# Confused about bushes



## AndyNC (Jul 18, 2011)

Hi,

I'm making a router table for my dewalt 625EK. Following Bill Hynton in principle.

I've made the mounting plate and the top and now need to make the cutout in the top for the mounting plate.

So I used a 10mm cutter and a 17mm guide bush. (I only have a 17mm)

Now reading and doing a few simple drawings if I make the internal template using the above the combination and then use the same combination for the cut out in the table top, the offsets etc should be the same. ie the inside template hole should be 13.5mm larger than the mounting plate and then the cutout in the top should be 13.5mm smaller,

I made the internal template but when I measure it up against the mounting plate I find it's 2mm out.

Am I making the wrong assumptions about the offsets or this a skill issue?

Many thanks

Andy


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## tomp913 (Mar 7, 2014)

I get confused on this sometimes, and find that it's easier to make a quick sketch. Assuming that both templates are female, I think that the sizes would be per the attached sketch. What gets confusing is that you're cutting on opposite sides of the cutter, depending on which part you're making - hopefully I've got the math correct (on the second attempt).


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## Phil P (Jul 25, 2010)

Hi Andy

In metric you don't get the nice relationship ratios between measurements that you do in Imperial (one of the very few advantages of Imperial TBH). I've just revistied this - to do this in metric with a 10mm cutter and standard (off the shelf) guide bushes you'd need to make the first cut using a 20mm guide bush on the inside of the template, then swap to a 40mm guide bush with the 10mm cutter for the outside cut. Which will work

With Imperial your first cut needs to be something like 1/4 in cutter with 3/8in guide bush followed by 3/8in cutter with 1in guide bush.

Regards

Phil


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## AndyNC (Jul 18, 2011)

Hi, tomp913

I've looked at your sketch and I realised the error of my way. I've been thinking about all wrong. I haven't checked your maths but now you given me a good pointer I'll re-try my own calculations.

Also since my OP I've noticed that I was using a 12.7mm cutter so nothing would have added up. Luckily I did trial cuts.

So a new sketch and new calculations after tea.

Many thanks

Andy


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## RainMan 2.0 (May 6, 2014)

Andy this drove me nuts at first ,as I forgot to take into consideration the bit width

I did a little video to help me understand the error of my ways 

http://youtu.be/bBTrI15ad04


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## tomp913 (Mar 7, 2014)

*Easy Jig to cut Top*

Andy,

If you have already made the mounting plate, and have a pattern bit with the top bearing, here's an easy way to make an exact size cutout in the table top - fix the mounting plate in place, snug the strips around it as shown and cut around the inside of the strips for a (hopefully) perfect fit for the mounting plate. This is what's shown/recommended for those who use a "store bought" aluminum mounting plate. The plus is that no specific template is needed for the table cutout.

Tom


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## AndyNC (Jul 18, 2011)

Hi All,

with out replying to specific posts:
I thank you for your assistance.
I can't get a 40mm bush readily (£8.50) but 32mm (£2.50) is readily available and I need to check If I have a 10mm bit. ( I though that was what I was using but not as it turns out).

Having read your info I think I can produce a spread sheet for my calculations and pick a bush and tool. I need to buy some more because most of the bits I have are old, worn and HSS and I only have the one 17mm bush supplied with my MOF96.

I like the idea of using strip tacked round the mounting plate. The only fly in the ointment is that I radiused the corners of the mounting plate using a coin so I may have troubles get a tool of the correct size so I don't get them filled with dust and chippings.


I'll let you know how I get on. It may not be for a week or so because I have to fit a cooker hood and a bathroom extractor next week end.


Cheers
Andy

I've just done a spread sheet and the difference between the bushes doing an internal and external cut using the same tool is twice the tool diameter. I need to make the spread sheet a little more explanatory before publishing.


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## leeajones (Apr 9, 2013)

This might help - you'll need to use a conversion chart (which is easy to find on the web) to solve your problem:

The most important thing to learn about using bushings is the offset—the distance between the cutting edge of the router bit and the outside edge of the bushing.
The offset is the key to creating jigs and templates to cut the sizes and shapes you want. To determine the offset, subtract the bit diameter from the bushing diameter and divide by two. For example, with a 3⁄4-in.-dia. bushing and a 1⁄2-in.-dia. bit, the difference is 1⁄4 in. Half that, or 1⁄8 in., is the offset, so the edge of the template must be 1⁄8 in. from the edge of the cut.

LJones


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## Jimwarren (Jan 13, 2015)

Hi can anybody tell me what is the most used makita 3612 s guide bush . I would like to thank everybody for all help I recived. Jim


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## Phil P (Jul 25, 2010)

Jimwarren said:


> Hi can anybody tell me what is the most used makita 3612 s guide bush . I would like to thank everybody for all help I recived. Jim


Probably 30mm, Jim, because that's the one you use with kitchen worktop jigs

Regards

Phil


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## Phil P (Jul 25, 2010)

Hi Andy



AndyNC said:


> I like the idea of using strip tacked round the mounting plate. The only fly in the ointment is that I radiused the corners of the mounting plate using a coin so I may have troubles get a tool of the correct size so I don't get them filled with dust and chippings.


I tack stuff round like that quite a bit (e.g. Belfast cut-outs on hardwood worktops). As to the radiused corners, what about drilling-out the corners of the opening with something like a Forstner or even a spade bit of the correct diameter and "connecting the dots" (i.e. routing corner hole to corner hole) with the router. You may need a hand saw/jigsaw/padsaw and a file just to clean up the corners a little, but it is "doable"

Regards

Phil


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## AndyNC (Jul 18, 2011)

Phil P said:


> Hi Andy
> I tack stuff round like that quite a bit (e.g. Belfast cut-outs on hardwood worktops). As to the radiused corners, what about drilling-out the corners of the opening with something like a Forstner or even a spade bit of the correct diameter and "connecting the dots" (i.e. routing corner hole to corner hole) with the router. You may need a hand saw/jigsaw/padsaw and a file just to clean up the corners a little, but it is "doable"
> 
> Regards
> ...


Hi Phil,

Good idea and very tempting. I have a good set of forstner bits given to me by my Dad along with the rest of his workshop. 
I only have a bottom bearing follower so either way I'm going to have to buy some more tools, bits and/or bushes.

At the moment I only have a 17 and 28mm bushes and a couple of well worn straight bits, I think I'll be better off progressing in a way that builds up my tool set with more general purpose items.

Many thanks

Andy


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## Phil P (Jul 25, 2010)

AndyNC said:


> At the moment I only have a 17 and 28mm bushes and a couple of well worn straight bits, I think I'll be better off progressing in a way that builds up my tool set with more general purpose items.


Hi Andy

There is a really slippery slope called tool buying....... Just remember the one who dies with the most tools, wins! 

17 and 28mm are slightly odd sizes TBH, but maybe I'm just saying that because most manufactured router jigs (e.g. Trend) use 16 and 30mm in the main. If you want a cheaper source of guide bushes, try Axminster. Their steel bushes are very reasonably priced at under £3 a pop , or £21 for a set of 12. I have to say I don't have a full set - only the ones I've needed. I tend to buy stuff like that when I'm passing their Warrington store rather than pay postage

Regards

Phil


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## harrysin (Jan 15, 2007)

The calculation for the size of opening in a template is: guide dia.-bit dia + size of the finished opening. Where practical I use a 40 mm guide with a 10mm bit. For example, if we want the opening in the table to be 250mm X 150mm then using this combination will gives us: 40-10+250mm by 40-10+150mm which makes the opening in the template:
280mm X 180mm. For a rebate all round we can change to a 20mm guide with a 5mm bit which is 20-5=15÷2=a 7.5mm rebate. The beauty of a 40mm template guide is that all chucks will pass through it, giving far more depth of cut compared to a chuck which has to stop before hitting a smaller guide.
The two shots show the easy, accurate to make a template with a square/rectangular
opening.
For many years a Makita 3612C was my main hand held router but last year I retired it to be permanently on skis and replaced it with a Makita RP2301FC


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## Jimwarren (Jan 13, 2015)

Thank you Phil . You are so kind. Jim


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## AndyNC (Jul 18, 2011)

*Sorted*

Hi All,

Did the calculations again and use 14mm bush and 6mm bit followed buy 26mm bush and a 6mm bit.

Worked OK except the cutout was about 0.5mm or so deeper than required. Used a bit of modelling filler and tapped it down.

Of coarse this is where you find that the table top is not dead flat.

Overall a usable item. I need to make legs etc for it now.

Cheers

Andy


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## RMIGHTY1 (Nov 5, 2014)

I'm thinkin, I'm thinkin... :wacko:


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## AndyNC (Jul 18, 2011)

Didn't see all the posts till just now.

Many thanks for advice.



Phil P said:


> Hi Andy
> 
> There is a really slippery slope called tool buying....... Just remember the one who dies with the most tools, wins! ..........


I'm getting close, the most tools that is. Also have my Dad's lifetime of tools as well helps.

I bought the bush set and a new 6mm router from Axminster, it's only 10mins down the road.

Cheers

Andy


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