Holding Parts Down While Cutting

[Oldbill]

I could use some ideas on how people hold down parts while cutting them through.
I've just finished my Rockcliff CNC and have cut parts by clamping the outside edges but I have not cut through yet.

I will be cutting parts such as clock gears and framework.

Any help would be greatly appreciated.

By the way thanks ger21 for steering me in the right directions for offsets, works great!

Thank you,

Oldbill

[osphoto]

I've been using double sided tape, carpet tape as I understand its called. I get mine from Harbor Freight. Its thin and work very well for me. HomeDepot sales it also, but that seems thicker and is double the cost of HF.

I also bolted/screwed my work down to my table. My "work table" is leveled, .75inch MDF table. Which is bolted to my mill table.

I have a CNC router made of all MDF. It was cheap enough to get me started and its held up well enough to cut aluminum. The machine was primerred and painted so its holding up well to fluids.

[Oldbill]

Thanks osphoto, double back tape - never thought of that, I'll give it a try.

My cnc router is also made of 3/4" MDF, primed and painted. My work table was built up to accept "T" slot nuts for hold down. It's amazing how these things work.

Regards,
Oldbill

[mxtras]

Vacuum works, but not well for small parts.

There are several thing you can do. The use of tabs to hold the part is always an easy option, but on something like a gear, it may interfere with the precision of the part, obviously.

In this case, is it possible to use a few small holes and secure the part with fasteners? Creativity here is useful - if you have windows cut out, you can cut mating parts to the window feature and then insert them after the windows are cut but before the perimeter cut and run a screw through them to clamp the part.

Does that make sense?

Scott

[dertsap]

this may sound crazy but the first test i did on my first machine build i had used the hot gluegun to hold down the test piece by tacking it in a few spots , it worked so well ive continued to use it , it holds the part down great while cutting and the glue peels off the finished part quite easily once it is complete

[jdell42]

sounds quick and easy for a lot of parts... but for parts that require an accurate z depth it might not be the best approach... but very creative.

I have used double sided carpet tape.. but for thin parts your risk destroying the part trying to remove it from the tape.

The best method I have found is using brass screws to screw it to the table. I use brass in case the bit hits a screw it wont cause too much damage.

[CPierce18]

My table bed is made from 1/2" PVC. When I first built the table, its was slightly out of parallel with the bridge, so what I did was take a 1/2" bit and surface the whole table so it was parallel and my Z would be level. The attached picture is what I use to hold my work down. I have 4 of those perminintly on the table just to get my part squared up to start, then I screw down a few others as required to hold it in place. The legs are a little longer so it will hold constant pressure on the part. It's only PVC so if the router strays off a little, no damage done. I engrave a company logo (little larger then a business card) on a customer-supplied box. I shim it up if needed, and hold is in place with my hold-downs. (you can see it at www.pierceworks.net) Also, I just did an engraving of my company name in a piece of 1/4" plexi-glass .007 deep. They work great. The only problem with these is the legs break off when they wear out. I think my new design for these will be circular... screw hole off center so when I turn it, it will get progressively tighter. I'll post a few pictures later if I can find a digital camera.

[Oldbill]

Thanks one and all on your suggestions - they sure will help.

A great forum is indeed populated by great people.

Nice work C.Pierce, I visited your website.

Bill

[ImanCarrot]

For small parts I use Tippex (typing correction fluid)- it sets like concrete and can be cleaned off using acetone- the cutting forces I'm using are very low though- probably wouldn't stand up to anything heavy.

I also use Ultraviolet curing adhesive- it cures in minutes and is "peelable" when you want it off.

Big heavy magnets are useful too if they don't get in the way.

[jgro]

I use both hot glue and super glue. To use the hot glue, I put washers down on the cutting bed and then put dabs of glue down. When I set my stock, it rests on the washers which makes the stock sit parallel to the cutting bed. I leave the washers under the part for roughing operations, but when I get to finishing or profiling cuts, I remove them ( I always leave them stick out from the stock so I can get them out).

The super glue works well on parts where you don't care if the backside(the part you are putting the glue on) is not cosmetic. It will create a divot where the glue was. I only use a few dots of it in the corners and in the middle. When I use super glue, I always use a sacrificial piece under it so that I don't damage my cutting bed. To separate the parts, I just put the part at a 45 degree angle against the corner of my workbench and press. The glue will separate from the sacrificial piece. Then I use a sharp chisel to remove any remaining glue.

jgro

[dertsap]

Originally Posted by jgro I use both hot glue and super glue. To use the hot glue, I put washers down on the cutting bed and then put dabs of glue down. When I set my stock, it rests on the washers which makes the stock sit parallel to the cutting bed. I leave the washers under the part for roughing operations, but when I get to finishing or profiling cuts, I remove them ( I always leave them stick out from the stock so I can get them out). jgro

great idea ,i'll have to try that

[ImanCarrot]