Routing translam birch plywood end grain - Router Forums
 9Likes
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 15 (permalink) Old 09-22-2018, 04:58 AM Thread Starter
Registered User
 
Join Date: Sep 2018
Country: Italy
First Name: Robin
Posts: 6
 
Default Routing translam birch plywood end grain

Hi all, first post from a routing newbie. I have a tricky job to do and am looking for advice from the experts.

I have a pair of speaker cabinets that ive had cnc cut from 21mm birch plywood. Ive now glued them up and done the first pass of sanding. At some point soon i need to rout speaker openings in the stacked side of the cabinets.

These will be recessed drivers, so the front edge of the cut needs to be clean as a whistle. Ive had a stainless steel circle jig fabricated for my cheap palm router with plunge base.

Hole needs to be 14 cm dia. down to 1cm depth, then an inner hole of 12 cm dia. all the way through 20mm

Im looking for advice on the best method and bits to use. I figure all the experts are here! Ive already been advised on a spiral downcut bit for the edge, and one person said an o-flute will give the cleanest edge. (brands whiteside and freud suggested) Local carpenter when asked for a quote said he wouldnt touch the job with a bargepole.

Ive attached images showing the cabinets, the circle jig, the internal cabinet structure, and a 3d model showing the hole placement.

Any advice greatly appreciated, im a noob, and these cabinets are basically irreplaceable. 😕
Attached Thumbnails
Click image for larger version

Name:	IMG_20180910_095734_1537609909148.jpg
Views:	383
Size:	401.6 KB
ID:	360085  

Click image for larger version

Name:	IMG_20180920_110241_1537609926334.jpg
Views:	124
Size:	754.9 KB
ID:	360087  

Click image for larger version

Name:	IMG_20180910_095752_1537609963326.jpg
Views:	217
Size:	390.2 KB
ID:	360089  

Click image for larger version

Name:	IMG_20180920_110802_1537609981382.jpg
Views:	139
Size:	664.7 KB
ID:	360091  

Robinlawrie is offline  
Sponsored Links
Advertisement
 
post #2 of 15 (permalink) Old 09-22-2018, 10:40 AM
Registered User
 
DaninVan's Avatar
 
Join Date: Dec 2011
Country: Canada
First Name: Dan
Posts: 13,835
 
Default

Hey, Robin; welcome! I'm not sure if you were using the term 'carpenter' loosely or not, but this is more in the realm of cabinet making or furniture making. Even an experienced finish carpenter might not want to tackle this.
In theory it's not really that complicated but the work that's already been done on it, not to mention the to-date expense, is a bit daunting.
So far they look pretty impressive!
If you fill in your profile with a bit of info about yourself, other members will get a better sense of your level of experience, and generally where you're located.
DaninVan is offline  
post #3 of 15 (permalink) Old 09-22-2018, 11:37 AM
Registered User
 
TenGees's Avatar
 
Join Date: Sep 2012
Country: Canada
First Name: Paul
Posts: 1,499
 
Default

One thing that I'd be concerned about is when you've cut through, your center pin will be loose. Maybe you can clamp something in behind the face to keep your center. I would make very shallow passes on the exposed part of the hole. Do you have any scrap you could test cut?
JFPNCM and DaninVan like this.

Sent from my Hallicrafters S-40 using morse code.
TenGees is offline  
Sponsored Links
Advertisement
 
post #4 of 15 (permalink) Old 09-22-2018, 12:05 PM
Moderation Team
 
Cherryville Chuck's Avatar
 
Join Date: Sep 2010
Country: Canada
First Name: Charles
Posts: 14,870
 
Default

Paul's point is a good one. Your circle jig requires that there be something under the piece you are routing to hold it together (a sacrificial substrate). I'm not sure that's possible in this instance. The alternative to that is to use the circle jig to cut a template that you would clamp to the box and then use an appropriate bit to rout with. I would jigsaw or use a hole cutter to get close to the finished size before routing because when the loose center falls in while routing it can hit the bit and cause it to wobble which will leave a mark on the rim of the hole.

There are two ways to use a template like I described. One is to use a bearing guided bit directly against the edge of the template. The second is to use a template guide installed in the base of the router and the template guide follows the edge of the template. In this method you have to account for the difference between the diameter of the guide bushing compared to the diameter of the bit you are using but the advantage of this method is that you can use straight bits or spirals that don't have a guide bearing.

A down shear spiral will give you the cleanest top edge but I wouldn't try to cut the hole out with it. When the spiral makes contact with the wood it wants to force the router up off the surface so the more wood you cut, the stronger the upward forces. I would just want to clean up an edge with one because of that. Buy a good bit to do this with. Whiteside, Freud, CMT, or Amana. Amana has some Chinese made ones that aren't great quality, but the Israeli made ones are good. I hear that Freud does too but their Italian made bits are good. Not sure about CMT. I believe that Whiteside is strictly US made in North Carolina and may be your best bet.
DaninVan and TenGees like this.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
Cherryville Chuck is offline  
post #5 of 15 (permalink) Old 09-22-2018, 12:21 PM
Forum Contributor
 
DesertRatTom's Avatar
 
Join Date: Jul 2012
Country: United States
First Name: Tom
Posts: 15,658
 
Default

Welcome. If I'm reading this right, you're needing to cut a rabbet, which is something like a mini shelf. A rabbeting bit, preferable with a changeable bearing is a good way to start. Cut the 1cm depth of the larger opening using your circle cutting jig. You might have to make two passes to get the width of the rabbet with your trim router. For the second pass, you will cut the full smaller circle using the same jig, but this time you will route down through the entire thickness of the material. With a trim router's limited power, you will not want to cut more than 3-4 mm at a time.

I'm assuming the pieces are not yet assembled, at least I hope they aren't. This should also produce a nice finished opening.

The other alternative is to make a template of MDF the size of the larger opening. Cut the smaller opening through with your circle jig. Then tape the template in place and use a rabbeting bit with a bearing to cut the width of the rabbet. Go very slow because your router isn't very powerful and that's a heavy bit. I like the first method better.

The comment about cutting the circle, you can use several pieces of double sided (carpet) tape to keep everything stable while you make your cuts. Make the final cut through slowly and in small increments to limit lateral forces.

Very interesting looking speaker enclosures.
JFPNCM and DaninVan like this.

The more I do, the less I accomplish.

Last edited by DesertRatTom; 09-22-2018 at 12:28 PM.
DesertRatTom is offline  
post #6 of 15 (permalink) Old 09-24-2018, 02:26 AM Thread Starter
Registered User
 
Join Date: Sep 2018
Country: Italy
First Name: Robin
Posts: 6
 
Default

Thanks for all the kind replies.

ive glued up the cabinets in sections, with the central parts glued in stacks, and the wider elements separate for now. this is to allow sanding of the recessed areas.. ive almost finished that phase of the sanding. after that i will glue them up completely, apart from the top panel, to allow continued access, and sand the whole speaker, probably with the top clamped on temporarily.

regarding the circle jig, my idea was to rout the outer circle down to the depth of the lip (circa 1cm) then rout the inner circle through, apart from a few tabs around the circumference which i would leave a couple of mm of wood, to hold the centre in place. after routing i would cut out the tabs using a hand saw or stanley knife.

i wasnt sure wether to rout the clean outer edge first (mm depth by mm depth) using the downcut bit, then do the rest with a decent straight cut bit, or, rout out the outer edge a few mm inside the final edge using the straight cut, then use the downcut to slowly enlarge the hole out to the final dimension.

i have been advised the second option, but to my (inexperienced) mind, the first cut with the straight edge risks weakening/damaging the end-grain of the ply for a good few mm either side of the cut, which could compromise the cleanliness of the finishing cuts with the downcut spiral...

what do we think here?


the carpenter (yes im using the term loosely, im translating from the italian "falegname".. these guys do everything from window frames to furniture restoration... there is also an "ebanista" in town, which i believe translates to "cabinet maker" but ive no idea of his skills) suggested cutting inner circle with a hole saw, and then use one of those bits with the bearing on ( im not sure of the name) to run around the edge of that to get the lip.. however a) the roughness of the inner circle would cause imperfections in the edge i am following it to produce,and b) ive only seen those types of bit with a straight edge, which i know is inferior for producing a clean edge..

finally, if i buy a decent straight bit and a spiral downcut bit, and use them with my circle jig, they will be useful for basically any other project.. useful given the cost of decent bits.. if i buy a specific bit for "following" a hole, it will only be useful for other projects where i need that exact size lip again..


thanks for the pointers re. bits.. for the spiral bit i was stuck deciding between a whiteside standard downcut spiral, or a freud o-flute downcut, which have basically the same price. One guy on the diyaudio forums swore by the o-flute as he said it makes a cleaner cut on plywood.. ive read conflicting stuff after which says the more flutes, the cleaner the cut, so im confused...!

my main fear is the unusual nature of the wood to cut.. its all basically end grain, with a change of direction every 2mm, and any number of potentially weak laminations or areas of thicker glue... it will be finished with a transparent coating, so anything more than small single lamination damage will look very ugly.
Robinlawrie is offline  
post #7 of 15 (permalink) Old 09-24-2018, 11:14 AM
Moderation Team
 
Cherryville Chuck's Avatar
 
Join Date: Sep 2010
Country: Canada
First Name: Charles
Posts: 14,870
 
Default

Robin one of the issues with a hole in any material except mdf is that you are going to go crossways to the grain at least twice. With layers of ply it's more than that. Anytime I build with ply I like to cap the visible laminations with a strip of solid wood. It's easy to finish. I'm still not 100% sure what you need but if the hole is getting covered then your biggest worry is not leaving a ragged upper edge which a downshear bit will help solve. If you need a lipped hole then as someone else pointed out, use a rabbeting bit. I think Freud and CMT have them with downshear cutting edges. That's something you could check on. They should be easy to come by there.

If you need a smooth bore I would be tempted to drill it with a hole saw if you can match the bit to the diameter you need. Sanding sleeves like these: Sanding Drum Kits - Lee Valley Tools will smooth the hole but you have to watch or you'll get the hole out of round with them as they have no guide.
Herb Stoops likes this.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
Cherryville Chuck is offline  
post #8 of 15 (permalink) Old 09-24-2018, 02:33 PM Thread Starter
Registered User
 
Join Date: Sep 2018
Country: Italy
First Name: Robin
Posts: 6
 
Default

Thanks for the further reply. The hole will contain a recessed speaker driver, so the top edge of the cut is the critical bit. (see my attached images earlier..) Although, unless i make the hole exactly the same size as the speaker, there will be a small gap around the speaker, where you will see the wall of the hole.

However the critical thing is the front face (which is *all* plywood end grain, and that is the defining feature of the design of the cabinets, so covering it with veneer is a no-no)

so, question is, as above: is it better to "rough out" the hole with a straight edged bit a couple of mm small, then finish it with a full depth (1cm) pass with the downcut bit to take those last 2mm off cleanly, or is to better to cut the hole in very (1mm or so) shallow passes with the downcut bit? - my concerns are in my previous post.. Cheers!
Robinlawrie is offline  
post #9 of 15 (permalink) Old 09-24-2018, 04:03 PM
Forum Contributor
 
Herb Stoops's Avatar
 
Join Date: Oct 2014
Country: United States
First Name: Herb
Posts: 7,352
 
Default

You might consider covering the whole face with painters masking tape to protect it from tearing out around the end grain cuts, and also for ease of laying out the concentric circles.
Herb
Herb Stoops is offline  
post #10 of 15 (permalink) Old 09-24-2018, 05:48 PM
Moderation Team
 
Cherryville Chuck's Avatar
 
Join Date: Sep 2010
Country: Canada
First Name: Charles
Posts: 14,870
 
Default

The speakers don't come with a trim ring? Anyway, general rule when plunging is to take a depth no deeper than the bit's diameter. Cleaning up an edge (flush trimming) you can go more but you have to watch because a long bit will chatter, even in only trimming a light pass. That compounds when you are using small shank bits like 1/4 or 6mm. Larger diameter shafts are more stable but won't fit your trim router. One of the advantages of using a guide bushing with an external template is that you could keep making successively deeper passes with one bit but to go any depth with a top bearing pattern bit you might need several different lengths.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
Cherryville Chuck is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Router Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Gluing End Grain patlaw Tools and Woodworking 6 03-24-2016 03:52 PM
Applying a coat of size to end grain? Ray Newman Tools and Woodworking 5 01-28-2016 09:00 AM
Ski question os smoothing end grain, bit, speed, etc TanOak Portable Routing 4 11-07-2010 09:03 AM
Routing Plywood Edges beemerbob Table-mounted Routing 1 12-16-2006 04:04 PM
Routing end grain Pop_pop1 Table-mounted Routing 8 09-22-2004 12:24 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome