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Tool Post Grinder

January Project of the Month [3]
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Cobra

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#1
I have been building some small engine models and particularly when doing the pistons and cylinders thought it would be great to have a tool post grinder. Well, I didn't like the price for one so decided that it would make a good project. Using one of the Wrokshop series of books on spindles, I started doing some sketches. I want a grinder that will do both OD and ID grinding.
These are some of the sketches that have started to project.
 

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Cobra

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#2
Made progress on the grinder.
Started on the spindle bodies for OD and ID grinding.
18.jpg
These are the pieces for the OD spindle. The shaft is 1/2".
19.jpg
The body holds the two bearings at each end with 32 tpi theads for the end caps. The sleeves in the upper photo provide support to the inner race of the bearings.
20.jpg
The pulley for drive belt was made with a form tool and then the keyway broached on the lathe.
17.jpg
The assembled spindle just needing the washers and stone.
23.jpg
I went with 4" wheels, 1" diameter. Picked up two, one 80 grit and the other 120 from McMaster-Carr.
 

Cobra

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#3
Making the pulleys and nuts.

1.jpg
First time trying to make a keyway on the lathe. I made up a holder from O1 drill rod and ground a cutting tool from a broken end mill.

2.jpg
I was pleased with how it cut with the exception of the first try where I took too big a bite and it just banged into the end and didn't cut anything.

3.jpg
4.jpg
5.jpg

7.jpg
Made up the nuts with 1/2-32 thread and milled flats with a hexagon holder. Don't know why I waited so long to pick up the 5C holders.
 

Cobra

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#4
The ID spindle was started in much the same way as the OD. The spindle has a threaded end to allow the use of differing length quills for the internal grinding.
The spindle body is complete but have not done the quills yet. Hopefully later next week.
11.jpg
13.jpg
 

chips&more

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#5
LOOOOOKING GOOOOOD! Gray colored wheels are typically found on things like bench grinders and are of a harder composition. White colored wheels are softer and work well on tool post grinders. This is NOT the gospel, just a starting point. If you can’t find 4” white wheels (cheap enough) with the proper hole size. Not a problem. You can easily procure 7” wheels. Make a bushing and mount it on a bench grinder. Take all this outside and dress it down to your desired diameter. A star-toothed dresser works well for this. It’s amazing how fast it all happens. And wear a respirator and safety glasses…Good Luck,Dave.
 

Cobra

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#6
The frame of the grinder is make from 3/4" steel with aluminium uprights.
21.jpg
25.jpg
The motor (a re-purposed laminate trim router) and the spindle are held by clamps in the uprights.
I reversed the rotation of the motor and am using a speed control to keep the RPM in the safe range for the 4" wheels. They are limited to 6200 rpm.
26.jpg
28.jpg
The guard for the wheel was made up out of 1/8" mild steel. It will accommodate smaller wheels if needed.
 

Cobra

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#7
Finished the hold-down and the dresser today to give it a try on the lathe.
30.jpg
32.jpg
Used a piece of 5/8-18 fine threaded rod for the post and a 1-1/8" nut for hold down.

33.jpg
34.jpg
The dresser is made from aluminium sized to accommodate a 1/2" shaft single point diamond dresser.

15.jpg
16.jpg
15.1.jpg
Grinder mounted on the compound slide. Covered up the ways and dressed the 80 grit stone. Used a vacuum to keep the dust away from the lathe as much as possible but wondered if anyone uses a spray of water to keep the dust down.
Worked well for a first try but learned a few things.
Think I will make a longer base for the grinder to move it back for larger diameter work.
Need to add some sort of threaded tensioner for the belt to make it easier to adjust the belt tension.

Now need to finish the ID quills.
 

Cobra

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#8
LOOOOOKING GOOOOOD! Gray colored wheels are typically found on things like bench grinders and are of a harder composition. White colored wheels are softer and work well on tool post grinders. This is NOT the gospel, just a starting point. If you can’t find 4” white wheels (cheap enough) with the proper hole size. Not a problem. You can easily procure 7” wheels. Make a bushing and mount it on a bench grinder. Take all this outside and dress it down to your desired diameter. A star-toothed dresser works well for this. It’s amazing how fast it all happens. And wear a respirator and safety glasses…Good Luck,Dave.
Great idea Dave. Spent a lot of time looking for wheels.
 

Cobra

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#9
Working on the ID quills.
Made up a fixture to hold the quills that mimics the end of the spindle.
Made the fixture from O1 drill rod and the spindle from 41L40.

42.JPG 44.JPG
Worked well using the collet chuck instead of the four jaw.

42.JPG 44.JPG 35.JPG 36.JPG 37.JPG 39.JPG 40.JPG 41.JPG

Single pointed the threads for the 1/4-28 insert end and for the 40tpi to fit the Dremel collet nut. The Dremel nut is a weird size 0.2756-40 tpi.

46.JPG

Quill installed on the spindle.
 

Andre

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#11
I found those Dremel chucks have to be run on extremely accurate threads, or else they don't run true. One or two thousandths of slack on the OD and they don't hold perfectly true.

Anyways, very nice work. If you find any vibrations induced by the cog belt, try a round polyethylene belt. You'll probably be fine though.
 

Silverbullet

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#13
Looks good should do all you need. I could never see paying what they want for a tool post grinder. Old junk even brings a $100.00 OR more on used ones. The high priced one won't do any better then yours ill bet you have less then a $100.00 invested . Ill eventually build one too. Thanks for showing yours .
Every different idea helps.
 
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