Universal Grinder Fine Feed Adjuster

[jjr2001]

One of the limitations on my tool and cutter (plus surface) grinder was the coarse vertical feed on the motor carriage. I came up with an approach that still allows fast vertical traverse but also allows a very fine down feed for the grinder. It took a bit longer to make than I thought it would but it was worth the effort.

Based on a simple ramp and using a 5/16-18 piece of all thread, one steel ramp and one brass ramp and aluminum for the housing. It has about .250" travel up or down. The screw moves the ramp by one inch to move the height .250" so it is very fine. Positioning is just by sliding it up or down until the adjuster contacts the motor mount and then locking the brass locking knob. The 1/2-10 original lead screw "floats" in its lower mounting block so when I need the fineness I simply run the adjuster up to the bottom of the grinder mount and back off the 1/2-10 lead screw. Gravity and the brass knob on the left side do the adjusting. The carriage has separate aluminum knobs that lock it in place once the desired height is reached.

Cheers, JR

Here is a link to the tool and cutter grinder:
http://www.homemadetools.net/forum/s...9982#post71647

[Okapi]

Hi,
Really a good idea, it can give very precise adjustments with a minimum of calculation, but only if you don't forget the geometry lessons when young at school…

[jjr2001]

Good point.

So far I just need it to adjust in a very fine increments and it does that quite well. I just ground a 1" ball form a ball bearing and made it flat on one side. Actually needed to turn it almost 1/4 turn for each pass with the grinder. If I need to know a specific amount of travel I will probably cheat and just measure total travel and calibrate the knob to that. I need to engrave something anyhow, just for fun..

Cheers, JR

[ncollar]

Hi,
Really a good idea, it can give very precise adjustments with a minimum of calculation, but only if you don't forget the geometry lessons when young at school…

All that math is alright if that is the way you do it. I would put a mark on the face of the knob with a marker and a DTI, make one revolution of knob, then figure out how many lines you would like to put on the dial. If one rev is .0010 then 10 lines would be .0001 per line. No math to error.
Nelson

[jjr2001]

Hello ncollar, Actually the knob is graduated. Post 17 shows the knob detail with the long lines being .001 and the half lines being .0005.
It does not show up that well in the thumbnail but if the thumb nail is clicked to large size the graduations shows up.
No calculations required.

Thanks for checking in.

Cheers, JR

[mklotz]

All that math is alright if that is the way you do it. I would put a mark on the face of the knob with a marker and a DTI, make one revolution of knob, then figure out how many lines you would like to put on the dial. If one rev is .0010 then 10 lines would be .0001 per line. No math to error.
Nelson

The problem with that approach is that if you want one full revolution to be some "nice" number (e.g. 0.010) rather than some inconvenient increment, you must take account of the mathematics of the design. (Besides, you'll never learn any math if you avoid opportunities to use it in practical problems.)

The brass wedge will rise by:

P * tan(A)

for every revolution of the screw driving the steel wedge. Here

P = screw pitch = 1/tpi
A = wedge angle

Let H = desired rise for every revolution of adjusting screw. Then we can solve for the required wedge angle...

H = P * tan(A)

A = arctan (H/P)

As an example, for ten thousandths rise per revolution of an 18 tpi screw, we have...

H = 0.010
P = 1/18

A = arctan (0.18) = 10.2 deg

[ncollar]

Marv
Math and history was my best subjects in school. I forgot so much of that it would be like going back to school, but once you learn to ride a bicycle you never forget how to. I guess I just do it the easiest way to me, the KISS theory.
Merry Christmas
Nelson

[jjr2001]

Thanks for the detailed math explanation to the problem Marv. I can use that on my next wedge lift system.

I must admit that I used the DTI method to get a "close" solution. I just looked at my setup and found that
I have a .001" error in a full turn of the knob. One line is close to .001 but just a bit short. I usually work to .001"
for most of my builds and that is more than I usually need..However I always spend considerable time
fitting up the parts. So time could be saved with using the proper math for the solution.

Thanks again and Cheers, JR

[jotasierra]

Muy original el sistema, trataré de hacer algo parecido en mi cortadora de cerámicos, :aplausos:

[jjr2001]

Muy original el sistema, trataré de hacer algo parecido en mi cortadora de cerámicos, :aplausos:

Thank You, JR