I searched but didn't find anything directly relating to the advantage/disadvantage of 3 way vs 4 way split collets. Mainly collets like 5c, 16c, 3j etc. I see collets in the same size, style that can have 3 splits or 4 splits. Is one ever preferred over the other? I'm referring to round if that makes a difference.
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Any practial difference between 3 way split vs 4 way split collets?
- Thread starter slowneasy
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I think the fewest slits practically manufacturable is the key as it presents the largest inside surface to the work (especially important in small collets). A 3 lobe collet will also better grip rolled and ground barstock as it tends to have a trilobular shape from being manufactured.
I'd imagine 4 jaw collets would be easier to make as far as the slitting operation goes, so I'd have to imagine the 3 jaw must have been beneficial enough throughout history to justify the added difficulty.
The more slits there are, the more capable the collet is to conform to different diameter bar stock. An ER20 collet for example has 8 slits on the face (as well as 8 on the rear, different mechanic, but I think it illustrates my point) and has a large "crush" range to grip tools smaller than the stated collet size.
I'd imagine 4 jaw collets would be easier to make as far as the slitting operation goes, so I'd have to imagine the 3 jaw must have been beneficial enough throughout history to justify the added difficulty.
The more slits there are, the more capable the collet is to conform to different diameter bar stock. An ER20 collet for example has 8 slits on the face (as well as 8 on the rear, different mechanic, but I think it illustrates my point) and has a large "crush" range to grip tools smaller than the stated collet size.
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Almost all 5C collets are 3 way splits, the only 4 split that I have seen would be for square and rectangular stock, and some of the odd sizes/types of collets like the 5ST. Take a look at the Hardinge collet listings. A 3 split, similar to a 3J scroll chuck can hold more irregular found stock vs. a 4 way split. The major downside of a 3 split collet is a very narrow clamping range vs. say ER collets which have many slits and are more collapsible.
I was thinking somewhat along those lines with the four way having a very slight advantage in gripping size. I wasn't sure if one was easier to manufacturer or not. Hadn't thought like that as I was just assuming the slit was cut one at a time. For sure the three way is more common so was thinking that maybe the four way was needed for some specialty reason. I have some four way split and three way coming in different round sizes and will see first hand if I think there might be an advantage to one over the other.
I had left out the ER style because they are a different breed if you will. From my understanding, designed more as a tool holder than work holder although the different styles do both.
I had left out the ER style because they are a different breed if you will. From my understanding, designed more as a tool holder than work holder although the different styles do both.
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I have a variety of collets including R8, 5C, 2S, and a number of specialty collets for drill grinders ,and tapping heads. They all have 3 slots 120* apart except for the drill grinder collets I made in the shop. In my opinion the 3 slot collets have better gripping force due to the larger face on each section, and less propensity to collect chips since there are fewer slots and they are wider.
The 4 slot collets I made work fine, but there isn't much force applied when grinding drills as opposed to actually drilling or milling a hole or slot. When purchasing collets be sure to look at the specifications. My 5C Hardinge collets have a clamping range of +.007" to -.002". The cheaper Shars ones have a clamping range of +.000" to -.008"
As for the Hardinge clamping range you can clamp down on smaller diameter stock, but you run the risk permanently deforming the collet. As mentioned in another thread it isn't wise to try to respreads the fingers. In all likelihood you'll break the collet.
The 4 slot collets I made work fine, but there isn't much force applied when grinding drills as opposed to actually drilling or milling a hole or slot. When purchasing collets be sure to look at the specifications. My 5C Hardinge collets have a clamping range of +.007" to -.002". The cheaper Shars ones have a clamping range of +.000" to -.008"
As for the Hardinge clamping range you can clamp down on smaller diameter stock, but you run the risk permanently deforming the collet. As mentioned in another thread it isn't wise to try to respreads the fingers. In all likelihood you'll break the collet.