How to make accurate long vertical mitres.

[dalpets]

Hi,

I am not a professional or hobby carpenter but I have a need to make a one off cabinet with 45 degree mitre corners on the four sides for an amplifier project. The sides are pine - dimensions 89mm x 19mm. I am working to plans.

I have struggled to get accurate mitre joints on the 89 mm vertical sides using a hand mitre saw, not the most basic box type, but one with raised vertical guides & an angle adjustment base.

I've come to the conclusion, that with the tool I have, it is much more difficult to make an accurate mitre, the longer the mitre joint is, in this case 89mm, than for a relatively easy mitre joint on a shallow picture frame.

I don't want to spend large amounts of money for a one off project, so is there a relatively cheap alternative to the tool I have, for more accurate mitres.

Thanks

[Luke Maddux]

I don't usually say this, but I think that in this case you'd be better off with a machine. If your mitre box isn't cutting correctly, it's probably because it's not sharp enough or there is some kind of "play" or otherwise fault in the setup of the mitre box. Sharpening a saw requires considerable practice and skill, and fixing the mitre box could really be anyone's guess.

So, for a one off project, I would look for a friend in the Adelaide area (almost certainly easy to find on these boards) and use their table saw. By the time you troubleshoot the mitre box and hand saw, it's likely that you would've spent more time solving this problem than just driving somewhere, making the cuts, and driving home.

Best case scenario you get a two-fer and someone can both make your cuts and fix your mitre sawing setup.

Worst case scenario you meet someone with a mutual interest in woodworking and, if I know my Aussie culture, get a free cup of tea out of the deal.

Good luck,
Luke

[AlexS]

What Luke said, unless you have a disc sander or linisher. If you do, you can set up a fence at 45* to the sander and perpendicular to the table. Mark out the mitres with a knife, then, with the piece held against the fence, sand the mitre. When you get to the cut on the outside of the mitre, a thin feather of wood will appear, telling you that you're done.

I'll try to find a photo of what I mean.

[ian]

Are you cutting across the grain or along the grain.

If cutting along the grain, a mitre saw will cause you grief as it tries to follow the grain.

easiest is, as suggest by Luke, find an accomplise on these forums.

fixing the issue yourself likely involves spending more than you want to on additional tooling

[dalpets]

At 45 degrees I have to be cutting across the grain.

[dalpets]

.............................................

[ian]

Hi,

I have a need to make a one off cabinet with 45 degree mitre corners on the four sides for an amplifier project. The sides are pine - dimensions 89mm x 19mm. I am working to plans.

I have struggled to get accurate mitre joints on the 89 mm vertical sides using a hand mitre saw, not the most basic box type, but one with raised vertical guides & an angle adjustment base.

I don't want to spend large amounts of money for a one off project, so is there a relatively cheap alternative to the tool I have, for more accurate mitres.


Are you cutting across the grain or along the grain.

If cutting along the grain, a mitre saw will cause you grief as it tries to follow the grain.


At 45 degrees I have to be cutting across the grain.Hi dalpets

there's a design issue here. Not that it's likely to be critical if the enclosure is only small,
but if the vertical sides are cross grain, your box will change its height with changes in the moisture content of the pine. "Normal" is for the grain to be arranged so that it is parallel to the long axis of a construction.

if you can make yourself a 45 degree wedge, to place in teh floor of your miter box, you can cut the long miters by sawing through the 19mm thickness

[Cal]

Dalpets, I am in Strathalbyn and can cut them for you if you wish?


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[Kuffy]

Dalpets, are making something along the lines of the following image? This is just a picture of a box that I made for a client a while back for some power supplys for amplifier boxes. But it illustrates the general idea, I think.

399858

The way I cut the mitres for these boxes was using my panelsaw/tablesaw with the blade tilted over at 45degrees. I did it this way because I can.

A few other ways it can be done
-compound miter saw
-miter box with a handsaw, refining the cut faces with a disc/edge sander or a 45 degree shooting board and hand plane.
-just a hand plane

[dalpets]

Thanks Cal,

I might need to get back to you.

[dalpets]

As a matter of interest what power equipment would a professional carpenter use to make a mitre in an 89mm tall work piece for a box setup?
From what I have seen a compound mitre saw would not achieve this.

[Luke Maddux]

My understanding is that a larger compound mitre saw would cut through 89mm THICK stock.

I just want to clarify something. You keep referring to "89mm tall" stock. This seems like you're either just choosing the word "tall" instead of "thick", which is a bit confusing, or otherwise are you talking in terms of centimeters and accidentally saying "mm"? You said you're working to a plan. Can we get a link to the plan, or possibly a photo of the plan?

To answer your latest question, a CARPENTER would probably just use a compound mitre saw and then just leave it. He wouldn't worry much about the aesthetics, or the cleanliness of the joint, he would probably use nails to secure it instead of glue, and it would probably either be painted or sealed by moulding. He would be creating the mitre for an immovable object (building), so he would have complete control over the stresses which would be placed on the mitre, and would have an understanding of where he did and did not need to apply more attention to detail in order to get it to stay put for decades without the applied forces changing very much.

And that's NOT what you want to do, which is why the answer isn't as straightforward as I think you might want it to be. You have a box that is likely going to be picked up and moved around, possibly mishandled. It may have things stacked on it in an uneven manner, slammed down onto it, etc. etc. You need to think like that, and that's how a woodworker (all of us on here) thinks.

So a mitre joint may not be appropriate at all. Usually when the grain runs into itself and terminates cross-grain at a mitre, like in a picture frame, it's glued and secured with v-shaped nails. But keep in mind that a picture frame is like that mitre joint that the carpenter built in the house. It's not subjected to changing stresses. In a piece of furniture, or a speaker box, those stresses change all the time and, as a result, more sophisticated joinery is needed at end grain corners, like a mortise and tenon joint or a dovetail joint, both of which can be cut in such a way as to create a visible mitre and hide the actual joinery.

With all of that said, I really do think that we could provide the best advice if we see the plan, but if you're certain that mitre joints are the appropriate joint, then I would find someone with a larger, 12" blade compound mitre or radial arm saw. Making the eight cuts you'd need to do your 4 corner mitre would take less than five minutes.

Cheers,
Luke

[ian]

As a matter of interest what power equipment would a professional carpenter use to make a mitre in an 89mm tall work piece for a box setup?
From what I have seen a compound mitre saw would not achieve this.
89mm (vertical) is close to the maximum capacity of a Makita 260mm sliding compound miter saw cutting at 45 degrees (as though making a picture frame), and about 20mm less than the capacity of 12" model.
working with the 89mm dimension on the table (i.e. the 19mm thickness is vertical and the blade is tilted to 45 degrees) the 10" Makita has almost 200 mm of additional cutting capacity.

My, now almost 20 year, Makita will still cut accurate 45 degree miters -- if I clamp the work piece to the table before cutting. However, if I only hold the piece by hand, the wood will move ever so slightly as it is cut throwing the miter off. Note the fence on my Makita is adjustable and when new needed to be tweaked a little bit to bring the 90 and 45 degree cuts to spot on.

another option is a table saw with the blade tilted to 45 degrees -- it takes a bit of fiddling to adjust the blade relative to the table so that it's spot on at 45 degrees, but it's doable. And many box makers have set their table saw up to achieve accurate 45 degrees off the blade.

the alternative is to get close to 45 degrees off the blade and then use a 45 degree shooting board (or a miter guillotine) to get the 45 degrees spot-on.
http://www.leevalley.com/US/images/item/woodworking/saws/03h0101s5.jpg

[dalpets]

When I was talking of height I was referring to my hand mitre saw and the positioning of the piece, rather than than its thickness.399931
Can a compound drop saw achieve the same result ie., can the blade be tilted as is the case with a table saw, with the piece in flat mode to cut a 89mm long mitre across the 19mm thickness.

[ian]

When I was talking of height I was referring to my hand mitre saw and the positioning of the piece, rather than than its thickness.399931
Can a compound drop saw achieve the same result ie., can the blade be tilted as is the case with a table saw, with the piece in flat mode to cut a 89mm long mitre across the 19mm thickness.yes,

but unless you're spending serious bickies, don't expect a result any better than you are getting with your Jorgenson(?) Plastic(?) mitre box.

If you own a hand plane, you best option will be to make a 45 degree shooting board and shoot the miters to an exact 45 degrees.

[dalpets]

Ian,

Thanks.

Could you point me to an online instructable to make such a 'shooting board'

[Sam]

I'd use a shooting board but to accurately shoot the mitres you need to cut accurate mitres to begin with - for the shooting board. Or shim your shooting board...lots of mucking about if your only building one box. Take Cal up on his offer....or use butt joints.
Mitres arent as easy as it looks in ikea.

[Kuffy]

Can a compound drop saw achieve the same result ie., can the blade be tilted as is the case with a table saw, with the piece in flat mode to cut a 89mm long mitre across the 19mm thickness.

In the first 20 or 30secs this video shows a sliding compound miter saw in action cutting a 45 degree miter across the width of the board. It's a pretty bad example because the operator is anything but smooth and deliberate with his actions, but it gets the point across well enough.


https://www.youtube.com/watch?v=0cbVStFIlq0

[Bendigo Bob]

Ian,

Thanks.

Could you point me to an online instructable to make such a 'shooting board'

Just in case you haven't seen this. Mitch Peacock's idea seems most usable. Some I've seen are far too complex.

https://www.youtube.com/watch?v=nV6m9dLuFTo

[ian]

Ian,

Thanks.

Could you point me to an online instructable to make such a 'shooting board'
here's one from Tom Fidgen -- Mitre Shooting Board - THE UNPLUGGED WOODSHOP TORONTO (http://www.theunpluggedwoodshop.com/mitre-shooting-board.html)
much fancier than it needs to be for just one box.

I have a picture of one that consists of 4 pieces of MDF screwed together. Essentially it's a 45 degree ramp added to a standard shooting board.

Drafting triangles are a good source of accurate low cost 45 degree references.

[Cal]

Come up to Strathalbyn and we can stuff it up together, you won't feel so bad then! [emoji1]seriously would be happy to help before you get too confused. I can't see what you linked to you comment, try posting it up again or pm me the design your after. I'm off collecting a tree in the morning but should be home most of the weekend.

Are you trying to get a box made like this? http://uploads.tapatalk-cdn.com/20161118/9fa616898d85a2cbfb9f58219ce3b5c9.jpg

[dalpets]

399973

[Cal]

Easy done with the tools I have. Will take a bit of time setting it up. Mitres are the easy part.


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[auscab]

A Mitre Jack is a way of doing it on a bench . They turn up for sale sometimes .
Here is a nice video of one being used.


https://vimeo.com/126329537

A decent block with a 45 degree angle on the end clamped down over the end of your board at the edge of a table or bench could be another way of doing it .

look at these images as well .

https://www.google.com.au/search?q=Miter+jack&client=firefox-b&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj1t57vrrPQAhUDpZQKHV4yCM0Q_AUICCgB&biw=1120&bih=571

Rob