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View Full Version : Need help identifying an insert hold down screw



lost_cause
01-04-2013, 07:24 PM
I recently bought a used lathe and it came with a pretty good assortment of indexable carbide tooling. There was one boring bar where the hold down screw was worn enough that I'd like to replace it, but I don't know what it is. I took a couple pictures, but my phone didn't do it any justice, so I'm going to try to describe it and see if anyone can help me.

The boring bar is a 3/8" diameter x 6" long carbide shank and the insert is a WCMT 21.51

With a caliper the hold down screw measures 0.092", or 2.34mm and the thread looks to be 0.45mm pitch. I was able to loosen the screw with a T8 screwdriver, so I'm guessing that it is an M2.5x0.45 T8 screw. From end to end the screw measures 5.7mm, but since the screw has a beveled head, I don't know how the length is supposed to be measured.

I've got to place an Enco order soon, and I'm hoping someone can help me determine what they carry that will be a compatible screw. Any guesses?

http://i908.photobucket.com/albums/ac286/lost_cause_photos/0104131751a_zpsbcc331bf.jpg

Optics Curmudgeon
01-04-2013, 07:33 PM
Yep, it's a screw, I think. From the "photo" you can't tell much else. Seriously, a photo that big, and out of focus to boot?

lost_cause
01-04-2013, 07:54 PM
Sorry, with the small size of the parts my phone didn't have much of a chance. I only added the photo to give the general shape of the screw to show that it was tapered. I'm hoping someone here has a similar sized tool and would recognize it and be able to tell me a brand and part I can match it to, since mine has no markings on it.

Oldguy
01-05-2013, 01:44 AM
I don't use inserts, but from the little I've seen, it seems that there almost are many different screws as there are inserts. Are there any identifying marks on the holder? If there are, then we can zero in on the manufacturer and determine the correct screw. In short, need more info.

Glenn

LKeithR
01-05-2013, 02:26 AM
Go online and check some supplier websites. Many of them show replacement screws. Travers (for example) has multiple listings. Most are listed by part no.--for a specific bar or holder--but they do have some dimensions. In the style you're looking for they show 6-40, 8-32, 10-32 and 1/4-20 screws of the type you need. Also some metric ones if that happens to be what you're looking for...

dian
01-05-2013, 04:05 AM
i have successfully machined a 60 taper on a standard screw. but this one is a Little on the small side.

beanbag
01-05-2013, 04:36 AM
M2.5x0.45 T8 screw.

This is the correct size. The taper is 60 deg. The length does not matter much because usually the tool holders are threaded through. As you can see when you put the screw into the insert, even a little bit of thread will stick out below the insert and screw into the tool holder. You can get these easily on ebay.

Forrest Addy
01-05-2013, 05:17 AM
Many of the replacible parts (screws, shims, clamps etc) are standardized to a degree, more so in later designs. If you happen to find an indexible insert carbide turning tooling catalog you may very well finf your screw listed there. The parts need not be expensive if you shop around.

KenLok parts are available only from Kennametal last I heard and don't forget your plastic when you go shopping for them.

bob ward
01-05-2013, 08:40 AM
Try these guys

http://www.valumaxcorporation.com/catalog.html

RussZHC
01-05-2013, 09:58 AM
Flipped through the online Enco catalog last night and replacement screws are on a few different pages and sort of hidden away (more because there are not many listed than anything else), if it were me I'd check that you get a socket style to match your others (there were some shown as having a hex/Allen head...I just find it aggravating when there is that one oddball :mad:)...for sizes it seems as if the I.C. of the insert is the place to start...

lost_cause
01-05-2013, 11:13 AM
Flipped through the online Enco catalog last night and replacement screws are on a few different pages and sort of hidden away (more because there are not many listed than anything else), if it were me I'd check that you get a socket style to match your others (there were some shown as having a hex/Allen head...I just find it aggravating when there is that one oddball :mad:)...for sizes it seems as if the I.C. of the insert is the place to start...

I've probably spent more time searching for these screws than I will using the boring bar. I have a 2011 printed Enco catalog and I have gone through that, and tried searching the specifics of many insert screws in the online catalog with no success yet. If I had to guess, I'd say the boring bar is a Circle Machine QCBIW-375-6-3R, but there are absolutely no markings on the bar to be certain. The lot of tooling I got did include two other Circle Machine 5/16" boring bars - those had the markings on the shank and were easily identified. Even if I am correct in the identification of the bar, I can't find any spare parts for that one in the Enco catalog.

A few posts up, beanbag agreed with my guess on the screw size, and I found these on ebay:
http://www.ebay.com/itm/10-Pieces-THFC-042-Spade-Drill-Lock-Screw-72556-T8-2-5XT8-OD139902-/160773360203?pt=LH_DefaultDomain_0&hash=item256ed6ca4b

I'm thinking I'll probably drop the $12.50 and buy that pack of 10 screws. I've spent far too much time searching for them already. Those seem correct, even down to the exact length.

RussZHC
01-05-2013, 06:49 PM
I am quite green at this insert thing so...Enco online = P219 is Interstate, P 216 is Carmex, P 208 is generic "hex socket", P 231 is Borite, P 207 is SECO...these all list screws but be careful when looking, there are shim screws, clamp screws as well as insert screws. In some cases there is only a replacement part number listed (which helps the searching none but does not say said screw could not work) and sometimes they only say "replacement screw".
In some cases they list a specific thread but in at least one example, IF I read it correctly, two different bars using the same size of inscribed circle inserts had different thread count screws listed (implying that the head of the screw made contact with the insert correctly but was not the same thread). Some cases the appearance is the screw is "proprietary" which makes no sense if the insert is being made to a given standard, depending on your perspective.

This is precisely why a lot of my "downloaded files" are various manufacturers catalogs, only way I have a shot at cross referencing...agree again on having to spend way too much time on this sort of thing AND best I can figure "they" are adding different shapes almost constantly (last 6 months or so seems to be more regards milling tooling)

Edit: for what it is worth, in inserts, there are cylindrical holes (4th letter in code, A/M/G), cylindrical w counter sink 40 to 60 degrees (4th letter, W/T/Q/U),
cylindrical w counter sink 70 to 80 degrees (4th letter, B/H) so that effects the underside of the screw head and then it has to be long enough to account for the thickness of insert (last number in 32nds)