32x Kennametals in different configs (L, R, Face) and cut down to 1/2" to fit my toolpost. Total investment, $15 ($5 x 3).

SmoggyTurnip
03-06-2008, 02:42 PM
I have been thinking about making my own holder for these inserts. Looking at http://shopswarf.orcon.net.nz/ansiinsert.html it says the "M" in TCMT means a tolerance of +/- .002 to +/- .005, ummm what is the point of the +/- .002? If it is +/- .005 then it is +/- .005 isn't it. Why not say +/- .000000001 to +/- .005?

torker
03-06-2008, 03:05 PM
.002 means they are ALWAYS .002 to big or .002 too small. Nowhere did they say they could make them to proper size :D

macona
03-06-2008, 04:40 PM
Since you are stripping out the screw trying to tighten them maybe the screws are soft and stretching under tension while cutting. Once the stretch a bit the screw just vibrates loose.

airsmith282
03-06-2008, 06:35 PM
i got the same set from busy bee and have had problems as well with the screws getting lose on them, there ok if you can tighten the screw up pretty hard but also frustrating as the allen key holes mess up fast as well, i have decided to put them aside for now till i can make some really good screws for them and i have goneback to HSS blanks to make my own cutters for now , i want ot get better quaility tooling but no funds right now, the other thing youll notices with thoes cheapies is your ODS get a bit messed up as well whhen the screws get even the slighest bit lose so yet another reason i have decided to not use them again untill i can fix the issues with them ,, you do get what you pay for thats for sure ...

BadDog
03-06-2008, 07:26 PM
With "good" holders readily available, and MUCH cheaper, with common inserts, I can't imagine how Enco or LMS ever sell a set of those things. My Kennametals are good industrial tools, TPG inserts are CHEAP and common, they fit "right" every time, good hardware that isn't going to strip or come loose. The only scenario that I could ever see buying those thing is if you have a small lathe and NO milling capability. Even an SB9 (though why you would want carbide inserts on one is a totally different point <grin>) with an angle plate and "packing" could eventually mill these down to fit a 1/2 holder. The only slightly hard part is that they are amazingly "tough" and will require a good carbide EM (I used a 1/2 3 flute rougher).

Like I said, I paid $5 each for mine, but you see them all the time on ebay for $10-$15 tops. Out here machine tool stuff goes high at auction, but I've seen whole boxes full of these things (1-2 dozen or more!) selling for $20-$30, usually late in the day when all the "good stuff" is gone...