Until I retire in a couple of years, my clients are all college students. Most from my own class, but occasionally a student from other classes/sections. The help I provide is problem solving relating to how to connect the parts of their furniture designs.
The problem arises when working over email and trusting the information/drawings/dimensions provided by the students. Latest was just the last two days CNCing mortises and tenons to put together a complex set of leg parts for a small table.
Digital file arrives with no thickness information provided. I ask the student how thick the wood is her parts are cut from. 1.5 inches thick she insists.
So I draw up all the toolpaths needed. 11 in all. All assume that tenons and related mortises will be centered in the 1.5" thickness of her parts. I create a DXF file with outlines of her parts with allowances for all the tenons on their ends, and email her the file. Critical angles are documented. She is to print/plot the file, then spray stick drawings to her board blanks to cut out the shapes I'm expecting/relying on.
Jumping to the end I'll mention the parts all fit together perfectly, and her table stood up beautifully/solidly.
Backing up two days though I met her in the college fab lab to start cutting tenons on all the pieces using a Probotix GX2525 I have set up for for vertical and angled clamping of parts under the spindle. Left and right sides could use the same file/setup for a given centered tenon cut. Very first piece cut the tenon appeared to NOT be centered in the width. Correct distance from front edge. Tenon the correct size. A quick measure of two boards together showed 2+15/16" width where it should have read 3". Her boards turned out all to be 1/32" thinner than 1.5" thick.
Ultimately this meant I had to keep track of every toolpath making adjustments to where my X direction was homed to. Some tenons needed to be 3/8" from the back side. Some needed to be 3/8" from the front side. There was no room for a mistake here or her assembled pieces would not be flush.
After cutting a few pairs I realized lefts and rights were not exactly the same shape. Ends I'd homed to varied a little bit, meaning alignment of tenon or mortise from an edge would be different between the two parts even though they were cut using the same jig/setup. This meant every drawing I had needed slight movement of vector shapes to account for where they actually got cut on her parts. 1/32" was the common adjustment needed.
The lesson I keep relearning is that you can't trust a client/student to know precisely how thick a board is. Secondly, you can't trust a student to cut parts out exactly to shape even if you provide the precise drawing patterns to use. 😆
4D
The problem arises when working over email and trusting the information/drawings/dimensions provided by the students. Latest was just the last two days CNCing mortises and tenons to put together a complex set of leg parts for a small table.
Digital file arrives with no thickness information provided. I ask the student how thick the wood is her parts are cut from. 1.5 inches thick she insists.
So I draw up all the toolpaths needed. 11 in all. All assume that tenons and related mortises will be centered in the 1.5" thickness of her parts. I create a DXF file with outlines of her parts with allowances for all the tenons on their ends, and email her the file. Critical angles are documented. She is to print/plot the file, then spray stick drawings to her board blanks to cut out the shapes I'm expecting/relying on.
Jumping to the end I'll mention the parts all fit together perfectly, and her table stood up beautifully/solidly.
Backing up two days though I met her in the college fab lab to start cutting tenons on all the pieces using a Probotix GX2525 I have set up for for vertical and angled clamping of parts under the spindle. Left and right sides could use the same file/setup for a given centered tenon cut. Very first piece cut the tenon appeared to NOT be centered in the width. Correct distance from front edge. Tenon the correct size. A quick measure of two boards together showed 2+15/16" width where it should have read 3". Her boards turned out all to be 1/32" thinner than 1.5" thick.
Ultimately this meant I had to keep track of every toolpath making adjustments to where my X direction was homed to. Some tenons needed to be 3/8" from the back side. Some needed to be 3/8" from the front side. There was no room for a mistake here or her assembled pieces would not be flush.
After cutting a few pairs I realized lefts and rights were not exactly the same shape. Ends I'd homed to varied a little bit, meaning alignment of tenon or mortise from an edge would be different between the two parts even though they were cut using the same jig/setup. This meant every drawing I had needed slight movement of vector shapes to account for where they actually got cut on her parts. 1/32" was the common adjustment needed.
The lesson I keep relearning is that you can't trust a client/student to know precisely how thick a board is. Secondly, you can't trust a student to cut parts out exactly to shape even if you provide the precise drawing patterns to use. 😆
4D