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Soft jaws

Chucks

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Bob Brown 106/04/2020 17:50:04
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1010 forum posts
127 photos

How many here use soft jaws to hold parts in a lathe?

I've used them in to machine multiple parts as it means there is repeatability.

Mick B106/04/2020 18:03:27
1552 forum posts
83 photos
Posted by Bob Brown 1 on 06/04/2020 17:50:04:

How many here use soft jaws to hold parts in a lathe?

I've used them in to machine multiple parts as it means there is repeatability.

I use mine often. Not only do you get good concentricity but you can make a reliable shoulder for locating thin parts for facing work. I've found recesses of 3 increasing diameters allow me to do most work without further modification.

Edited By Mick B1 on 06/04/2020 18:04:12

Brian H06/04/2020 18:17:29
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1580 forum posts
104 photos

I use them occasionally but it's not very often that I need to rechuck for second op but they are extremely useful.

Brian

JasonB06/04/2020 18:24:30
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Moderator
17852 forum posts
1954 photos
1 articles

I use mine quite a lot, like Mick I find them yery useful for thin work where a recess only 1mm deep will hold work quite securely provided you are not silly with heavy cuts

old mart06/04/2020 18:44:13
1532 forum posts
136 photos

I have soft jaws for PB 5" chucks, a 125mm Chinese chuck and the 6 3/4" Pratt with the serrated jaws, which also has two sets of hard jaws. The 5" Pratt Burnerd chucks have lots of soft jaws, mostly bought cheap as job lots. They vary from 90% good to 90% used up. The worn out ones were milled to make them slot and tenon master jaws, and I have sets of aluminium top soft jaws to bolt onto them. Other worn out ones were milled to take short pieces of 1 1/2" AF hexagon brass stock which can be rotated one flat at a time using a central screw. They don't get used often, but are very useful when accuracy is needed. I used the serrated chuck to hold the X axis leadscrew of the Tom Senior mill when extending and evening out the threads, on conjunction with the tailstock, fixed and travelling steadies, all at once.

Chris Gunn06/04/2020 19:40:02
319 forum posts
22 photos

I use mine a lot, I have only bought 1 set, and they have lasted me since I had my Bantam, perhaps 35 years ago. That is because I made a dozen sets of bolt on jaws from 20 x 40 steel bar when the originals almost wore out, and have about 2 sets left, I will soon have to make some more for the next 35 years. If one has to turn a job around, and turn the opposite end true, then soft jaws are the answer, as well as for holding thin stuff. One can also weld bits on to the jaws to hold extra large diameter items or odd shaped items.

Chris Gunn

John Baron06/04/2020 19:41:14
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279 forum posts
122 photos

Hi Guys,

 

Soft lathe jaws is something that is needed to ensure concentricity and repeatably ! Normally a three jaw chuck will display a few thou run out.

These are mine, I've just replaced them with new ones.

18-02-2020-002.jpg

Edited By John Baron on 06/04/2020 19:41:39

Martin Kyte06/04/2020 19:44:49
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1804 forum posts
33 photos

They are a good way to extend the usefullness of a very worn out chuck. Also prticularly usefull for holding thin circular parts by turning a step into the first few mm of the jaws to locate work against a true running surface.

They are the kind of thing I don't use often but are an absolute godsent when required.

regards Martin

old mart06/04/2020 21:31:52
1532 forum posts
136 photos

I bought these recently, not that I needed them, but because they were cheap.

_igp2550.jpg

mick07/04/2020 16:51:52
389 forum posts
44 photos

An old turners trick from an old turner. If your using hard jaws to produce several identicial parts and you need to remove the parts from the chuck for different operations like roughing all the parts and then finishing, simply select a jaw say No.1 and draw two lines on the part either side of the jaw. If the back face of the part is tight against the face of the chuck they should all go back as near as dammit.

old mart07/04/2020 20:33:07
1532 forum posts
136 photos

Mick, I have done that once or twice when producing a female thread when there was no alternative to trying for size on the mating thread. The last one was a nut of about 2 3/4" diameter to hold the head onto the gearbox shaft of a Brantley helicopter. This was to lift the aircraft. I have a picture of the hollow shaft, rotated the wrong way round taken before making the nut. I took the nut out of the chuck about three times before getting a good match.

sam_0810.jpg

Edited By old mart on 07/04/2020 20:36:35

Chris Gunn07/04/2020 22:25:13
319 forum posts
22 photos

John, I do something similar, but use cap head screws and a deeper bolt on jaw, and counterbore the holes as deep as I can, then one can use the whole of the soft face for work holding, and for much longer too. it does not matter if you bore a recess through a screw hole, it will still run true and hold. You can hold much bigger diameter work too, should you need to do so.

Chris Gunn

Chris Gunn07/04/2020 22:28:29
319 forum posts
22 photos

Old M, those jaws look similar to the ones that fit on Alfred Herbert chucks I used back in the day, on a Ward capstan lathe. We used them to hold gear blanks during machining, and these had to be very true.

Chris Gunn

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