Dont buy this product

[fairchild]

Im so frustrated I could chew neutronium...........
Making my 3/4 mdf nose rib cutting jig. All done except for cutting the 2 big round holes. Wen all the way across town to the only place that stocked a fly cutter.
Wood river brand. Got home- set it up in the milling machine to test on some scrap. I replaced the central bit with a smooth pin so as not to make the hole bigger as it was cutting.
First strike----- the bit in the center is metric - 6 mm. So I machined a steel pin on the lathe to fit into it and be 1/4 on the rest. Put that in it. Turned on mill. end of pin
is out of round by about 1/4 inch. Put pin in lathe -- not the pin. the I took the fly cutter apart and put it into the lathe. The central hole where the bit goes is off center AND
crooked. Typical chinese quality. Tried boring the hole out with a 1/4 inch boring bar to true it. The allen screw hole caught on the bar and ruined my boring bar.
Tried putting a steel plug in the end and re-drilling..... that didnt work either. Im basicly going to throw the piece of dirt away. Nothing on it is worth saving. Total waste
of money and time. It was a wind river model. the "general" brand one is also chinese and looks pretty much the same. Those are the only ones I know of.

The only way I can think of to cut the MDF circle accurately is with some kind of circle jig on the dremel. make many shallow passes from both sides. Dremel makes one
but NO ONE has it in stock. Not sure if I had it if it would be rigid enough.

I can finish up the edges of the hole on the spindle sander --- but i want the holes square and evenly circular and of constant accurate radius.
Looks like I will have to make my own circle cutting tool for the dremel.

Wow- this is frustrating........ remind me NEVER to buy chinese. ever again..... getting fed up with foreign made "products" that approximate steel with play dough.......
And fed up with american CEO's whos greed wont allow them to stock anything BUT chinese ...... They couldnt give a rats's ass if whatever it is works for more than
15 sec in the hands of the consumer. All they care about is their 40 million golden parachute when they are fired by the directors for running the company into the ground.

Is it any wonder I spend more time making tools than using them ?

any great ideas on how to cut a clean , round accurate hole in 3/4 mdf ?

Tim

[jaredyates]

It is frustrating when things don't go as expected, but reading all that, it sounds like you might be overthinking things a bit. Did you try to cut any holes with it as-supplied?

[Chris In Milwaukee]

If you have time to wait for mail order, ATS carries a nice fly cutter that has lasted me a long time. Solid, and most of all, straight. I bought a couple of Menards fly cutters and they were both out of round and wobbly. Bleh.

[tbaylx]

Yup the accuracy isn’t great...but it’s a lightning hole. If it’s a bit out of round or over/under sized it’s not going to hurt anything. I’d try cutting with it as is and see what happens. It’s like buying from princess auto/harbour freight. The stuff is mostly junk but sometimes junk gets the job done for pennies on the dollar

[Chris In Milwaukee]

Truth. I was able to tweak it into a tolerable state. I used it to cut my lightening holes in my main spar. Worked out pretty well. They look circular.

Finished off with Scotchbrite and all was well.

[Chewie]

Those big holes in my form block backer are 7" across. That was bigger than my circle cutter could do, so I just whipped out what I could and drum sanded the rest. They looked about right.

[BTAZ]

Given you have a mill and a lathe, why not save the crossbar/tool bit holder and make up a new arbor that runs true?

I started out with two of indeterminate origin and they both were crap. Suffered through making the router templates and also used one for the lightening holes in my aileron spars. After that, found out I could get good quality hole saws on E-bay for about $15/pc and purchased two different sizes for the spar lightening holes.

But if I needed one again, I would spend a bit of time at the lathe and mill and make one.

[davzLSA]

Hi Fairchild, I agree with you about chineese junk and the mind set of the greedy businesses that sell them. I try to buy American made products when ever I can. That is one reason I went with the GM Corvair engine for my LSA. 1960's Detroit steel you cant beat it then or now. On the subject of the 3/4 MDF why dont you just try a hole saw? Good luck with your build.

David

[fairchild]

I may try to rebuild the junk hole saw by making a new arbor- but the arbor has a D shaped cross hole. Maybe I can weld a new en on for the center bit.
Or it might be ahead to order the ATS one if it runs true out of the box.

Maybe I am mechanically anal or something.... but I just cant stand make in imprecise on a tool which will be making multiple parts. Maybe its the thought of
duplicating an error over and over again........

I thought about hole saws but most of the holes appear to be in betweeners.

I found a solution that seemed to work more or less- but it did give a very good result.
Got the router base for my dremel. Cut a piece of plexiglas that the base would friction fit into. Then I drilled a 1/4 hole in the plex for a pivot point. Then I just cut down
about 1/16 per pass. cut 3/8 from each side. Hole was nearly slick and 100% round and crisp. Then about 5 really light passes on the sandiing drum and a coat of
varnish. It worked nice except I didnt have the perfect bit. Had regular bits but they got a little too hot in the MDF at full RPM. Had a carbide one but it had too fine teeth.
Probably need a solid carbide 1/8 curcuit board drill. MDF generates a lot of heat. It was slow but worked pretty well.

Dremel makes a circle cutter but no one in town had one. (as usual-)

Tim
Will try to post a pic if I can figure out how----

[fairchild]

This is the home made dremel circle cutter. On the right is the hole it cut. Worked good- just slow. (but better than fast and sloppy--)
Tim

[tbaylx]

You can use a router circle jig to make very nice holes in mdf as well. Not going to help you on the spars but it's perfect for the MDF