# Pm1340gt Spider With Dial Test Indicator



## mksj (Apr 5, 2016)

Not sure where to post this, but it can be adapted to most lathes. I built my spider support for the PM1340GT lathe awhile ago, but it was always a tight fit to the cover, the OD of the spider is 2.5". I had a set of spider holes very close to the cover, but could not use Allen cap screws because of clearance issues. After seeing a number of other lathe owners bore out their drive cover for their spiders, I decided to do likewise. My boring head was at it's max extension at 3", ran it at ~250 RPM and bored in 0.050" increments. The new spider hole was properly on center. I then proceeded to bore and tap another set of 4 staggered holes further out on my spider so I could use cap screws as an alternative. The cap screws are 3/8"-24 fine thread with 1/4" brass tips milled down to 0.200" at the tip.

To indicate stock in the spider, I wanted something more permanent but easily removable, and that it wouldn't be in the way when I had finished using it. I ended up using an old Zero-Set indicator attachment, which is normally used to center holes on a mill. The dial test indicator is a long reach, so it clears the Allen screws when indicating. Inexpensive Zero-Set copies are available on the internet (eBay) for $30-40. Probably want one where the clamp on the bars is two pieces (for easy removal) as opposed to the one piece like Shar's. I mounted a simple dual rail system (two 0.250" bars on 0.750" centers) to the drive end cover using aluminum brackets, the  Zero-Set slides back on the bar for use, and it has a vernier control for fine control, and they also have a height control. Shown I am indicating a 0.625" and 0.200" bar stock. Takes almost no time to true up the bar, and then just slide the indicator forward out of the way.

The support bars are adaptable to a wide range of add ons, indicators, etc. It is important to mock everything up to check your distances and clearances with the spider bolts fully extended. The PM1340GT cover has a vertical and a 7 degree slant where the blocks attach, so takes a little machining to fit the blocks to this cover.

Boring the drive cover.






Zero-Set plus copy





 Spider indicator support





Indicating large and small rod


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## jbolt (Apr 5, 2016)

Great idea. Nicely done!


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## Bamban (Apr 5, 2016)

Mark,

That is a great idea. I do a lot of AR barrels, this would make work a lot easier that using a magnetic base sitting on top of the headstock cover and a 2 inch indicator.


nez


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## RIO (Apr 5, 2016)

WOW.
RIO


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## Lonnie (Apr 6, 2016)

That looks great Mark! Added to my list of projects.

Thanks for posting.


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## AirWolf (Apr 6, 2016)

I like it!! This one is has been moved to top of the list of projects!


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## zmotorsports (Apr 12, 2016)

Very nice setup Mark. 

Mike.


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## sanddan (Jan 9, 2017)

I did a pretty basic spider, mostly to mount the magnet for the speed sensor. I used aluminum as I had the perfect piece for this project. As others have mentioned, I had to bore out the hole in the cover which was an excuse to get it centered. I still need to get longer screws and add brass tips.


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## bss1 (Jan 9, 2017)

I guess with all of these you have to remove the spider screws to remove the gear cover?  I have the material to make mine but waiting to hone my skills a little before proceeding. Also I don't have a indexer or dividing head for my mill to properly drill the locations for the screws.


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## jbolt (Jan 9, 2017)

bss1 said:


> I guess with all of these you have to remove the spider screws to remove the gear cover?  I have the material to make mine but waiting to hone my skills a little before proceeding. Also I don't have a indexer or dividing head for my mill to properly drill the locations for the screws.



On my PM-1440GT I use set screws which can be run in flush to pull the cover off with them in but I usually leave them out until I need them. On my old lathe it seemed no matter what I did, lock nuts, snug thread etc. one of those suckers would work itself loose while running. Not cool. I just got in the habit of keeping them out.

Easy to drill without an indexer. Find the center for the first hole location, center drill and and then drill all the way through both sides. Turn the part approx 90 deg, insert a rod through the drilled holes and use an indicator to measure each side and adjust until equal.

The quick and dirty method would be to mark the face with lines at zero and 90 deg and use a square to eyeball the lines. Usually close enough.


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## bss1 (Jan 9, 2017)

Got ya. Thanks!



Sent from my iPad using Tapatalk


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## Silverbullet (Jan 12, 2017)

Nice build , I like the indicator set up . Keeps the barrel from whipping loose. Do you get any harmonic vibration when cutting.? I used to machine long and extra long cleaning rods for TRAP shooters. One old buddy of mine had a 56" barrel perazzi . YUPP shot it leaning it by his belly. Wheelchair shooter , top shooter too. Not shooting anymore but lots of pictures in trap magazine s in the past. But that's another story, my brass rods use to sing even when locked in front and back. Aluminum rods would do the same but show chatter in the finish. Still have a couple dozen in my van , if it didn't cost so much to ship I'd sell them on eBay. I found if I stuffed a rag in around the spindle it stopped the singing and chatter. 
Been fifteen years since I made any. Just wondering if the barrels sing.


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