Thread: Lock Mitre Cutter

Congratulations on mastering this. Looks good.

Mine is still in the bottom drawer!

Brian

Years ago I bought "Jig making For The Router" by Roy Sutton; in it he shows a design for a mitre lock workpiece holding jig for use on a router table; it looks a bit like this one:

45_degree_lock_mitre8.jpg

The two pieces which flank the workpiece are mainly for alignment and holding the timber but also provide a "run out" for the cutter and stop breakout on end grain.

I can confirm it works very well; I used it to construct two dozen simple boxes out of 3/4" Taswegian oak with no spelching. I still have it in the shed but I'm not home until the end of the month if you want to see pictures of it.

Funny that this post should appear today

I've just spent the weekend trying to get a result with a freud 9.5 - 19mm ML bit and one of these https://www.timbecon.com.au/infinity...tre-setup-jigs which was supposed to make things a lot easier

It was one of the most frustrating things I've ever tried with no favourable result, and I hadn't even got to the end grain yet

A sled or similar set up would probably help a lot

but for now my bit and guage are going into the bottom drawer, safe and sound for another day

I'll keep on improving my dovetails

cheers
Hodgo

Watch out you're gong to have the "mitre" expert writing realms and realms to you.

Hmmm… I dub that thingy the “Insanity Set Up Jig”

All you need is a piece of timber the same thickness as the workpiece with an accurately scribed line down the centre. You set the fence so that the end of the central sticky-out bit of the cutter lines up with the line vertically, and the cutter height is set to align the bottom edge of the central sticky-out bit with the line horizontally.

Use a marking gauge to mark the centreline; not a pencil.

Hi All,

I took some more pic's. I use a lot of scrap to test & make disposable jig's. This simple jig worked very well stopped tear out on exit & held the stock firmly.

CMT Router Mitre Bit 10.jpgCMT Router Mitre Bit11.jpgCMT Router Mitre Bit12.jpgCMT Router Mitre Bit13.jpgCMT Router Mitre Bit14.jpgCMT Router Mitre Bit15.jpg

In my opinion this type of joint works on wide stock, one of my early attempts I cut the joints on a wide board then after I cut out the required side pieces. This doesn't give any grain matching though.

For small boxes I use standard cut miters trued up on the shooting board then either 1/8' splined or use some keys after glue up.

Cheers

I have seen a suggestion of using stacked removable spacers on the fence to reduce the depth of cut for both horizontal and vertical cuts. Make either cut, remove the spacer and make another cut etc until you get to the bare fence which has been set for the correct depth. Reduces the amount of wood being removed each pass and gives a cleaner finish with less chip out. Definitely back up the cut as well.

Fiddly to set up correctly - need a tallish fence on the table - yes some of the short grain -will go bye byes - nature of the beast -try to back up ALL cuts.

Originally Posted by Hodgo

I've just spent the weekend trying to get a result with a freud 9.5 - 19mm ML bit and one of these https://www.timbecon.com.au/infinity...tre-setup-jigs which was supposed to make things a lot easier

It was one of the most frustrating things I've ever tried with no favourable result, and I hadn't even got to the end grain yet

.....

but for now my bit and guage are going into the bottom drawer, safe and sound for another day

Ditto, except I've spent more than this weekend doing my head in by carefully following the set up instructions many times and still not getting proper fits.

Originally Posted by malb

I have seen a suggestion of using stacked removable spacers on the fence to reduce the depth of cut for both horizontal and vertical cuts. Make either cut, remove the spacer and make another cut etc until you get to the bare fence which has been set for the correct depth. Reduces the amount of wood being removed each pass and gives a cleaner finish with less chip out. Definitely back up the cut as well.

Did this many times on 19mm scrap radiata pine workpiece with two 6mm MDF spacers clamped to fence. Cut once and remove front spacer. Cut second time and remove second spacer. Cut third time against fence.

Ridiculous amount of time spent doing this which, according to various videos including Timbecon's one of the bit and Infinity jig I bought from them months ago and finally got around to using can be done easily in one pass. https://www.timbecon.com.au/lock-mit...r-bit-jig-kits

Not on my router set at recommended 18,000 RPM which bogs down at anything more than a glacial feed rate with the time consuming spacers, never mind a single cut like all the advertising material for these wonder bits. Did a bit better on single speed 22,000 RPM router with more grunt, but unwise from safety viewpoint.

I've tried this on everything from a hand held workpiece on a router table against a fence to a workpiece clamped down on a sliding table guide square to a square fence.

I read and re-read the Infinity jig instructions and researched it many times between tests, but still couldn't get it to do what it promises. At least Google threw up plenty of other people having the same problems I did, so I didn't feel uniquely stupid and incompetent.

One interesting result was that I was using scrap 19mm radiata pine for test pieces which didn't machine as well as a couple of tests on scrap Australian hardwood recycled framing timber, although the hardwood put a much bigger load on the router but cut cleaner and with less tear out on the final piece leaving the cutter.

There are many ways to join a mitre for a box frame, which is what I wanted it for. This has to be the most attractive and efficient in theory and the absolute worst in practice, although I might change my mind if I could be bothered spending another few weeks at the wrong end of my life to find out how to make this thing live up to its advertising.

I bought on of these bits in the mid 1990's. I was just starting my (hobbyist) woodworking journey. I was building a TV cabinet for my TV with storage underneath for VHS tapes with my father, who was as old as I am now back then. Any way he said one of those lock mitre bits would be really useful to make drawer boxes so I bought one for $75. That was a lot of money back then.

I had a Triton router table at the time and, of course, the diameter of the bit was larger than the hole in the table. Consequently, I never ever used the bit. I still have it unused somewhere in the shed.

Hi gang, My woodwork mate down the road bought a set of these. I checked them out, looked at the huge jig he was making to try and use it. Definitely not for me. Looks way too dangerous. I'll stick to my dovetails and finger joints. I very rarely use mitre joints.

Paul

Originally Posted by Pauls321

I checked them out, looked at the huge jig he was making to try and use it. Definitely not for me. Looks way too dangerous.

I agree.

The bit is too wide to leave the collar in the router table, so when you're doing the vertical piece there's about 50mm of timber against the bit that's unsupported on the bottom. This requires you to keep the timber flat on the infeed side and hopefully match it up on the outfeed side while the bit is chewing into the timber. Not easy when you're using narrow timber, although you can get around this somewhat by using wider timber and ripping it after the router work.

There are videos of people doing this freehand in a single pass, but from my three attempts at this (none of which resulted in a full cut before I ended the experiment) I decided it was more excitement than I needed when the timber gets slightly off line and gives you the opportunity to find out how much damage a couple of horsepower can do at 18,000 RPM, so building a jig was the next step. I decided that this was more work than I wanted to do, probably only to find that I still couldn't get a decent joint.

I could have used featherboards to hold the vertical timber against the fence but this still wouldn't deal with the main problem of keeping the timber perfectly flat on the table as it passes the bit.

I had to give it another go. After all, there's no great skill involved. It's just simple machine set up and operation. If other people can do it, I should be able to.

And so it came to pass, after spending half the day sorting it out.

Made this temporary jig for the vertical piece with the Gripper thingy. Need to press down on the workpiece with one hand to keep it flat to the table, but it passes the collar gap okay and way better than I could do freehand even with featherboards holding it against the fence. Not that keen on using the blue clamp in case it came loose with vibration, but by then the cutter would be engaged in the workpiece. The bigger worry was what would happen to the workpiece and my hand holding it down if the workpiece moved.

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IMG_1547.jpg

Finally got a pretty good result.

IMG_1539.jpg

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Alas, it's not perfect like it's supposed to be. It's a few degrees off square when closed up.

IMG_1542.jpg

It takes way too long to machine in three passes. I wouldn't consider using this tool unless I was going to do a lot of pieces at the same time. Not worth the time and effort for just one set of box or drawer or whatever sides.

On the positive side, I now have reference pieces for easy set up of the bit in the unlikely event I ever use it again.