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Group Project: Dividing Head - The Build
- Thread starter Flyinfool
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- Mar 25, 2013
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I tried making a D bit out of O1 tool steel. It didn't make very nice holes. I could try grinding one out of an HSS Center drill. UGG. I guess I'll look at tapered and Mills. Thanks.
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@Flyinfool Another potential issue check the clearance between the index pin knob and the trunnion. It looks like interference will prevent you from pulling back on the index knob. Does it need to be smaller?
FYI, I did not turn the center of the trunnion down smaller than 3.000. If I did, the worm mount would be partly hanging out in space. Also, the engraving would be on a radiused surface
FYI, I did not turn the center of the trunnion down smaller than 3.000. If I did, the worm mount would be partly hanging out in space. Also, the engraving would be on a radiused surface
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Scratch that- I see now that 2 trunnion locks are required. I assume this it the same assembly used twice? I am still concerned that one might not be able to pull this pin back the required .250" without hitting the trunnion. The cross section drawing is not exactly correct as it does not show the flats on the trunnion where the spindle passes through. Also the trunnion is not of smaller ID at its mid section, which is shown in other views.
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@Flyinfool - I am worried about the trunnion lock/spindle lock. I may be reading the designs wrong but here is what I see.
In the cross section diagram on page 2, the spring for the pin goes from the flange on the pin all the way through the bushing and into the knob. This is not possible since the bushing has a 3/16 hole for the pin. This would force the spring to stay in the bushing and therefore it would need to compress to a length of about .250 when retracted. I don't think this is possible or desirable. I don't think the bushing could be made much longer? Also, this pin is critical to making the spindle index accurate. It cannot have any play in it so close fitting holes are necessary.
This needs attention but I do not have any great ideas at this time. Deleting the spring is possible? I am wondering if swapping the spring loaded pin for a screw advanced pin would be a choice? That would be less convenient but would preserve accuracy.
The trunnion lock bushing could be made longer and so that may work with a minor modification.
EDIT: My wife is pretty smart. She looked at this and said "cut the spring shorter." That might actually be a good solution.
In the cross section diagram on page 2, the spring for the pin goes from the flange on the pin all the way through the bushing and into the knob. This is not possible since the bushing has a 3/16 hole for the pin. This would force the spring to stay in the bushing and therefore it would need to compress to a length of about .250 when retracted. I don't think this is possible or desirable. I don't think the bushing could be made much longer? Also, this pin is critical to making the spindle index accurate. It cannot have any play in it so close fitting holes are necessary.
This needs attention but I do not have any great ideas at this time. Deleting the spring is possible? I am wondering if swapping the spring loaded pin for a screw advanced pin would be a choice? That would be less convenient but would preserve accuracy.
The trunnion lock bushing could be made longer and so that may work with a minor modification.
EDIT: My wife is pretty smart. She looked at this and said "cut the spring shorter." That might actually be a good solution.
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I decided to upgrade my spindle bushings to the ones with less clearance. These are 1.502 ID. Perfect fit!
I had to re-bore the spindle holes to 1.750 to accept the bushings.
I am now working on a new spindle clamp. This is aluminum and has a 1.500 spindle hole. Clamping force would be better on the original 2.000 hole in the plans but I went with a 1.5" ER32 spindle. Hopefully this will be enough.
I also used counterbores instead of countersinks. I hope this will leave a little clearance for alignment with the spindle.
I finished the spindle index. This will be shrink fit onto the spindle. I need some dry ice for that. I used a tapered end mill to make the holes as recommended by @extropic. Worked great!
I had to re-bore the spindle holes to 1.750 to accept the bushings.
I am now working on a new spindle clamp. This is aluminum and has a 1.500 spindle hole. Clamping force would be better on the original 2.000 hole in the plans but I went with a 1.5" ER32 spindle. Hopefully this will be enough.
I also used counterbores instead of countersinks. I hope this will leave a little clearance for alignment with the spindle.
I finished the spindle index. This will be shrink fit onto the spindle. I need some dry ice for that. I used a tapered end mill to make the holes as recommended by @extropic. Worked great!
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Here is the update:
I am still wrestling with the issue of the spindle index pin. Here is what I see as a problem:
As it is currently drawn, the bushing and the knob take up .625 in length. The travel of the pin is .250. The allowed space is less than .750. That results in -0.125". This is a problem. Any change to the thickness of these parts impacts the ability to use the dowel pin to hold the index pin back. Even is you resolve this it will be darn hard to get your fingers in there to pull the pin.
I am considering a threaded pin with a 1" dia knurled handle that you can advance by turning? Not as quick as a spring loaded pin.
Please look at the drawings and see if something else occurs to you!
I am still wrestling with the issue of the spindle index pin. Here is what I see as a problem:
As it is currently drawn, the bushing and the knob take up .625 in length. The travel of the pin is .250. The allowed space is less than .750. That results in -0.125". This is a problem. Any change to the thickness of these parts impacts the ability to use the dowel pin to hold the index pin back. Even is you resolve this it will be darn hard to get your fingers in there to pull the pin.
I am considering a threaded pin with a 1" dia knurled handle that you can advance by turning? Not as quick as a spring loaded pin.
Please look at the drawings and see if something else occurs to you!
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@rwm
It's good to see the thing finally materializing. Looking good.
Here is an idea for you to consider regarding the index pin. I suggest making it a slip (Joe Pie would call it a "Gage Fit") fit (no spring, no threads) with a tapered tip to match the holes in the index plate. The suggestion is based on a more common 5C Spindex. It also assumes there is a lock that will secure the spindle from being disturbed by cutting tool induced forces/vibrations. The shallow taper in the indexing holes should allow the pin to be self retaining enough for any, IMHO, normal indexing application consistent with the overall design.
It's good to see the thing finally materializing. Looking good.
Here is an idea for you to consider regarding the index pin. I suggest making it a slip (Joe Pie would call it a "Gage Fit") fit (no spring, no threads) with a tapered tip to match the holes in the index plate. The suggestion is based on a more common 5C Spindex. It also assumes there is a lock that will secure the spindle from being disturbed by cutting tool induced forces/vibrations. The shallow taper in the indexing holes should allow the pin to be self retaining enough for any, IMHO, normal indexing application consistent with the overall design.
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- Mar 25, 2013
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This is how I am leaning. I am also toying with a pin that is half threaded but that could be finicky.
Edit:
The gap shown above is really confined. Instead of a knob, I am now thinking about a pin with a hub on the back end and a long dowel pin pressed into place across the diameter. Say like a .500 hub with a .188 dowel pin across it. The pin would be easier to grab from each side. Hmmmm.
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