What is an acceptable amount of "gap" in a mitre?

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fieldsframing

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Jun 28, 2011
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Milledgeville, Ga
You guys are going to catch on pretty soon that I have only been framing for two and a half years and I'm completely honest when it comes to my level of skill. I'm learning, growing and passionate about becoming the best framer I can be, but a great deal of my questions are going to be simple issues to most of you, things that I'm still trying to get the hang of and methods that I want badly to perfect and I'm extremely grateful for the guidance of seasoned framers on this site. With that being said, what is an acceptable amount of gap or space in a mitre? Obviously I'm striving for there to be none but even when I've had to order moulding chopped and joined due to width limitations on my current equipment I've noticed some degree of gap on either the front face of the profile but more repeatedly on the outside or back of the profile. This has been my greatest source of struggle thus far and I don't want to use fillers and putty, nor do I want to waste unnecessary amounts of moulding, I want a tightly closed mitre on all joining surfaces!! As a reference, I'm currently cutting moulding with an older foot-operated Jyden chopper and joining with an air operated mitre mite VN 42 v-nailer. Also, are there any references or training materials that you could refer to assist me in my quest for the perfect mitre? Thanks a million!!!
 
Miters should be tight but if not a small amount of filler wax will close the seams. Are you located anywhere near me, if so you can come by and I'll show you what you need to know.
 
Jeff, you're willingness to help is really incredible! I'm located in middle Georgia, almost two hours south of Atlanta, so, close in a grand scheme of things but not close enough for a quick trip out that way. I'm about 6 hours away from you I believe... I'm getting better at my joining and of course some mouldings present more of a challenge than others but I am improving. Your offer is certainly tempting enough to consider making a weekend trip sometime however.
 
In our shop, we will not accept any amount of gap in the mitre. We always use filler to touch them up as necessary.

Gaps in the mitre will occur either when cutting or joining.

When cutting with the chopper, make sure that the moulding is flat against the bottom and back supports. If it starts to roll forward when chopping you will get the gap in the top and back of the moulding. Make smaller notch cuts as needed.

When joining, make sure that the back and top are not showing any gaps before inserting the v-nails.

Always cut and join a few scrap pieces of moulding as tests before making the final customer's frame.

Good luck!
 
Does your VN 42 have 3 knobs on the fence. If so the single outer knob is used to open and close the angle of the fence to help get tighter miters.
 
Thanks Eric, I don't want any gap at all either! I just always felt like using filler (even minimally) was like cheating or not "professional". I mean, I know they make the stuff for that reason I guess just feel like I'm giving in to an imperfect corner when I use it.
 
Jeff, my v-nailer has two knobs on the right and one on the left. I've hesitated to adjust these out fear that the fence wouldn't be a square 45 degrees but now that I think about it the knob that you're referring to should not effect the "square-ness" of the joint. I've also found that when I do play with those knobs I end up with three really great mitres and one pain in the ### mitre... Any tips in avoiding that?
 
First thing you should do is use a plastic triangle to properly align the center marks on those 3 knobs. Push it into the 90 degree corner and adjust the single out knob until square. If the center line is not properly aligned use an allen wrench to loosen the set screw in the side of the knob and swing to center than tighten. Now stand it upright against the fence on the one side and square and align the center mark. Repeat for the other side and the center points will be your starting point.

The problem of a fourth corner should only happen on very small frames or smallish frames of very wide mouldings. You will also want to be sure your chopper is properly aligned as well. Imperfect cuts make for nearly impossible perfect joins.
 
I will routinely make sure that my v-nailer is set up squarely but I do so using a metal speed square, hopefully it's as accurate as the plastic ones. Checking proper alignment on my chopper seems to be a bit more difficult but I understand exactly what you mean b/c I've wrestled before with imperfect chops after installing newly sharpened blades. If the blades aren't set properly by even the smallest amount my chops would be way off. Do you have a recommendation for how to go about checking the alignment of my chopper? Should I just pull the blades up all the way to the to the guard rail and measure on the left and right of the blades to make sure it's at a perfect 45?
 
Back fence is the adjustment to your chopper. Take a 4' metal ruler and loosen the adjustable back fences. Hold the metal ruler against the outfeed table against the back of the guide on the extension. Now swing the left and right adjustable fences against the metal ruler and tighten them in place. The 45 degree angles are stationary so that is all that is needed. If you don't have a four foot metal ruler they sell them at Lowes for less than $10.
 
Wow... I feel ignorant in admitting this but I've honestly never altered that adjustment! I've played with how the blades line up to each other but that's it. Man, you're really "schooling" me Jeff!
 
The 'left-fence tweak' is often all that is needed. The right fence should align perfectly with the measuring arm - once set should never be moved.
The left fence can be shifted slightly off the 45deg to cure any gaps. The thing is, even if you set the angles exactly to 45deg, they don't necessarily cut a 45deg mitre. Sounds weird? Read on..... You are cutting wood which is a natural material and has a bit of 'spring' in it. Depending on how sharp the blades are and how well they have been ground, the cut can go off slightly. A tiny error is multiplied x4 on a frame. Also the wider the moulding the more this will show because of the diverging angle. This is why sometimes you get three perfect corners and a gap in the last one.
The trick is to deflect the left fence a tiny amount. If you are getting a gap on the inside, slacken the left fence and move it toward you. I'm talking a hairs breath here. Use a piece of scrap timber to test this. Cut a frame and see if there is a gap. Tweak the fence and do it again. If the gap is smaller, tweak the fence a bit more. If you start to get a gap on the outside then you have overcooked it. It's a bit tedious, but you will eventually get a feel for the setting.
I aim to make it so that when you have joined three corners, the last two faces are ever-so-slightly apart. Then when you pin the last one the inside of all the other joins is given a nice squeeze. That's assuming you place the outer v-nails first, which has always been my practice.

Of course all that is assuming that the moulding is dead straight. ;)
 
You know, I never thought about trying to move the fences (re: alligning my single mitre saw). I've always had some gapping with cuts it makes, and just accepted the fact that I'd have to fill those frames. I just cut a frame on it a few minutes ago; I'm going to see how it does and maybe adjust the fences.
 
You've been given amazing advice, all of which I do.

As mentioned, some mouldings, especially if they have a lot of gesso can lead to a frame not joining well. I never touch the settings on my guillotine once set up correctly. One normally picks that up once the mouldings have been cut. What I do then is recut it slightly. I use old blades or thin slithers of board to change the angle ever so slightly that it enters the blades at.

Good luck, I'm sure you're going to do amazing work.
 
Jeff Rodier said:
Back fence is the adjustment to your chopper. Take a 4' metal ruler and loosen the adjustable back fences. Hold the metal ruler against the outfeed table against the back of the guide on the extension. Now swing the left and right adjustable fences against the metal ruler and tighten them in place. The 45 degree angles are stationary so that is all that is needed. If you don't have a four foot metal ruler they sell them at Lowes for less than $10.
Click to expand...

This may well work if you're cutting soft woods, but we have never found it successful in cutting hard woods. Our fences are never in a straight line, and in fact we have to check (and often adjust) them per set of blades that are on them. Again, a hard wood is less forgiving in making a tight join, as the wood will not squish up the way a soft wood will. We adjust each side separately, and our customers tell us that no one supplies chops that fit together as well as ours.

From our website, here's the method we use:


  • Get a piece of flat stock (such as strainer). Something 1½" to 3" wide and ¼" to ½" thick works great. Cut the right end of it (with the left blade).
  • Cut a piece 3 to 6" long (the best length will vary based on the width of material and how big your square is).
  • Now take that piece, flip it over and re-cut the second end, but with the left blade. Now you will have a piece where both ends were cut with the same knife and angle. This will double any error, making it easier to see and correct.
  • Hold the two 45° angles against the inside surfaces of an accurate square. A machinist's scale is preferable. Observe if there is a gap at the inside or outside:
    • If there is a gap at the point the angle is too obtuse. With a chopper, you will need to loosen the fence and push it away from you. For a saw, check your manual for applicable adjustments.
    • If the gap is on the inside the angle is too acute and you will need to pull the chopper fence towards you.
    • Re-cut both ends, re-check and repeat until you can't see light anywhere
  • Start over at point 1. for the other side.
 
OK, let just say the chop I made is less than perfect. (happened once a while ago:) :) )

Would a Masterclamp help draw the corner together?

Doug
 
This is all really great advice guys! I'm soaking it up and I know that what I need is more time in the shop but the guidance that I'm receiving from all of you will make that time much more profitable!!
 
And here's a follow up question: How do you guys address mouldings (in my experience a lot of gold and silver moulding) that chip away on the back of the profile? Even with freshly sharpened blades and when I have all four corners joined well I'm still left with chips in the surface that need to be filled. What's going on here? How do I remedy it?
 
Stop buying cheap carpy/PITA moulding.

IF a moulding costs you money.... pitch it. Even if you thought you got a great deal.

We got in a box of $1.69/ft moulding. They had changed the shell mix and it dried
to slow and was really soft...... so wrap marks all over it.

We called and I said either sell it to me at $.25/ft.... or send a call tag. They went through
what they had.... and it was all the same. So with a little fight.... I got it for .25.
Sounds like a deal.... right?

I had to make the frames, then refinish them.. with black Krylon. But... the under coat was
still that soft carp skin..... the sample is gone!

AND it was one of our staples..... that used to be great.... back when it was $1.30/ft.
 
Some mouldings just aren't chopper-friendly. There's a lot of stuff about with a rock-hard composition coating. A saw is the weapon of choice for this. Could be that it's made (to a price) with the mass-production ready-made market in mind. There has also been a drop-off in wood quality over the years. Manufacturers have to source the stuff at the right price and will try and shave the costs. That said, there are certain 'magic' mouldings that suit your needs and are a joy to use. Takes time to find them though. My advice is to try a small quantity first to see how it performs.
 
Yeah, I think I understand what you mean. I'm beginning to be able to look at the side profile of a sample moulding and determine whether or not it's going to give me problems. My initial thought when starting my business was that I needed to have as many moulding samples as I could fit on my walls. Now I'm starting to pick through them and get rid of some of the more pesky frames.
 
There are profiles that can be tricky to cut. I'm thinking of ones with a scooped middle and raised front and back. The blades bite the front edge and already have established a track when they bite into the back edge. If you don't set your rabbet supports just right, the moulding can tip forward slightly as the pressure is applied at the front and tip back again when the blades hit the back. You can feel the moulding wriggling a bit. If this happens, twiddle the supports so that by the time you come to do the final stroke there is no movement.

I think we have all been guilty of getting carried away when confronted with a reps case of samples and ordering lots of goodies. I've still got stuff I bought 20 years ago. :o
 
Thanks Steve..... my feelings also....

As one of my old bosses used to say... "If you can insert a
pink slip in it - - the slip is yours."

One of the fastest ways to deal with that bugga-boo forth corner
that isn't nice, is the judicious use of a corner vice and a Japanese razor saw.
 
I am using a Morso chopper and have found that if the blades are not sharp it is impossible to get a perfect 45 degree cut and a perfect mitre. I also glue up the frames prior to underpinning them so I can make sure the corners are as perfect as I can get them. Once in a while they will break apart doing this, but this rarely happens.
 
Try using Corner Weld or Maxim glue. I've never glued before v-nailing but there are some that do it mostly due to v-nailer limitations.
 
I get it that some "die hard framers" enjoy the "wood working" aspect of chopping and joining frames, and would never wish to pay the additional cost for someone else to do this part of the job -- it's just part of your business model and a profitable part of that.

However, I just want to mention to a new custom framer that join services are available through some suppliers, like Larson-Juhl, and this CAN be especially cost effective for the mouldings that are known to be very chippy and/or difficult.

The benefit here is: if it isn't perfect, it can be sent back for a replacement at their cost and delivered in a couple of days. No inventory, no scrap or waste, and no do-overs for the shop (labor cost/time). Based on the moulding, you can decide if you want to use the join service or join it yourself.

The joins from our regional L-J facility are typically dead-on perfect. In the past year, the need to putty and/or touch up has gone way down to nearly zero; I heard they installed new and more precise equipment and it shows. No gaps at all, nice clean corners.

Not a wood worker, my passion is the design, matting, and mounting to produce a fine conservation framed piece, so it doesn't kill me to allow a vendor to join a frame, it feels like we are partners in the entire process and I get to focus my time and energy on what I do best.

By all means, practice and perfect your techniques as a framer based on your passion, and it sounds like part of that is perfecting the joining techniques and experience that will apply to working with thousands of different finishes and shapes. Mastering that craftsmanship is a wonderful goal.

Also know that sometimes it can be cost effective to pass on the difficult or risky jobs to a supplier and let them "eat" the scrap; i.e. know when to UTILIZE your suppliers' services. It can be tried a time or two just to test it out for yourself without a standard committment either way, because they are flexible on an order-by-order basis. Some moulding finishes were just not designed with joining in mind, it seems!

Yes, it costs more if you just consider the cost of the moulding length, VS chopped VS joined... but be sure to calculate in the other aspects of labor, wasted lengths, storing the excess moulding for goodness knows how long, etc.

Cheers and good luck!
 
I have never been a fan of v-nailing after the glue has set up. Seems a bit cart-before-the-horse to me. But whatever works.... :thumbsup:

What I do with wider frames though is to use biscuits and a strap clamp. Not one of the wimpy clamps made for picture framing. A HD one that you can cinch up with a wrench. I typically would cut a biscuit slot near to the inside of the mitre. Glue up all four corners and throw the clamp around. At this stage you can jiggle the joints into place while tightening the clamp bit by bit. When all is aligned, give the clamp an extra twitch and then take the whole issue to the pinner and put a few vnails near the outer edge. Very good method if you are joining a big frame single handed. You have great control and the biscuits will hold the join in alignment vertically, but allow a bit of movement laterally. Gluing all four corners at once also spreads any slight angle errors around the four corners instead of having them accumulate on the last corner.
 
From the responses here I am guessing that nobody else has to deal with slightly twisted or warped mounding. While we all strive for perfect corners that you can't slip a sheet of paper between, it does happen and I am betting that all those that claim other wise are stretching the truth just a bit.
 
It is also more effective to throw a corner sample in the trash than to pay a bunch of extra money to have it joined by a vendor. If a moulding is a problem why would you want to try to keep track of problems and then have it sell enough for the vendor so they make more. What happens to those who haven't used the problem moulding before and have to buy it twice so they can get a joined frame. Kill the sample so the moulding finds a timely death.
 
FrameMakers said:
From the responses here I am guessing that nobody else has to deal with slightly twisted or warped mounding. While we all strive for perfect corners that you can't slip a sheet of paper between, it does happen and I am betting that all those that claim other wise are stretching the truth just a bit.
Click to expand...

No stretching going on here, Mr Dave. First of all, if it's twisted or warped, it doesn't get used, it goes back to the supplier. And if you can slip a piece of paper between the joints, it gets reworked until it's tight. How do you expect the glue to hold if the two pieces aren't touching?

Would you buy a house where all the woodwork had gaps (or filled with wood filler). Or cabinetry with shoddy seams and mitres. Or would you buy a piece of fine furniture with open seams and less than perfect finishes....I think not. In my view, picture frames are a piece of fine woodworking.

And if you're farming this portion of the project out, like some have suggested....along with having someone else cut your mats....etc. you're not a picture framer. You're an assembler of parts. So why not send the artwork to your distributor and have them do the drymounting, glass cutting and fitup. Whoops, so much for "custom framing".

Sorry about the rant but, there comes a point where, if your going to practice a trade (whatever that trade may be) then you need to acquire all the skills necessary to be successful in that endeavor. This includes getting some professional training, learn the skills of the trade, attending trade shows, using quality materials and equipping your shop with the proper tools to do a top notch job.
 
I need to say that Dave's work quality is above 99% of this industry. He is more likely to recut a frame than 99% of the industry because he owns more moulding than most framers would use in 5 years time. Framing is the only job he has ever had and been an owner for more than 20 years and had as many as 6 locations including warehouse in the past. Everything is great in theory but there are many times that 99.5% perfection is the best you can hope for and Dave is honest about that.

I don't know if all of your comments are directed at Dave but just so others know he is easily in the top 1% of quality in this industry.
 
Funny stuff, twisted moulding. Sometimes you try and use a bit that would make a good propeller and the frame comes out perfect. Other times you get a twisted frame from what appears to be a straight stick.

There are a few tricks I have learned to compensate for a slight twist. They don't always work - depends on the nature of the twist and the shape of the moulding. Some twists are very localised.

I would agree that most of the time it's fruitless to try and use a twisted rail. Especially if the other three sides are OK.
 
Jeff Rodier said:
I need to say that Dave's work quality is above 99% of this industry. He is more likely to recut a frame than 99% of the industry because he owns more moulding than most framers would use in 5 years time. Framing is the only job he has ever had and been an owner for more than 20 years and had as many as 6 locations including warehouse in the past. Everything is great in theory but there are many times that 99.5% perfection is the best you can hope for and Dave is honest about that.

I don't know if all of your comments are directed at Dave but just so others know he is easily in the top 1% of quality in this industry.
Click to expand...

Only comment directed toward Dave was in response to "stretching the truth". All other comments are to those for which the comments may or may not apply.
 
That is the way I took it too Steve :)
 
@fieldsframing:

The best money I ever spent for curing frustration was a corner sander. I try to keep my equipment adjusted but can fine-tune it with the sander and it also takes care of the chops we get in that need a little adjusting. If you tweak your cutting equipment and then give your chop a couple of turns in the sander you will have beautiful corners!
 
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