View Full Version : What Size is this???

12-19-2003, 08:10 PM
I got this lathe tool:


It's 3/8 by 3/8 tool that uses TNMG221 type of carbide inserts.

What size is this allen wrench does this take. The ones that I got with the HF indexable tool set (1/4 type) is too big or not the right shape (possibly due to SAE to Metric differences).

No visible name brand or markings. I got about 60 still in the box inserts with this, but no tiny allen tool.



12-19-2003, 08:59 PM
If the toolholder is Chinese, the hex in the Allen screw probably does not bear any resemblance to anything Imperial or Metric. I don't know how they do that.
See if you can remove it with a hammer and punch and replace it with a real screw.

Peter S
12-19-2003, 09:15 PM
If you have some vernier calipers, measure the across flats of the socket.

The "internal" points of your caliper should fit inside there OK.

If you have decided that it is not an inch size, and if you only have 'inch' verniers, take your inch decimal reading and multiply it by 25.4 to get metric size.

For example, if you measure it as .059" that x 25.4 equals 1.5mm.

Standard metric sizes are 2.5, 2, 1.5, 1.27,

Get yourself a set of Unbrako inch and metric allen keys, they will last you for years to come.

Forrest Addy
12-19-2003, 09:41 PM
Compounding the problem it might be a "Torx" head screw. On smaller sizes and beat up screws it's easy to confuse them with Allen. Peer closely with a hand lens.

Only Torx wrenches safely drive Torx head screws. Allen wrenches frequently wreck them.

12-19-2003, 10:14 PM
Take it to someplace where they sell lots of allen wrenches and see if any fit.

12-19-2003, 11:55 PM
tend to agree with JCHannum up there....if its Chinese (or even <cough, sputter> Indian)..best to get the original screw out altogether and "soup that baby up" with real hardware !!! Should be able to pick up a torx screw/driver at anyplace that sells the inserts...good luck!

12-20-2003, 01:38 AM

Normally it should be a T7 torx which is more or less standard fare for 3/8" shank tools. When you get it out make sure you coat the new torx scre in moly-cote or copper-cote high temp anti-seize compound. I prefer the copper-cote myself. The insert socket has to be spotless before bedding the insert. Normally insert screw require considerable force to remove them after use - don't be surprised at this.

12-20-2003, 03:34 AM
That is not a torx. It is a hex if you examine the pic closely. My wife sells inserts just like that, both carbide and diamond tipped but will not have a chance to check out the holder screw size until Monday.


Jerry, just take a hex wrench slightly oversize and carefully stone it down to the right size. I've done this lots of times.

[This message has been edited by Evan (edited 12-20-2003).]

12-20-2003, 01:51 PM
I will probabaly stone down a wrench until it fits. I really like to get a set of small allen wrench to keep onhand. Evan does you wife sell them, or anyone know who does?


12-20-2003, 02:23 PM
That doesn't look like the "right" screw for that size insert. Looks more like a standard flat head screw has been used.

Insert hold down screws usually have a much smaller head with respect to the insert size.

Is this new? Maybe someone substituted?

Jerry, you shouldn't ahve any trouble finding small Allen wrenches in inch or metric.

12-20-2003, 02:59 PM
These came from a person whose father was a machinist and passed away a few years ago and they are finding odds and ends while getting the family home ready to sell.

I will probably stone on small one that I have to size and use it for now.

Many thanks,


12-21-2003, 01:05 AM
I found my small electronic set of screw drivers, mini nex drivers and what not that I bought from Radio Shack years ago. The hex head is a #4 hex or .05 Allen.

Problem solved.

Thanks to one and all, and Happy Holidays


12-21-2003, 05:21 PM
I called my local non chain hardware st0ore, they had the .05 allen keys for $.15 each, I bought two.


12-22-2003, 01:37 PM
jfsmith I know you found the items already but for anyones future need here are the sizes. Screws Numbers on box are CSFS440-38 SCR FLt HD/VIS Tete Plt 3/8 this were ordered through Aclands. Have Wrench's that fit Numbers on boxes 01-19-02 1/16 Short Arm Allen Wrenches. These go with our Diamond or Carbide cutters I sell these for IMW Machines.

[This message has been edited by Betterhalf (edited 12-22-2003).]