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JET JTM-4VS-1 Knee Mill ~ Z-Axis Knee Powerfeed
- Thread starter Scott(GA)
- Start date
A couple of weeks ago I started the process of mounting the JET Milling Machine's Z-Axis Powerfeed's Limit Switch Bracket.
There isn't a lot of space between the One Shot Lubrication plumbing and the upper Z-Axis lock. I positioned the Bracket and used a transfer punch to locate the center of the upper mounting hole.
I used a center drill to give the #4 drill bit a chance to start in the correct position. I used a small machinist square to ensure I was drilling the hole perpendicular to the side of the Mill. The blue tape was wrapped around the drill bit to give me a reference for the depth of the hole.
The #4 bit was the correct bit for a 1/4"-20 tapped hole with a 60% thread depth.
I used a 1/4-20 Taper Tap; followed by a Plug Tap and then a Bottoming Tap to prepare the hole to receive the upper machine bolt.
Continued in the nest post...
There isn't a lot of space between the One Shot Lubrication plumbing and the upper Z-Axis lock. I positioned the Bracket and used a transfer punch to locate the center of the upper mounting hole.
I used a center drill to give the #4 drill bit a chance to start in the correct position. I used a small machinist square to ensure I was drilling the hole perpendicular to the side of the Mill. The blue tape was wrapped around the drill bit to give me a reference for the depth of the hole.
The #4 bit was the correct bit for a 1/4"-20 tapped hole with a 60% thread depth.
I used a 1/4-20 Taper Tap; followed by a Plug Tap and then a Bottoming Tap to prepare the hole to receive the upper machine bolt.
Continued in the nest post...
Continued...
The hole was finished. This is only the second time I've tapped a hole for a bolt. I have to admit I was a bit concerned about doing this on my JET Mill. Time to see if I did it right.
I screwed a 1/4"-20 machine bolt into the hole... Looks like it worked!
I mounted the bracket using this upper hole to allow me to locate the center of the bottom hole.
Once again, a transfer punch was used to locate the center of the hole.
The bottom hole was prepared as the upper was. I was pleased to find that everything lined up and the base of the Bracket assembly was mounted to the Mill.
Continued in next post...
The hole was finished. This is only the second time I've tapped a hole for a bolt. I have to admit I was a bit concerned about doing this on my JET Mill. Time to see if I did it right.
I screwed a 1/4"-20 machine bolt into the hole... Looks like it worked!
I mounted the bracket using this upper hole to allow me to locate the center of the bottom hole.
Once again, a transfer punch was used to locate the center of the hole.
The bottom hole was prepared as the upper was. I was pleased to find that everything lined up and the base of the Bracket assembly was mounted to the Mill.
Continued in next post...
Continued...
The first part of the Bracket assembly was mounted to the Mill. As the pictures show, there wasn't a lot of clearance between the plumbing & the locking bolt.
This was all I had time for on that day a couple of weeks ago. I finally returned to the remainder of the installation a couple of days ago.
The first part of the Bracket assembly was mounted to the Mill. As the pictures show, there wasn't a lot of clearance between the plumbing & the locking bolt.
This was all I had time for on that day a couple of weeks ago. I finally returned to the remainder of the installation a couple of days ago.
on June 12th I had enough time available to continue working on the JET Milling Machine's Z-Axis Powerfeed Limit Switch installation.
The Limit Switch Stops live in two pieces of aluminum channel.
The aluminum channel is held together with a bracket and 4 screws, washers & nuts.
With the aluminum channel assembled, I now combined the components of the Limit Switch Bracket. I then held the aluminum channel in various positions on the side of the Milling Machine's pedestal until I felt comfortable that I'd found a satisfactory operating location.
Using the upper standoff bracket as a guide, I used a transfer punch to locate the center of the aluminum channel's upper fastener.
Using a #22 drill bit, I drilled and tapped the hole for a #10-24 screw.
I tested it with a screw and all seemed to be well.
Continued in the next post...
The Limit Switch Stops live in two pieces of aluminum channel.
The aluminum channel is held together with a bracket and 4 screws, washers & nuts.
With the aluminum channel assembled, I now combined the components of the Limit Switch Bracket. I then held the aluminum channel in various positions on the side of the Milling Machine's pedestal until I felt comfortable that I'd found a satisfactory operating location.
Using the upper standoff bracket as a guide, I used a transfer punch to locate the center of the aluminum channel's upper fastener.
Using a #22 drill bit, I drilled and tapped the hole for a #10-24 screw.
I tested it with a screw and all seemed to be well.
Continued in the next post...
Continued...
I mounted the aluminum channel to the Milling Machine using the top screw hole.
I used the transfer punch again to locate the bottom hole. I drilled and tapped the bottom hole as I had done the upper.
I mounted the aluminum channel by screwing the remaining fastener into bottom hole. I then located the stops at the upper and lower range of the Z-Axis.
This pretty well completes the Z-Axis Powerfeed installation. All that remains is to drill a 5mm hole through the Z-Axis Powerfeed shaft (white arrow points to the location) and drive in a pin.
...I have to get some metric drill bits.
Scott
I mounted the aluminum channel to the Milling Machine using the top screw hole.
I used the transfer punch again to locate the bottom hole. I drilled and tapped the bottom hole as I had done the upper.
I mounted the aluminum channel by screwing the remaining fastener into bottom hole. I then located the stops at the upper and lower range of the Z-Axis.
This pretty well completes the Z-Axis Powerfeed installation. All that remains is to drill a 5mm hole through the Z-Axis Powerfeed shaft (white arrow points to the location) and drive in a pin.
...I have to get some metric drill bits.
Scott
About a week ago I was working on the JET Mill's Z-Axis Powerfeed. At that time I had completed the installation of the Limit Switch Bracket.
The two tasks that remained were the drilling of a 5mm hole into the shaft of the Powerfeed followed by inserting a spring pin into the hole.
I procured a set of metric drill bits earlier this week. Today I thought I had time to finish this project.
The 5mm hole needs to be drilled where the white arrow is pointing.
I was concerned about my ability to drill a hole freehand through the coupler. I thought it would be better to do this on the JET Mill and then use a hand drill to finish the job on the shaft. I was playing around with how to set this up when I heard a small voice whispering in my ear...
"Is it possible", the voice said, "that drilling through the coupler without it being on a shaft will gall the internal threads?"
This did seem like a reasonable concern and I could fix it (I thought) by inserting a bolt into the coupler during the drilling process.
Without thinking about it too much, I grabbed the coupler and went back to the house basement where my hardware cabinets are. I had some 3/4" bolts and some 1" bolts. The coupler fell somewhere in between. The largest metric bolt I had was 14mm - much to small.
Off to the local Hardware Store. The Hardware Store had 7/8"-9 bolts and that barely started to thread onto the coupler and then stopped. The largest metric bolt they had was 16mm. I was leaning towards this being a metric thread at this point and I was guessing at a size of 22mm.
A Tractor Supply store was close by and they tend to carry larger hardware but I didn't know if they were going to have metric in larger sizes. They had 20mm but no 22mm bolts.
I returned home and did what I should have done before I went on that wild goose chase. I measured the shaft's threads.
I got a surprise.
The metric thread gauges didn't really match. 2.0 pitch was close but didn't quite match.
SAE 12 matched exactly! I measured across the shaft's threads with a calipers and came up with .853"
7/8"-12?
22mm with not quite 2.0?
Two questions:
What thread am I dealing with here?
Do I need to be concerned about damaging the threads if I drill through the coupler without something threaded through the coupler?
Scott
The two tasks that remained were the drilling of a 5mm hole into the shaft of the Powerfeed followed by inserting a spring pin into the hole.
I procured a set of metric drill bits earlier this week. Today I thought I had time to finish this project.
The 5mm hole needs to be drilled where the white arrow is pointing.
I was concerned about my ability to drill a hole freehand through the coupler. I thought it would be better to do this on the JET Mill and then use a hand drill to finish the job on the shaft. I was playing around with how to set this up when I heard a small voice whispering in my ear...
"Is it possible", the voice said, "that drilling through the coupler without it being on a shaft will gall the internal threads?"
This did seem like a reasonable concern and I could fix it (I thought) by inserting a bolt into the coupler during the drilling process.
Without thinking about it too much, I grabbed the coupler and went back to the house basement where my hardware cabinets are. I had some 3/4" bolts and some 1" bolts. The coupler fell somewhere in between. The largest metric bolt I had was 14mm - much to small.
Off to the local Hardware Store. The Hardware Store had 7/8"-9 bolts and that barely started to thread onto the coupler and then stopped. The largest metric bolt they had was 16mm. I was leaning towards this being a metric thread at this point and I was guessing at a size of 22mm.
A Tractor Supply store was close by and they tend to carry larger hardware but I didn't know if they were going to have metric in larger sizes. They had 20mm but no 22mm bolts.
I returned home and did what I should have done before I went on that wild goose chase. I measured the shaft's threads.
I got a surprise.
The metric thread gauges didn't really match. 2.0 pitch was close but didn't quite match.
SAE 12 matched exactly! I measured across the shaft's threads with a calipers and came up with .853"
7/8"-12?
22mm with not quite 2.0?
Two questions:
What thread am I dealing with here?
Do I need to be concerned about damaging the threads if I drill through the coupler without something threaded through the coupler?
Scott
