- Joined
- Nov 28, 2011
- Messages
- 287
I recently finished a simple shop built surface grinder. I had been thinking about an SGA for a while, but the design of my forty some year old Bader required too many compromises.
Natlek’s surface grinder got me thinking some more, but then I cam across an SGA built by Rhidian Knives. Rhid was kind enough to share the critical details of his design…. 1) cold rolled steel sliding on cold rolled steel 2) a single pivot point 3) micrometer control 4) no ball bearings . It’s not pretty but it’s simple and held tolerances of less than most of the SGA’a
You can see Rhid’s SGA in action at https://www.instagram.com/p/B7O0Nl2H5pC/
I decided to build my surface grinder around my Baldor Buffer. I mounted a 2.5” x 6” aluminum drive wheel on the right hand shaft of the buffer, leaving the left side free to keep using with buffing wheels. The buffer is bolted down to a 3/8” thick steel plate on hardened steel pads, as are the other components, except for the backstabs idler.
Per Rhid, the slide is 3/4” x 4” cold rolled steel. The sliding table is 1/2” x 4” cold rolled steel. I decided to upgrade the guide pieces that keep the table on track to hardened 1/16” x 1” O1.
The cold rolled slide pivots on a precision 3/8” axle / bolt. The hole through the 4” dimension of the cold rolled was drilled and reamed by a local machinist. The aluminum bracket that holds the pivot was made for me by Callum at MCMachineWorks.com.
A lucky visit to a local scrap yard provided me with most of the rest of the parts….. all of which came from a single machine…… a bunch of nicely anodized aluminum flat plate and angles; dozens of precision socket head screws; precision round bar; and a heavy, precision dovetail slide that’s indexed in .01mm increments (it moves 1 mm per revolution and has better than an inch of total movement.
Callum had also milled for me an aluminum chuck. But the N52 Neodymium magnets I ordered from AliExpress were not N52 strength - they barely stuck to each other. So I changed plans…
An Ebay seller was offering 2” x 8” work holding electromagnets for a reasonable price. So I bought one, as well as a 120V DC 3A power supply from Amazon.. I wired into the power supply a DPDT switch to make it easy to reverse polarity to aid in releasing the work from the magnet.
Other than the precision reamed hole and pivot, most of the assembly tolerances were pretty loose. This allowed me to accurately tighten the tolerances and square things up with shims under the buffer and under the round bar mounted on the dovetail slide that supports the back of the cold rolled slide.
Once assembled, I trued the aluminum wheel in place, then did a light surfacing of the chuck.
The first piece I ground was an odd shaped piece of 440C. The narrow end was almost .001” thinner than the wide end. I’m thinking the odd shaped piece might be exerting different forces on the Trizact belt - more at the narrow end than the wide end and this is what’s causing the additional .variance in thickness. I tried reversing direction of the piece, but results were the same.
I next ground a piece of 440C that still had the mill scale 1.5” x 6” and the finish ground piece had a variance of no more than .0005” over the length and width.
The third attempt was two pieces of 154cpm 1” x 4” laid end to end. They had a very uneven “belt finish” on them. I ground off a total of about .010” and again had a tolerance of no more than .0005” across the length and width.
I’m really pleased with the results. I think the success of Rhids design is a result of its simplicity. The steel against steel slide has zero tolerance and the downward force being exerted by the wheel on the 2” combined thickness of steel (slide, sliding table and chuck) is solidly supported on each end (by a 3/8” pivot and the dovetail slide) The slide just has no where to go.
I plan to add some flexible dust covers to keep the grinding dust off of the slide. And we’ll see if wear becomes an issue with the steel on steel sliding components.
Saludos
J
Natlek’s surface grinder got me thinking some more, but then I cam across an SGA built by Rhidian Knives. Rhid was kind enough to share the critical details of his design…. 1) cold rolled steel sliding on cold rolled steel 2) a single pivot point 3) micrometer control 4) no ball bearings . It’s not pretty but it’s simple and held tolerances of less than most of the SGA’a
You can see Rhid’s SGA in action at https://www.instagram.com/p/B7O0Nl2H5pC/
I decided to build my surface grinder around my Baldor Buffer. I mounted a 2.5” x 6” aluminum drive wheel on the right hand shaft of the buffer, leaving the left side free to keep using with buffing wheels. The buffer is bolted down to a 3/8” thick steel plate on hardened steel pads, as are the other components, except for the backstabs idler.
Per Rhid, the slide is 3/4” x 4” cold rolled steel. The sliding table is 1/2” x 4” cold rolled steel. I decided to upgrade the guide pieces that keep the table on track to hardened 1/16” x 1” O1.
The cold rolled slide pivots on a precision 3/8” axle / bolt. The hole through the 4” dimension of the cold rolled was drilled and reamed by a local machinist. The aluminum bracket that holds the pivot was made for me by Callum at MCMachineWorks.com.
A lucky visit to a local scrap yard provided me with most of the rest of the parts….. all of which came from a single machine…… a bunch of nicely anodized aluminum flat plate and angles; dozens of precision socket head screws; precision round bar; and a heavy, precision dovetail slide that’s indexed in .01mm increments (it moves 1 mm per revolution and has better than an inch of total movement.
Callum had also milled for me an aluminum chuck. But the N52 Neodymium magnets I ordered from AliExpress were not N52 strength - they barely stuck to each other. So I changed plans…
An Ebay seller was offering 2” x 8” work holding electromagnets for a reasonable price. So I bought one, as well as a 120V DC 3A power supply from Amazon.. I wired into the power supply a DPDT switch to make it easy to reverse polarity to aid in releasing the work from the magnet.
Other than the precision reamed hole and pivot, most of the assembly tolerances were pretty loose. This allowed me to accurately tighten the tolerances and square things up with shims under the buffer and under the round bar mounted on the dovetail slide that supports the back of the cold rolled slide.
Once assembled, I trued the aluminum wheel in place, then did a light surfacing of the chuck.
The first piece I ground was an odd shaped piece of 440C. The narrow end was almost .001” thinner than the wide end. I’m thinking the odd shaped piece might be exerting different forces on the Trizact belt - more at the narrow end than the wide end and this is what’s causing the additional .variance in thickness. I tried reversing direction of the piece, but results were the same.
I next ground a piece of 440C that still had the mill scale 1.5” x 6” and the finish ground piece had a variance of no more than .0005” over the length and width.
The third attempt was two pieces of 154cpm 1” x 4” laid end to end. They had a very uneven “belt finish” on them. I ground off a total of about .010” and again had a tolerance of no more than .0005” across the length and width.
I’m really pleased with the results. I think the success of Rhids design is a result of its simplicity. The steel against steel slide has zero tolerance and the downward force being exerted by the wheel on the 2” combined thickness of steel (slide, sliding table and chuck) is solidly supported on each end (by a 3/8” pivot and the dovetail slide) The slide just has no where to go.
I plan to add some flexible dust covers to keep the grinding dust off of the slide. And we’ll see if wear becomes an issue with the steel on steel sliding components.
Saludos
J
