Hold It Down Over There!

[rgreever]

Fellow ShopBotters!

I just thought I would share what I've been working on--new hold down solutions for our PRS Alpha...

Backstory: I inherited this machine when I started this job Dec. '15, and slowly, I'm adding my own personal touches to it. When I came on the scene, the ShopBot was rarely used; cast away in deep, dark bowels of the shop. My sole purpose in this life is to resurrect ol' Bessie and make her a functioning member of our shop's operation once again! Through trial and error, pokin' and hopin', a little elbow grease, a little googly-goo, and of course, lotsa help from this forum, she's comin' around.

The way I had been doing it, (holding it down, that is), was the old-fashioned way. Using c-clamps around the sides of the piece where I could, and screwing down into the spoilboard wherever possible. As many of you know, this gets old really quick. It works, but it's just not that efficient or pretty.

Slowly but surely, I'm making progress. I've added 1.5" x 1.5" T-Slot rails to the outside edge, and I've cut a t-slot into the top layer of the MDF at 12" increments down the x-axis of the table. Here's what I've got so far:
27588
2758927590

I'm using 1/4-20 carriage bolts, and this T-Slot router bit that I found fits just right. It allows the carriage bolt to slide on in, and the collar is just narrow enough to keep the bolt from spinning so you can tighten the hold down clamps. Eventually, I'd like to add T-Slot rails to the full length of the table, but that would require major alterations to the existing set-up. So this is the temporary stopgap until I can find the downtime to really get into it.

If anyone in the peanut gallery has anything to add, I'd love to hear about it. Comments, questions, suggestions, criticism, heckling...It's all welcome!

[barrowj]

I started with the T-Track and ended up with a system of 1/4" inserts which I keep as a template. Whenever I plan a job, I take into account the existing inserts by adding the template of inserts and if I have to add more, then I know where the existing ones are at. By using the existing inserts whenever I can it makes the job setup super easy but if I have to add some then knowing where the existing ones are helps. I then add the new ones to the template and save it. Yes, it does create 2" total waste, 1" on each side of the material. I make several products out of hardwood of different species but always the same size and this makes it easy to position in the same spot every time and also since I center the material using the inserts I can flip the job without issue.

Joe

[wwaldner]

I just finished up a fixture that seems to hold some promise. Most of the design has been discussed here.

27602

This is kind of a trial run to see how it works out. Generally I rely on Vacuum fixtures and such, but I think this will come in handy. I simply made the fixture and bolt it to the top of the spoilboard using tee nuts under the table. This allows me to easily remove the fixture from the bed. The fixture is 'indexed' to the table so I can easily reposition and move to 0,0. The tracks are used are 80/20 with the live nubs for the stops. The cam clamps are made by shopfox.

If you look closely, I circled a couple of index holes on the right of the fixture. These are drilled in the fixture to allow me to find an exact location on the fixture. The nubs that I use for stops are aligned to these index holes which allow me to find the exact location of x,y on the part being cut. Placing the workpiece on the fixture automatically aligns it to a fixed xy position that I can zero the machine to.
wayne

[James M]

Your jig is interesting, I can visualize some different ways that I could use such a hold down jig. Thanks for sharing.

I also use shopfox clamps. However, I've not seen the nubs before. Where did you find the nubs?

James

[wwaldner]

I purchased the 80/20 stuff from 80/20's ebay store.
http://www.ebay.com/itm/370152544291?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT