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4

20" Production Drill Press

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maker of things

Hermit
H-M Supporter-Premium Member
Joined
Jul 23, 2014
Messages
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179
#1
More of a overview than review of the Central Machinery 20" Production drill press. #39955 and #61484. Luckily I got a 61484 as it has a MT4 spindle instead of MT3 on the 39955. Same as my lathe tailstock.
upload_2016-5-31_16-8-37.png
It's good to have a friend to help lift the heavy pieces.

The head is split to permit adjusting the quill. Cover does not have to be removed to do this, I just wanted to see what it looked like.
upload_2016-5-31_16-9-13.png

I popped the arbor out and removed the belts. I did not get even .001" of movement through a full rotation by hand of the spindle.
upload_2016-5-31_16-10-18.png

The provided arbor tir was .002"
upload_2016-5-31_16-10-53.png

With the provided chuck installed the outside of the body measured .003" tir
upload_2016-5-31_16-11-20.png

A 1/2" dowel chucked up ran out about .006" 1" down from the end of the chuck.
upload_2016-5-31_16-11-55.png

Then I chucked up a length of 3/4" ground drill rod
upload_2016-5-31_16-12-22.png

I zeroed out the indicator and plunged the quill it's full travel and read a little over .005" deviation front to back
upload_2016-5-31_16-12-59.png

And again about .005 sided to side
upload_2016-5-31_16-13-31.png


At full extension I zeroed the indicator and again rotated by hand. I measured .01" TIR at nearly 10" from the chuck.
upload_2016-5-31_16-13-56.png


I forgot to check the table to spindle while I had the drill rod in and just grabbed a chunk of 5/8 1018 crs and a Starrett 6" square.
Front to back:
upload_2016-5-31_16-14-36.png

and side to side
upload_2016-5-31_16-15-0.png

So that's the conclusion of the technical section. Next up, fit and finish.
 
Last edited:

maker of things

Hermit
H-M Supporter-Premium Member
Joined
Jul 23, 2014
Messages
339
Likes
179
#2
So based on the fact that the important part of the machine seems to be decent (and the fact that I promptly washed my receipt in my shirt pocket DOH!) I opted to deal with a few quality issues rather than go through the ordeal of trying to get replacements.
The first thing I identified was the crank handle for adjusting the table was drilled fairly off center so it wobbled badly and could not be pushed tight up against the casting.
upload_2016-5-30_7-32-43.png
This view shows pretty well how far off the hole is. I opted to make an arbor and turn the back of the handle arm true to the bore.
upload_2016-5-30_7-34-42.png

The next thing was more cosmetic than functional. When the table was cast, there was a lot of porosity at the sprue that resulted in perforations.
upload_2016-5-30_7-36-17.png
upload_2016-5-30_7-41-0.png
Structurally the table is sound so I gave it the old JB weld repair. I drenched the area in brake cleaner and wire brushed from the top side. When dry I put some duck tape on the bottom then mixed up the epoxy and spread it in. I don't plan to use much liquid but I figured chips would tend to get stuck and it would be harder to clean up after it had cutting oil and chips in it.
upload_2016-5-30_7-41-27.png
The third thing is closer to a functional issue. The pulley (all of them are metal) on the motor vibrated and worked the set screw loose. When I made a cursory examination with calipers I found the bore of the pulley to be .750" and the motor shaft to be .744". Most likely there is some taper in the pulley bore as well but I didn't feel like pursuing it further. I cut a strip of paper and ran it over the blade of a scissors to make it curl and sneeked it in between the shaft and pulley and that solved the wobble for now.
upload_2016-5-30_7-50-18.png
The cover is also all metal.
Now for the important question, does it work? I knocked the drill chuck arbor out and replaced it with a 1" taper shank drill bit. I clamped down a chunk of 1/2 x 1 1/2 1018 crs. After changing the belts to the orientation that indicates 180 rpm. I turned the machine on and hit it with the non contact tach, 180 spot on. I then drilled through using no pilot hole and minimal pecking. Once the bit got started the belt slipped, but after giving it additional tension had no further slippage.
upload_2016-5-30_7-55-46.png
The T slots are 5/8 and after a fairly aggressive clean up with files, mostly in the bottom of the "t", standard t nuts fit in all the slots. All in all with the ubiquitous 20% off coupon the machine was $448 + tax. The "identical" machine from Grizzly on sale with freight was $774 and the Jet was nearly $1k.
 
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