- Joined
- Jan 1, 2014
- Messages
- 233
Have been regrinding my drills by hand so was really interested in the threads on this subject (Lets Talk Drill Grinders), and, also that the small swivel grinding attachments can do a decent job. Got one and set it up to use against a grinder wheel. Soon thought it would be nice to use it against a flat platen vice the curve of a wheel (or side), then wanted a better way to control the grind than flipping the drill as one went along. The result was a conversion of one end of a grinder to a belt sander and making an adjustable base to control the attachment.
Started by removing one end casting of the motor and turning a shoulder for a mounting ring to which the sander frame (1/4” x 4” flat bar 44W) is bolted. Used the lathe DRO and a probe to act as a CMM for checking how much casting was left at the thinnest point, which was .250”, so figured that was still strong enough. The drive pulley is 4” OD x 2-1/2” wide 6061 AL with a .010” crown which drives a 2x28 belt at 3600 SFPM. The take-up pulley is 2” OD on ball bearings mounted in a yoke. Had several ideas for tensioning the belt but in the end used a thumb wheel against a spring on the yoke shaft. Two thumb screws adjust the tracking by acting against a small tab attached to the side of the yoke. The twisting action controls the tracking very nicely. A platform at the bottom of the frame supports the swivel grinding attachment. The adjustable base makes it easy to grind one side to finish, flip the drill, then feed the second face forward to the same exact position. Among all the other necessary bits and bobs the fixture base was milled it out and fitted with a block of 6061(+ JB Weld) to accommodate tapped holes and an underside channel to fit and slide on a rail on the base. The graduated dial has .002” increments which gives accurate control via a 7/16”-20 TPI feed screw. An added plus is that the fixture can easily be moved side to side by loosening one thumb screw underside so that you are not using just one spot on the belt! Also the whole fixture is easily removed by loosening the same thumb screw and sliding it off sideways. This frees up the sander for an accessory adjustable platform with 0 to 45 degree movement for normal sanding and grinding tool bits.
Have ground 1/8” to 1/2” drill bits so far. The larger bits look very good compared to information by Joseph Mazoff gleaned from this forum. The 1/8” bit has too much of a chisel angle so will have to work that out.
Thanks for looking.
Canuck75
Started by removing one end casting of the motor and turning a shoulder for a mounting ring to which the sander frame (1/4” x 4” flat bar 44W) is bolted. Used the lathe DRO and a probe to act as a CMM for checking how much casting was left at the thinnest point, which was .250”, so figured that was still strong enough. The drive pulley is 4” OD x 2-1/2” wide 6061 AL with a .010” crown which drives a 2x28 belt at 3600 SFPM. The take-up pulley is 2” OD on ball bearings mounted in a yoke. Had several ideas for tensioning the belt but in the end used a thumb wheel against a spring on the yoke shaft. Two thumb screws adjust the tracking by acting against a small tab attached to the side of the yoke. The twisting action controls the tracking very nicely. A platform at the bottom of the frame supports the swivel grinding attachment. The adjustable base makes it easy to grind one side to finish, flip the drill, then feed the second face forward to the same exact position. Among all the other necessary bits and bobs the fixture base was milled it out and fitted with a block of 6061(+ JB Weld) to accommodate tapped holes and an underside channel to fit and slide on a rail on the base. The graduated dial has .002” increments which gives accurate control via a 7/16”-20 TPI feed screw. An added plus is that the fixture can easily be moved side to side by loosening one thumb screw underside so that you are not using just one spot on the belt! Also the whole fixture is easily removed by loosening the same thumb screw and sliding it off sideways. This frees up the sander for an accessory adjustable platform with 0 to 45 degree movement for normal sanding and grinding tool bits.
Have ground 1/8” to 1/2” drill bits so far. The larger bits look very good compared to information by Joseph Mazoff gleaned from this forum. The 1/8” bit has too much of a chisel angle so will have to work that out.
Thanks for looking.
Canuck75
