<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w
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ontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--> A couple of days ago a post on a professional machinists forum caught my attention describing one of the most simple yet effective modifications to a common shop tool.
The writer, whose ID I cannot recall, started his post by describing the sometimes irritating process of using a small arbor press. He went through the procedure that we encounter from time to time: installing odd-shaped pieces of scrap material to support a workpiece, trying to hold a drift tool while operating the ram handle – in short, all of the frustrations involved with using this tool.
The author then described his solution for many of these problems and I duplicated it. This is a nice after-dinner project, it doesn’t take long at all, requires minimal skill and very little cost. Here’s how it all worked out for me.
The arbor press is first disassembled and the ram removed.
The ram is installed in the lathe, centered in a 4-jaw chuck then drilled and tapped. The ram in this small "0" frame press is 0.750 square and I chose ½-20UNF-2B as being appropriate for the size.
As suggested by the writer, I obtained a half-dozen “grade 8” bolts – these happened to be available at my local hardware store but that is not common. Might have to order them. The grade 8 bolts will form the basis of the tooling for the arbor press. They are hard enough to withstand lots of wear, malleable enough not to shatter while still machinable.
Although I didn’t photograph the next step, it consisted of milling two flats on the bolts, in my case .438 to fit a 7/16 open-end wrench. (I used a 3/8 solid carbide end mill running at about 2400 RPM, fed moderately by hand.) The purpose of the flats is to allow the use of a wrench to install/remove tooling from the threaded hole in the arbor press ram.
A collet block, as shown below, was employed to secure the bolts while milling. (Obviously the collet block was installed in the mill vise.)
Rather than chucking the bolts for the next modification and deforming the threads, I used the tapped hole in the ram to hold them. The ram had not been removed from the lathe so inserting the bolts in the tapped hole with a lock nut was a convenient way to turn the head off and then turn the diameter to any desired dimension.
As previously noted, grade 8 bolts are very tough items. They exhibit hardness greater than Rockwell 30 C (about the same as pre-hardened 4140 steel). The use of C5 carbide tooling is suggested but there is a problem in that turning off the bolt heads is an interrupted cut, at least in the beginning.
The process should be done carefully to avoid chipping the carbide cutter. I tried to be careful but on the final bolt I managed to chip the cutter. Fortunately it was a cheap 3/8 AR brazed tool picked from eBay for less than a buck. (For that price, it's not worth dressing the cutter with a diamond file.)
After turning off the head, turn the body to the desired diameter. (In my case, I wanted five drift tools of the following diameters: .435, .373, .310, .248 and .124.) I did most of the turning at about 1600 RPM and .003 IPR. I would have preferred a much higher speed but my larger lathe is limited to 1600 RPM. However, the chips were still coming off dark blue, as we'd like and the finish was OK.
The first four bolts were modified with no issues but the final one, .124 diameter, required a little care because of deflection from the cutting tool. I selected the sharpest carbide cutter I could find, which turned out to be an insert, and made the part.
Here's a shop-made carriage stop used to obtain uniform lengths of the turned drift portions of the modified bolts. (Bluing obtained by parking the cleaned parts over the burner of my gas stove. When the desired color was reached, parts were dunked in the ubiquitous can of used motor oil.) The lower locking thumbwheel was an experiment; one of the rollers was removed from the knurl. I sort of like the resulting appearance and will use it often now - also knurling pressure is diminished as a benefit of removing one of the knurls.
The next step was not photographed and it consisted only of putting the modified bolts in a smaller lathe equipped with collets, for wire brush de-burring. Here is the finished set of drifts with my beat-up, 42 year old HP-11C shop calculator.
And finally, here is a 3/8 drift installed in the ram after the press was reassembled.
The five tools that I made are simple drifts used (for example) to install or remove press-fitted parts or perhaps cold-heading small unhardened parts. Another use for these simple tools could be as gasket punches, perhaps using a bench block as a die as shown above. (Bench block is held in place with double-back carpet tape.)
Clearly one can expand the idea and design various types of tooling for the arbor press as needed for special situations.
I thought that the entire idea was very clever and I particularly liked the original author’s idea of using modified Grade 8 hardware to eliminate the need for heat treatment.
<!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]-->
unctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <wontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--> A couple of days ago a post on a professional machinists forum caught my attention describing one of the most simple yet effective modifications to a common shop tool.The writer, whose ID I cannot recall, started his post by describing the sometimes irritating process of using a small arbor press. He went through the procedure that we encounter from time to time: installing odd-shaped pieces of scrap material to support a workpiece, trying to hold a drift tool while operating the ram handle – in short, all of the frustrations involved with using this tool.
The author then described his solution for many of these problems and I duplicated it. This is a nice after-dinner project, it doesn’t take long at all, requires minimal skill and very little cost. Here’s how it all worked out for me.
The arbor press is first disassembled and the ram removed.
The ram is installed in the lathe, centered in a 4-jaw chuck then drilled and tapped. The ram in this small "0" frame press is 0.750 square and I chose ½-20UNF-2B as being appropriate for the size.
As suggested by the writer, I obtained a half-dozen “grade 8” bolts – these happened to be available at my local hardware store but that is not common. Might have to order them. The grade 8 bolts will form the basis of the tooling for the arbor press. They are hard enough to withstand lots of wear, malleable enough not to shatter while still machinable.
Although I didn’t photograph the next step, it consisted of milling two flats on the bolts, in my case .438 to fit a 7/16 open-end wrench. (I used a 3/8 solid carbide end mill running at about 2400 RPM, fed moderately by hand.) The purpose of the flats is to allow the use of a wrench to install/remove tooling from the threaded hole in the arbor press ram.
A collet block, as shown below, was employed to secure the bolts while milling. (Obviously the collet block was installed in the mill vise.)
Rather than chucking the bolts for the next modification and deforming the threads, I used the tapped hole in the ram to hold them. The ram had not been removed from the lathe so inserting the bolts in the tapped hole with a lock nut was a convenient way to turn the head off and then turn the diameter to any desired dimension.
As previously noted, grade 8 bolts are very tough items. They exhibit hardness greater than Rockwell 30 C (about the same as pre-hardened 4140 steel). The use of C5 carbide tooling is suggested but there is a problem in that turning off the bolt heads is an interrupted cut, at least in the beginning.
The process should be done carefully to avoid chipping the carbide cutter. I tried to be careful but on the final bolt I managed to chip the cutter. Fortunately it was a cheap 3/8 AR brazed tool picked from eBay for less than a buck. (For that price, it's not worth dressing the cutter with a diamond file.)
After turning off the head, turn the body to the desired diameter. (In my case, I wanted five drift tools of the following diameters: .435, .373, .310, .248 and .124.) I did most of the turning at about 1600 RPM and .003 IPR. I would have preferred a much higher speed but my larger lathe is limited to 1600 RPM. However, the chips were still coming off dark blue, as we'd like and the finish was OK.
The first four bolts were modified with no issues but the final one, .124 diameter, required a little care because of deflection from the cutting tool. I selected the sharpest carbide cutter I could find, which turned out to be an insert, and made the part.
Here's a shop-made carriage stop used to obtain uniform lengths of the turned drift portions of the modified bolts. (Bluing obtained by parking the cleaned parts over the burner of my gas stove. When the desired color was reached, parts were dunked in the ubiquitous can of used motor oil.) The lower locking thumbwheel was an experiment; one of the rollers was removed from the knurl. I sort of like the resulting appearance and will use it often now - also knurling pressure is diminished as a benefit of removing one of the knurls.
The next step was not photographed and it consisted only of putting the modified bolts in a smaller lathe equipped with collets, for wire brush de-burring. Here is the finished set of drifts with my beat-up, 42 year old HP-11C shop calculator.
And finally, here is a 3/8 drift installed in the ram after the press was reassembled.
The five tools that I made are simple drifts used (for example) to install or remove press-fitted parts or perhaps cold-heading small unhardened parts. Another use for these simple tools could be as gasket punches, perhaps using a bench block as a die as shown above. (Bench block is held in place with double-back carpet tape.)
Clearly one can expand the idea and design various types of tooling for the arbor press as needed for special situations.
I thought that the entire idea was very clever and I particularly liked the original author’s idea of using modified Grade 8 hardware to eliminate the need for heat treatment.
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