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1 1/2 8tpi 3 and 4 Jaw Threaded Chucks
- Thread starter YotaBota
- Start date
I got the first one from Shars then the next two from grizzly
I used DYK Post in Calgary to bring them in from Sweetgrass
The back plates are threaded
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If you’re referring to the new chucks I’m unsure . Haven’t seen them yet. @YotaBota would know
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Got back to the start of this thread. The chucks are 1.5" 8 TPI.
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Tom Kitta
Ultra Member
I almost though about getting yet another 4 jaw but I would need to place somehow a back plate on on for D1-3.
Here I am making new back plate for the 4 jaw chuck from scratch. Back is done I am just removing extra scrap metal from the front. Donor was a round scrap piece of 1018 steel (its soft).
So far the TIR is +- 0.001 which is good enough for cheap Chinese 4 Jaw.
Its a 6" plate. Insert is almost dead. RPM start 70 end 150.
![IMG_20200211_220827[1].jpg](https://canadianhobbymetalworkers.com/attachments/img_20200211_220827-1-jpg.7607/ "IMG_20200211_220827[1].jpg")
Here I am making new back plate for the 4 jaw chuck from scratch. Back is done I am just removing extra scrap metal from the front. Donor was a round scrap piece of 1018 steel (its soft).
So far the TIR is +- 0.001 which is good enough for cheap Chinese 4 Jaw.
Its a 6" plate. Insert is almost dead. RPM start 70 end 150.
Tom Kitta
Ultra Member
Yes it does, just over 7 degrees taper, at the widest point it is 2.15 inches wide. My main problem is/ was figuring out how to measure 2.15 on a tapered bore - supposed accuracy of the bore in book is + 0.0005 - which I have not figured out how to measure even close to that accuracy. According to this https://en.wikipedia.org/wiki/Bore_gauge I would need a ring gauge. But since taper is so shallow that does not really help that much - there are supposedly special taper measuring tools.
If I was making many of these the suggestion is to make oneself a plug gauge - you would simply put it into bore and see how much it sticks out - if it does not - then you got perfect bore.
That's why I asked. A while back I bought a faceplate that had the proper taper angle as evidenced by bluing, but it still had a small gap between the vertical face of the spindle & back plate. So when the cam locks tightened it would lodge at some slightly cocked angle. The spindle nose is 2 surface contact fit, the cone and the vertical face, simultaneously. I made a ghetto lap tool from low shrink epoxy putty using a known good spindle as a mold & slowly worked at it blueing & fitting. It was a PITA but it worked. If I did it again I would cast an entire circular plug & use lapping compound.
On a short distance like the width of taper nose you could probably set your compound up to replicate the actual spindle taper with 10ths DTI, ensuring you were absolutely on center, lock that setting & turn the taper. But yes you need a reliable way to measure the bore as it progressively opens up which is complicated in that it you are measuring a relatively sharp corner lip as opposed to a cylindrical bore. Having a dummy plug mimicking the spindle itself would be the best because you could just press it in & progressively creep up on flush. But it would have to be a very accurate plug. Buying a semi finished back plate with pre-machined taper isn't looking so bad now LOL I was thinking along these lines, buying an offshore D1-4 chuck backplate just to give me a head start on the spindle bore issue.
Let us know how you make out!
On a short distance like the width of taper nose you could probably set your compound up to replicate the actual spindle taper with 10ths DTI, ensuring you were absolutely on center, lock that setting & turn the taper. But yes you need a reliable way to measure the bore as it progressively opens up which is complicated in that it you are measuring a relatively sharp corner lip as opposed to a cylindrical bore. Having a dummy plug mimicking the spindle itself would be the best because you could just press it in & progressively creep up on flush. But it would have to be a very accurate plug. Buying a semi finished back plate with pre-machined taper isn't looking so bad now LOL I was thinking along these lines, buying an offshore D1-4 chuck backplate just to give me a head start on the spindle bore issue.
Let us know how you make out!
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Tom Kitta
Ultra Member
Well the dept of the cone seems to be always more then the actual cone height. In D1-3 if I remember correctly it should be 7/16. The chuck I have with its German made back plate the depth is .59 when I made mine I did it a bit less at around .51.
I did replicate the angle from the original chuck. It seems faster then sine bar methods - besides I have no experience with these so I may get it wrong.
My primitive method simply involved cutting the taper close enough but little under size. Then through about 10 (!!!) repetitive checking of fit I used some sand paper to expand the dimension. Probably by maybe just over 0.002.
Yeah buying actual back plate seems to be a much less time consuming process - at least you don't run into "cool" issues as to figure out what is the angle offset of the locking screws on the pins. It appears to be 18 degrees plus for D1-3 and 12 degrees plus for D1-6. And it has to be a plus... I did a minus and it does not work for D1-3 but does for my D1-6....
Also fun fact is that the circle for the pins in D1-3 is 70.6mm but at least on German chuck the locking screws appear to be on touch smaller bolt circle - in addition to the offset...
Thus a bit of reverse engineering is needed.
The pins themselves are also not easy to make - the locking indent is 3/8 and 0.04 deep - you get it from the 3/8 diameter of the bolt heads. Pins are 9/16. But the actual locking indent is not really a 3/4 - it is "close" but one side is "rolled" a bit bigger then what a 3/4 ball end mill makes. Same on D1-6 - its not a straight cut by 3/4 ball end mill - its more involved.
I did replicate the angle from the original chuck. It seems faster then sine bar methods - besides I have no experience with these so I may get it wrong.
My primitive method simply involved cutting the taper close enough but little under size. Then through about 10 (!!!) repetitive checking of fit I used some sand paper to expand the dimension. Probably by maybe just over 0.002.
Yeah buying actual back plate seems to be a much less time consuming process - at least you don't run into "cool" issues as to figure out what is the angle offset of the locking screws on the pins. It appears to be 18 degrees plus for D1-3 and 12 degrees plus for D1-6. And it has to be a plus... I did a minus and it does not work for D1-3 but does for my D1-6....
Also fun fact is that the circle for the pins in D1-3 is 70.6mm but at least on German chuck the locking screws appear to be on touch smaller bolt circle - in addition to the offset...
Thus a bit of reverse engineering is needed.
The pins themselves are also not easy to make - the locking indent is 3/8 and 0.04 deep - you get it from the 3/8 diameter of the bolt heads. Pins are 9/16. But the actual locking indent is not really a 3/4 - it is "close" but one side is "rolled" a bit bigger then what a 3/4 ball end mill makes. Same on D1-6 - its not a straight cut by 3/4 ball end mill - its more involved.
Kelly McLaughlin
Well-Known Member
I bought two 4 jaws after reading your post, The closest atlas 6" 4 jaw I could find was in the mid three's US and then needed a backing plate so for the 9 x 20 guys it'a find for sure! Thanks for posting it!
I'll have to talk to Ron and see what I get for commission
. Ron said I should buy a bunch and sell them, damn, probably could have made a couple of bucks. As I said before, they need a good cleanup and mine needed a bit of honing to get all the jaws to run smooth but it works really well.
. Ron said I should buy a bunch and sell them, damn, probably could have made a couple of bucks. As I said before, they need a good cleanup and mine needed a bit of honing to get all the jaws to run smooth but it works really well.
I'll pick the second one up off you and split the shipping.
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W
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I’ll post pics of the 3 jaw later tonight, it is in disassembly right now. The threaded backplate came off simple enough, could probably machine another easily. Really nice fit of the threaded backplate though ( could hardly seem the seam )
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